Ground Improvement and Geosynthetics

The transportation infrastructure in coastal regions of Australia has been expanded in recent years due to high population density and increased traffic volume. Such expansions require the application of ground improvement techniques to improve performance and sustainability of the infrastructure. In this paper, innovative ground improvement techniques applicable to railway embankments, port reclamation and embankment fills are discussed. For ballasted rail tracks, the performance of different types of geosynthetics for improving the stability and drainage of railway tracks under high cyclic loading is investigated. Instrumented tracks were conducted to measure the in-situ stresses and deformations of ballast at Bulli, New South Wales (NSW), Australia. Furthermore, stabilization of soft formation soils underneath rail tracks using prefabricated vertical drains (PVDs) is also studied through finite element analyses and field measurements at Sandgate. The innovative use of the mixtures of coal wash (CW) and steel furnace slag (SFS) as the reclamation fill is demonstrated through laboratory and field investigations at the Outer Harbor extension of Port Kembla in Wollongong, NSW. The optimum CW-SFS mixtures that may meet most of the geotechnical specifications are proposed to be used as an effective structural fill. Finally, the design of the combined vacuum and surcharge fill system and the construction of the road embankment are described using a case study from the Pacific Highway upgrade project. Field data are presented and interpreted to demonstrate how the embankments performed during construction in both vacuum and non-vacuum areas.

It is a well established fact that the response of a soil mass can be considerably improved by inserting vertical reinforcement around the periphery of the footing. The improved soil mass behaves as a coherent mass and shows promising results. This can be advantageous to satisfy the strength as well as settlement criterion of a foundation system. Moreover, the desired results could be accomplished without disturbing the existing footings of a structural system. In the present paper, the results are derived through parametric study. These are presented in the form of design charts that can be employed to decide the geometric parameters of vertical inserts to obtain the desired response of the foundation system in terms of bearing capacity and settlement. Finite element software viz: PLAXIS is used to develop a parametric numerical model of the foundation system. It is used to determine the percentage reduction in absolute or differential settlement and relative improvement of bearing capacity achieved by inserting vertical inserts around a rectangular footing. In the present study, it is found that the load bearing capacity of existing footings may be increased by inserting vertical inserts up to 137%. For improving maximum load bearing capacity, edge distance of vertical inserts should be as minimal as possible. The overall and differential settlement of footing may be reduced to 40% and 5%, respectively. It is also observed that optimum C/C spacing of vertical inserts is 2.66-3.33 times the diameter of vertical inserts.

The construction of embankments on soft soils is a common problem. Soft soil cannot sustain external loads without having large deformations. Piled embankments system provides a possible solution for the construction of roads and railways over soft soils. Until now, the system behaviour could only be described by analytical models such as those included in British or German codes. This paper describes research undertaken to investigate the effects of pile embankment construction in soft soils. Experimental results are used to help investigate arching effect developed due to differential settlement between pile and surrounding soft soil. A numerical parametric study was carried out to examine the impact of various soil parameters on the pile-embankment system behaviour. The outcome of the parametric study implemented using numerical analysis has been investigated and discussed throughout this paper. Based on the numerical analysis carried out in this research, it was found that the earth pressure coefficient normalized by the passive earth pressure K_p plotted on a vertical profile at the midpoint between piles can give a good illustration of arching behaviour. The findings presented in this paper can be considered as guides for numerical analysis and design criteria of soil arching for embankments constructed over piles.

Rigid-flexible pile composite foundation of lime-soil pile and CFG pile can eliminate collapsibility and improve bearing capacity of subgrade. Five kinds of load test of large model casing in 150 cm × 100 cm × 100 cm have been made for research working properties in multi-type-pile composite foundation. We respectively designed fulfilled subgrade, lime-soil pile composite subgrade, CFG pile composite subgrade, lime-soil pile and CFG pile composite subgrade (4 pile type), lime-soil pile and CFG pile composite subgrade (9 pile type). In the test, we use the dial indicator measuring displacement and the pressure cell measuring the soil stress between piles in multi-type-pile composite foundation. By analysis load-settlement curve and load-sharing ration pile and soil in different multi-type-pile composite foundation, contrast to load-bearing characteristics between conventional composite foundation and multi-type-pile composite foundation. The results indicate that bearing mechanism of rigid-flexible pile composite subgrade is the flexible pile and the adjacent soil undertakes most of the load when the load is small, with the increase of load, the adjustment of the mattress layer plays a role, the rigid pile bearing capacity rapid increase and decision the ultimate bearing capacity of rigid-flexible pile composite foundation. The stress ratio of soil, lime-soil pile and CFG pile equal to 1:1.8:5.7 when the composite foundation failed. Combined with practical engineering, we put forward a practical design formula for calculation of bearing capacity in rigid-flexible pile composite foundation

The piled embankment - consisting of the foundation, pile, pile caps, and the earth-filling embankment - is a complex soil-structure system. One of the working principles of the rigid pile supported embankment is the soil arching effect. Many factors - such as the surcharge load over the fill, consolidation of soft soil foundation, and differential settlements between piles and around the soil - would play a role. In this paper, a numerical model of rigid pile supported embankment was built using ABAQUS software. A series of numerical analyses was performed to research the shape of soil arching for different fills and different loads on the fill. In the numerical analyses, the fill of embankment is silty clay or gravelly soil, and the material of foundation is soft soil. Silty clay, gravelly soil and soft soil are simulated as elastic-plastic material following the Coulomb friction law. Piles conformed to a linear elastic law. After the calculation, the following results were obtained: (a) the shape of soil arching in 2D would be a trigon; (b) soil arching height would grow with loads on the surface of fills; and (c) the angle of soil arching changed with the load increasing on the fill and depended on the fill characteristics, such as peak internal friction angle, cohesion and elasticity modulus.

The use of dissimilar piles below a raft is a relatively innovative concept and can optimize the design of a piled raft. This paper discusses a pile length optimization method. To analyze non-linear behaviour of piles, a "cut-off" method was adopted to limit pile capacity in the integral equation considering linear behaviour of piles. In this method, adjacent non-yielding piles take more loads when some piles start to yield (i.e., reaching their individual ultimate load capacity). A pile-square rigid raft system was analyzed to illustrate the effects of the proposed approach. The analysis showed that the stiffness of the piled raft decreased after considering the load cut-off. The load cut-off procedure could make the distribution of the reactions for short piles more reasonable in terms of their locations and lengths. The optimized design using dissimilar piles would create a more economical solution than the design with uniform piles.

