Applied Mechanics and Materials Vols. 170-173

Abstract: A compound method which includes overall site stability analysis, stratum stability analysis on deep excavation boundary and 3D FEM is proposed to evaluate the effect of building settlement due to adjacent deep excavation. A typical deep excavation project was used to evaluate the feasibility of the compound method. The analysis results indicate the ground stability analysis is useful to understand the stratum situation of deep excavation and adjacent area. In 3D FEM, undulate stratum can simulate the supporting system of more accurately. The compound method brings a new analysis method for foundation pit project in complex environment and complex geological conditions.

Abstract: The stress-strain of triaxial rheological test for rock can be divided into three stages: initial attenuation rheological stabilization rheoligical and speedup rheological stages, the damage is rapid increased in the speedup stage. Damage mechanics is introduced into the Nishihara rheological model, a new rheological constitutive model is established which is combined with the concept of effective stress. The mechanical parameters are recognized by the experimental test data of greenschist. Computing result shows that, the presented model can described the mechanical characteristics in different rheological stage very well, and the error between simulated result and test data is small.

Abstract: Hierarchical genetic algorithm (HGA) are widely used in most engineering, this paper aims to propose an optimization model of soil-nail bracing by application the hierarchical genetic algorithm. In the process of optimization, soil nailing cost is setted as the objective function and the internal overall stability of the soil nailing is setted as primary controlling factor. Finally, an example is cited to verify the optimization model. By comparison the traditional genetic algorithm with the HGA, it is concluded that HGA optimization model of soil-nail bracing gets better economic effect.

Abstract: It is difficult to operate on the hydraulic-filled mucky soil foundation which the water content is high, so the vacuum preloading method with no sand cushion is used to deal with the foundation in some areas in China. Although there are still many problems in it’s application, such as, the effective range of the prefabricated vertical drains(PVDs) is small, the surrounding soil is easy to be accumulated and the soil strength increases little. For these problems, a laboratory model test on dredger fills made from the 4th layer of the Shanghai mucky soil by vacuum preloading with no sand cushion is performed. The changes and distributions in the settlement, water contents, permeability, plasticity index and grain composition of the dredger fill are studied in the process of the vacuum preloading. It is found that the water contents and permeability of the soft clay near the PVD (the diameter is about 40 to 50cm) are much lower than the outside, while the content of fine particles, plasticity index and soil strength near the PVD is much higher than the others. The measured data shows that the fine particles gather to a soil column at the center of the PVD under the action of vacuum negative pressure, then the permeability and the grain composition of the soil around the PVD is changed. As a result, soil parameters are not evenly distributed. Finally, some suggestions about how to reduce the non-uniformity are proposed.

Abstract: In the premise of mechanics model and the kinetic equation, the numerical simulation model of pile-soil system has been established with MATLAB, and the numerical analytic solution of kinetic equation has been got by fourth-order Runge-Kutta. And the relationship curves between the pile-soil interface’s friction and time, displacement, acceleration and velocity of the pile have been mainly studied when the exciting amplitude is 100kN, 200kN respectively. With the work, the exciting amplitude will be obtained. In this way, the friction of the pile-soil can be decreased and work efficiency can be improved; besides this paper can also provide a further theoretical basis of pile pressing machine's dynamic optimization.

Abstract: Generally, it is difficult to control the trench stability and panel joint permeability in the construction of a diaphragm wall. The high construction cost is inevitable because of the environmental pollution due to the slurry, waste of water consumption, and debris disposal treatment. A new technique, called the dry trenching diaphragm wall with self-guided double-rectangular-casing, is thereafter developed in the current study to avoid these problems. In this technique, two pieces of rectangular steel casing are driven in sequence and guided each other. The trench is made by squeezing into the soft soil. The panel alignment and straightness are assured without any joints due to the dry concrete pouring instead of the influences of the slurry. Compared to the regular diaphragm wall, the technique is an environment-friendly, less emissive and energy-conserved one by eliminating the slurry pollution with the low cost. It shows that the quality of panel connection is reliable, and the permeation-proof performance is superior with high efficiency in wall-forming due to non-joint interlocking.

Abstract: The liquefaction of soil around the pile and the friction resistance between the pile-soil may be greatly affected by the various vibration conditions in the process of vibration piling. The efficiency of the pile may be affected by the above situation. And how to increase the piling speed is the key component studied in related field. The plane contact element is adapted in this paper to establish the system of pile-soil dynamics model. The piling process is simulated by changing the parameters such as, the amplitude and frequency of vibration force, and the stiffness and damping of soil. Then the influence on piling speed by every parameter can be studied. The way to raise piling speed can be achieved, and it provides theoretical guidance for practical application.

Abstract: In many fields such as scientific experiment, economic analysis, etc, the exact measurement of the variables is difficult to obtain owing to the effects of various kinds of factors. In the application of economics, the relationship between the variables is too complex. The problem of dealing with the observed variables with measurement errors has been a vexing problem. In this paper, the estimation method of the capital asset pricing model with measurement errors is given, which effectively solves the problem that variables can not be observed precisely in the capital asset pricing model. The empirical analysis is presented.

Abstract: Present research results have verified the significant soil reinforcement effect of dewatering. But the reinforcement effect of dewatering suffers ignorance in current excavation design process due to lack of systematic experimental study on the strengthening mechanism, causing a certain amount of waste. This paper first theoretically describes the relationship between the increase of soil shear strength and that of compression modulus owing to pumping, then investigates the influence of well-point pumping on Shanghai soil’s shear strength and deformation properties through indoor test. The results may provide useful suggestions for future excavation support design.

Abstract: Based on stress distribution characteristics of pressure-dispersive ground anchor, a new construction equipment was developed for sub-expanding, thus the effective diameter of anchoring body was enlarged, the anchoring capacity was enhanced and the project cost was saved. With on site pull-out test of this type anchor, the study on anchoring mechanism and its application value showed that it could greatly improve the safety and reliability of the anchoring technology.