Applied Mechanics and Materials Vols. 353-356

Abstract: The landslides often due to the rainfall and the excavation inside. Although both of them could influenced the stability of the slope, in the different combination of the condition of rainfall and excavation. The results would make a big difference from condition. The analysis results of Finite Element Method have a large difference with the actual situation, especially in the large deformation and landslide. Therefore, we use the Distinct Element Method to simulate and analysis the collapse of Zengziya in Chongqing. We collect different parameters to simulate the changed conditions of the combination of rainfall, half excavation and whole excavation. Then we will get the data of displacement of the rock and the stress redistribution of the slope. By the analysis of the those data, and the comparison from the field situation, we will draw a conclusion that the main factors of the landslides is the rainfall, and the excavation sometimes can simulate the landslides. At last, our research results can make some help of the practical engineering.

Abstract: Through the field vibration measurement of 50m and 80m deep holes under road traffic load, the attenuation law of displacement in holes with depth under traffic and traffic-free conditions was discussed in the time and frequency domains. Some conclusions were drawn as follows: RMS attenuation factor was close to 0.2 and the displacement is obviously reduced at a depth of about 40m; the peak frequency decreased as the depth gradually increased. Compared with the attenuation law in elastic half-space Rayleigh wave, it was found that the horizontal displacement reduced more slowly than the elastic half-space Rayleigh wave and the attenuation factor was gradually close to the attenuation curve of the elastic half-space Rayleigh wave with the increase of the depth; the attenuation factor of the vertical displacement gradually reduced as the depth increased and reduced much faster than elastic half-space Rayleigh wave.

Abstract: Displacement and its grow are critical to the stability of rock slope, in this thesis, by applying Genetic Neural Network to modeling the data obtained by monitoring, the patterns and trends of slope deformation are analyzed and predicted, and therefore supply the reliable basis for slope management.

Abstract: By controlling moisture content to control matrix suction indirectly, three typical unsaturated remolded mixed-soil from west Sichuan are studied by the consolidated untrained triaxial shear test .The test data show that for different kinds of soil samples, the sample with less amount of clay and high content of quartz has bigger internal friction angle relatively, and the sample with hydrophilic mineral and high content of clay has bigger cohesive force. Meanwhile, for the sample without or less hydrophilic mineral, cohesive force is affected mainly by water content, and for the sample with large content of hydrophilic mineral, water content and dry density affect cohesive force together. For a certain sample, the variation of moisture content and dry density affects internal friction angle less, while affects cohesive force more. In addition, the change of internal friction angle resulting from the variation of matrix suction is less, and cohesive force increases as matrix suction increases.

Abstract: Settlement reducing pile foundation has recently been proposed as an important progress in the design theory of pile foundation, which is one type of deformation-based foundations. Compared with the common design method, settlement reducing pile foundation can greatly reduce the number of required piles. Aimed to the influence of pile cap, cushion, pile spacing, pile length on bearing behavior of settlement reducing pile foundation, the indoor tests on steel pipe settlement reducing pile foundation for immersed tunnel were carried out in sand. Based on uniform design, the six groups of tests with 3×4 pile groups were conducted, furthermore, earth pressure, axial force of pile shaft, and foundation settlement were measured. When the load applied increased, the plastic failure of the soil occurred under the corner of immersed tunnel. The result shows that the earth pressure distribution against immersed tunnel is similar to the normal base reaction in sand which is big in the center and small in the border. The correlation analysis result indicates that apply pile cap, reduce cushion thickness, increase pile spacing and increase pile length can increase the pile load sharing ratio. Compared with the average value of correlation coefficient of each influencing factor, pile length has the most remarkable effect on the pile load sharing ratio, then cushion and pile cap, and pile spacing has the minimal effect among these influencing factors. The research can provide a reference for design of relevant projects.

Abstract: A test is conducted to get the soil-water characteristic curve for three typical composite unsaturated soils in west Sichuan, considering its physical composition, physical form and dry density. Test data shows that the variation of physical composition, particle size and dry density can result in great change of soil-water characteristic curve. The bigger the dry density is and the more hydrophilic mineral it has, the more gently the soil-water characteristic curve is, and the higher dry density soil sample has higher residual moisture content. In addition, matrix suction decreased with less clay content and more content under the same water content. For three typical composite unsaturated soils, the change of soil-water characteristic curve resulting from variation of dry density is less in bigger water content, and is more in lower water content.

Abstract: A mechanical behavior of solid waste during foundation pit excavation is discussed on the base of the in-situ monitoring results of earth pressure and field measured data in solid waste. During excavation, the soil strength increases, which is mostly because of the variances of characteristics of soil in unloading state. Measurement of earth pressure is less than computation, and the value gradually decreases during excavation. In the end, it tends to be stable or slightly higher than the minimum. Compared with soft soil, the change is not only related to the deformation but also the change of soil property, especially, the influence of fiber to the shear strength of solid waste. By analyzing changing characteristics of earth pressure in solid waste, from the surface of earth within 0m~5m, experience value of lateral earth pressure coefficient is 0.35 during excavation and 0.25 after excavation, and within 5m~10m, the value is 0.55 during excavation and 0.45 after excavation.The conclusions will provide the reference for future similar projects.

Abstract: According to the highway subgrade engineering construction period serious delaying by rainy climate for a long time in the tropical rainy regions. The key process of the subgrade construction affected by climate is roadbed filling turning. Binding the law of rainy, Considered the continuous available period for filling turning as a random variable to analyze the correlation with its frequency, established the regression formula, the values of correlation coefficient is more than 0.95, shows that the continuous available period for filling turning presents good exponential relationship, A new statistical method of continuous available period for filling turning called selecting time construction concept was put forward. According the feasible probability of the continuous available period for filling turning, put forward a new grade division method for roadbed filling. Optimized the construction organization of the subgrade engineering by the statistical function of continuous available period for roadbed filling turning, and proved its reliability and achievability. Demonstration and reference were provided for the highway construction and local standardization in southern rainy regions.

Abstract: Red-sandstone granular soil reinforced with gabion-mesh is a new concept of composite reinforced soil. In order to reveal the mechanical properties of this composite reinforced soil, a series of laboratory triaxial compression tests on specimens reinforced with gabion-mesh were carried out, and 3D discrete element method was introduced to simulate the triaxial tests. The macro stress-strain relation of red-sandstone specimens reinforced with gabion-mesh was reproduced by the 3D discrete element model. The results show that 3D discrete element method is an ideal technique to study the meso-mechanical nature characteristics of gabion-mesh reinforced red-sandstone granular soil.

Abstract: The bearing capacity of shallow foundations resting on a soil layer with a finite depth over bedrock has been studied for years by many investigators. Farzaneh et al (2010) introduced a rigorous bearing capacity analysis based on the upper bound state theorem, using a log-spiral surface algorithm. This paper presents a thorough evaluation of this collapse mechanism and subsequently, a modified failure mechanism is introduced. The collapse mechanism consists of rigid blocks under combined rotational and transitional movements. The effects of the loading parameters on bearing capacity results are then discussed. The findings of this study are compared with the original limit state mechanism as well as previously published solutions, emphasising the accuracy and efficiency of the modified mechanisms. Furthermore, parametric studies are carried out to evaluate the ultimate bearing capacity of shallow foundations resting on a restricted soil, layer using the proposed mechanism. Design tables are finally presented for practical use in geotechnical engineering.