Vibro-compaction or vibro-flotation has been utilized extensively throughout the United States as a means of densification of predominantly granular soils to increase allowable bearing pressures, reduce settlements and mitigate liquefaction. In the coastal areas of South Florida, vibro-compaction has been used predominantly to densify the upper approximately 10 feet (3 m) to 30 feet (9 m) of typically sedimentary, fine- to medium-grained sand to allow support of structures typically less than 15 stories in height on shallow foundations. More recently, vibro-replacement (aka stone columns) has been utilized to provide stiffening or higher modulus gravel/stone column elements into and/or through weakly cemented limestones and densify interbedded or interlayered granular soils. The relative level of cementation or strength of the limestones and constituents of the interbedded and interlayered sands, which exhibit variable levels of carbonate cementation, are key factors in determining the resulting mechanism of ground improvement. Several case histories are presented providing the results of post-treatment testing. The results of full-scale footing load tests and building monitoring to confirm the total and differential settlements throughout the structure are presented as well.

Deep mixing (DM) is one of the most commonly used techniques to improve soft soils under embankments. When Bishop's modified method and Spencer's three-part wedge method are used to analyze slope stability of column-supported embankments, they assume that the embankment fails along a slip plane through soils and DM columns that mobilize their shear strengths. However, some numerical studies and centrifugal model tests showed that DM columns might fail in a form of bending or rotation under an embankment loading. The three-dimensional (3-D) finite element method incorporated in the ABAQUS software was used in this study to investigate the failure modes of DM column-supported embankments over soft soils. The subsoil consisted of a 10-m-thick soft soil layer, underlain by a 2-m-thick dense sand layer. Two conditions were considered in the numerical models: (1) the DM columns were embedded into the dense sand layer and (2) the DM column bases were seated on the top of the sand layer. The shear strength reduction technique was implemented to evaluate the factors of safety of the DM column-supported embankments over soft soils. The factors of safety computed by the numerical analyses were compared with those using Bishop's modified method and Spencer's three-part wedge method. Numerical results indicated that the failure modes of bending and rotation might happen to the DM columns. Bishop's modified method yielded a higher factor of safety than those from the numerical method and Spencer's three-part wedge method.

Based on the characteristics of high vertical bearing capacity but low horizontal bearing capacity of the cement soil, a field test on cement-soil piles and reinforced cement-soil piles (which are arranged cylindrical glass fiber geogrid under lateral load) is carried out. The working mechanism and horizontal bearing capacity of cement-soil pile reinforced with fiberglass geogrid of single pile and double-row piles under horizontal load is analyzed. The results show that pile under horizontal loads have different failure modes by different geogrid distribution of reinforcements. Horizontal bearing capacity increased more or less by fiberglass geogrid for single pile and double-row piles. Horizontal bearing capacity of double-row piles whose front pile arranged two layers fiberglass geogrid are significantly improved. Under the premise that the pile is not destroyed, a higher value of the horizontal displacement and inclination of the pile is, the greater tension of geogrid can afford, the higher value of horizontal bearing capacity are. It is concluded that the horizontal bearing capacity of pile can be improved to ensure the safety of the pile by the appropriate geogrid-reinforcement and increasing the number of rows of the pile.

Foundations constructed on soft soil often require columns to increase bearing capacity and reduce total and differential settlements. Columns can be: (1) flexible (e.g., stone columns and sand compaction columns); (2) semi-rigid [e.g., deep mixed (DM) columns and jet-grouted columns]; and (3) rigid (e.g., vibro-concrete columns). Research has demonstrated that columns can also accelerate the consolidation of soft foundations by column drainage and stress transfer. In this paper, a three-dimensional, coupled, numerical analysis was adopted to study the consolidation behavior of soft foundations improved with two types of composite columns. For example, a DM column or jet-grouted column can be installed in the middle of the stone column or sand column. In this composite column, the stone column or sand column provides drainage while the DM column or jet-grouted column provides stiffness. Columns and soil in this study were modeled as elastic materials and one quarter of the unit cell was used due to the symmetry. To demonstrate the benefit of the composite columns in accelerating consolidation, two soft foundations improved with stone columns and DM columns were analyzed for comparison purposes. The numerical results show that both column drainage and stress transfer contributed to the acceleration of the consolidation of the soft foundations improved with composite columns. In addition, a parametric study was conducted to evaluate the influence of the stiffness of DM columns on the rate of the consolidation of the soft foundation improved with composite columns.

In this paper, jet grouting technology is briefly introduced and the recent development of jet-grouting methods for the infrastructure construction in Shanghai are presented. Recent research activities include theoretical modeling of the diameter of a jet-grouted column and a case history of the practice of the Rodin Jet Pile (RJP) method. A generalized approach for predicting the diameter of a jet-grouted column is introduced and used to analyze the measured diameters of RJP jet grouted columns. It was shown that jet-grouted columns formed by the RJP method are larger than that using the conventional triple fluid system by about 36% on average.

Grouting reinforcement is one of the most commonly used methods of subgrade treatment in soft-soil areas. In order to evaluate the grouting reinforcement effect of high-speed railway subgrade, a series of laboratory tests - such as direct shear test, compression test, and permeability test - was carried out on the Shanghai mucky clay injected with cement slurry. Based on analysis of the test results, the rational range of slurry content and water-cement ratio remain the possibility to be drawn. For the sake of further understanding the variation law of displacement, stress, and plastic zone, a series of numerical simulations was carried out on the soft soil subgrade reinforced with grouted slurry under the dynamic loading of a high-speed train. According to the results on the numerical simulation, obtaining the rational grouting scheme and grouting pressure is achievable. The research results can provide a reference for similar projects.

This paper describes the innovative application of jet grouting to improve the stability of a bottom-up construction in sensitive glacial silts. The construction involved a 51- to 69.5-ft-deep excavation supported by internally-braced secant pile walls adjacent to existing fragile buildings which needed to be protected. The excavation design was complicated by the large difference in subgrade levels within the excavation. An integrated grout slab and gravity wall was pre-formed in situ prior to excavation using jet grouting to enhance excavation support. Numerical modeling was used to study the behavior of the jet grout elements for controlling deep-seated inward wall movement. The results of quality control testing on cored samples taken through the grouted glacial silts are discussed. Inclinometers installed in the secant pile walls confirmed that wall deflections achieved during excavation were less than 1.2 in. (or 0.15% of excavation depth).

