Applied Mechanics and Materials Vols. 353-356

Abstract: For exploring the attenuation law of limestone dynamic elastic modulus (DEM) under fatigue cyclic loading, 24 limestone specimens were used to conduct dynamic uniaxial cyclic compressive tests under different loading frequencies and stress amplitudes on MTS Test System. The tests results confirmed that the decrease of DEM goes through three different stages with the increase of cyclic numbers. And, there is no distinct correlation between three-stage evolution rule of DEM and frequencies as well as stress amplitudes. The degeneration of DEM is caused by accumulation of micro-cracks and damage increase in rock specimen. Thus, based on attenuation rule of DEM, a fatigue damage evolution model which can depict the first two stages of limestone fatigue damage development was proposed.

Abstract: Simulated electric field distribution in concrete by using of ANSYS finite element analysis software, researched influences of some factors on electric field strength and electric potential in concrete. Which include resistivity of cement soil and its electric field strength are inversely proportional and the electric potential distribution is less affected by resistivity changes, applied voltage is proportional to electric field strength and potential, the more the number of cathode induces the greater and uniform of the strength, electric field distribution within cement soil becomes sparse and its values are relatively smaller with the anode spacing increasing, electric field strength of cement-soil is more intensive and its distribution is more uniform and also its values is relatively larger with the decreasing of cathode spacing.

Abstract: Characteristic analysis of rainfall variation can offer technical support to flood prevention. Based on annual precipitation data of eleven major stations in Zhuzhaoxin River Basin from 1964 to 2008, Kendall method was applied to analyze the evolution tendency. Moving t-test and orderly clustering analysis method were discussed with sudden change points. Then spectrum density graph of variance was used to analyze precipitation variation period. The result showed that the variation of rainfall was obvious; the sudden change points occurred in 1976, 1986 and 2002; Precipitation variation periods were three years and seven years.

Abstract: Open-mining forms high steep rock slope, slope stability is affected by geological environment, structure, stratum, lithology, hydro-geology, rock structure, structural plane appearance, slope azimuth with spatial combination relations. After mining the bared slope with weathering, due to heavy rainfall, earthquake and other factors causes secondary disasters and serious impact on people's life and property safety. This paper is based on a comprehensive investigation, statistic and classification of the status quo and failure patterns of the rock slope and treatment method is simulated and analyzed, pros and cons of various treatment methods were compared, to provide the decision-making reference for similar mines management, and basis of theory and practice , to build green mines and sustainable environment.

Abstract: This article describes the pumping test procedures and test results of the subway project 30m deep excavation dewatering in thick aquifer. A groundwater three-dimensional seepage numerical calculation model is established. We use the model to calculate and compare the calculated results and the actual results, obtain hydrogeological parameters by inversion. Further, we have a numerical simulation study on deep excavation dewatering with the hydrogeological parameters, the Simulation results and excavation pre-dewatering test results are consistent. Test results show that the model can reflect the deep excavation dewatering process with complex geological conditions.

Abstract: According to large deformation and supporting problem ofroadway surrounding rock under deep high stress caused by broken-expanddeformation, supporting numerical simulation and optimization on a roadway werestudied. Two primary support scheme of medium length anchor with self-drillinganchor and short pre-stressed anchor withself-drilling anchor and three secondary support scheme of 5m, 6mand 7m length cable were proposedbased on roadway engineering characteristics; Calculationparameters of support structureparameters and surrounding rock were determined based on broken-expanddeformation mechanism, and scheme were calculated respectively; Deformation, plasticzone and stable state of surrounding rock under different support were analyzedbased on results individually, and optimal support scheme were opted. Theresults showed that roadway used 5.5~6.0manchor cable as secondary support whose stability factor can be achieved 1.28could meet productive requirement.

Abstract: When the distance between two opposite excavation face is too small, the explosive load of one excavation face may causes rock failure of the other excavation face and result in engineering accidents. In this paper, the dynamic response of rock pillar between two opposite excavation faces during one explosive excavation cycle is investigated. An aftereffect function is adopted to reflect the viscoelastic properties of deep rock mass, and the explicit difference scheme of stress field is derived and then implemented by Matlab programs. The transient stress field of rock pillar is computed by coupling the initial stress field and the explosive waves. The analogies between the minimal safe distance and those influence factors such as explosive excavation load, rock mechanical properties, in-situ stresses, are fulfilled by this method. The back analysis results of a real case indicate that the results of presented method agree well with the actual situation.

Abstract: An asymmetric twin arched tunnel is designed to meet the line development of triple track railway in accordance with ground geological condition and topography in this paper. A partition wall is adopted to support the double arches of the tunnel, and the pilot drift and bench cut method is utilized to preserve the safe excavation of the double arch tunnel in poor rock mass in the paper. The design technique and construction method may guide the driving of such tunnels under similar condition.

Abstract: Structural design and construction process for a subway station consists of two tunnels with large transection are discussed according to its function and geological conditions of rock mass in this paper. A composite lining is designed to support surrounding rock, and partial bench cut method, side drift method are utilized to build the special subway transfer station in rock mass. The practice of the designed scenario proves to be a great success and attains the safe construction of the station by tunneling method.

Abstract: Numerical simulations of rock-buried tunnel collapse under plane pulse loads propagated from ground were performed using the nonlinear FEM software of LS-DYNA, the difference of structure collapse between the cases with initial stress-strain conditions being concerned and not concerned was observed. The calculations indicate that, provided other conditions are equal, when initial state is taken into account the collapse is more serious than that regardless of initial conditions. Initial stress-strain state has much influence on the underground structure’s dynamic response, hence the initial conditions should not be ignored when doing dynamic analysis of underground structures.