Innovative and Sustainable Use of Geomaterials and Geosystems

Road construction over soft ground presents a considerable technical challenge. Such roads often serve remote communities and carry low levels of traffic. Construction and maintenance must be achieved within limited budgets. The two main approaches to such construction are aboveground (floating) and belowground (buried) construction; costly lightweight construction materials are desirable. The use of light-weight, British Standard tire bales is described. Issues related to the use of tire bales, such as sustainability, waste management, costs, and end of life are highlighted and their use in constructing road foundations over soft ground described.

Reservoir sediments (RS) are difficult to dispose of because of their high water content and soft nature. This study proposed a novel approach using RS as an ingredient in controlled low strength materials (CLSM) and then reinforced it with geobag to facilitate the storage and for backfill applications. Test results have shown that initially geotextile provided significant contribution for the strength improvement of RS-based CLSM. However, the effect of reinforcement appears to be highly dependent on the types of geotextile and the original strength of RS-based CLSM. The results show a promising solution to reuse reservoir sediment, save the natural resource of granular fill, and ensure the quality of backfill constructions in most cases.

Identifying the outliers from the correlation verifying test data is essential to the roller-integrated compaction measurement (IRICM). Due to the variant filler properties, lift thickness, moisture ratio, and various roller modes, outliers may arise and result in the misunderstanding of the relationships between the roller-integrated compaction measurement values (IRCMV) and in-situ compaction test values (IICTV). The distance-based outlier model was established to characterize the dispersion degree of the data. Then the estimation neighbor method was used to identify the out-of-trend points, the outliers. The RICM field experiment was conducted in the calibration strips to test and verify the proposed method. The results revealed that the proposed method enabled the correlation and regression coefficients more accurate. This research demonstrates that the outlier analysis techniques for data preprocessing could be applied to RICM.

In this paper, laboratory experiment and numerical methods are used to study the macro- and meso-scale mechanical behavior of the caisson during sinking. Macroscale behaviors including the earth pressure at the toe and on the side wall of the caisson are investigated. Discrete element method code PFC3D and finite different method code FLAC3D are coupled to simulate and explore the soil behaviors around the caisson. The macroscale behaviors of the caisson are explained from the mesoscale analysis based on the interaction between the caisson and the soils. The results are thought to be useful and have some guidance for the design and construction of the caisson in the future.

Reclaimed concrete aggregate (RCA) is used as replacement or mixed with virgin aggregates to be used in embankments, hot-mix asphalt (HMA), Portland cement concrete, and base/sub-base layers in pavement systems. However, RCA has not received a lot of attention as a drainage media because of low abrasion resistance, which causes excess fines content, and the potential of clogging material on filter fabrics. The performance of RCA as drainage material has not been evaluated by many researchers, and the limited information restricts its use. This paper describes the testing methods used to evaluate RCA as a French drain material; the French drain system collects water runoff from the road pavement and transfers it to slotted pipes underground and then filters through aggregate. RCA was tested for its physical properties including specific gravity, unit weight, percent voids, absorption, and abrasion resistance. RCA cleaning/washing methods were also applied to evaluate the fines removal processes. A petrographic examination was conducted by using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray diffracation (XRD). The permeability of RCA was also tested using the No. 4 gradation. The results showed that RCA has a high abrasion value, that is, it is very susceptible to breaking down from abrasion during transportation, stockpiling, or placing. The permeability tests show that the No. 4 gradation does not restrict the flow of water; however, the flow rate is highly dependent on the hydraulic system itself.

Recycling of wasted soil becomes a hot issue due to the difficulty of disposal, whereas stiff soil is limited for construction. This paper investigates the properties of air-foam stabilized soil made from dredged soil recycled by air-foam stabilization method such as strength, resilient modulus, and evaluation of the pavement performance when using it as pavement sub-base material. Air-foam stabilized soil samples are prepared by mixing soil and water with various cement and air-foam contents. The unconfined compression test and the resonant column test are conducted; then, the relationship between the unconfined compressive strength and the resilient modulus of air-foam stabilized soil is evaluated. The resilient modulus values are applied in a layered elastic model to predict the allowable number of load repetitions based on fatigue cracking and rutting. According to the pavement performance, air-foam stabilized soil is sustainable and suitable in the role of pavement sub-base material.

This paper utilizes numerical method to simulate the application of geosynthetic reinforced soil retaining structures. The SLOPE/W computer program was employed in this study to introduce the calculation of the reinforcement forces and the strengthening mechanical behavior of the soil structure as well as the failure mode. When using the SLOPE/W program for analyzing geosynthetic reinforced soil retaining structure, each layer of the reinforcement was considered with the identical tensile force on the sliding surface on the same slice. Once the reinforcements committed pull-out failure, they bore different tensile forces. Although the reinforcement committed break-off failure, the reinforcement tensile forces were the same. The unique component is the neat consideration for making the different required length of reinforcement. Under the circumstance of the failure surface not cutting through the reinforcement, it did not provide any resistance force. In addition, SLOPE/W was used for the slope stability analysis of the geosynthetic reinforced soil retaining structure built in FoGuang University, Ilan County, Taiwan. Slope condition in the absence of the reinforcement gave the factor of safety as 0.93, which did not meet the requirement of slope stability at all. With the support of reinforcements, the safety factor was increased to 2.19, which matches the specification under normal conditions.