Mount Merapi is one of the most active volcanoes in the world with eruptions every two to five years. Frequent eruptions, with the resultant volcanic ash, have become an important environmental issue when it is not effectively reduced. In engineering practice, utilization of volcanic ash as substitution material is limited. Indonesia has a large road on soft soil, and volcanic ash can be used as an alternative soil improvement. The objectives focus on the effect of volcanic ash content as substitution material for soil stabilization and also as a new approach, in view of environmental aspects, for soft-soil improvement. Engineering properties of soil mixture, the effect of volcanic ash content and its fines level are discussed. The fineness of volcanic ash (pozzolan) is a primary factor in the stabilization process. Utilization of volcanic ash with a grain size passing sieve number 270 is more effective. The effect of volcanic ash content on soil stabilization can: (1) improve the engineering properties of soft soil; (2) change the grain size distribution curve by decreasing the fine fraction; (3) decrease consistency limits and become non-plastic soil; (4) increase bearing capacity; and, (5) decrease swelling potential. The addition of 35% volcanic ash and 9% lime gives the most significant effect on soil improvement.

Lime-ground granulated blast-furnace slag (GGBS) blends have been widely used in soil stabilization applications. More recently, reactive MgO-GGBS blends were shown to outperform lime-GGBS blends in terms of various engineering properties of the stabilized soils. Although the use of MgO or CaO in blends has been investigated, their combined use with GGBS has not. This paper considers the calcined dolomite as a source of MgO-CaO combination and investigates the use of calcined natural dolomite-GGBS blends in the stabilization of a clayey soil and a clayey silty sand. The influence of the calcination temperature, soil type, dosages of binder and curing period on the properties of the stabilized soils were studied by unconfined compressive strength (UCS), elastic stiffness (E₅₀), XRD analysis and SEM. This initial work revealed that calcined dolomite-GGBS blends are practical and are an effective option for soil stabilization.

Subgrade soils are important materials to support highways. For the past few decades, the resilient modulus (M_R) has been used for characterizing the stress-strain behavior of subgrades subjected to repeated vehicle loadings. Actually, instead of natural soils, lime-stabilized soils were applied widely to improve subgrade performance in wetting areas; but, M_R of lime-stabilized soil was not investigated sufficiently. In this paper, to estimate the influence of stress state, moisture content and compaction energy on M_R, specimens were compacted at different water contents (w_opt and w_opt±3%) with relative compaction of 90, 94 and 96%. Then, a series of repeated triaxial tests was carried out with confining pressures of 15, 30, 45 and 60 kPa, and deviator stresses of 60, 75, 95 and 125 kPa. Finally, results were fit to the three-parameter model recommended in NCHRP1-28A to determine the k_1-3 coefficients. It was found that the predicted regression coefficients compared well with measured ones.

This paper presents a constitutive model - referred to as the Cemented Cam Clay (CCC) model - to precisely simulate the cementation degradation of cement-treated clays. Various laboratory experiments show that the effect of cementation gradually diminishes as the confining pressure increases (particularly at high effective confining pressures) due to breakdown of cementation bonds. The main concepts and formulations of the CCC model, including elasto-plastic stress-strain relationships, are presented within the framework of the critical state concept and inspired by the Modified Cam Clay (MCC) model. The special characteristic of the proposed model includes a modified mean effective stress capturing cementation degradation. In addition, the failure envelope is formulated to describe the beneficial effect of cementation at low mean effective pressure range, while it merges with the Critical State Line of reconstituted cement-clay mixture as the confining pressure continues to increase. The performance of the proposed model is evaluated against triaxial test results from cement-treated Aberdeen soil. The model predictions provide good agreement with triaxial test results, particularly at high effective confining pressures.

Colloidal nanosilica is a new kind of chemical grout material for filling the small gaps of fine-grained soil. Compared to traditional material-silicate sodium, which has been synonymous with "chemical grout" for many years, the advantages and disadvantages of colloidal nanosilica should be studied. In this paper, permanence is the focus. Hence, laboratory test was adopted to study the stability of the pure gels and long-term effect of sand-gel mixtures of the two materials. Samples of Fontainebleau sand injected by nanosilica and sodium silicate were conserved in atmosphere, water, salt solution and acid solution for 8 different time periods. The shrinkage of the pure gels was measured first. Then, the porosity test by saturation method was adopted to analyze and compare the porosity change in terms of the two different materials, different immersed environments, and different conserving times. The results show that the pure gel of nanosilica is much more stable than the pure gel of silicate sodium in all of the environments from the aspect of shrinkage rate. The same law is followed for the sand-gel mixtures. Nanosilica is more stable when immersed in water, which is a valuable characteristic for grouting. Although nanosilica is less stable when immersed in saline and acid solutions, it is much more stable than silicate sodium.

Electro-osmotic consolidation is an effective method for soft ground improvement. A novel technique, called "anode follow-up for electro-osmotic consolidation of soft clay", is proposed. A series of electro-osmotic consolidation experiments with different anode follow-up programs were carried out to investigate the influence of anode follow-up to electro-osmotic consolidation. In the electro-osmotic process, the electric current, shear strength, volume of drained flow, water content, and soil conductivity were monitored. Test results show that anode follow-up can promote the effectiveness of electro-osmotic consolidation and reduce the resistance of anodic region obviously in the circuit. The effect is the best when anode follow-up is applied for the first time. When the current density is relatively low, anode follow-up will promote the electro-osmotic process. Soil conductivity decreases in cathodic region is due to the electro-chemical reaction.

Polarity reversal and current intermittence are two attainable approaches to improve the electro-osmosis effect as well as to reduce energy consumption. The objective of this paper is to evaluate the impact of polarity reversal and current intermittence on electro-osmosis and, furthermore, to optimize the electrifying process. Laboratory tests were performed with different reversal intervals and distributions of power on-off time. Drainage and current were monitored to investigate the reinforced effect. It is demonstrated that proper design in current intermittence can excessively enhance the electro-osmotic effect. Conversely, polarity reversal has an indistinctive effect and is not recommended. Furthermore, disputes in published literature concerning polarity reversal and current intermittence were also discussed. This paper provides good guidance on the electrifying process for practical application of electro-osmosis.

