Grouting 2017: Grouting, Drilling, and Verification

Bio-mediated and bio-inspired improvement of granular soils via microbially induced CaCO₃ precipitation (MICP), enzyme induced CaCO₃ precipitation (EICP), and microbially induced desaturation and precipitation (MIDP), techniques sometimes referred to bio-grouting, have attracted an increasing amount of attention in the past decade. MICP and EICP are techniques which rely upon the hydrolysis of urea as catalyzed by the enzyme urease. MIDP is a technique that relies upon dissimilatory reduction of nitrate and also desaturates the soil via biogas generation. MICP and MIDP are bio-mediated process, as they rely on living organisms. EICP may be considered a bio-inspired technique as, while it employs biologically generated free urease, no living organisms are involved in the precipitation reaction. Bio-grouting has the potential to serve as a sustainable technique for a variety of soil improvement applications. While bio-grouting has not been commercialized, promising results have been obtained in the laboratory and limited field trials.

Enzyme induced carbonate precipitation (EICP) for vertical columnar stabilization and soil nailing has been demonstrated in bench scale testing. In EICP, precipitation of calcium carbonate (CaCO₃) is induced via hydrolysis of urea using free urease enzyme. The enzyme is introduced into the soil in an aqueous solution containing urea and calcium ions to precipitate CaCO₃. The precipitated CaCO₃ improves the strength and stiffness and increases dilatancy of the soil by filling soil pores, roughening the soil particles, and binding the particles together. EICP was used to improve soil around 51 mm- and 76 mm-diameter vertical perforated plastic pipes in 19 L buckets and a 1 m³ soil box, respectively. EICP solution was also injected through a 9.5-mm diameter perforated tube to create inclined columns to model soil nails. These tests demonstrate the feasibility of using EICP to create cemented soil columns for foundation support and soil nailing.

Microbially induced calcite precipitation (MICP) is an environmentally conscious soil improvement technique that can improve the geotechnical properties of granular soils through the precipitation of calcite on soil particle surfaces and at particle contacts. In this study, synthesis of results from 47 soil column experiments involving 14 different soil materials was completed to provide a preliminary characterization of the range of engineering properties obtainable with MICP ground improvement. Following treatment, soil column specimens had unconfined compressive strengths ranging from 0.22 to 5.34 MPa, shear wave velocities ranging from 151 to 1469 m/s, and hydraulic conductivity reductions ranging from 0 to 3.5 orders of magnitude. Relationships between post-treatment soil improvement, soil properties, and calcite content suggest that D₁₀ particle size and fines content may significantly influence unconfined compressive strength and hydraulic conductivity, however, shear wave velocity may be less sensitive to these material differences. In addition, a comparison of final calcite contents between experiments suggests that soil fines contents up to 13% may not significantly affect calcite precipitation efficiency. An overview of the MICP reaction, biological treatment approaches, and process monitoring methods are also provided to introduce the bio-mediated soil improvement technology.

Over the past decade, recent developments between the geotechnical and life science disciplines have establish microbial induced calcite precipitation (MICP) as a novel ground improvement method. This method improves the static and dynamic mechanical properties of the soil while maintaining its environmentally friendly characteristics. Its application process lends itself to increased compatibility with varying infrastructure where other methods pose issues due to constraints. Currently, there are no established methods to properly assess the level of improvement, or adequately predict the expected performance for a given level of cementation. It is envisioned that numerical simulations will hold the key. With this in mind, a model was developed that incorporates the key aspects of the improved biomaterial for the purpose of comparing the lightly cemented and the original uncemented soils to illustrate the potential of the MICP method. Specifically, the model incorporates the ability to capture the behavior and transition from the cemented state to the uncemented state while maintaining adherence to the controlling factors of void ratio and confining stress. This paper focuses on the changes of shear stiffness and shear strength as a result of the degradation of the calcite (CaCO₃) cementation in the MICP soils.

The state of the art of geotechnical grouting projects has advanced considerably in the last decade. Notable achievements include the use of computer-aided grouting systems, balanced stable grouts, automated batching, measurement while drilling, borehole digital mapping and deviation measuring tools. When new tools and techniques are employed on projects it is inevitable that older practices that are thought were serving well now prove to be detrimental to overall project success. There are two areas that are significant contributing factors for failure that have not evolved in step with the technical advancements to date. These areas are budget costing (pricing, data and measurement) and scheduling (planning, sequence and effort). This paper examines the costing side of the modern grouting project referencing scheduling only as required. The structure of how a project is priced has a significant effect on a project’s chance for success. New techniques and equipment must be integrated into the whole project costing equation to optimize success for all stakeholders. This has not been the case in many projects in the past few years because for all the successes there appear to have been significant failures also. The simple fact that most geotechnical grouting projects cannot be precisely defined at the onset is a fundamental flaw if commercial requirements are not created to accommodate this variability for all stakeholders’ best interests.