The total improved potential energy of the system with anchor was modified by meshless method. The discrete equations of the system were derived. According to the variation principle, the anchorage problem of plate with oblique crack was studied by numerical under axial tension. Based on different elastic modulus of the anchor and various anchoring schemes, the equivalent elastic modulus of the system with anchor, the maximum stress at crack tip, and the rupture loads were researched. The best solutions were provided for improving equivalent elastic modulus and rupture load of structure. The results showed that elastic modulus of anchoring material has essential effect on inhibiting crack propagation and improving mechanical properties of jointed crack mass. The elastic modulus of anchoring material was 1-30 times as elastic modulus of the base material, which can achieve better anchoring effect.

Geosynthetic materials, such as geogrid or geotextile, are often used to compose a reinforced earth to improve the engineering properties of weak soils. These materials provide extra tensile resistance by interaction with surrounding soils. The geosynthetic materials have long been used to reinforce earth slopes, but relatively little study have been performed on their usage for the reinforcement of shallow foundations. To provide practice engineers with parameters to optimize their design, the effectiveness of reinforced shallow foundation was studied numerically by using a commercial finite difference program - Fast Lagrangian Analysis of Continua (FLAC). The bearing capacity of an unreinforced strip foundation was simulated and compared with Terzaghi's theoretical solution to verify the correctness of the numerical model. The effects of various parameters, such as the burial depth, length of the reinforcement material, number of reinforcement layers, arrangement of reinforcement layers, and the strength of soil on the bearing capacity were then studied. Results of this study verified that the reinforced shallow foundation can provide higher bearing capacity, especially for weak soils. It was found that a buried depth of 0.4 times the width of foundation yields the optimum bearing capacity increase. The most economical reinforcement length is about two to three times the width of the foundation. Adding an additional layer of reinforcement was found to further increase the bearing capacity.

Being a mountainous country, a lot of landslides and debris flow happen very often in South Korea. Many researchers tried to find accurate criteria to predict it by analyzing all influence factors. Rainfall, particularly, is one of the most important factor,s because its properties can be changed dramatically in a short period of time. However, until now, it isunclearwhich antecedent rainfall duration is the most critical one and best for landslide prediction. In this study, an analysis on multiple cases of antecedent rainfall duration was conducted basing on the concept, "Within the same rainfall duration, the one with the most rainfall precipitation is the critical one." A true or false experiment was carried out based on the concept (true when the cumulated rainfall precipitation within antecedent rainfall duration is maximum and false when it is not). The concept was proved to be true in many cases. The highest percentage of individual case was found in 40 days with 88.9% and two cases combination was found in 1 h and 40 days, 3 h and 40 days, and 1 day and 40 days with 91.7% of overall data.

Recent advances in surface wave measurement capabilities allow for field collection of both human activity induced ground vibrations and background ambient noise caused microtremors. With designed sensor arrays, the passive surface wave survey provides a non-invasive seismic exploration method for subsurface profiling. In comparison to conventional geotechnical borehole tests, it is less expensive and it shows swiftness for site characterization over a large area. In this paper, the benefits of the surface wave survey method in earthquake geotechnical engineering for local site characterization were highlighted with case studies. A series of passive surface wave field measurements were performed by using sensor arrays. The collected data were processed to obtain the soil shear wave velocity profile and the fundamental site resonance frequency. Discussions were extended to compare the functionality of different accelerometers that were used as receivers in microtremor measurement. The accelerometer-based sensor array was found to be capable of collecting valid data for surface wave analysis.

To study the development of negative skin friction on piles, a field test on three identical piles was carried out. In the test, the loads on pile top were added first, and then ground surcharges were applied while the pile top settlement was stable. According to the test results, additional settlement induced while surcharges became larger, the additional settlement rates of piles increased with the increase of the load at the pile top at the initial stages of the surcharge. The increasing speed of the additional stress of the upper part of the pile slowed down while the load at the pile top increased. The increase of the load at the pile top postponed the appearance of negative skin friction. At the testing stage, the negative skin friction that surrounded the piles increased as the loading time continued. In all levels of the loads, the neutral point position moved down as the loading time continued. The steady neutral point position moved up with the increase of the load at the pile top. The fitting curve matches well with the test result.

This study obtained ground response data of clay soils subjected to airblast loading through small-scale field experiments. A total of 24 explosive blasts were conducted on clay soils. Binary explosive charges were suspended above the soil with explosive masses ranging from 0.9 to 100.9 g and suspended heights ranging from 2.5 to 7.6 cm (1 to 3 in) above the clay surface. Results included air overpressure, ground vibration, and crater geometry data. Relationships were developed to describe vibration attenuation and the amount of energy generated by the blast events. Crater geometry was related to explosive mass to characterize the energy transmitted into the soil. The experiment results provided a data set with which to predict the results of air blast loads on clay soils.