Advanced Materials Research Vols. 446-449

Abstract: Gravity forces can significantly affect the support pressure required for equilibrium of a tunnel, especially in shallow tunnels, weak materials and/or large excavations. In the present paper, the calculation model is founded by FLAC3D, to study the effect of tunnel excavation to the rock mass. In the modeling, different types of material are considered, and different loads are considered. And finally, the effect of grouting in tunnel is studied to compare the shear strain increment and vertical displacement of rock mass.

Abstract: Roadway insulation and active cooling supporting structure is a complex system, and the mechanical properties play an important roal in its safety. Analyse the shotcrete layer pattern heat insulation structure by Midas-GTS software, calculation results shows that tensile stress zone appears in the top and bottom of heat insulation layer, while the will compressive stress area appears in two sides of the roadway insulation layer; in the case of 500m buried depth, heat insulation layer material, such as vitreous micro-bead, can well meet the engineering mechanical strength requirements.

Abstract: In this paper, Dongrong mine encountered soft rock geological problems as the research object, from the field investigation, laboratory analysis, program design and numerical simulation of four aspects of the problem spread out concrete research. Combining engineering geological conditions and scene construction condition, adopt big deformation nonlinearity theory and design procedures. Study the instability of soft rock tunnel, rock mineral composition and structure. Soft rock tunnel shoring method has carried out the three-dimensional numerical simulation.Studies have shown that pre-stressed anchor supporting technology can effectively control the roof deformation, single-arch bottom floor heave phenomenon can be reduced.

Abstract: In this paper, by using the nonlinear winkle foundation beam model the theory pile load displacement curve that corresponding to the model test were calculated, which were compared to the model test results, When this approach, the k used in winkle foundation beam model is the same in model test. According to this method the relationship between the soil force modulus coefficient k and the weakening compressive strength of pile diameter of 0.042 m and 0.02 m were determined, which combined with the value calculation results of other different pile diameter by 3 d finite element ,then the equation of k of different pile diameter and soil strength were determined.

Abstract: Cambridge model gets the extensive application, which has advantages of rigorous theoretical derivation and model parameters which can entirely be obtained by triaxial tests, while it has deficiencies of the narrow applicative scope and describing the dilatancy hardly. As the most widely used strength theory, Mohr-Coulomb model can directly represent shear strength of soil material simply, without consideration for compression deformation yet. On account of the critical state of dilatancy defined comprehensively, this paper based on the description of dilatancy combines the advantage of Cambridge model and Mohr-Coulomb strength theory, applying to compression deformation and conciseness of Mohr-coulomb model, reflecting shear deformation and puts forward an elastic-plastic model—Coulomb-Cam model. At last, this constitutive model, proved by the contrast of numerical simulation and GDS triaxial tests is of the priority in representing the dilatancy and work-softening rationally.

Abstract: The study collected a great deal of testing data, including the physical properties of soil before dynamic compaction and in-situ test and laboratory test data after dynamic consolidation, from twenty-eight engineering practices about dynamic consolidation granite residual soils(GRS) backfill foundation in power construction in Guangdong province over the past fifteen years. The backfill were classified into three types according to the fraction of soil, the corresponding foundations were classified into three types too. Base on the plate loading testing (PLT), the suitability of testing the bearing capacity and deformation modulus of dynamic Consolidation backfill foundation, by dynamic penetrating testing (DPT), standard penetrating testing (SPT) and laboratory soil testing (LST), were evaluated. The statistic relationships between SPT, DPT blow count and the bearing capacity, deformation modulus of dynamic consolidation backfill foundation were also generalized; as well as the factors influent the testing results were analyzed. And the accuracy of adopting two common region specifications to determine the bearing capacity and deformation modulus were analyzes. This article has some reference value on ground treatment detection of dynamic consolidation backfill foundation with similar engineering geological conditions.

Abstract: Based on deep in-situ stresses measurement data in new and old mines of Huainan mining area, in-situ stresses characteristic is researched by statistical analysis with multiple methods. Research results indicate that in-situ stresses of deep rock mass in Huainan mining area are located at high level. Scatter plots of vertical stresses, horizontal principal stresses and lateral pressure ratios variation with depth are presented, then, respective regression equation is obtained. The statistical results are helpful to finding out macroscopical characteristic of deep in-situ stresses field in Huainan mining area. The research results can also provide important reference frame for design and computation of underground caverns in Huainan mining area.

Abstract: A practical saturated sand elastic-plastic dynamic constitutive model was developed on the base of Handin-Drnevich class nonlinear lag model and multidimensional model. In this model, during the calculation of loading before soil reaches yielding, unloading and inverse loading, corrected Handin-Drnevich equivalent nonlinear model was adopted; after soil yielding, based on the idea of multidimensional model, the composite hardening law which combines isotropy hardening and follow-up hardening, corrected Mohr-Coulomb yielding criterion and correlation flow principle were adopted. A fully coupled three dimension effective stress dynamic analysis procedure was developed on the base of this model. The seismic response of liquefaction foundation reinforced by stone columns was analyzed by the developed procedure. The research shows that with the diameter of stone columns increasing, the excess pore water pressure in soil between piles decreases; with the spacing of columns increasing, the excess pore water pressure increases. The influence of both is major in middle and lower level of composite foundation.

Abstract: In order to research matrix suction how to influence the shear strengt of unsaturated silty sand. Based on the analysis of the Soil-water characteristic of unsaturated silty sand through pressure plate instrument test,the suction control direct shear tests under the different suction condition of unsaturated silty sand are studied. And then, the microscopic structure of two kinds soil sample with different water content are scanned to analyze the relationship between the matrix suction and the shear strengt of unsaturated silty sand. The results of the research show that unsaturated silty sand different from unsaturated clayey soil.When water content gradually reduce, the soil shear strength of unsaturated silty sand is not always increased with the increase of matrix suction, but there is a "peak effect".The appearance of "peak effect" is due to unsaturated silty sand has own microstructure characteristics.On the other hand, when the moisture content reduction constantly,the existence form of moisture change gradually.The two factors lead to the effect area of matrix suction change constantly,and then influence shear strengt of unsaturated silty sand to appear "peak effect". In addition,the stress environment also can influence contribution degree of matrix suction to the shear strengt of unsaturated silty sand.

Abstract: The non-mining damage of shaft liner in deep and thick overburden occurred frequently in China. This causes heavy losses to the coal industry in China. The paper had a discussion on theories that explain the breaking mechanism of the mine shaft liner. As pointed out, the mining activities could make underground water table dropping and the strata consolidation and compaction could cause the overburden subsidence. Therefore a vertical additional force would be affected on the mine shaft liner and the vertical additional force would be the main factor to cause breakings on the mine shaft liner. According to the cause, the paper holds that a monitoring system should be built to monitor the additional strain of the mine shaft liner. Based on the analysis of these data, the safety of the mine shaft liner can be accuracy evaluated and timely forecasted. Therefore the mine liner breaking could be prevented before fracture by decreasing the vertical force or strengthening mine shaft liner.