The Stockholm Bypass is a new route for the European highway (E4) which will connect the southern and northern parts of the Stockholm County. In total over 18 km of the bypass are to be constructed in rock tunnels. The environmental permit for the project is an allowable leakage in the range of 2-5 l/min per 100 m tunnel. To meet this, continuous pre-grouting of the tunnels will be performed. However, since the geological conditions vary along the tunnel, investigation of the ground conditions ahead of the tunnel face is performed by registration of MWD-data (measurement while drilling) from the pre-grouting holes. The work flow requires that the contractor drills every second hole in a grouting fan and sends MWD-data to the client. As the contractor drills the remaining grout holes, the client evaluates the MWD-data and decides if and where additional grout holes shall be drilled. The MWD-data will provide the client with a tool to forecast ground conditions ahead of the face and, together with the results of previous grouting screens and water inflow measurements optimize the grouting works for the encountered geological conditions.

The raising of Hazelmere Dam by an unprecedented 7 m required technology never before seen in the KwaZulu Natal region of South Africa. Extensive feasibility studies established that the optimum solution to facilitate the raising was to install 84 high capacity rock anchors through the concrete superstructure into the underlying rock. The anchors, installed in 355-mm boreholes, ranged in size from 49 to 91 strands (15.7-mm diameter) and were up to 90-m long. With test loads up to 19042 kN, these anchors equalled the largest ever installed on a post-tensioned dam. In order to quantify in situ rock/grout bond stresses, a comprehensive test anchor programme was commissioned and this involved the world’s largest sacrificial test anchors. The nature of the ground necessitated an extensive programme of pregrouting to ensure that the boreholes were sufficiently grout tight so that the primary load bearing anchor grout would retain its full integrity. The grouting of the corrosion protection system in anchors of this size called for innovative techniques to ensure successful execution and these aspects are also described in the paper which focuses primarily on the test anchor programme.

The safe and efficient drilling of overburden (fills and natural soils) and rock is integral to many specialty geotechnical construction techniques. The state of practice for overburden drilling techniques was most recently described by Bruce in 2012, and the history of down-the-hole (DTH) drilling for rock was provided by the authors in 2013. Thereafter, development and innovation have continued, principally to satisfy specialty contractors’ goals for systems providing faster production, lower costs, more consistent and reliable performances, and easier operation and maintenance. This paper describes more recent development in overburden drilling, and also reviews innovations in DTH methods operated by air, and by water.

The paper deals with a soil improvement by grouting carried out through tubes à manchettes of extraordinary length, installed inside HDD boreholes. As part of the Warsaw Subway Line No. 2 project, two twin TBM tunnels were required to cross under historical buildings. In order to mitigate the risk of settlements, a preliminary soil improvement was designed. Due to the particular layout of the buildings, an extreme solution was conceived, designed and applied. Starting from the surface, boreholes from 210-m to 260-m long were drilled by HDD technology. Each tunnel was fitted at its crown with 24 grouting pipes around the outside of the tunnel section to be bored. Grouting was performed by selective and repeated procedure, injecting first a high penetrability cement-based grout and then a silicate-based chemical mixture.

In order to sufficiently seal an underground facility in fractured rock, it is essential to obtain adequate grout spread into the surrounding fractures. The grout spread itself depends on parameters, the most significant of which are the filtration tendency and rheological properties. These properties can be affected by the applied pressure. High-frequency oscillating pressure has been shown to improve grout spread by virtue of reducing the grout viscosity. However, this method has not yet been industrialized due to the quick dissipation of the oscillation along a fracture. In a recent investigation, we examined a low-frequency rectangular pressure-impulse using a short slot. The results showed significant improvements in the injected grout volume in comparison to the static pressure results. In this paper, we examine the method in a considerably longer artificial fracture in order to investigate the dissipation of the pressure impulses. The study indicates the potential of the method to improve the grout spread in rock grouting.

Rock tunnel projects in Sweden always have an environmental demand linked to the acceptable effect on the groundwater level. In order to keep the impact from tunneling acceptable, continuous pre-grouting is usually practiced. However, the benefits of grouting measures vary along a tunnel and with it the need for grouting. This article presents a structured methodology that can be used to evaluate and identify preferential areas for grouting, and the results of its applications to existing projects. The methodology is based on a hydrogeological area description, combined with an analysis of the groutability of the fracture system and environmental demands to estimate the grouting demand along the tunnel. For low-permeable areas with low environmental demands, no grouting is needed. This is referred to as demand-assessed grouting. This paper presents an evaluation of four Scandinavian tunnels and the result indicates that continuous pre-grouting is only needed along 15-30% of the tunnel stretches. This indicates that substantial time and cost savings can be achieved by applying the methodology.

