Applied Mechanics and Materials Vols. 204-208

Abstract: Jiaohua Square Station of Harbin Metro Line 1 is built by PBA method with the existence of No. 7381 air defense tunnel. In order to control the ground settlement during PBA construction, numerical model is performed to analyse the surrounding rock pressure, plastic zone and structure internal force. The result shows the lower pilot headings have stronger impact on existing tunnel than the upper ones in that the lower ones get the loading effect while the upper ones the unloading effect. The internal force of air defense tunnel and ground displacement can be well controlled by reducing the area of lower pilot headings at the stages of pilot heading excavation, but the final surface settlement is unqualified. The scheme of lower big pilot heading in part with the support of portal frame meets the requirement of surface settlement. The in-situ surface settlement and the vault settlement of defense tunnel are essentially consistent with numerical results.

Abstract: As the down-hole refuge chamber is the last life support for miners, its stability structure is especially important in its design. This paper tested the loose circle of the surrounding rock of refuge chamber with double-hole method, proposed the related parameters of chamber support, and conducted numerical analysis for the deformation, damage and supporting effect of the surrounding rock by using FLAC. The result shows: the loose circle radius of this refuge chamber is about 1.7~2.0m；the surrounding rock of refuge room belongs to IV class with large loose circle, designs support parameters with anchor net spray built-up arch theory; the numerical analysis shows that the floor suffers from floor heave, so it needs to be set up with anti-arch structure and be filled with reinforcement material.

Abstract: Using the numerical analysis software FLAC3D, the stress concentration and drilling relief on the boring face of deep tunnel were analyzed through three dimensional numerical simulations, in which, the characteristics of stress concentration area distribution and the effect of depth on the stress concentration were the main works. The stress relief through drilling was also simulated. Through above studies, the results show that drilling is a very effective method to relief the concentrated stress. But the drilling layout, such as numbers of drilling, should be rational. Generally, the deeper the tunnel buried, the greater the degree of stress concentration, and more number of boreholes are required. All results in this paper provide a reference for the actual projects.

Abstract: This article successfully gives an elaboration on the operating principle of seismic reflection, acoustic logging as well as the methods and techniques through the engineering geological investigation on Maojingba super long tunnel, and resolves the key technical issues, thus providing valuable references for future similar projects.

Abstract: With the high-latitude and high-altitude tunnel built, researches on frost damage mechanism of the tunnel and prevention countermeasures have become imperative. By numerical simulation of tunnel lining-scaled model at different temperature boundary conditions, changes of the stress state with no insulation material and insulation materials of poly phenolic under water-saturated and natural conditions were discussed. Through the analysis, it’s indicated that the tunnel waterproofing and insulation are equally important in the alpine region. The results has important reference and guidance significance in design and construction of the tunnel under cold weather conditions.

Abstract: Explosion inside the entrance of a tunnel may produce strong blast wave in the tunnel. Taking effective measures to attenuate the air blast wave is very important. Numerical simulations were done on explosion inside the entrance of a tunnel in three different cases, no baffles, symmetrical baffles and stagger baffles arranged along the tunnel. It is found that the arrangement of baffles can attenuate the air blast wave effectively. The best arrangement of baffles is given and it is a reference for tunnel protective design and study.

Abstract: This paper summarizes the advantages of the immersed tunnel, reviews the application profiles of the immersed tunnel at home and abroad. Immersed tunnel design and construction process in the selection of structural, foundation treatment, joints waterproof, pipe sections of floating and sinking and other key technologies are analyzed and discussed. Finally, the analysis of the application prospects of the immersed tunnel, and pointed out that with the underground space development and utilization of the immersed tunnel because of its unique advantages and will certainly more and more popular.

Abstract: Protective technology is one of most effective technologies for regional gas control technology. Huainan Coal Field is a typical coal field with deep and low permeability multi coal-seams, and it is one of most serious coal field in gas disasters. Currently, Huainan Coal Field has completely entered the stage of extracting Group B coal-seams (average mining depth is about 650m). In order to research and obtain the results of stress relief of adjacent coal-seams after extracted protective coal-seam, taking advantage of the method of similar materials simulation test and taking 11415 longwall panel of Group B coal-seams of Panyi Coal Mine of Huainan Coal Field, the changing trends of abutment pressure, displacement as well as permeability of adjacent coal-seams are systematically studied. The researching results can provide safeguard for high-effective gas drainage, eliminate the risk of coal and gas outburst as well as high effective production.

Abstract: During the extraction of steeply inclined coal seams, the coal recovery ratio is low be-cause of the coal pillar loss and the production of waste rock is high due to lots of rock roadways which causes serious environmental pollution. This status is conflicted with the strategy of Clean Coal Mining and Green Coal Mining in China, so it is necessary to develop new coal mining method. In this paper, Downward Stratified Gangue Self-filling Method on the Flexible Shield (DSGSMFS) is put forward first. It means that the coal face is lain horizontally and advances along the dip; the flexible shield is used to separate the gob area; the waste rocks are self-filled downward to the top the shield; the coal is broken by drilling and blasting method under the shield, and the broken coal is transported by the electrical winch and the scraping mucker; the flexible shield moves downward automatically by the weight of itself and waste rocks. Field test shows that the strata displacement is effectively controlled by using DSGSMFS, so some coal pillars are recovered; as a result the problem of large quantity gangue and low coal recovery ratio in steep coal seam is solved. DSGSMFS is proved to be a new hopeful and effective coal green mining method.

Abstract: For comprehensive study the adverse engineering properties of Banxi Group slate along Changsha Metro Line 2, slate samples were tested and analyzed to research their mineral composition, physical and mechanical properties, weathered properties and disintegration. Test results show that sandy slate and argillite interbedded with each other, the main minerals of slate are quartz and clay minerals, the oxide are SiO2、Al2O3, the natural compressive strength of sandy slate is five to eight times that of argillite, its softening coefficient is less than 0.75, slate is easy to soften, argillite is easy to disintegration and the disintegration of sandy slate is medium grade. The adverse engineering characteristics lead to slate rock mass uneven with hard-soft. Differential weather of slate causes there are some bedrock weathered slots along Changsha Metro Line 2. So during construction, appropriate process and tool must be selected, control the tunnel oriented, strengthen the protection and shorten the bare time of rock mass.