Advanced Materials Research Vols. 243-249

Abstract: This study is expected to research the performance, behaviors and strength of soil nailing by field test, based on the engineering of soil nailing wall protection with the high and steep bedding stone cutting in Chong Qing - Huai Hua Railway in China. We test the nail force of different station on different row soil nailing with vibrating reinforcing meter. Some conclusion elicited such as the rule of nail force with nail length and time, the potential sliding surface and the rule of soil nailing wall earth pressure with the height of wall. The test results can be used as reference for the design and construction of soil nailing wall.

Abstract: This For mastering the effect of particle size to strength and deformation characteristics of sand under high pressure, DRS-1 high pressure direct shear test system is used in shear test for 3 groups of sand under pressure of 12 to 15 MPa. Through analysis of the test results, it is obtained that standard sand under high pressure shows strain hardening and volume contraction characteristics. The relationship curves of stress-strain and volume contraction-shear strain appear as hyperbola, they can be simulated by Duncan-Chang hyperbolic model. Sand with small particle size has better group, greater density and higher strength, but the shear contraction is not obvious. Sand with poor group has particle crushing under high pressure, which makes the soil particles rearrange and then the average porosity decreases at the same time large pores disappear, so finally it shows a more significant shear contraction characteristic.

Abstract: At-rest earth pressure codfficient,K₀,is very important in geotechnical engineering design and finite element analysis. At present, it’s treated as a constant usually for given soil in FEM analysis. However recent test results indicate that K₀ of both clay and sand varies with pressure increasing nonlinearly. It’s shown that Duncan-Chang model, a kind of hypoelastic model widely used, can reproduce K₀ varying with pressure. The calculating procedure of K₀ derived from Duncan-Chang’s E-B model is proposed, and then influence of model parameters on calculated K₀ is explored. Studies show that cohesionless soil’s calculated K₀ decreases with pressure increasing, while cohesive soil’s calculated K₀ increases with pressure increasing. Three of the seven model parameters, m, K_b and R_f, have a positive correlation with calculated K₀, and there is a negative correlation between the residual parameters and calculated K₀.The influence of seven model parameters on the calculated K₀ decreases gradually in the following order: m ,n, R_f, φ, c, K, K_b.

Abstract: The cover reverse construction excavation is one of the important construction methods which is used in digging extra-deep foundation system of underground continuous wall supporting. The earth pressure distribution and deformation is distinct from different construction methods. Even if the Construction methods and computer program is homogeneous, the earth pressure and deformation of the calculated showed various results because of different test parameters and different constitutive models, Through the application of practical engineering, The appropriate calculation parameters and constitutive model are found out in Abaqus program which is suitable for earth pressure and deformation of the diaphragm wall in the soft soil area.

Abstract: A stress calculation method has been established for the double layer shaft in special strata. After some simplifications of the mechanical model, the problem was broke down into three subproblems, and a Saint-Venant solution was obtained by solving and adding up each subproblem. An example for certain double layer shaft was presented, and the stress results were compared with the single layer shaft under the same conditions. The fourth strength theory was applied to study the safety of the shafts, and the results show that, the safety for the inner layer of the double layer shaft is better than the single layer shaft, while the safety of the outer layer is relatively worse. We indicate that the application of this double layer shaft is advantageous for the safety production of the mine, and the outer layer of this shaft is the fragile area that needs to be repaired primarily.

Abstract: Creep characteristic is one of the most important mechanical characteristics of rock. It controls the stability of rock engineering. Under step load conditon, the shear creep test of argillaceous siltstone which was collected in dam foundation is performed by using the RMT150c rock and soil mechanics testing machine. The shear creep curves under different normal stresses show that the argillaceous siltstone is very significant in creep, which should be considered in the stability analysis of dam foundation. According to the analysis of experimental results, the long-term shear strength parameters are determined to provide reference for engineering survey and design.

Abstract: The strength and deformation behaviors of unsaturated soil can be approximately described by elasto-plastic constitutive model that was proved by abundance academic and test researches. The Barcelona elastic-plastic model is an excellent model that can simulate the strength and deformation of unsaturated soil. But their calculated result of shear strength is low. So an improved Barcelona model is settled by using drop-shaped shear yield surface and hardening theory of dual stress. The results show that the improved model can more accurately predict the strength and deformation behaviors of unsaturated soil under suction-controlled triaxial compression stress states.

Abstract: The self-boring pressuremeter test has potential advantages over the conventional in situ method in the geotechnical investigation. It not only provides fundamental soil properties for the designer, but also plays more important role in the geotechnical analysis. With help of Cambridge self-boring model pressuremeter tests, some new application are studied in this paper as following: (1) Analysis of stress paths in clays adjacent to the cavity wall during self-boring pressuremeter test; (2) Experimental investigation on stiffness of soils at small strain under non-linear analysis; and (3) Study on magnitude of the changes in pore-water pressure of clays, which will help to enlarge the application of self-boring pressuremeter test in geotechnical engineering.

Abstract: There were better economic and social benefits which the construction wastes were the raw materials of weak foundation treatment. The cast-in-place expanded piles of construction waste showed the advantages of the dynamic replacement and compaction replacement. In the paper, the mechanism, design, construction technology and inspection of weak foundation treatment were studied. The result showed that the cast-in-place expanded piles of construction waste not only could save the cost in the waste transportation, but also decrease the cost in the foundation reinforcement and avoid the land contamination.

Abstract: According to the research status of construction spatial effects in large-long-deep foundation pit: mainly focus on numerical simulation, but theoretical research is not too many by now, a simplified method for calculating the construction spatial effects of large-long-deep foundation pit in cohesive soil was advanced. The soil layers around deep foundation pit were equal to cohesion-less isotropic soil mass by introducing the concept of equivalent internal friction angle. And then, by means of limit equilibrium analysis method combined with soil plasticity upper bound theory and associated flow rule, the spatial effects of two 3D failure modes: tension crack-shear and pure shear in deep foundation pit was studied concretely, and the corresponding formulas of spatial effects coefficient were put forward, also two examples were analyzed. The research results indicates that the method, which can complete by hand-calculation, avoids the defects of low efficiency, high cost and long period in numerical simulation, and the distribution characteristics and value size of spatial effects coefficient could be obtained directly from its calculation results, which can be used as guidance for the supporting structure, construction scheme design and the test points or sections choice in process of information monitoring.