In case of underground construction affected by groundwater, CIP (cast-in-place pile) method is generally used to solve the geohydraulic problem. However, as this method has poor connectivity between piles, an auxiliary cut-off method is required in many cases. In this study, a newly-developed cut-off wall (H-CIP) without auxiliary method, by using surfactant grout (Hi-FA), which improves anti-washout performance and infiltration ability, is introduced and the field applicability of H-CIP method is evaluated. CIP and H-CIP piles were installed under the same ground conditions and field and laboratory tests were conducted to verify the performance, respectively. As a result, a newly-contrived H-CIP method shows higher field performance in terms of cut-off and strength than conventional CIP method.

This paper presents the grouting methods used to successfully complete micropile installations in Karst geology and the quality controls and testing used to avoid failures. The techniques described in this paper were assembled from 15 years of design-build micropile experience working in Karst geology. This paper captures lessons learned for installation of micropiles and rock anchors installed in Karst geology including the use of modern, stable grouts with thixotropic additives, stage grouting of piles, and field quality controls used during the pile drilling and grouting process to minimize the risk of failures. The authors offer the perspectives of both the contractor and the design engineer regarding the design-build process, field and laboratory testing, grout mix designs, drilling and grouting methods, and field quality control for projects in Karst geology.

For around two decades of research and development in the field of grouting in hard jointed rock, the design process has taken some leaps forward. Stille and Gustafson, 2005 and Funehag and Gustafson 2008, shows how a grouting design can be computed. A grouting design in hard rock can based on the penetration length of grout in rock fractures. The design comprises considerations of the fracture apertures in the rock mass, the type of grout and its rheological properties and how the grout is injected i.e pressure and grouting times. When knowing these parameters an optimized geometry fitting the design is made. Thörn, et al, 2014 describes a fundamental analysis with a comprehensive tool to retrieve the fracture distribution and aperture distribution of the fractures crossing a cored borehole. The data needed about the core is geological mapping and hydraulic section tests. In Gustafson, Claesson and Fransson, (2013) a full derivation of a radial Bingham flow in a slit is described for constant pressure. By optimizing with a specific pressure and an efficient grouting time (efficient time means the time when the pressure has reached the designed pressure) a prognosis a more realistic time consumption for grouting can be computed. However, the time it takes to reach a certain pressure is dependent on the capacity of the pump and the how large the fractures widths are. For poorly chosen pumps together with large fractures the time to reach the design pressure can be significant. The overall objective for this new formulation was to involve the grouting pressure as a variable rather than constant. A pressure build-up mimic more a realistic pumping scenario which enables better prognosis of grouting works. This paper brings up this new formulation of the radial Bingham flow with variable injection pressure in slit. The benefits of this new formulation is that it can easily be integrated in other computer programs. One program that uses this new formulation is a grouting simulator owned and developed by Edvirt AB. The simulator has been used to pedagogically demonstrate how a variable pressure and restrictions in grout flow (the pump capacity) affect the penetration length. Further, the results show that it can be used to predict suitable pump capacity to fit the coming grouting works.

In some cases, permeation grouting can be a very cost effective soil improvement technique. Recently, the use of fine grained (microfine) cement has improved the performance of cement grouts by reducing bleeding and widening the range of soils that can be penetrated by grout. In this paper, an experimental study is conducted to evaluate the current practice for determining suspension grout stability. To do so, the performance of microfine cements over a range of water-to-cement ratios is evaluated and compared to its measured stability. First, traditional bleed column stability tests were performed on the different grout mixes. Then, a new method of determining grout stability while in motion is introduced, and its results are compared to the traditional bleed test results. Finally, constant flow permeation tests were performed through a two-foot long rigid wall permeameter using the different mixes. Lastly, the unconfined compressive strength of the grouted sand was measured as function of the distance from the injection point and the results were used to evaluate the efficiency of both grout stability methods in determining the filtration of the grout as it permeates through a porous medium. This paper presents data and preliminary results for the new stability test. Further results incorporating the use of lower water to cement ratio grouts and additives such as superplasticizers are to follow.

