Nowadays, geotextile reinforced soil walls are being used more often, and with that, the number of reports on the deformation of these soil walls is on the rise. But we do not yet fully understand what happens to the reinforcement material within the embankment when deformation occurs. To find out, the authors have studied density, water content ratio, velocity of elastic wave, and strength of reinforcement material of the deformed embankment interior, where the mudstone reinforcement wall was rebuilt after it had been damaged. Studies showed that penetrating groundwater and rain had weakened the mudstone used to construct the embankment, causing deformation. We also confirmed that some parts of the reinforcement material were much fragile and showed considerably lower deformation capacity compared with the new reinforcement material. These findings indicate the possibility of lowered strength and deformation capacity of reinforcement material within the damaged geotextile reinforcement soil wall.

抄録全体を表示

Natural fiber reinforcing materials have been introduced recently in geotechnical applications known as “Limited Life Geosynthetics (LLGs)” to provide extra lateral restraint and prevent the embankment from failing by rotation or splitting failure of an embankment on soft clay. The study was aimed to investigate slope stability of embankment on soft clay reinforced with woven Kenaf LLGs. There are two types of Kenaf LLGs including coated and non-coated with polyurethane for reduction of water absorption and increase their life time. The PLAXIS finite element software based on phi-c reduction and Slide 5.0 software using Bishop simplified method based on limit equilibrium were obtained to analyses the stability of full-scale test embankment on soft ground. The results of factors of safety were compared to confirm the applications of Kenaf LLGs. Consequently, this study confirms that the Kenaf LLGs can be applied for short term applications in order to improve the stability of embankment on soft clay.

抄録全体を表示

Bearing reinforcement, which is composed of a longitudinal member (steel deformed bar) and transverse (bearing) members (a set of equal angle steel), has been established as an effective earth reinforcement material. The equation for estimating the pullout resistance of this reinforcement in coarse-grained soils has been previously developed but not for fine-grained soil. Claystone soil, abundant in Mae Moh mine, is a fine-grained material when crushed and compacted. It was proposed to be a backfill material in the Bearing Reinforcement Earth (BRE) wall for mining activities. The pullout resistance mechanism of the bearing reinforcement embedded in the claystone soil is presented in this paper. The total pullout resistance is the sum of the pullout friction and bearing resistances. The pullout friction resistance is approximated from soil shear strength and interaction factor . The bearing pullout resistance of a single isolated transverse member can be approximated from the punching shear mechanism. The transverse member interference is classified into three zones, depending upon spacing and dimension of transverse member, S/B ratio. Based on a critical analysis of the test results, the pullout resistance equations for bearing reinforcement with different normal stresses, dimensions and spacing of transverse members embedded in claystone soils compacted at optimum point (optimum water content and maximum dry unit weight) are developed in term of total strength parameters.

抄録全体を表示

After decades of application of the modern composite material geogrid reinforced soil, its design can still be improved. With the development of increasingly strong techniques of numerical modeling (finite element or finite difference methods), attention is refocusing on correct modeling of the complex interaction behavior between the two materials as its description with common interface models has been unsatisfactory so far. A sophisticated large-scale biaxial compression test device at RWTH Aachen University with a transparent side wall has been developed, allowing the quantitative investigation of the soil-geogrid interaction mechanisms. In this study, a special test series of specimens, reinforced with geogrid samples with different numbers of longitudinal and transverse tensile members, is used to quantify the effects of the load transfer mechanisms on the global stress-strain behavior. Additionally, an interaction model, recently developed for pullout situations that explicitly takes into account the separate load transfer mechanisms, is transferred to the plane strain conditions of biaxial compression tests. First results, presented in this paper, are promising and show that the model is capable of describing the complex interaction between geogrid and soil.

抄録全体を表示

Geosynthetic is gaining attraction in civil engineering. Wrapping soils in geotextile bags (soilbag) as earth reinforcement gives astonishing rise in bearing capacity. To understand the fundamental mechanism and facilitate the development of soilbag’s constitutive relation, the authors develop and validate a computational model for studying the micro-mechanical behavior of soilbag using the Discrete Element Method (DEM). Plate loading on a woven geotextile bag is considered. Spatial difference in the wrapped soil’s stress states and fabric anisotropies due to geometrical and mechanical reasons are investigated. Linear and symmetrical stress paths are found at different probed locations. Upon the rupture of the woven structure, the geometrical fabric anisotropy is high and persistent. Analyzing the evolutions of the fabric anisotropies due to normal and tangential force and their relation with the geometrical fabric anisotropy help unveil the first and secondary mechanism of such reinforcement method, i.e. confinement and interlocking.

抄録全体を表示

This study evaluates the use of Electro-Kinetic (EK) techniques and geotextiles to dehydrate high water content sludge obtained from a local watershed reservoir. A model test provided the de-hydration process for the high water content sludge using a geo-bag and electro-kinetic technique. Different electrode metal materials with various setups and different voltages were used in this study. The liquid limits and plastic index of the sludge mud are 33% and 10%, respectively. Geo-bags were made from a polyester multi-filament geotextile. The diameter and height of the geo-bags are 24 cm and 36 cm, respectively. The preliminary study indicated that PET geotextile geo-bag is a good filtration material for high water content sludge for dehydration applications. Steel and aluminum are very corrosive materials for this process. Low de-hydration rates were obtained using a copper rod as the anode electrode. Stainless steel is a corrosion resistance material with a good dehydration performance. Using a single stainless steel rod with 60V for EK dehydration process would reduce the water content from 100% to around 50% within 4-8 hours. The decrease in electrode distance with increasing number of electrodes would increase the dehydration process efficiency. The results from this study can be a valuable reference for developing geotextiles with electro-kinetic techniques for full scale sludge dehydration applications.

抄録全体を表示

The authors have proposed a simple design method of the VD using PBD materials for horizontal drainage. This design method is the comparison of the required flow volume qA calculated from a Barron type equation and the drainable amount qV computed by solving simultaneous equation of the flow network. It was obvious that the measurement of flow quantity of the actual drain networks was important to prove the validity of this design method. Therefore, the flow quantity in the PBD network was measured in the PBD construction site of Osaka Bay area by applying temperature change of the flow water. As the results of this research, the followings were obtained;1) It was proved to be applicable to measure flow quantity in PBD material from the two sets of thermocouples inserted.2) As a result of observation, the measured value of the flow quantity in PBD was close to the predicted one especially for a vertical drain part. 3) It seems that the network of the vertical and horizontal PBD drain works effectively and consolidation is promoted smoothly. This means the use of PBD material as a substitute of sand mat might be practical for vertical drain method.

抄録全体を表示