In geotechnical applications of artificial ground freezing, safe design and execution require a correct prediction of the coupled thermo-hydro-mechanical behavior of soils subjected to freezing. In the context of thermo-poro-plasticity (Coussy, 2005), a three-phase finite element model of freezing soils is presented: (1) considering solid particles, liquid water and crystal ice as separate phases; and (2) mixture temperature, liquid pressure, and solid displacement as primary field variables. Through three fundamental physical laws (overall entropy balance, mass balance of liquid water and crystal ice, and overall momentum balance) and corresponding state relations, the model captures the most relevant couplings between the phase transition, the liquid transport within the pores, and the accompanying mechanical deformation. Particularly for the description of the poro-plastic mechanical behavior of the soil model, the enhanced Barcelona Basic Model (Nishimura et al., 2009) is adopted within a unified effective-stress-based framework. The macroscopic strength criterion of the freezing soil composite is improved through multi-scale strength homogenization based upon the linear comparison composite method (Ortega et al. 2011). The performance of the proposed model is demonstrated by re-analysis of a soil freezing test and AGF processes during tunneling.

Production of bio-energy from biomass results not only in bio-fuel, but also in coproducts containing lignin, modified lignin, and lignin derivatives. This study was performed to evaluate the feasibility of lignin used to stabilize silt in Jiangsu Province of China and to develop a new soil stabilizer for marine clay. A series of laboratory tests on unconfined compression strength (UCS), pH and electrical resistivity are carried on to study the mechanical properties, environmental effect and electrical properties of silt improved by lignin-based bioenergy coproduct. Scanning electron microscopy (SEM) is also used to analyze the variations of soil microstructure, and the mechanism of silt improved by lignin is preliminarily discussed. With the additive content increased, the unconfined compression strength of improved silt increased at first and then decreased. The optimum additive content should be 10% to 12%. With the curing time increased, the soil pH has a little increase. All the improved silt pH is lower than 10. The electrical resistivity of soil decreased with increasing additive content. The soil content of pore fluid is the control factor for the soil electrical resistivity. Silt improved by lignin-based bioenergy coproduct is carried primarily by filled pores and linked soil particles to form a more compact and stable soil structure. The results indicate that the coproduct lignin is an environmentally friendly, highly promising, new soil stabilizer.

This paper mainly introduces the design and construction of ground improvement intheQianhai reclamation area, Qianhai Bay, Shenzhen, China. The seabed water level in the reclamation area is about 2.0 to 3.0 m, the thickness of the soft soil ranges from 6.0 to 15.0 m, and the treated reclamation area is about 7.62 km². Different soft ground improvement methods were adopted to treat the marine soft soil and backfilled soil to satisfy the requirements of various development purposes, such as: (1) explosion method for the sea embankment construction; (2) riprapping used to strengthen dikes; (3) fill-surcharge preloading and vacuum-surcharge preloading used to treat the soft clayey soils, dynamic compaction, vibro-stone (sand) columns, deep cement mixing; and, (4) also used to treat road foundation soils. The features, advantages and limitations of these methods are discussed in the paper.

The Dynamic Replacement method has been widely used to increase the bearing capacity of soil foundations for various construction projects and earth structures (i.e., roadway embankment, ports, and retaining walls) due to its advantages of simple process, rapid construction, and economical cost. With the development of the technology, the dynamic replacement technique has been trending to usage of a high level of impact energy (for example, greater than 6000kN⋅m). However, the mechanism of reinforcement and the response of the soil by the high impact energy have not been well investigated. Model tests were carried out to investigate the performance of the saturated silly soil improved by the Dynamic Replacement method with high impact energy. The model test modeled the dynamic compact process using a different size of hammer model. The influence factors of cushion thickness and particle size of gravel material were studied. The ground deformation was monitored during the test.

The Integrated Pipeline (IPL) project - a collaborative effort between the Tarrant Regional Water District (TRWD) and Dallas Water Utilities (DWU) - will supply additional water to the Dallas/Fort Worth area. As part of a sustainability initiative, several studies were conducted to assess the reuse potential of excavated materials along the IPL project. One of these studies involved using the excavated material as an ingredient in a controlled low strength material, often known as CLSM or flowable fill. This flowable fill can be used as bedding and haunch material in pipeline construction. These CLSMs meet the specifications in the short term; however, their long-term performance should be verified in order to be successfully used in the field, especially when these materials are subjected to seasonal changes such as wetting and drying. Hence, durability studies were conducted on CLSMs from two different geologic formations, namely Eagle Ford and Queen City. The variations in retained strength and volumetric strain changes, along with the amount of stabilizer leached out of the CLSM samples at different durability cycles, are presented in this paper. It was observed that Eagle Ford soil CLSM lost more than 50% of its initial strength while Queen City sand CLSM lost approximately 50% of its initial strength when subjected to durability studies. The loss in strength was attributed to both volume change and stabilizer loss in the case of Eagle Ford soil, while stabilizer loss alone caused the loss of strength in the case of Queen City sand.

A laboratory investigation of the influence of different factors - including weight, size and towing speed of impact modules - on the effectiveness of impact roller (IR) compaction was carried out. An impact roller simulation device was developed to do the investigation and air pluviation technique was used to prepare loose, dry, sand specimens. The Chinese cone penetration tests in the position of impact craters in sand specimens with different passes of IR compaction were used to verify the effectiveness of IR compaction. Results of the laboratory tests show that the weight and towing speed of a module significantly affects the effectiveness of IR compaction, but the size of the module has little influence on effectiveness. It is mainly observed that better improvement can be achieved when heavier impact modules are used and towing speeds close to the optimum towing speed are adopted during IR compaction.

Design and construction engineers in many parts of the world are very much concerned with the expansive soil behaviour when subjected to moisture increase. The geotechnical practice in the northern parts of Saudi Arabia considered partial replacement and rock fill as a tool to minimize damage and upheaval forces acting on light structures. This approach was approved by the municipal authorities and became a routine practice, although many failures were reported in projects considered soil replacement. This research study is aimed at investigating soil replacement and its role in minimizing uplift forces and volume change. The test results were discussed in view of the swelling behaviour of Tabuk's expansive shale material. The success or failure of this treatment depends on specific conditions. The paper discusses the influence of backfill type on the effectiveness of this method.