Rock mass permeability testing has been performed to characterize rock formations since the early 20th century. It was further popularized by Maurice Lugeon (1933) after he defined a standard unit for quantifying the transmissive ability of rock discontinuities. As the dam and grouting industries developed and flourished in the latter half of the 20th century, more attention was devoted to better understanding water pressure testing and its application to rock grouting projects. Today, water pressure testing is a well-established practice and is one of many useful tools for characterizing rock formations. However, it seems the benefits of water testing may not be fully understood from a rock grouting perspective. In several recent grouting designs, the authors have observed that water pressure testing has been incorporated for the sole purpose of measuring the permeability of the untreated formation. Such a limited use of the test and results inhibits important evaluation of project quality and production efficiency. In the last two decades, the grouting industry has seemingly dedicated more effort toward technical interpretation of the water pressure test while not promoting its many practical and technical benefits. In this paper, the authors expound on numerous uses for water pressure testing which add to the overall value of a rock grouting program and advocate for increasing quality and production efficiency. To maintain such progress, geoprofessionals in these industries should maximize the application of available tools and continue promoting innovation in this dynamic field of work.

This paper will report a Tube-a-Manchette (TAM) grouting project carried out in the silty sand and gravel layer to seal off the bottom of a deep excavation against uplift of high groundwater pressure. The excavation was up to 33 m in depth and was retained by diaphragm wall 53 m deep. The base grouting zone covered the interface zone between sandy and gravel layers. TAM grouting method was adopted to do the grout injection. Cement-bentonite (CB) grout was injected in the first stage followed by sodium silicate grout (SL grout) in the second stage. Volume control grouting method was adopted here and the grouting pressure applied at each injection port was recorded. Based on the recorded pressure and the spatial coordinates of each injection port, a mapping of grouting pressure in the grouted zone was presented in 2D image using commercial software. The 2D grouting pressure contours at a given depth can be established based on the physical data recorded during base grouting. Meanwhile, it was also found that the deviation of drill holes alignment had no obvious effect on the 2D grouting pressure distribution, if a proper TAM grouting sequence and a lateral confinement of enclosed diaphragm wall can be provided.

Sweden has a long history of research within the field of rock fissure grouting in hard crystalline rock mass due to strict environmental requirements regarding allowable ground water draw down. These requirements normally implies that fractures down to aperture size between 50 to 100 µm needs to be sealed and within these ranges the size of the particles for cementitious grouting agents becomes a limiting factor. For a grouting design it is therefore of importance to consider the aperture size distribution of the rock mass in order to predict the groutability for both cementitious and non-cementitious grouting agents. Transmissivity data from hydraulic tests (water pressure tests) and number of fractures along a borehole can be assessed from core logging for further use as input for a statistical interpretation of fracture data to simulate an aperture size distribution. A methodology developed at Chalmers University of Technology in Gothenburg, Sweden, is proposed. The method is a statistical evaluation of groutability (SEG) and is based on the Pareto distribution. A computational design tool has been developed to simplify the use of the statistical evaluation and to make the research more accessible to end users, designers, in the grouting industry. The aim of this article is to present two case studies where the statistical interpretation of fracture data is performed by using the computational design tool and how the outcome can be of great use in finding a more accurate grouting design. The case studies include fracture data sets from two large infrastructure rock tunnel projects in Sweden; a road tunnel in Stockholm and a railroad tunnel in Gothenburg.

In general, all tunneling contracts in Sweden are based on performance contracts. There has been a large increase in the knowledge and understanding during the last decades in Sweden regarding sealing of rock tunnels using mostly cementitious rock fissure grouting. This increased know-how derives from extensive research and execution of continuous pre-grouting throughout different rock tunneling works in Sweden. However, there is still a large variety in grouting designs as well as in performance between, and even, within projects. In order to make sealing of tunnels more efficient the Swedish Transport Administration has initiated a project to establish a unified design approach for rock fissure grouting in hard crystalline rock. The aim of the design approach is to have a coherent and structured process and methodology for grouting design, resulting in an appropriate, similar and transparent design approach independent of designer. The purpose is thus to introduce explicit guidelines for grouting design and its presentation as grouting classes that will be used in technical specifications, bill of quantities and prognosis for further procurement of grouting works in performance contracts. The improved tendering document should result in reduced costs due to efficient design works followed by an easier procurement process for performance contracts along with improved grouting performance and hopefully also less claims/disputes. The design approach is not yet implemented. However, the design approach is based on known theories and experience that are now compiled into one comprehensive methodology.

