Advanced Materials Research Vols. 919-921

Abstract: The mechanical behavior of group piles under lateral load is a very complex process of pile-soil interaction. Due to the group effect, the lateral capacity of individual piles can not be fully developed. Deduction factors are applied to the lateral soil reaction, and then lateral analysis is performed for individual piles. After p-y curve for each pile is constructed, the soil pressure of group piles is the sum of soil pressure of single pile at the same deflection under one pile cap. The mechanical different behaviors of the front piles and the back piles are analyzed and compared based on a practical engineering.

Abstract: To research and analyze the additional stress distribution and change of granular materials, the model tests are used to observe vertical additional stress in different position and depth in different foundations. And the comparison between observed values both in different soils and single soils is conducted to analyze the transmission and attenuation of additional stress in granular materials. The research results show that the existing of boundary surface can lead to different vertical additional stress transmit obviously. And with the increasing of loading, the vertical additional stress differences between that of different soils get larger, meanwhile, the ratio of stress differences to smaller additional stress increases slightly. With the increasing of depth, the attenuation rate of vertical additional stress of silty soil changes much fast than that of fine sand. Wherever in horizontal direction or vertical direction, the vertical additional stress of fine sand which has higher compression modulus in different soils is slightly larger than that in single soil and transfers additional stress (loading) more under the same loading. To granular materials, inner friction structure effect is evident influence to additional stress transfer.

Abstract: Matric suction has great impact on the strength of soil. Some physico-mechanical indexes, such as the water content, dry density of soil, have close relationship with the matric suction. The experiments were conducted in the laboratory to study the relationship between the matric suction, the water content and dry density of unsaturated red clay. The filter paper method was used to get the soil-water characteristic curve of the unsaturated red clay. The results show that: water content has great impact on matrix suction. The soil-water characteristic curve can be divided into three stages. In low water content area, matrix suction decreases rapidly with the increase of water content.Then, the rate of change slows down after the inflection point. Matrix suction increases obviously with the increase of dry density under the condition of low water content, but the impact disappears under high water content. So the matrix suction is affected by dry density and water content.

Abstract: The transportation of tunnel elements is one of the most important procedures of immersed tunnel construction. To investigate the hydraulic resistance of tunnel elements during transportation, hydrodynamic scale model tests of the were carried out in a towing tank for the tunnel element transportation under wave action. The test results show that the hydraulic resistance is linear to the square of towing speed basically. The drag coefficients of the element under different water depths and dragging angles are calculated. The dragging coefficient decreases with the increase of water depth, and increases with the increase of the dragging angle. Finally, the influence of the wave is also discussed for the tunnel dragged in the open sea.

Abstract: Based on the typical adjacent project of extension of LianHuo expressway which is constructed on WenXiang tunnel, the finite difference software, Flac3D, is adopted to stimulate the process of the construction. In this paper, from two aspects, the deformation of profile and cross-section, serviceability state is analyzed in detail. In the profile plot, usually displacement of the invert arch is less than that of the vault, and affected by the mutual position of topography and excavation, the maximum displacement, 6.3mm, merges at 50m of the vault in the profile plot; in the cross-section plot, due to occurrence of unloading effect brought by overlying excavation, tunnel structure has the tendency of rising toward the excavation. The calculated result shows that the displacement of WenXiang tunnel locating on the line of ZhengZhou-Xi’an Railway High-speed can be well controlled by adopting the excavation method of layering excavation at vertical direction and section excavation at longitudinal direction, which makes the safety of serviceability state of extension of expressway and the operation of Railway High-speed.

Abstract: On the basis of the geological and environmental conditions of surrounding rock around a shallow subway tunnel used to cross a river in Chengdu subway line one, the ground treatment technique such as uplift piles, cast-in-place reinforced concrete slabs and site grouting have been summarized in the paper. The riverbed above shallow shield tunnel is reinforced with covering slabs and uplift piles; meanwhile, the surrounding rock is reinforced with cement and sodium silicate grout by high pressure grouting method conducted inside the tunnel. The practice of the scenario presented in the paper turns out to be a great success and shows that the treatment technique can be used to guide the design and construction of ground reinforcement for shallow tunnel used to cross urban rivers in subway lines by shield tunneling method under similar conditions.

Abstract: Focused on the mining method, the parameters of primary support, and the design method for the interface of metro station and air duct structure, what are encountered during the design of mining station in rock strata. Through the combination of numerical method and theoretical analysis, and the comparison with field measured data, we know that double-side-wall heading method is safe and feasible, design method based on plastic stage can be used for the checking of primary support structure, and the combination of support in advance and closed steel frame can insure the safety of the interface of metro station and air duct structure. Through analysis, the changes of displacement and stress are focused around vault and arch springer, and the decrease and increase of safety factor during construction are also made clear. The study can offer a reference for the similar project in the future.

Abstract: Grave protrusion coal seam tunnelling hydraulic cutting outburst prevention measure is a new technology in the world. The measure had been applied successfully to Jiaozuo Coal Group and run well. The mining areas of Heilongjiang are characterized by complex geological structures, more medium-thickness protrusion coal seam and abundant groundwater, on the basis of referring to technical parameters of the outburst prevention measures of Jiaozuo Coal Group, the outburst prevention mechanism of hydraulic cutting applied to medium-thickness protrusion coal seam was analyzed from the coal stress surrounding hole, internal forces of gas, stress concentrated zone and its moving speed, thickness of pressure released zone and intensity change of coal, and the feasibility of hydraulic cutting outburst prevention technique applied to Heilongjiang was verified. This provides theoretical basis for the technique applied to mining area of Heilongjiang Province.

Abstract: According to the 100㎡ high-speed tunnel cross-section which is generally used in high-speed railway of China, this paper develops a tunnel-air-train simulation model, based on the three-dimensional incompressible Navier-Stokes equations and the standard k-e turbulence model. Time-history variation rules and space distribution characteristics of train wind are studied respectively. The results show that: train wind is complex three-dimensional flow changing with time and space, air at the front of train flows away from the train head, while air at the rear of train flows to the train tail.

Abstract: The influence of tunnel’s span on rock mass quality is getting more and more recognition along with increasing large span tunnels’ construction. As national standard of China, BQ qualification is generally applied. Based on the measured data and numerical experiment, the relationship between surrounding rock displacement and quality evaluation is studied, and span effect correction factor is established. The modified rock quality index can provide the basis of guiding the design and construction of tunnels.