Advanced Materials Research Vols. 838-841

Abstract: How to determine the stress level of the boundary conditions of the model is a key issue in the study of geological structure and paleostress field, which is of great significance for geological structure research. The paper takes Chengzhuang coal area in Jincheng of Shanxi Province as an example to analyze its geological structure model and study the method to determine the paleotectonic stress level so as to make a contribution to study of establishing regional tectonic models.

Abstract: Beijing subway line 6 crossing under the existing line 4 is the first domestic method of using the mined tunnels crossing under the existing interval shield tunnel, during the crossing process, the key of engineering control is the displacement of existing line and construction line. Dynamic numerical simulation for the crossing process has been made by FLAC3D, and the displacement and its change law of the existing line and construction line with the different WSS reinforcement measures are obtained.The conclusion show that the WSS reinforcement measures of upper semi-section achieves the balance of safety and economy,but the uplift of WSS to the existing line should be noted in the actual construction.

Abstract: Based on the background of a highway, for tunnels with small spacing of complex stress condition, adopt various construction schemes for numerical simulation using Midas Gts finite element software under the condition of deep-buried small net distance tunnel. Use full-face excavation method, benching tunneling construction method and both side heading method to compare surrounding rock stress, surrounding rock deformation, internal force of bolt and shotcrete support system structure, lateral-wall displacement and stability of surrounding rock. Analyse displacement and stress change laws before and after the excavation of tunnel surrounding rock and supporting structure under different schemes.

Abstract: Tianpingzhai Tunnel on Dazhou-Wanzhou Expressway passes through the mined-out area, the spatial position of the goaf changes constantly comparing to the tunnel during excavation, and broken rock mass of the caving zone is most likely to collapse, which affects construction safety in return. Two dimensional computation models were built by using finite differential software FLAC to simulate excavation process when the coal-mined area is right above or below the tunnel. In 2D models, goaf strata were regarded as horizontal, and buried depth and coal thickness were limited to 300 meters and 0.5 meter respectively. The displacement around the tunnel, forces of primary lining, axial force of bolts and plastic zone of surrounding rock have been analyzed under these circumstances that the distances between tunnel and goaf are 1m, 6m and 12m. According to the results, when the distance between goaf and tunnel is less than 12 meters,underlying goaf has greater impact on the displacement around the tunnel and average axial force of bolts than overlying goaf, as well as the size of plastic zone of surrounding rock. Its strongly suggested to avoid underlying goaf if the tunnel have to pass through the mined-out area.

Abstract: A mathematical formula to calculate relative horizontal displacement of ground building due to blast vibration of surrounding rock for bored tunnel by drill and blast method is propounded on the basis of differential equation for dynamic vibration, and the mathematical expression is deduced by means of Laplace transforms. The main factors which influence the horizontal displacement of ground building subject to rock blasting are also discussed in the paper.

Abstract: Appling the M8 as the monitor objects and choosing the single-round shield tunnel with or without the steel spring floating slab and the DOT shield tunnel with straight joint as the research objects, the vertical vibration response of the track bed and the standard block in different conditions was compared. The peak vibration acceleration of two measuring points and vibration response time of the standard block in the DOT is smaller compared with the DOT and the single-round shield tunnel when a single train is through the monitoring section. Vibration response time and intensity of the DOT structure is increasing with two trains intersection. Compared to the other two shield tunnels, structural vibration response of the single-round shield tunnel is significantly decreased by the isolation effect of steel spring floating slab. For the vibration acceleration of the track bed and the standard block in the three types of shield tunnels, spectrum range is 0Hz~150Hz, and peak acceleration is in the same frequency range, which is 35Hz~70Hz. Peak vibration acceleration of the track bed is greater than that of the standard block.

Abstract: The study discusses a revised method of water detection through infrared acquisition technology. In the case of Xianghe tunnel construction, the authors built 3D infrared radiation field functions through 3D trend analysis. The separately calculated radiation intensity trend values and outliers were processed by the visualization software, Voxler, and transformed into 3D distribution graphs for further comparison and analysis. The result indicates that the technique and method applied in this article successfully eliminate the random interference and realize the detection of aquifer.

Abstract: The air flow and temperature variation in the subway tunnel are different in the railway tunnel. Its necessary to study the middle vent shaft in subway tunnel ventilation system. According to the primary design documents of one subway line in Chengdu, the paper sets up the metros geometric model which is used in the SES program and also does the simulation analysis of the biggest transportation capacity in the line. The simulation mainly analyzes the adoption of the middle vent shaft which is located in the running tunnel between the station A and B. Meanwhile it also analyzes the influence of middle vent shaft on the nearby piston vent shaft, the wall surface temperature and the air temperature in the tunnel. Finally it takes temperature as the estimated index, analyzes the advantages and disadvantages of the middle vent shaft and makes the theoretic accounts for the design. The comprehensive analysis is that this middle vent shaft could be canceled.

Abstract: Water rush and mud rush are two major problems during the process of tunnel construction, which can lead to big troubles. Advanced geological prediction should be carried out to prevent the emergency of water rush and mud rush during the construction in the karst and water-rich areas. Infrared detection technology is a way to detect the hidden water. In this paper, basic principles of model HY-304 infrared detection meter are described, and it is applied in Shuangbei Tunnel. By analyzing the predicted results and comparing it with the situation of excavation, the instrument is feasible as to water rush in karst areas and infrared detection technology has a great opportunity to be applied in the tunnel engineering under complex geological conditions.

Abstract: A finite element model (FEM) was proposed to analyze the model of floating slab track (FST) system based on elastic foundation in shield tunnel, and the equivalent model of continuous girder and theory of beam on elastic foundation were considered. Floating concrete slab eigenfrequencies can be calculated under the various combinations of subgrade reaction coefficient, steel spring support stiffness, fastener stiffness and thickness of the floating slab. The results show that geological conditions had certain effects on the eigenfrequencies of FST.