A new dike will be constructed around the fourth kimberlite pipe, named A21, of the Diavik Diamond Mine in the Canadian North West Territories. In August 2015 BAUER Foundations Canada, a subsidiary of BAUER Spezialtiefbau GmbH, based in Schrobenhausen, Germany, received a major contract with a value of around 65 million euros to create a cut-off wall for the Diavik Diamond Mine in Canada. Jet grouting and permeation grouting with cement based grouts will be carried out to form part of the water tightening core structure of the dike. This paper describes the permeation grouting techniques as well as the approach that will be used for the jet grouting for the sealing of the soil layers underneath the cut-off wall (Bauer CSM) and of the weathered rock zone, down to the partially fissured bedrock. Almost 70% of the grouting works have been completed within the end of 2016. The jet grouting site tests for season one have been completed in October 2016. Some aspects related to design and methods, the lessons learnt as well as the main challenges the have been faced within season one of the works (December 2016) are described into this paper.

Broadly graded soils are characterized by having high coefficient of uniformity and typically are deposited in fluvial and alluvial environments. Galciofluvial soils are common broadly graded soils found in glaciated areas in the northern Continental United States and other locations around the world. Particle sizes in glaciofluvial soils range from fine sand to boulder sizes and typically have very little fines. The coarse fraction poses some problems for drilling and some methods of grouting, but the greater problems occur due to internal instability. Internal instability results from the inability of the coarse fraction of the soil to act as a filter to prevent movement of the finer fraction. This causes water based drilling methods and grouting to wash the finer fraction out leaving the open graded coarse material. This can induce settlement of the ground surface during drilling and grouting. Drilling and grouting in these soils can also increase the permeability of the ground, require much larger volumes of grout to complete the project than initially anticipated, and limit the effectiveness of some grouting methods. While some practitioners are knowledgeable about these conditions and their impacts, the impacts to drilling and grouting have not been well documented in the literature. This paper presents a summary of the nature of these soils including appropriate references, a discussion of the specific impacts to drilling and grouting, and summaries of example cases where these soils have impacted construction cost schedule, and performance.

The activities for the construction of the Sail Tower, Jeddah, KSA, comprised piling, shoring (diaphragm wall, tie-back anchors and dewatering) and excavation works, including all related underground works for the foundation structure of the new building. Taking into account the severe hydro-geological condition, a grout blanket was designed to reduce the coralline limestone permeability in order to decrease notably the water inflow from the bottom of the excavation. With the grouting blanket in place and some wells for the dewatering purpose, the excavation within the structural diaphragm wall was performed under almost dry condition. This document describes the site proceeding and the results achieved at completion of grouting works, during dewatering and excavation works and some outlines related to the procedures and checks implemented for the grouting activity quality control.

This case study describes the grouting aspects of the foundation improvements carried out to remediate the settlement distress of a partially constructed new building located on the west coast of the Caribbean island of Barbados. The foundation remediation ultimately included the construction of a 280-foot-long sub-surface ‘sea-wall’, the installation of 174 micro-piles (providing direct and indirect support to the building) and the grouting of voids and interconnected fissures/fractures in the weak, vuggy, uncemented coralline limestone strata underlying the building foundations. An investigation of the cause(s) of the settlement, a flexible remediation design, and close monitoring of the drilling and grouting operations during construction were essential to the success of the project. In addition, contractor procurement and operation, based on an ‘Alliance’ contractual concept resulted in an excellent consultant-contractor team relationship throughout. This was key to the completion of the work within the tight schedule required by the owner.

This paper discusses the innovative approach employed at NYU Langone Medical Center’s Kimmel Pavilion to address two natural hazards with a single grouted element system. Poor subsurface conditions necessitated the use ground improvement to address the potential for seismically induced settlement while ground anchors were needed to provide uplift resistance during coastal flooding conditions. These hazards were compounded by physical and legal restrictions imposed by rail and sewer infrastructure passing below the site. As originally envisioned, the design called for a performance based compaction grouted program followed by installation of passive ground anchors. Prior to commencing general construction activities, Moretrench American Company proposed an alternative hybrid anchor to accomplish both design tasks using a single element. The system proved highly effective for both uses during a trial program and a full production program was implemented. A detailed testing program was performed for the production elements and included pre- and post-treatment borings and CPT’s, analyses, and tensile load tests.

Grouting technology has become a widespread ground improvement method used often for underground and foundation constructions. Owing to the importance of proper grout mix which includes the proportion of water–cement ratio, an attempt is made in the present investigation to get the compressive Strength of sand stabilized with cement in two ways i.e. Grouting and compacting, the sand and cement with required water content. An unconfined compressive strength test was conducted on grouted sand column with water cement ratio of 1.5, 2 and 2.5. The above experiments were repeated with an addition of 2% sulphonated naphthalene formaldehyde (SNF). The experimental results revealed that at lower water cement ratio higher unconfined compressive strength (UCC) is obtained. It was also observed the compressive strength increases with curing period. Another set of experiments were conducted in compacted cylindrical specimen with cement content varies from 2 to 15%. A correlation between UCC strength compacted cylindrical specimen with SNF and UCC strength compacted cylindrical specimen without SNF is established.