Widening, different from new construction, was easier to trigger subgrade defects such as differential settlement. Aimed at the performance of silty clay with low liquid limit, this study conducted a series of experiments to research the modulus and shearing strength in diverse working conditions. The experimental results revealed that this kind of soil has low modulus and shearing strength as well. In addition, this paper analyzed the construction safety in widening by using finite elements calculation and introduced a series of construction choices. Meanwhile, some treatments were adopted, under which the performance of widening subgrade during operational period was analyzed. Thus, a comprehensive treatment of this kind of soil for widening was suggested.

This paper describes the laboratory tests on small diameter polyvinyl chloride (PVC) pipes buried in unreinforced and geosynthetic reinforced sand subjected to static loading. The aim of the study was to evaluate the appropriateness of the combination of geocell and geogrid reinforcement system in protecting the underground utilities and buried pipelines. A pipe with external diameter of 75 mm and thickness of 1.4 mm was placed below the footing at different depths ranging from 1B to 2B (where B is the width of the footing). Commercially available Neoweb geocells and biaxial geogrids (SS-20) were used as the reinforcements. Results indicate that the use of the combination of geocell and the geogrid reinforcement system considerably reduces the deformation of the pipe as compared to an unreinforced bed. Above 50% reduction in the pressure and more than 40% reduction in the strain values were observed in the reinforced bed as compared to the unreinforced bed at different depths. Conversely, the performance of the foundation bed was also found to be marginally influenced by the position of the pipe, even in the presence of the relatively stiff reinforcement system.

Geogrid-reinforced granular soils have been widely used in pavement, railway, and retaining wall. Understanding the reinforcement mechanism is important to appropriately design those earth structures. 2D numerical models of geogrid-reinforced granular soil samples were created using the discrete element method. Biaxial compression tests were performed on the numerical soil samples. The numerical study focused on the influence factors that affect the reinforcement effect such as loading rate, boundary conditions, confining pressure, particle shape, and particle friction. The results show that loading rate and particle shape are dominant factors for geogrid-soil particle interaction. Recommendations have been provided for simulation of geogrid-reinforced soil using the discrete element method.

Geosynthetics have been used as reinforcement layers to bridge over underground voids or sinkholes and to support upper soil mass. In such applications, the geosynthetics (acting as tensioned membranes), together with the soil arching, sustain the stability and mitigate the subsidence of the soil mass. An experimental study was conducted to investigate the subsidence of the soil mass induced by the permissible deformation of the geosynthetic reinforcement. The study was conducted in a container with dimensions of 875×625×50 mm³ (L×H×W) with 7 trapdoors at the bottom. One of the trapdoors at the bottom of the container can be lowered to induce differential settlements. The soil was simulated by aluminum bars that have various diameters but uniform length of approximately 50 mm. The aluminum bars were intentionally used as the substitutes of soil particles to simulate the two-dimensional (2D) situations. A layer of geotextile was place underneath the "soil fill" to serve as the reinforcement. During the tests, the trapdoor was lowered and the induced movements of the "soil particles" and the deformation of the geosynthetic layer were recorded and quantified by the photogrammetry methods. The subsidence profiles at different elevations were developed. It was found that subsidence was decreased hyperbolically in the vertical direction and the lateral influence range appeared to be bounded by the active soil zone (i.e., within the two planes of 45+φ/2).

This paper presents experimental results from laboratory repeated plate load tests on unreinforced and reinforced model sections of unpaved road constructed in a steel test tank of 750 mm × 750 mm plane and 600 mm in height. Load was applied through a 150-mm diameter loading plate. Geocell reinforcement was used in the experiments for confining the granular sub-base. The effects of various parameters - such as height and position of geocell layer on the performance of these model road sections - were studied in the experiments. From the experimental results, it was observed that at higher settlements, the reinforced systems showedless permanent settlements and more elastic settlements than unreinforced systems. The secant modulus of the reinforced systems at any strain level was higher than that of the unreinforced systems. Increasing the height of the geocell layer resulted in improved performance up to a certain height of the geocell layer, beyond which, further increase in the height reduced the load resistance because of the inadequate granular overlay thickness.

Geogrids have been successfully used in highway applications for stabilization and reinforcement purposes. Recent research efforts have also been dedicated to study geogrids in railway applications, especially for ballast reinforcement. Ballast, typically containing large-sized aggregate particles with uniform gradation, is an essential layer in railway substructure to facilitate load distribution and drainage. However, the reinforcement effect of geogrids in ballast has not yet been thoroughly investigated. Especially with the accumulation of tonnage, ballast will increasingly get fouled due to aggregate degradation or contamination by other materials, affecting aggregate-geogrid interlock mechanism at different levels of degradation. In this study, monotonic triaxial strength tests - performed on both clean and fouled ballast specimens - have been reinforced by geogrids and tested using a large-scale triaxial test device recently developed at the University of Illinois specifically for ballast size aggregate materials. Two different geogrids with square- and triangular-shaped apertures are used in comparison. To further investigate the geogrid reinforcement mechanisms, an imaging based discrete element modeling (DEM) approach was also adopted with the capability to create actual ballast aggregate particles as three-dimensional polyhedron blocks having the same particle size distributions and imaging quantified average shapes and angularities. By addressing adequately the particulate nature of different sized and shaped ballast aggregate particles and their interactions with each other at contact points, and through the innovative use of membrane elements surrounding the cylindrical ballast specimen, the ballast DEM model accurately captured the strength behavior of both clean and degraded ballast specimens reinforced by geogrids with different aperture shapes.

To accommodate heavy truck loads, geosynthetic has been used as reinforcement to stabilize unpaved shoulders. However, while the geosynthetic changes the strength of the shoulder, it may also influence the vegetation that is planted on the shoulder. To study the effect of geosynthetic reinforcement on vegetation, outdoor vegetation tests were conducted. The primary method was to compare the growth of vegetation, mainly perennial ryegrass and tall fescue, on different mixes of soil at the same thickness with and without geosynthetic reinforcement. Geocell reinforcement was used in this study. Different base course and topsoil combinations were investigated, including: 50-mm-thick turf soil over 100-mm-thick aggregate; 50-mm-thick turf soil over 100-mm-thick soil-aggregate mixture (50% aggregate); 50-mm-thick turf soil over 100-mm-thick soil-aggregate mixture (65% aggregate), and 150-mm-thick soil-aggregate mixture (50% aggregate). Each test section was 1.5 meters long and 1.5 meters wide. During the test, soil moisture content, soil temperature, and precipitation were measured. To evaluate the vegetation growth, grass blade height, number of flowers and number of blades were recorded periodically. The effect of geocell inclusion on the vegetation was evaluated as compared with the vegetation without geocell.

