Application Of Unequal Length Double Piles In Chengdu Expansive Soil Foundation Engineering

With the increase in deep pit in Chengdu, and the red line from the construction site near the small problems became clear, control over the deformation Foundation also put forward higher requirements. Due to the expansion of the area in the eastern suburbs of Chengdu soil contains a lot of clay, after water softening, anchor, anchor rods can not soil excavation lateral friction of the proposed structure sufficient anchoring force, resulting in the region pit often appear danger of collapse, causing huge impact on people’s lives and property safety. Therefore, how to solve the expansive land area of urban construction projects in the excavation and environmental effects become hot and difficult problems in geotechnical engineering, technical security, economic and reasonable excavation architecture is a development direction of excavation and research priorities.Since the double-row piles supporting structure having a large overall height, lateral displacement is small, no need to provide support, easy construction, fast, no working face, etc., is widely used in slope reinforcement, side slope, excavation supporting other projects. However, the mechanism and the mechanical characteristic double piles unclear, design theory double pile immature, rely mainly on engineering experience. Based on the previous studies, based on the expansion of the land area of Chengdu Mandarin Oriental Plaza Foundation engineering background, physical and mechanical parameters of rock and soil characteristics foundation of research, combined with large-scale finite element analysis software MIDAS-GTS double FORCED BEHAVIOR row piles supporting structure comprises excluded double piles, pile spacing, pile stiffness, embedded depth, the nature and circumstances of soil around the pile length, ranging from modeling analysis, research the best double pile excellent design parameters proposed application of unequal length double pile in expansive soil excavation in Chengdu, and finally to a typical project as an example of the supporting structure simulation, combined with monitoring data to verify the reasonableness of the program for long double-row piles supporting structure non later expanded soil Foundation applications engineering experience, reducing the land area expansion project cost, and provide theoretical support for further optimization.The main results of this study are:(1) the physical characteristics of foundation and mechanical parameters of rock and soil were found not water-softening soil strength is about twice the water segment strength; strength parameters of expansive soil cohesion c and the water content is linear.(2) through the double-row piles different excluded, pile spacing, pile stiffness, embedded depth, the nature and circumstances of soil around the pile length, ranging from modeling analysis found that:(1)around the pile length ranging case, pile length changes in the back than the front pile pile more influence on the displacement and internal forces supporting structure, and the rear pile length increases to a certain value, less impact on the supporting structure, in which case the rear pile length optimal length, to reflect the economics of supporting design.(2)soil cohesion on the displacement of the supporting structure was larger than the internal force influence; internal friction angle has a greater impact on the displacement and internal force of supporting structure.(3)excluded appropriate to increase the displacement of supporting structure will be reduced, and with the excluded increases, reducing the displacement amplitude decreasing, as row spacing increases to a certain value after the change row spacing of supporting structure displacement of less impact, and the front pile moment gradually rising pile back moment is decreased.(3) Projects eastern suburbs of Chengdu Longquanyi area of comparison between calculated and measured values between the two analysis, numerical simulation. At the same time according to changes in the pile stress, stress crown beams and piles of earth pressure behind, analyze the shape of the force long double-row piles supporting structure like a non-expansive soil area. As long as the non-double-row piles retaining structure to provide after Expansive Soil Foundation application engineering experience, and provide theoretical support for further optimization of the design, while providing a reference for the region similar excavation supporting design.