Unconfined compressive strength (UCS) of high plasticity clayey soil mixed with various amounts of cement and four dispersive agents was evaluated to investigate the effectiveness of the agents combined with the cement on the stabilization of the soil. A series of unconfined compression tests was conducted for the clay specimen mixed with 5 and 10% of cement and four chemical agents such as sodium hexametaphosphate, aluminum sulfate, sodium carbonate, and sodium silicate with 0, 5, 10, and 20% of concentrations. The strength of the cement-soil mixture tends to mostly decrease when the mixture includes the agent. However, at low concentrations of aluminum sulfate (5%) and sodium carbonate (5% and 10%), the average UCS the soil-chemical agent-cement mixtures slightly increased compared to that of pure clay due to increasing the flocculation of the clay in the mixture. At high concentrations (20%) of all chemical agents, the UCS decreased considerably. With increase in cement content from 0 to 10% in the mixture, the degree of the UCS reduction remarkably increased. For 10% of cement, the UCS reduction is the highest for all soil mixtures containing chemical agent-cement, which is more than three times higher compared to that for the soil mixtures without cement.

The flow of suspensions through porous media is a complex phenomenon owing to the diversity of the mechanisms involved. It is important to determine the filtration behavior to understand the decline in injectivity of suspension as flow progresses and for that, knowledge of the rate of particle deposition is crucial. In this paper, a numerical model has been developed for the permeation of bentonite suspension grout through granular soil. The filtration model defines the rate of deposition of solid particles which depends on the rheology and concentration of grout, particle size and shape of suspended particle, grain size distribution of porous media, and physio-chemical interaction of grout with the porous medium through which it is flowing. The novelty of the newly proposed numerical model is that it accounts for the change in rheology of grout and the porosity and permeability of the porous medium as a function of the deposition of particles, none of which has been considered in the past. In this paper, six filtration models were used with different filtration coefficients and solid deposition empirical relationships. It was found that using a filtration coefficient that increases linearly with cumulative solid deposition was best suited to model the filtration mechanism of bentonite suspension grout permeation in granular soil. Bentonite content profile along the height of the sand column determined numerically using the proposed filtration model was similar to that obtained from the experimental results from post-permeation analysis.

Permeation grouting has been used as a cost-effective low disturbance ground improvement technology, which allowed geotechnical engineers to help improving soil properties to be suitable for different engineering activities. While permeation grouting can be a very useful fix to problematic soils, its success is dependent on the quality of the grout propagation, particularly the uniformity and extent of grout coverage. One quality control measure that has been adapted for years is the pressure versus time curve for constant flow grouting. An experimental study using 2 ft (61 cm) sand columns was performed using different grout mixes to assess the ability of pressure-time curves to predict the effectiveness of permeation grouting. Monitoring of grout front propagation in the sand column, and measurement of the grouted soil strength allowed a direct evaluation of the grouting process and the grouted soil. The results showed that although the pressure-time curves can capture filtration in most cases, they can be misleading for some grout mixes.

This research focused on the development of quantitative guidelines to evaluate the effectiveness of a grout curtain in porous media using piezometric and hydraulic flow data. In this study, a laboratory-scale physical seepage model was developed to aid in the understanding and development methodology to evaluate the effectiveness of a grout curtain. A new performance parameter was developed based on a normalization scheme that utilized the area of the grout curtain and the area of the improved media. The normalization scheme combined with model-based Lugeon values that correspond to pore pressure and flow rate measurements at different soil relative densities and grout curtain spacings, produced a mathematical equation that can be used to quantify the effectiveness of a grout curtain. This study found a relationship that takes into account soil porosity, grout curtain spacing and a new performance parameter that can be used to help predict the effectiveness of a grout curtain.

