Applied Mechanics and Materials Vols. 353-356

Abstract: Scientific supporting design is of great significance to ensure coal roadway stability. The three-step supporting design method is put forward for coal roadway support: The first step is preliminary design, determine the range of each supporting parameter according to the theoretical calculation and supporting experiences; the second step is numerical simulation calculation, choose the reasonable one through the comparison of schemes; the third step is field monitoring, verify the scheme applicability. After applying the three-step supporting design method to study 3# coal seam roadway in Guandi mine, the optimal supporting scheme is obtained, and good results of underground roadway are achieved, which ensure the stability of roadway surrounding rock. Meanwhile, some rules are summarized which provide references for future roadway supporting design.

Abstract: Based on the theory of the Terzaghi 1-D consolidation and the linear compressibility of soil, a rational method for regionalization of recompression and compression in the distribution of the excess pore-water pressure under overloading-unloading was presented. A simple generalized expression of the ground settlement rate applied to insufficient-load preloading, equal-load preloading, surcharge preloading and a time expression of insufficient-load preloading, surcharge preloading relative to equal-load preloading were further derived. The relationship mechanism of settlement rate and time of insufficient-load preloading, surcharge preloading relative to equal-load preloading are discussed based on the same allowed post-construction settlement.

Abstract: A three-dimensional numerical simulation about gravel pile reinforcing liquefiable silt foundation was built, and the influence of gravel pile on the liquefiable silt anti-liquefaction was discussed. Results show that under seismic load, gravel pile has obvious cushioning effect, and compared with natural foundation, the maximum horizontal vibration acceleration of the gravel pile composite foundation surface layer is obviously decreased; drainage effect of gravel pile is very significant and the larger is the gravel pile permeability coefficient, the better is the drainage effect; as earthquake intensity largens, silt liquefaction scope increases; of both natural foundation and composite foundation, the pore pressure ratio variation with depth is that the middle is bigger than the top and bottom, and middle layers are more likely to be liquefied; the greater is the seismic acceleration, the larger is the shear stress.

Abstract: Based on the triaxial test results of soft soils, an error back propagation network predicting model for deformation property of soft soil is built. Improved BP neural network model is trained by additional momentum term, adaptive learning rate and Bayesian regularization performance function. Research shows that improved BP neural network model applied to predict soft soil foundation settlement, has fast computation, high accuracy, strong generalization ability, and good capability of matching the real data and the measured one. According to test data, the creep models can avoid any artificial assumption of complex constitutive equation, and can reflect nonlinear creep properties of soft soil objectively, thus has better fault-tolerance and more convenient than the traditional method.

Abstract: Mechanical and deformation characteristics of pile-anchor retaining structure was analyzed by using numerical simulation method. The rationality of numerical model was also verified through comparing measured data in field test and numerical results. On the basis of this numerical model, Mechanical and deformation characteristics of supporting structure under the condition of different soil replacement ratio (m) was analyzed. The results show that: mechanical and deformation characteristics of supporting structure was improved by improving soil which behind retaining pile. The higher the soil replacement rate is, the effect to mechanical and deformation characteristics of supporting structure was more obvious.

Abstract: A complex building's excavation has the characteristics of wide excavation area, irregular shape, and partly being surrounded by dense adjacent buildings. In addition, the excavation depths vary in different areas. According to the characteristics of the project and the situations of the construction plan, two schemes are discussed in this paper. Through the discussion, the relations between internal force of the retaining structure, the deformation, the surrounding settlement and the bracing structure are analyzed in details.

Abstract: Damping ditch was dug beside the underground pipeline so as to prevent housing from damage and reduce displacement of underground pipelines caused by dynamic vibration. Different damping ditches were simulated and field measurement was tested. Research shows that vibration and squeezing effect cannot be neglected, and damping ditch can decrease the vibration and squeezing effect. The deeper and nearer to the housing the damping ditch is, the better the damping effect is. The underground pipelines displacement is slight, when the damping ditch is between underground pipelines and tamping points and much closer to the former. Otherwise, if the damping ditch is considerably closer to the tamping points, the displacement is comparatively large.

Abstract: putting out a new pile type, that is, making the precast concrete pile with a vertical side channel and pouring the yellow sand, which lead to the pile had the self-draining function, reduce the soil squeezing effect of precast concrete pile construction in saturated soft clay, that is, the design principles and methods of self-draining pile. Indoor model test showed that the self-draining piles could reduce the pore water pressure, and its effect was obviously, its role is equivalent to sand wells, sand bags wells or plastic drain board, which meet the requirements of the construction technique.

Abstract: Swelling rock has the properties of swelling and creep. Researches on coupling between swelling and creep have not yet been carried out. The expansive Paleogene mudstone is used to laboratory uniaxial compression tests, to find the coupling regularity between swelling and creep under different initial water contents, influent modes and loading methods. For coupling, the creep curves show similar characteristic of non-coupling. The creep deformation increases obviously and the long-term strength decreases comparing with non-coupling. With increasing initial water content, the creep deformation increases for coupling. The creep deformation increases with the enlargement of water-absorption area during the coupling creep. For single-stage and multi-stage loading, the creep regularity is similar to non-coupling. The sample will have a permanent residual deformation when unloaded at the second stable creep stage. The long-term strength of swelling rock is greater than the swelling pressure and the long-term strength is lower than that of non-coupling.

Abstract: According to the actual monitoring data of mining environment and rock burst happening on the 3511 fully-mechanized workface in Anyuan coal mine, the research of the rock burst on the workface and its surrounding rock of gob-side entry is done and the reasonable supporting scheme is determined. The research results are of great guiding importance to the coal mining that has similar condition, provide scientific basis for the control technology of rock burst on the workface and its gob-side entry as well as the reasonable identification of support parameters on the gob-side tunnel, and supply technology protection in order to accelerate the advancing speed of workface. Finally it can produce larger economic benefit.