Advanced Materials Research Vols. 671-674

Abstract: This paper summarizes the design of open-cut subway station in Chengdu Metro line one. The station is built by cut and cover method and divided into three special parts with four different cross-sections used for main line and transfer track. Such retaining techniques as bored piles, steel pipe struts, soil nails, rock-bolts, steel-meshes, shotcrete and anchored steel cables are comprehensively used to maintain the stability of foundation pit. The anti-buoyancy coefficient of the open cut station is also derived and attains the requirement of safety and stability for the foundation pit after the utilization of these enclosure measures. The application of the design and construction technique for the subway station may provide guidance for the building of analogous subway station under similar geological and hydrogeological conditions in Chengdu.

Abstract: Sesmic dynamic response of Fiber Reinforced Concrete tunnel lining is studied in contrast to the plain concrete. Based on similar theory, model test has been carried out through the 5m×5m triaxial shaking table by inputting sesmic wave, then the damage characteristics of tunnel lining is acquired.The test results show that both the plain concrete and fiber concrete is brocken by sesmic load, but fracture form is not the same,the crack on Fiber concrete is narrow and sawtooth , the crack on plain concrete is wide and straight.Fiber concrete lining strain-time curve is sawtooth partly, it’s vibration reponse is a little lagger than that of plain concrete.It indicats that kinematic velocity of concrete granule is decreased and sesmic energe is absorbed by fiber cohesive force,then frequence amplitude can be reduced.So fiber concrete can be proved as fine anti-seismic material.

Abstract: THM coupling is an important process in engineering rock mass. In order to study the mechanism of THM coupling in surrounding rock of deep rock roadway in coalmine, the interactions between THM fields were analyzed, and the governing equations of THM coupling were given. Finally, a model of rock roadway with aquifer is simulated, and the distribution of pore pressure as well as the thermal and stress fields were obtained after some steps of calculation.

Abstract: The control of concrete crack is a complicated and difficult problem for civil engineering. It is more difficult to control the crack of the concrete poured in winter. Thorough the analysis of the construction of Shenyang subway in winter, a combination of methods are applied. Frost proof and decreasing the temperature stress of concrete are considered together. The combination of antifreezing measures and decreasing the temperature stress of concrete make the construction quality arrive a satisfying level.

Abstract: Supporting by pre-stress bolt is a kind of active support. It was widely used to support the Coal lane. To improve the stability of surrounding rock through choosing reasonable row spacing and geometric parameters of the bolt in the process of supporting was always a hotspot that exited important engineering significance. In this paper using the software ANSYS to analysis the additional stress field of surrounding rock under the action of the single and multiple pre-stress bolt, Gain the mechanical mechanism of that it will form a stress arch in surrounding rock if supporting lane by bolt, and the arch structure can make good use of the capacity of the surrounding rock to stable itself, thus we can get the purpose of stabling lane.

Abstract: B1 coal seam located at -550m level in Liangbei Coal Mine is a typical "three-soft" seam. The coal roadway with a depth of 610-750m lies under the critical softening depth of the roadway, and its support difficulty coefficient is 1.5-2.0. The coal has poor air permeability, high gas content and high gas pressure, so danger degree of the gas outburst is relatively strong. The coal seam was destroyed in a disastrous state by more than 100 boreholes for gas outburst prevention during the excavation. This results in the difficulty in the roadway support. Engineering geological characteristics of the coal roadway at 11 mining area are introduced. Based on the engineering geo-mechanics method, the reasons of deformation and failure of the coal roadway are analyzed. In view of problems in excavation and support, as well as the type of the coal roadway deformation mechanism, the borehole parameters are optimized for the gas outburst prevention, and bolt-net-cable coupling support with high convex steel-belt is used to control the coal roadway stability at 11 mining area. Practice shows that the effect is fine.

Abstract: Qianqiu Coal Mine, Yima Coal Group Company Limited, China, has been mining the gently-inclined and hugely-thick coal seam #2-3. The overburden above the coal seam has hugely-thick conglomerate strata with more than 400m thickness, which has significant effects on the strata behaviors of the coal face with sublevel caving. Therefore, study on strata behaviors has an important practical significance to surrounding rocks control and safety production at the coal face. Using theoretical analysis and field observation methods, the following conclusions can be drawn: (1) the surrounding rocks of the coal face with sublevel caving belongs to difficult control one, i.e., it is the surrounding rocks control of roof and floor at the coal face that is difficult. At last, hydraulic supports with sublevel caving of pattern ZF7000-18/28 and their reasonable matching equipment were chosen. (2) The law of strata behaviors of the coal face was observed. Strata behaviors of the coal face were significant and inconsistent at different coal face zones. The parameters of roof weighting interval and roof weighting strength at the coal face were obtained. The maximum value of supporting resistance during periodical weighting was 4307.70kN, being 61.54% of supports rating resistance. Therefore, the supports at the coal face had a higher reliability. Mine production-model with one-mine and one-face can be realized, which promotes the construction of a modernization mine with high production and high efficiency.

Abstract: Subway engineering is a long range program. Metro structure waterproof is a major technology to ensure the durability of structure. With the experience accumulation and technical maturity of our country's subway construction, waterproof technology is developing fast. The design concept and material of underground waterproof stay updated. According to the Shenyang subway metro construction experience, this article do a research on the on the cold regions based on the geological conditions and climate characteristics. Focusing on the subarea waterproof and natural sodium bentonite soil waterproof blanket are described, this article make a detail analysis on the proof about the design concept, waterproofing system, material selection, construction technology and other aspects. The content of this article has been in the works in practical application, which can provides reference for other similar project .

Abstract: The tunnel and the understructure works are excavated in the rock or the soil. In comparison with surface engineering, design construction and maintenance of understructure works are more complicated. Especially, after the underground rock or soil is excavated, the large deformation which generated by the crustal stress field change, will bring the great difficulty for supports and protections of surrounding rock. Based on this fact, this paper introduces the current research of formation mechanism of surrounding-rock large distortion that was met in the construction and operation of the tunnel and understructure works, and the prevention measure that was adopted at home and abroad currently. New knowledge is acquired through study; this will draw very useful reference to deeply-buried long tunnel construction in the future.

Abstract: Salt expansion deformation of the saline soil is a common form of the roadbed disease in Saline Soil Area. Salt expansion of saline soil refers to volume expansion by the impact of periodic climate changes in nature. Particle distribution characteristics, compaction characteristics, salt composition and salinity and so on are studied to evaluate the basic engineering properties of saline soil in the location of the project. Seven freeze-thaw cycles test and (no) load single-cooling test are designed to clarify the relation between salt expansion and temperature changes, moisture content, overburden pressure. The results provide design and construction experiences for high-grade highway projects in natural coarse saline soil area.