Triaxial geogrid provides more uniform tensile resistance in all directions compared to biaxialgeogrid. Therefore, it more efficiently provides lateral restraint to aggregate during traffic loading. The performance of geogrid-stabilized unbound aggregate courses over weak subgrade has been studied over the years by many researchers. Previous studies show that the permanent deformation and vertical stress are reduced with the inclusion of geogrid. However, not many research studies have evaluated the influence of geogrid in resilient deformation and horizontal stress of base and subgrade. In this study, cyclic plate loading tests were performed in a geotechnical testing box (2 m × 2.2 m × 2 m) on unstabilized and triaxialgeogrid-stabilized sections at the University of Kansas. A 0.23-m-thick Kansas type AB aggregate was placed on soft subgrade. Cyclic plate loading was applied through a 0.3-m-diameter plate. To investigate the effect of load intensity, the plate load was increased from 5 to 45 kN in this study. Both permanent and resilient deformations were monitored by transducers placed at varying distances from the center of the loading plate at subgrade and surface. Vertical and horizontal stresses within base and top of the subgradelayer were also monitored by pressure cells. Test results indicate that the inclusion of a triaxial geogrid reduced surface and subgrade permanent deformations of the test sections. The resilient deformation did not change much during the loading at lower intensities, but increased significantly at higher loading intensities. The geogrid-stabilized base had higher horizontal stresses than the unstabilized base, indicating stiffness increase in the base course due to the lateral restraint of the geogrid. The test results also show that the horizontal pressures within the subgrade were significantly reduced by using a geogrid.

This paper presents a laboratory evaluation of the performance of geogrid-reinforced base materials using loaded wheel tester (LWT). Asphalt pavement analyzer (APA) was used as a platform to test the rut resistance of three types of base materials reinforced with two types of geogrids. The test results show that LWT was able to identify the reinforcing effect of geogrids, indicating that LWT is a promising tool for testing geogrid reinforcement in pavement base.

A total of 5.0-km rural roads have been constructed using jute geotextiles (JGT) as field trials in different geophysical locations of Bangladesh. The project sites were so selected that subgrade California bearing ratio (CBR) values of more than 3.0% were not achievable without adopting special means. On top of subgrade, first, an improved subgrade (ISG) layer of 75 mm compacted sand is placed. Right above this ISG layer, the specified JGT is laid with proper overlapping and pegging. After this, another layer of ISG is placed. The rest of construction of pavement follows usual practice of placing a sub-base layer followed by a base layer and black top. A series of monitoring and performance evaluation has been undertaken at different time intervals by obtaining field CBR values along the same road sections to evaluate the efficacy of JGT. The test results reveal that the load-carrying capacity of the road sections increases from 1.5 to 7.0 times due to use of JGT over a range of time interval. It is hypothesized that the load-carrying capacity of JGT reinforced subgrades increases through three different mechanisms: (1) membrane action of JGT until it decomposes; (2) absorption of moisture from subgrade by JGT resulting in an increased dry density of subgrade; and, (3) consolidation of subgrade due to surcharge load of ISG, sub-base and base layer along with a percentage of traffic load. It may be noted that the economic benefit and durability enhancement of the rural roads constructed using JGT are the obvious consequences.

The interaction between soil and geosynthetics is a significant factor for analysis and design of reinforced earth structures which is simplified as pullout resistance. This paper presents the results of pullout tests aimed at studying the interaction of reinforced sand. The relative performance of different forms of geosynthetic reinforcement (i.e. planar reinforcement and three-dimensional grid-rib reinforcements) is compared. Samples of sand reinforced with geosynthetics in four different forms are tested in a pullout test and results are analyzed to evaluate the soil-grid interaction improvement in sand due to reinforcement in different forms. Based on experimental results, a strength model of the soil reinforced with grid-rib elements was developed. The comparison between theoretical and experimental results was favorable, thus confirming the suitability of the proposed approach.

Geosynthetics in foundation beds demonstrate their beneficial effects only after considerable settlements, since the strains occurring during initial settlements are insufficient to mobilize significant tensile load in the geosynthetic. Prestressing the reinforcement is a promising technique to overcome this shortcoming. This paper presents results from a series of laboratory scale bearing capacity tests carried out on model square footings to investigate the improvement in bearing capacity of geosynthetic reinforced foundation bed overlying weak ground due to prestressing the reinforcement. Prestressing the reinforcement in foundation bed results in significant improvement of bearing capacity of weak soil. A numerical model is suggested to predict the improvement in bearing capacity of footings with all the three cases - i.e., Granular Bed (GB), Reinforced Granular Bed (RGB), or Prestressed RGB on weak soil - by assuming a punching shear mechanism. These predictions are compared with laboratory scale experimental results. The proposed model is found to give good prediction of bearing capacity improvement. Finite element analyses are carried out using the FE program PLAXIS to study the effect of prestressing the reinforcement. Results obtained from finite element analyses are found to be in reasonably good agreement with the experimental results.

Some model tests have shown that the H-V reinforcement system behaves more uniform, carries greater surcharge, and settles less than the equivalent strip one. However, the mechanism of the H-V reinforced soil foundation is still not well understood. FEM is a useful method to investigate the soil foundation. The different types of foundations can be multiple simulated byafinite element. Through comparing the difference of stress and displacement distribution in strip and H-V reinforced soil foundation, the friction on the surface of strip and H-V reinforcement, and the stress distribution on a vertical inclusion of H-V reinforcement. It can be concluded that beside the tension membrane reinforcement mechanism, the H-V reinforcement of relatively small vertical inclusions height behaves as a shallow beam that deflects under the footing loading leading to higher contact pressure underneath. The H-V reinforced base acts as a mattress to restrain the soil from moving upward/downward outside the loading area, redistributes the footing load over a wider area, and reduces the settlement which, in turn, principally improves the bearing capacity and reduces the settlement of foundation.

An embankment was constructed with five test sections, each containing a different combination of erosion treatment methods. The objective was to provide treatments that would limit erosion until annual grasses were rooted. Treatments included combinations of geofibers with synthetic fluid or polymer emulsion. Control sections on each end of the embankment were set to provide contrast to the treated sections. A three-pronged approach was adopted to compare treatments and determine which was most effective. The first feature involved typical soil test methods for evaluating erosion at the field site. The second feature developed a methodology to determine critical shear stress for treated and untreated soils. The third feature involved construction of a laboratory-scale model of the embankment to simulate an extreme erosion environment. The results of these tests showed that more studies of the use of geofibers and nontraditional liquid additives for erosion control are warranted. While there was some discrepancy as to which of the treatments is the most effective, it is safe to say they all could be useful. Grass did not grow on the site treated with EnviroKleen, so if having grass is necessary, that product would not be recommended.

