Advanced Materials Research Vols. 261-263

Abstract: A modified shear displacement method is presented to analyze the load-settlement response of a single pile in homogenous soil using two models. One model adopts a hyperbolic model to simulate the stress-strain relationship of soil under shear stress before failure occurs, and the other model uses a non-linear stress-strain relationship to evaluate the load-displacement behavior of the soil beneath the pile base. Comparisons of the load-settlement responses between the present modified model and the model suggested by Randolph and Wroth are given to demonstrate the effectiveness and accuracy of the proposed modified method.

Abstract: The excavation of deep foundation pit is very complex in the field of geotechnical engineering, how to control the deformation of deep foundation pit and protect the environment is of great significance. This paper analyzed the deformation mechanism of pile-anchor joint supporting structure in detail, established a model for deformation controlling based on the reliability theory, and then analyzed the sensitivities of prestressed, pile stiffness, spacing and soil properties to foundation deformation. Combined with an engineering example, this paper verifies the stability and effectiveness of the model for deformation controlling. This study will provide some reference to similar projects.

Abstract: Three-dimensional (3D) analytical solution of soil deformation induced by ground loss in shield tunnelling construction was researched. It is put forward that the ground loss ratio is not a fixed value, but changes in driving direction. The calculation formula of ground loss ratio in driving direction was deduced. Based on two-dimensional (2D) analytical solution of uniform ground movement model of shield tunnelling, the three-dimensional analytical solution of ground deformation induced by ground loss is deduced. The settlement in vertical direction and the displacement in lateral horizontal direction at any point can be calculated; and the method is only applied to the construction phase. In analytical calculation: the predicted soil displacements are in good agreement with the measured values, and the method is easy to use; the closer the soil to tunnel is, the faster the lateral horizontal displacement changes; the extent of change of lateral horizontal displacement in longitudinal direction is smaller than displacement in lateral direction.

Abstract: When the full weathered granite is regarded as highway subgrade filling material, it is restricted to the application because of its high mica content, lax construction, bad water stability, and small cohesion. For these reasons, the full weathered granite soil should be improved before using for subgrade filling, and the cement was taken as an improver in this paper. The dynamic and static characteristics of cement stabilized soils were studied systemically. It was shown from the experiment results that there is a decrease in the content of mica and clay, and an increase of quattz of the cement stabilized soils. The unconfined strength of the cement stabilized full weathered granite increases linearly with the increase in cement content. There is power function relationship between water stability coefficient and the cement content. The unconfined strength and water stability coefficient increases with degree of compaction and with age as well, while the increasing rate decrease with age. The dynamic strength of the cement stabilized full weathered granite increased with the increase of the degree of compaction and the cement content. However, as the water content increases, the dynamic strength increased first and then decreases, there is an optimum moisture content. A linear model was proposed to describe the dynamic modulus and dynamic relationship between the stress amplitude. The results can provide an important reference for engineering practice.

Abstract: Thermal properties are very important physical indices of soils which could be applied to estimate the thermal capacity of environmental control system of underground infrastructures. At present, the existing ideal prediction models of thermal conductivity were not suitable for soil which in fact had very complicated internal fabric. For this purpose, SEM images of soil specimens were taken and digitized with binarizing process by using self-developed software package – ImgAnsys for image analysis, and the treated images were successfully input into ANSYS and analyzed based on the two-dimensional heat transient transferring model. It was found that the simulating results were closely consistent with experimental results, which could illustrate the feasibility of this new experimental method.

Abstract: Red clay soil is widely distributed in south China, the microstructure of red clay soil was studied applying scanning electron microscopy (SEM), and the X-ray diffraction analysis (XRD) test found that a large number of swelling inducing minerals, for example, montmorillonite, illite-montmorillonite or chlorite-smectite were contained in the red clay soil. Shield tunneling in this kind of stratum is prone to arising “cake” and “arch” phenomena and it prone to lead screw conveyor device unsmooth dumping, so soil improvement measures must be taken. Foam as the most advanced soil conditioner has been widely used in shield construction. Using self-developed foam agent, experimental research on foam conditioning red clay soil was carried out, test results show that foam can not only significantly reduce the soil shear strength, but also can greatly enhance the soil's compressibility and fluidity, which is significant for the smooth dumping and excavation face stability maintenance.

Abstract: Criterion and classification are two important content of swelling soft rock research. On the basis of the study of predecessors’ achievements, the percentage of hydrophilic minerals is considered as a key index of the new standard, and the saturated water absorption, limit swelling increment, limit swelling force are considered as main indexes. Finally, the new standard is used to analyze and study on the projects in references.

Abstract: Appraisal of dam slope safety is essential for security and stability of the dyke that has been constructed for many years. According to the requirements of the appraisal of dam safety, the stability analysis of slope of Shegang dyke has been carried out by using Sweden circular-arc method, Bishop method, Engineer Corps method and Lowe method four methods under many kinds of working conditions and some conditions when the saturation line raising. Combined with the design code form embankment dam, the calculation results can be analyzed. The analysis can show that the security indexes of anti-slide under four kinds of working conditions and some conditions when the saturation line raising meet the requirements of the design code. This can provide basis for the reinforcement design of the dam, which also has a certain directive significance for the safe operation and observation of the dam in the future.

Abstract: The landslides of expansive rock cutting slope was the most serious and difficultly treating engineering problem for highway construction. The K9+600-K10+800 section of Beijing Western Sixth Ring highway was an expansive rock deep cutting slope, the problem of which was firstly encountered for Beijing highway construction. In this paper, the causes and characteristics of expansive rock slope failure were analyzed based on the engineering geology and rock properties of this section. In addition, the geogrid reinforced flexible supporting treatment measure was presented and its design scheme and construction approach were introduced. This method with the characteristics of “preserving moisture and antiseepage” and “softness and hardness” could resolve this kind of expansive rock slope problem effectively and economically.

Abstract: By combining indoor model experiment and numerical simulation, the analysis of pile-bucket foundation bearing capacity under pressure load was conducted, and the bearing capacity can be enhanced by enlarging the three main dimensions of pile-bucket foundation: diameter of bucket, height of bucket and length of pile. By enlarging the diameter of bucket by 1.5 times while maintaining the two other dimensions, the bearing capacity can be enhanced by 140%;the bearing capacity can be enhanced by 15% when the height of bucket is enlarged by 2 times; the bearing capacity can be enhanced by 14% when the pile length is enlarged by 30% ,that means the variation of bucket diameter affects the pile-bucket foundation bearing capacity most, apart from that the variation of bucket diameter also holds the most obvious effect on the ground foundation soil body in crosswise scope, the bucket diameter of 3# pile-bucket was 1.5 times that of 1# pile-bucket, after the surrounding soil broke, the influence scope on crosswise soil surface was enhanced by the size 3.8 times breadth of bucket diameter; and the pile-length variation keeps the largest effect on surrounding soil body in-depth, the depth of effect on grounding soil of 1#pile-bucket is enlarged by 925mm comparing by 2#pile-bucket (approximately 9 times of bucket diameter) ; By conducting indoor-model pressure bearing capacity experiment on pile –bucket foundation,bucket foundation and circular-shape shallow foundation with same diameter, the limiting bearing capacity of pile-bucket foundation is 3.2 times that of circular-shape shallow foundation and 1.26 times that of bucket foundation, a manifestation of the bearing capacity advantage of pile-bucket foundation.