Many of today’s grouting projects, specifically those related to earthen dams and levees, require careful control with regards to the grout injection pressure used. Embankments and fracture zones in the rock must be protected against hydraulic fracturing during drilling, water pressure testing and grouting operations. The best way to effectively manage injection pressures during all phases of construction is to measure the pressure being exerted in the ground at the point of injection in real-time. Development of down-the-hole tooling that can measure pressures above and at the injection zone has given rise to the prospect of precisely monitoring and thereby facilitating the determination of the actual effective pressure acting upon the ground. Furthermore, the reaction of the surrounding strata can be precisely measured and analyzed. During the exploratory drilling and grouting program at the U.S. Army Corps of Engineers (USACE) Rough River Dam, an instrumented packer assembly, with injection pressure and column pressure sensors, was used for all facets of work including barrier bag inflation, casing installation, water testing, and rock grouting. Along with the instrumented packer, a calibrated gauge at the collar of the hole was used and all data recorded. This paper will compare two methods of calculating effective grouting pressures applied to the surrounding overburden and rock. The first method is the current industry standard of measuring the pressure at the collar of the hole and calculating the resulting effective pressure after taking into account the various dynamic line and head losses. The second method measures effective pressure at the point of injection using an instrumented packer. This second method, first presented, has now been applied to other grouting activities successfully executed during the Exploratory Drilling and Grouting program at the Rough River Dam. A number of benefits have been observed when using the instrumented packer on this grouting project. One of these benefits is the precise grouting of annular space and detection of grout loss during casing grout operations. Another advantage to using this device is the detection of packer by-pass during water pressure testing and grouting operations. It has also been observed that false refusals for thicker mix designs are non-existent using an instrumented packer while this phenomenon has been found to exist with traditional grouting methods. Finally, the pressure applied to barrier bags can be precisely monitored and controlled using an instrumented packer to ensure the bags are not over-pressurized during inflation.

The paper describes two case histories of compaction grouting projects where geotechnical instrumentation was required in parallel to automatic monitoring of grouting performance parameters in order to prevent damages to adjacent structures. Both projects involved compaction grouting in very close proximity to water lines. The first project involved six 18-foot (5.5-m) diameter discharge pipes below the siphon house of a pumping plant on the California Aqueduct. The joint between steel lined pipes and concrete pipes had gradually opened due to piping and seepage and ground improvement by compaction grouting under the pipe joints was required. Submersible 3D crackmeters for quick installation by divers across the contact joints between the pipes were developed for this project and were read automatically in parallel to compaction grouting pressures, flows and total injected volumes. The second project involved three 4-foot (1.2-m) diameter HDPE water inlet conduits at a lift station of a city near Los Angeles. Very loose soil zones and possible open voids were known to exist around the lift station structures as a result of shoring removal and flooding of the excavations during construction. Therefore ground improvement by compaction grouting around and below the conduits was needed and combined settlement and diameter sensors were specifically developed to be installed in the water conduits and were read automatically in parallel to compaction grouting pressures, flows and total injected volumes. In both of those projects, grouting could not have proceeded safely without monitoring of the water lines. All parties recognized that monitoring was essential because of the high consequences and costs that would have resulted from damages to the water lines and disruption of service.

Modern site investigations combining geophysical imaging with conventional exploratory borings can offer a significant improvement in the cost effective application of grouting for Karst risk reduction. This paper provides case histories of projects where the authors have utilized geophysical imaging to improve the understanding of subsurface conditions on difficult Karst sites when conventional soil borings or soundings failed to provide adequate data to arrive at a cost effective solution. The addition of modern imaging techniques allows for more accurate and cost-effective grouting designed to target specific Karst features rather than simply blanketing an area with grout injections. This paper provides 3 case histories where the grouting contractor utilized geophysical methods to study the work area prior to grouting for the purpose of minimizing the cost of the grouting program. One of these case studies describes the use of geophysical methods to locate the active Karst features beneath a water-filled pond and select an appropriate grouting pattern for remediation. Two other case studies within this paper present the use of Geophysical imaging to allow the cost effective use of cap grouting beneath proposed shallow foundations in an area with active Karst features instead of converting the structures to a deep foundation system of drilled shafts or micropiles.

This paper points out inconsistencies in grout testing and reports. Many of these topics have been presented in the grouting literature–sometimes even furthering the inconsistency. Reporting issues include water to cement ratio and other testing basis. Many tests have traditions that do not necessarily follow the referenced testing standard–1 liter Marsh as an example. Testing discussed includes set time, Marsh, bleed, and pressure filtration. Set time has been measured many ways including coffee cup tilt, while this paper revives and endorses the use of the easily carried pocket penetrometer. The goal is to provide topics to clarify in presenting and evaluating grout test data and to clarify in specifications.

