Applied Mechanics and Materials Vols. 638-640

Abstract: In order to analyze the construction processing for No.1 shaft of Weihe Tunnel on Baoji-Lanzhou Passenger-dedicated Railway, a two-dimensional numerical model for the simulation of the shaft was built with the finite difference method. Mohr-Coulomb model was chosen as the soil constitutive model. The result shows that the maximum lateral displacement appears at the upper part of the shaft, and the lateral displacement is in effective constraint at the shaft’s bottom. After the construction, the maximum uplift at the shaft’s bottom is in the center, while the uplift decreases from the shaft’s center to its both sides. The maximum pressure stress turns up at the bottom sides of the shaft, and the maximum tensile stress appears at the middle of the shaft.

Abstract: In view of the southwest region of Inner Mongolia encountered in the process of shaft construction of fissure aquifer water inrush problem, take the Great Wall No. 5 mine as an engineering example, key technology of the southwest region of Inner Mongolia shaft over aquifer such as freezing method, grouting method, water prospecting method are analyzed, curbing the aquifer of the adverse effects of shaft construction effectively, solving the difficult problem such as the loading and transportation of waste rock, it provides the reference of prevention and control of water for similar conditions in western region of shaft construction.

Abstract: Subway is an important part of city traffic system. Once terrorist attack happens in the subway, it might lead to strong response of concrete lining, which seriously threatens the safety of lives and properties. The analysis of the subway concrete lining damage under blast load has become an important question. By the means of finite element software AUTODYN, this essay simulates the highly nonlinear response and dynamic damage of concrete lining when 100kg TNT explodes different altitude above bottom of subway tunnel. It analyses attenuation of pressure and influence on the structure of concrete lining. The damage of concrete lining mainly concentrated in the vicinity of explosion source. Different explosive height will lead to different dynamic damage of concrete lining.

Abstract: The cracking and developing of structural surfaces is one of the main causes for surrounding rock mass large deformation and failure in deep underground cavern excavation. A numerical simulation method for discontinuous structural surface development is proposed based on the transient unloading of excavation load during underground cavern excavation. The program will automatically evaluate every substep in the dynamic calculation, and determine if the development stops and the cracking direction based on dynamic fracture mechanics. The penalty function is adopted to simulate the opening and sliding characteristic of structural surfaces. And the cracking path would be shown by iterative calculation. Results show that, the lateral pressure coefficient (LPC) is the main factor of cracking direction. When structural surface is shallow to the side wall, the crack would develop to the surface of the side wall. When it is deep enough into the side wall, the cracking might stop before it goes to the surface of the side wall. The accuracy of this simulation is verified by the comparison to relative laboratory tests.

Abstract: The utilization of the underground space mainly focuses on the following aspects: underground traffic, underground commerce, underground garage, underground amusement spots and urban disaster prevention facilities, for example, the air-raid shelters. Based on the analysis of the characteristics and reasons of the fire in the underground buildings, and with a (or a half) basement of the library in a university as its study object, the FDS of the CFD software is used to carry on a field simulation by setting two fire scenarios and five measuring points. This paper also studies the change process of temperature and visibility in different time and different regions and analyzes the smoke movement regulation with model in this underground space. A conclusion is drawn that, the temperature in each measuring point would rise up quickly in a short time with 131 seconds as its available safe egress time (ASET) of the editorial catalogue room, reaching and even surpassing 60 ̊C, as the safety threshold human can withstand, and that finally tend to a relatively stable point.

Abstract: Under the assumptions of plane strain, vertical normal stress and shear stress distribution in surrounding rock of rectangular tunnels before and after installing anchor cable are studied. And according to the mechanics of materials, the formula of stress distribution in the roof is corrected. According to the corrected formula of the stress distribution, the dangerous points are found. And the dangerous point location does not change before and after installing anchor cable. It still locates in the middle and ends of roadway roof. Just the dangerous stress value decreases after installing anchor cable. There are the maximum tensile stress in the midpoint roof and the maximum shear stress on both ends of the roof.

Abstract: The variation of temperature distribution in the cup-shaped frozen soil wall is real-timely monitored during the whole process of the horizontal freezing reinforcement project in Yixian Bridge Station, the first phase in Line 2 of Nanjing Subway. The development characteristic of the temperature field at different depth is analyzed, and the formation time and developing speed of the frozen soil wall is further calculated. The monitoring results show that, the average growth rate of the temperature field at the interface between the frozen soil and the underground continuous wall is significantly faster than the one in the cylinder reinforced area.There is significant differences in the average growth rate of temperature field in the frozen soil wall at different area of the reinforcing plates.

Abstract: The entity model of slope arch framework in highway was monitored in stress and displacement at different time. Though the date of different points collected, the mechanical mechanism can be studied, and the analysis was done between calculation results and entity model. The studying results show that the stress of point were increasing at first and then mitigating, and the stress increase undulating as the distance from the slope top increase. The date of monitor and finite element analysis model indicate that the point on the arch toe is the worst stress place, and the total displacement increase nonlinear as the distance from the slope top increases, and the bump phenomenon exists in the bottom of slope, the points are likely to be broken.

Abstract: This paper focused on five kinds of methods for water inflow of typical sections in a long deep buried tunnel under conditions of high ground stress and high water pressure (referred to as “two high conditions”). The methods are based on groundwater dynamics formulae and practical experience. Results show that calculation data by the method 5 is the maximum. There is little difference of calculation results between the formulae 1 and 2 or between the formulae 3 and 5. The calculation methods and results of the water inflow can provide prevention of gushing water of a long deep buried tunnel under the two high conditions with scientific basis.

Abstract: Based on the project of a foundation pit engineering adjacent to existing tunnel of Kunming metro line 1, a 3D calculation model is established in consideration the interaction of foundation pit support structures, tunnel structure and soil. In this paper, the authors have simulated the foundation pit excavation process in three conditions, and analyzed the changing laws of the lateral displacement and internal force of the tunnel induced by adjacent excavation under different conditions. Calculation results show that the distributions and the values of the displacement and internal force of the tunnel are obviously different under three different construction technologies, and the “jump dig” is the optimum excavation scheme due to the restriction in the excavation of foundation pit, and the lateral deformation of tunnel structure is smallest in this condition. The conclusion can provide a theoretical basis for similar excavation engineering construction.