Advanced Materials Research Vols. 261-263

Abstract: The characters on double-row pile retaining structures are affected significantly by spatial effects. In this paper, double-row pile retaining structures are simulated numerically in three-dimension by finite element software PLAXIS. The behavior differences among piles in different positions around the foundation pit are analyzed. The results show that the deformation and moment are biggest in the middle of long side of the foundation pit. It is suggested that the earth pressure between the rows above the pit bottom is close to active earth pressure.

Abstract: Based on self-designed flume model device of sandy debris flow, the experiments under artificial rainfall were carried out to study the debris flow failure mode of different grain size. By using the Digital Photogrammetry for Deformation Measurement GEODOG, the failure process and displacement field of sandy debris flow were analyzed. The studies indicate that the failure mode of medium sand is Retrogressive Toe Sliding as the movement of particle concentrated on sand anterior of flume model. The failure mode of fine sand is Flow-slide Failure as the movement of particle concentrated on sand in the rear of flume model.

Abstract: Physical model test about the interaction between tunnel structure and soil under circler tunnel crossing the ground fissure belt with 60° was carried out, measuring the longitudinal strains of structure, the relative displacement at the bottom of the tunnel and the surrounding rock pressure. The test results show the deformation on the tunnel structure with circular cross-section is a composition of bending, shearing and twisting. The main deformation in first stage of settlement is bending, but the twisting deformation is more outstanding after the void appears at the bottom of the tunnel. Structural deformation in hanging wall is larger than that of the footwall, whereas structural stress in footwall is larger than that of the hanging wall. The segmentation of lining tunnel structure should be utilized to fit the distortion, bending and shearing in the metro tunnel aslant crossing the ground fissure belt. Twisting action should be considered in the structural design, and the tunnel structure in footwall should be strengthened by using high-performance concrete.

Abstract: Based on field settlement monitoring data in construction of Hangzhou Qiantang River tunnel, the settlements of the embankment induced by two shields respectively were compared. The study shows that: 1.The settlements of the embankment induced by the west shield are larger, which are accounted for sustained rainfall, severe fluctuation of the chamber pressure, lack of construction experience and worse control of shield driving parameters. 2. Peck equation is applicable to settlement fitting in this case history. Trough back-analysis, the traverse tough-width parameter and ground volume loss range from 0.33 to 0.47, 0.99% to 1.57% respectively for the embankment settlements above the west tunnel, and from 0.24 to 0.34, 0.25% to 0.52% for the east tunnel. 3. Good control of shield driving parameters contributes to small disturbance to surrounding soils, thereby decreasing the induced settlements of the embankment.

Abstract: The liquefaction for saturated silty foundation can be usually incurred under dynamic loading, such as vehicular loading and earthquakes. The silty soil liquefaction caused by earthquake is mostly the direct reason for the foundation invalidation and the structure collapse. To analyze the liquefaction behavior of saturated silty soil from Anhui Province under high seismic shock, a series of dynamic triaxial tests are carried out under the given density of remolded saturated silt with different confining pressure conditions varying from 1 m to 10 m depth in the laboratory. The increasing law of liquefaction resistance of the remolded saturated silt in Anhui province, dynamic intensity and the process of excess pore pressure are obtained from the dynamic triaxial test research. Meanwhile, the maximum liquefaction depth and the dynamic deformation properties are also illuminated based on dynamic triaxial tests, which can provide scientific data to further make engineering measures preventing the silty foundation from liquefying.

Abstract: Based on the Catastrophe Theory, the catastrophe model of rock destabilization educed by equilibrium relation of work-energy increment from energy conservation principle belongs to the fold catastrophe model. Condition and process of rock destabilization were analyzed, and rock destabilization critical condition was given, the end of rock destabilization is confirmed strictly. The energy importing rate J=0,system destabilization critical condition, implicates Cook stiffness criterion, Using energy importing rate, understanding in the stability of rock stability can be improved from qualitative understanding to quantitative description. The elastic energy releasing illustration given in paper contain rich amount of information and have great significance in understanding the behavior and law of rock destabilization.

Abstract: This paper introduces a variable-interval method that automatically selects the most suitable ground points along the longitudinal road alignment, with variable intervals between successive ground points. The accuracy of the total earthwork volume using cross sections at these selected locations will be more accurate. A genetic algorithm with a least squares objective function is used to locate the most suitable ground points.

Abstract: Clay soils and their related behavior has always been the subject of many studies. Recent researches show some interests in investigation of inclusion of randomly distributed fiber in clay. Reinforcing subgarde in pavement systems has always been an issue. This study focuses on effect of fiber inclusion on the strength of subgrade material. Natural fiber was used for this investigation. Fiber contents and length have been changed during these tests. The fiber percentage varied from 0 % (for unreinforced samples) to 3% and fiber length varied from 15mm to 65mm. In addition, as the other alternative 0.5% cement material was put in fiber composite to see the performance of composite. Clay was selected as soil. Triaxial Consolidated Undrained (CU) compression tests were carried out to investigate behavior of the composite under different condition. The fiber length and fiber content found to play important rule on the strength of fiber reinforced composite. Furthermore it was observed that ductility of sample increased by fiber inclusion. Cement percentage also found to be a good tool to stabilize soil composite.

Abstract: Composite soils have been widely used in civil engineering applications, especially in slopes, embankment dam and landfills. This paper aims to investigate effect of fiber inclusion on compaction characteristic of composite soil (i.e. clay composite). A series of laboratory tests carried out to evaluate fiber effect on optimum water content and maximum dry unit weight of composite soils. Clay was selected as soil part of the composite and plastic fiber was used as reinforcement. The fiber parameters differed from one test to another, as fiber length varied from 10 mm to 35mm and fiber content were selected as 0.1% and 0.4%. For each test, compaction curved derived and the results were compared. The results proved that inclusion of fiber affected compaction behaviour of samples so that increasing in fiber content and length caused increasing in Optimum Moisture Content (OMC) and slightly decreased maximum dry unit weight.

Abstract: Reinforced soil has been among the most effective soil modification materials. Its use has been expanded rapidly into civil engineering, geotechnical engineering and pavement engineering. Reinforcing subgarde in pavement systems has always been an issue. This study focuses on effect of fibre inclusion on the modulus of elasticity of subgrade material. Plastic fibre was used for this investigation. Fibre contents and aspect ratio have been changed during these tests. The fibre percentage varied from 0 % (for unreinforced samples) to 3%. Clay was used as sub grade material. Unconfined compression tests were carried out to investigate behaviour of the composite under different condition. The fibre length and fibre content found to play important rule on the modulus of elasticity of fibre. Furthermore it was observed that ductility of sample increased by fibre inclusion.