Laboratory scale model slopes reinforced with waste carpet fibers were made in a rigid tank with dimensions of 800 mm x 300 mm x 500 mm. Bearing capacities of the strip footing rested on non-reinforced and fiber-reinforced model slopes with 1%, 3% and 5% fiber content were compared at 20% footing displacement ratio. The influence of location of footing on the bearing capacity was studied with placing the footing at different edge distances from the crest of the footing (i.e., 150 mm, 100 mm and 0). Suction probe sensors were installed at appropriate locations on the rear side of the model slope to measure the pore-water pressure generated due to the footing pressure. Results showed that fiber reinforcement increased the bearing resistance of the model slopes significantly. Inclusion of 5% fiber increased the bearing resistance by 271% compared to that of non-reinforced model slope at the footing edge distance ratio of 3. The location of footing was found to affect the load-carrying capacity of the fiber-reinforced model slope. The increase in the edge distance ratio of the footing increased the load-carrying capacity of the model slope.

Geosynthetic reinforced soil-retaining structures (GRSRS) take over the role of the conventional retaining walls step by step and become the mainstream of retaining structures in Taiwan because of the advantages of easy construction, low construction cost, short construction period, better deformation tolerance, earthwork amount balance and good seismic resistance ability. Nonetheless, during the well-known Taiwan 921 Chi-Chi Earthquake, many GRSRS have been destroyed. In order to understand the performance of the seismic behavior of the GRSRS during the earthquake, the finite element program, PLAXIS, is employed to explore the seismic response of GRSRS. The numerical simulation process focuses on the Young's modulus of soil, the stiffness modulus of the geosynthetic reinforcement, and different magnitude scales of seismic data to perform parametric study. Numerical simulation of GRSRS can predict the maximum acceleration under different conditions under the earthquake by using different parameters, and it is hopeful to provide information for geotechnical engineers during the design phase.

The geosynthetic reinforced embankment is composed of pavement, embankment fills, geosynthetic layer and foundation soil. Due to the non-uniform displacement of embankment fill under loading and existence of supporting structures such as piles, shear stress will occur in the foundation soil. In this paper, an analytical model is proposed for geosynthetic reinforced embankment. Embankment fill is modeled as a Timoshenko beam imbedded with a geosynthetic layer, and the pavement is simulated by an Euler-Bernoulli beam. Two types of beam models are employed so that both bending moment and shear stress in the embankment are taken into consideration. Based on the theories of the Euler-Bernoulli beam and the Timoshenko beam, governing equations are proposed for geosynthetic reinforced embankment on an elastic foundation. The analytical solution has been derived using appropriate continuity and boundary conditions under strip loading. It can be observed that the length of the pavement structure and foundation soil stiffness have much influence on the displacement and bending moment distributions of the embankment system.

The new anchorage-reinforced technology in the highway subgrade widening project is put forward in order to realize the effective joining between the new and the existing subgrade. The anchoring mechanism of anchoring bar and the function mechanism of geogrids in the joining between the new and the existing subgrade are analyzed in this paper. The design method of anchorage-reinforced composite structure is studied. Based on the FEM, the characteristics of the ground settlement and horizontal displacement, sungrade surface settlement and the geogrids stress are researched according to the three subgrade widening schemes; that is, excavation step only, excavation step + geogrid reinforcement, and excavation step + geogrid reinforcement + anchor bolt. These study results can be used as a reference for future studies and designs of highway subgrade widening projects.

In this paper, the stability of a real case MSE wall was analyzed using a finite difference numerical analysis program and a limit equilibrium slope stability program. It was found that the two programs determined similar factors of safety for the wall, but different critical failure surfaces. Such a discrepancy was due to the different underlying assumptions associated with the two analysis techniques. Considering the complexity of many real-world projects, it is recommended that two or more independent analyses using different techniques should be considered in order to obtain a better evaluation of the wall stability.

Dhs 800 m (USD 218 m) Mina Al Fajer Resort project commenced in June 2007. The project - covering an area of 777,025 square feet - includes a marina, mountain villas, solarium villas, marina apartments and a five-star hotel. The layout of the mountain villas was designed to form a number of rows of villas at different levels forming terraces up the hillside on the sea-front. The mountain villas and the road connecting the terraces at different levels required construction of retaining walls up to 18-m heights and having an overall face area of 20,000 m². Based on successful completion of a number of projects in the same region, TensarTechTW1 (ME) Wall System was chosen by the client. Some of the challenges facing the designer were: (1) the design of the reinforced soil structures to support structures with low tolerance to movement, such as concrete housing frames and swimming pools; (2) limited available space for geogrid placement; (3) tight construction schedule; and (4) architectural project requirements comprising frequent and acute corners on the wall layout. The chosen TensarTech TW1 (ME) Wall System proved to be a very successful solution that is inherently flexible enough to deal with the project requirements and resulting in cost-effective and maintenance-free structures designed to last for 120 years.

A verified numerical Fast Lagrangian Analysis of Continua (FLAC) code is used to investigate the influence of concrete- and granular-block interface properties on reinforcement loads in polyester geogrid-reinforced soil (modular) block walls seated on a rigid foundation. A nonlinear interface model simulating interfaces between concrete blocks and concrete or granular soil leveling pads calibrated against laboratory direct shear tests is implemented within the FLAC code. The code is then used to simulate 3.6-, 6- and 9-m-high block walls constructed in stages. The numerical results show that the increase in wall height during wall construction for the same wall increases the interface tangent stiffness. However, the concrete pad results in higher interface tangent stiffness compared to the granular soil pad case when other conditions are equal. For 3.6-m-high walls, the load carried by the toe when using the granular soil leveling pad is 14% less than for the concrete pad case. For 9-m-high walls, the difference in load carried by the toe for the two different leveling pads is less than 10%. The predicted reinforcement loads at the same elevation over the bottom 1/3 of the wall height for the concrete pad case are smaller than those for the granular soil pad case, but are similar over the remaining height of the wall. The results also show that the predicted reinforcement loads using the K-stiffness Method capture the trend in numerical results for the two leveling pad conditions, but are conservative (i.e. safer for design), particularly for the higher walls.

