Abstract: In this paper, Ground deformation in shield tunneling construction is researched. It is put forward that ground deformation is caused by three reasons, which are ground loss, the positive thrust and the friction. By solving the three-part respectively, the three-dimensional solution formula can be obtained after superposing these. This method is used to calculate the tunnel construction phase at any point in the level of vertical settlement and horizontal displacement. As shown in analytical calculation, the predicted ground displacements of this method are in good agreement with the measured values.
Abstract: The stability and failure mode for a 3D vertical slope with transverse earthquake load and surcharge have been an interesting issue, especially in building excavation and wharf engineering. In order to further reveal the seismic and surcharge effect, a three-dimensional elasto-plastic finite element(FE) code combined with a strength reduction procedure is used to yield a factor of safety and failure mode for a vertical slopes under two horizontal direction pseudo-static(PS) coefficient and surcharge on the slope top, respectively. Comparative studies are carried out to investigate the effect of seismic coefficient, surcharge intensity and location on the stability and the failure mechanism for a 3D vertical slope including an inclined weak layer. Several important findings are also achieved.
Abstract: Based on the different methods of computing the soil consolidation coefficient by excess pore pressure dissipation datum on CPTU, through computing the soil consolidation coefficient by different methods on the datum of CPTU model test and CPTU application research on Pearl River Delta, the applicability on different methods of computing consolidation coefficient by CPTU has been studied. The results show that on the computing value of consolidation coefficient, TB10041-2003 is more conservative; because of poor applicability on Strain Path Method and difficulty for obtaining t100 on Zhu-Xiaolin Method and α on Empirical Coefficient Method, some results can not be solved, so Strain Path Method and Zhu-Xiaolin Method and Empirical Coefficient Method are poor in engineering application; the computing way and the computing result on Zhang-Chenghou Method are similar with Torstensson Method with 50% consolidation degree. The achieved result can provide a foundation for further study for CPTU application research.
Abstract: To increase the bearing capacity of piles, the protruding technique proves to be both reliable and effective. The spiral protruding pile is a variation of this kind that can be applied to dry soil conditions. A practical formula is proposed for designing spiral protruding multi-disk cast-in-place piles. Also illustrated here is the project in which spiral protruding piles were applied with great success in terms of techniques and costs, while its unique advantages under certain conditions can be viewed. The paper aims to provide solid basis for research, design and further application of this type of pile.
Abstract: Inbetween the many factors, which will influence the distribution character of initial stress in a mountain, different angle of mountain slopes and horizontal geostress will have important effects on it. Therefore, stress distribution in mountains under different slope angles with considering different lateral coefficients of initial stress is studied using numerical method in here. In this paper, the initial geostress distribution of mountain at typical vertical profiles are studied in the gravity field, with the slope angles being 30°, 45° and 60°, respectively. After the calculation, it can be known that the actual initial vertical stresses may be 2-5 times of the gravitational stresses calculated by direct depth gh for some zones. Meanwhile, it reveals that different horizontal geostress has a momentous impact on it as well. Computation of damage-fracture model for jointed rock is adopted to analyze the rock stability of a cavern. Comparison of the rock stability excavated in a mountain area or under a flat surface is made also.
Abstract: According to the essential features of countertendency fracture rock slopes and the geology condition of engineering. The stability of slope is calculated and evaluated by the following methods, including the stability analysis of slope with multiple-steps and Goodman-Bray's stability analysis of toppling slope. Moreover, we can put forward retaining structure which is based on grid beam, this is rely on results that have calculated according to the above theory, such as the characteristics of slope, parameter of rock and supporting density, and simulation the retaining structure in the method of numerical simulation.
Abstract: The soil-water characteristic defines the relationship between the soil suction and gravimetric water content, w, or the volumetric water content, θ, or the degree of saturation, S. It is a convenient method to predict water content in the subgrade using the curve. But in the field tests of subgrades, the compaction degree of soil became lower with time than initially designed. With the purpose of finding out effect of compaction degree on soil-water characteristic curve, a study to the SWCC (soil-water characteristic curve) of Chongming low liquid limit clay using filter paper method was carried out and is presented in this paper. Specimens of different water contents were prepared by absorbing different amount of water, in order to better simulate the process of wetting of subgrade soil. After the filter paper test, the soil-water characteristic curve was fitted with two models, and then the effect of compaction degree on the curve was analyzed. The figures show that the compaction degree of the specimen will decrease with higher water content, and from the gravimetric water content-matric suction curve, it is found that compaction degree has an effect on air-entry value and water storage capacity.
Abstract: The vertical earth pressure on the top of ditch-buried culverts was analyzed theoretically under the condition of trapezoidal ditch and square culverts. A calculation model to evaluate the earth pressure on the top of the culverts based on Duncan earth model was established. The study results show that the height of plane of equal settlement decreases and turns to a constant gradually as the depth of soil overlying culverts increases. The primary influencing factors of earth pressure are the ditch width and the ratio of height to width of the culverts and the foundation. Each of them can make the coefficient of earth pressure increase or decrease more than 30%. When the width of the culverts become wider, ditch buried culverts turn to projecting buried culverts gradually, and the uniform calculation theory of earth pressure on the top of ditch-buried culverts and positive buried culverts is formed.
Abstract: In mining area, the ground surface level is lowered and curved after the claps of cover-layers of coal-seams evacuated regions. The curvature variation of ground surface causes the variation of contact-surface relation between the structure base and the ground foundation. For this research, the position of maximum curvature variation point is predicted. At this position, for the potentially worst case, the contact-length between structure base and ground foundation is calculated. Then, the internal bending moment within the structure base caused by the ground foundation curvature variation is formulated by taking the contact-length as variable. The results show that the base bending moment is a function of fourth power of contact-length. Based on this result, the critical value of contact-length in mining area is established. Hence, the critical contact-length concept can be taken as a measure of curvature variation in mining area.
Abstract: The finite models of U-steel support, grid steel frame, hollow steel tube support and concrete filled steel tube support were established, of which mechanical property and influencing factor such as bearing capacity, support effect etc. was analyzed. Comparative analysis of economic benefit was carried out through research of material dosage and support effect index. The contractible joint for concrete filled steel tube was designed, and their mechanical characteristic was analyzed through test. The results show that the supporting performance of concrete filled steel tube support is related to confinement coefficient. Compared with traditional support, the concrete filled steel tube support has high bearing capacity, intensive later strength, good ductility, various standards and well economic benefits, and in conjunction with contractible joint, it is able to implement functions of quantitatively increasing resistance and yielding. Properly designed through optimization analysis on associated effects, the concrete filled steel tube support can meet supporting demand of deep soft rock and joint broken rock.