In construction, grouting is used to improve or alter the natural properties of soil or rock by injecting a grout into the pores or fractures of the formation. In order to predict the grout penetration progress and maximum penetration length, modern methods for grouting design involve a detailed knowledge of the rheological properties of the used grout. Today, rheological properties of grouts are measured either in a laboratory with conventional rheometers or in the field with simple devices. Due to the complex flow behavior of cement-based grouts, being non-Newtonian yield stress fluids with history and time dependent rheological properties, the results are non-consistent, device dependent and strongly influenced by the test procedure and operator. No standard measurement method is available for rheological characterization of grouts in the grouting industry today. In order to improve this unfortunate situation a new complete measuring methodology, based on pulsed ultrasound, is proposed. The method has been tested for cement-based grouts, with good results. In this work, a new container-based field laboratory is presented, equipped with the Flow-Viz system, which is designed for in-line measurements of rheological properties of cement-based grouts under field-like conditions. Results obtained under field-like conditions are presented in order to demonstrate the applicability of the new system.

In spite of the sophistication varying, real time computer monitoring of pressure grouting parameters is now readily available and often used. Although a wide variety of geotechnical and structural instrumentation is also readily available, its use to detect changes in the affected geomaterial, the ground surface, or influence on nearby structures, and substructure during grouting, is not so common. The use of these modern tools to control the grout injection, however, allows us to work safely, even in the most sensitive and developed urban environments and industrial settings, containing both surface, and underground piping, structures, and substructure. A timely review of readily available geotechnical and structural instruments, and their advantageous use in grouting is made along with discussion of various computer monitoring techniques and use. Optimal display and application of monitoring data will be discussed, as well as its value for sharing, further analysis, and as permanent documentation of the actual grouting work. Some brief case histories of actual use, and how the combination of these two valuable monitoring tools allowed sensitive grouting applications to be made safely, is provided.

Despite of the significant development of grouting theories and technologies, very little have been implemented in field. The recent theoretical development leads to the estimation of the propagation of grout inside one dimensional and two dimensional geometries, which implies that the unnecessary spread of grout can be reduced. The yield stress and viscosity is required to estimate the spread of grout. Due to thixotropic nature; the yield stress depends on the shear history and shear rate, generated during propagation. Therefore, during the design of grouting, the estimation of grout spread should be designed considering a definite shear rate at the grout front for required spread. This implies that, the yield stress and viscosity of grout needs to be continuously measured in-line during grouting. In addition, the shear rate needs to be estimated to choose the design value of yield stress. In this work, the ultrasound based flow-viz industrial rheometer was successfully used to perform in-line measurement of the rheological properties and visualize the flow profiles of cement grout. In addition, a non-dimensional nomogram was developed based on a ‘semi-analytical’ approach to estimate the shear rate at the grout front. The relevant design parameters can be obtained from the nomogram for the corresponding relative spread of the grout, and it can therefore be used as a simple design tool for cement grouting.

Real time electronic monitoring has become standard for rock grouting. By the early 1980s, its use had already become a reality, but in only a few places worldwide. From the earliest work using paper chart recorders, to the introduction of the personal computer, through to use of the present, sophisticated, parallel multi-hole computer recording software, real-time monitoring has evolved significantly over the last 30 years. This paper tracks the history of the development of the techniques and gadgetry, and explores the trials and tribulations experienced along the way. The issues that resulted in nearly a 10 year gap between original introduction of electronic monitoring methods and general acceptance by those originally skeptical of its advantages are explored, highlighting the immense benefits that have been achieved in improving rates of constructability of grout curtains, and with better quality. Some insights for future advances are then suggested.

Grouting of underground constructions is important to decrease water inflow into constructions. It is therefore important to use grout with good penetration ability to achieve this goal. The purpose of this paper is to show issues connected to measuring of the penetration ability of cement-based grouts in the field with a filter pump and penetrability meter and show the need for improvement or use of some other method. Three main reasons which contribute to a different estimated critical aperture with these two methods are: different maximum test volume in regression analysis of measured data, limited maximum test volume in the filter pump, and different test pressure. Test volume should be related to volume of designed grout spread in the critical aperture and test pressure should be related to grout spread velocity in the field.

A full-scale field testing program was conducted in Christchurch, New Zealand, to assess the effectiveness of soil stiffening and/or densification caused by the installation of shallow, low-mobility grout (LMG) columns. The LMG columns were designed to be 4 m long and were installed at three different test areas for the purpose of liquefaction mitigation in loose silty sands. Direct-push crosshole (DPCH) seismic testing was performed on unimproved ground and on ground that was improved with the LMG columns. The purpose of the DPCH testing was to verify the integrity of the LMG columns and to identify any changes in soil stiffness created by their installation. The crosshole testing involved sampling the unimproved and improved ground conditions with horizontally propagating shear waves at depths ranging from 0.4 to 5.0 m in 0.2-m increments. The seismic verification method clearly delineated zones of change and LMG column variability. The verification results were confirmed by post-characterization trenching.