In recent years, mechanically stabilized earth (MSE) walls have been proposed as support for bridge abutments on shallow foundations due to significant cost savings over conventional pile-supported designs. This paper presents new research on numerical modeling of a realistic MSE wall-supported bridge abutment using the finite difference program FLAC-2D. MSE abutments are typically subjected to much larger loads from bridge superstructures than conventional MSE walls. An MSE bridge abutment with a flexible wall facing is a complex system that includes granular backfill, reinforcement, concrete facing blocks, and a shallow foundation for the abutment structure. In the numerical simulations, soil-block, block-block, and soil-abutment interactions were simulated using interface elements, and soil-geogrid interactions were simulated using cable elements. The MSE abutment is subjected to a vertical bridge load of 200 kPa. Results are presented for static conditions and include lower wall facing displacements, abutment structure settlements, maximum tensile forces in the reinforcement, lateral earth pressures, and vertical stresses under the abutment structure and at the soil foundation level. The numerical results are discussed with regard to practical field applications.

Geosynthetic tube has been used for dike constructions on soft ground. We need methods to design geosynthetic tubes that rest on deformable foundation. In this paper, 2D analytical and numerical methods are proposed to analyze the stress and deformation of the impermeable geosynthetic tubes resting on deformable foundation. The analytical method is proposed by using the 1D consolidation relationship or the e-log-p curve as an approximation. As the stress-strain relationship is nonlinear, this method is better than the Winkler method. The vertical pressure distribution in the soil is calculated using the Boussinesq equation. Numerical analyses are also carried out to evaluate the accuracy of the proposed method and to achieve good agreement between the results from the analytical method and those from the numerical methods.

Compensated raft foundation is used to support heavily loaded structures resting on soft and low-permeable soils. It also aids in the reduction in settlement due to lowering of the stress transferred to the underlying soil. Such soils often require pre-loading and pre-treating with vertical drains to arrest the majority of the final settlement under the actual construction in less time. This paper reports the attainable efficacy in adopting the above methods for the foundation of the 10^th Boy's Hostel at the Indian Institute of Technology, Guwahati. Soft, clayey, and marshy fill soil is prevalent in the hostel site. FEM modelling using PLAXIS 2D v2012 has been used to interpret the possible benefit of the adopted method. In comparison to the condition when no preload was used, it has been observed that the application of staged preloading resulted in a reduction of the total settlement in the range of 45-90%. Moreover, in comparison to the untreated soil, the application of vertical drains significantly accelerated the rate of consolidation and dissipation of pore-pressure (~30-50% and 15-25 times, respectively). The comparative results reveal that the adoption of the above methods will substantially help improve the settlement characteristics of the soft soil site in discussion.

For many years, expanded polystyrene (EPS) geofoam has been successfully used as construction material in the field of geotechnical engineering due to its wide variety of applications, such as compressible inclusion in retaining walls and lightweight fill material in embankments. The present paper describes numerical modeling results carried out on EPS geofoam as compressible inclusion in retaining walls subjected to strip surcharge loading. Three different densities of EPS geofoam - 15, 20, and 30 kg/m³ - were used as compressible inclusions. The shape of EPS geofoam compressible inclusions used in the present study is orthogonal, i.e., constant thickness with depth. For each density, three different thicknesses (50, 100 and 150 mm) were considered. In India, thermal power plants produce enormous quantities of fly ash as by-product. Fly ash disposal and utilization in an environmentally friendly manner is a major concern in India. This study also focuses on using fly ash as an alternative backfill material in retaining walls. The plane strain finite element simulation was carried out using commercially available Plaxis 2D software. The backfill fly ash and compressible inclusion EPS geofoam were modeled as linear elastic perfectly plastic materials with Mohr-Coulomb failure criteria. The numerical results indicate that EPS geofoam placed between the retaining wall and the backfill fly ash has a good effect on reducing the horizontal deformation of facing panel, backfill settlements and lateral pressure.

EPS geofoam blocks underlying compacted soil and structural loads become subjected to multi-axial loading. Effects of confining pressure on the stress-strain behavior of EPS geofoam have been investigated in previous studies. Some studies found increases in confining stress lead to corresponding decreases in both modulus and compressive strength. Increasing confining stress has also been reported to result in higher compressive strength. Regardless of the sense and attributed significance of the effects of confinement on EPS geofoam behavior, the implied effects on performance are generally not considered in practice. A series of triaxial compression tests was conducted on EPS geofoam of different densities and over a range of confining pressures. Results from the investigation indicate increases in confinement lead to decreases in yield stress and post-yield compressive resistances, depending on the EPS density and range of confining pressures. The sense and practical significance of confining stress effects are discussed. An approach for incorporating the more significant effects of confining stress on EPS geofoam behavior is considered.

Expanded polystyrene (EPS) geofoam is a lightweight, compressible material that can be used to protect buried infrastructure in areas with high-to-moderate seismicity. This paper summarizes recent research conducted at the University of Utah regarding the seismic design and construction of EPS geosystems to improve the seismic resiliency of pipelines and buried structures, particularly at normal fault crossings. It discusses the development and verification of an EPS cover/backfill system to protect buried pipelines and other structures from potential rupture caused by permanent ground deformation (e.g., tectonic faulting, subsidence, liquefaction, and landslide). Full-scale experiments and numerical modeling show that a light-weight cover system constructed, in part, with EPS block offers significant benefits in protecting buried pipelines from the damaging effects of offset caused by permanent ground deformation. The prototype EPS cover system significantly reduced the vertical uplift force and stresses imposed on the buried pipe system as it was subjected to uplift through the EPS cover system.

The construction on the soft clay which extends in many areas in Egypt is considered a big challenge. The soil of Port-Said is one of the inverted soils such as Frankfurt and Shanghais. Herein, extended poly-styrene (EPS) geofoam was used to replace the soft soil in order to control settlement under raft foundation. In this study, a two-dimensional finite difference numerical method was adopted. This numerical method was first verified against experimental data and then used for the analysis of the raft using EPS in a parametric study. The parametric study was extended to consider the change of the density and thickness of geofoam layers and the number of floors. Comparison was made between cases with geofoam replacement and those without geofoam. Discussion for the numerical results was performed and conclusions were drawn.