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随着基坑分层挖深,在侧壁土体自重作用下,土楔体滑移斜面会处于主动极限平衡状态(向下滑移)。在此状态下由锚杆或支顶对侧壁施加的预压力传至土楔体滑移面上,在土粒间产生的压应力、剪应力、摩阻抗剪强度增量能平衡阻止斜面向下滑动。当继续挖深可使其再处于上述状态。基于这一概念结合莫尔作用应力及库仑强度理论推证导出:抗剪应力强度增量与主应力增量之间函数式,再归并导得:大小主压应力增量相关公式。给出基坑挖深土楔体内应力分布图,建立侧向预压力与基坑顶面竖向荷载作用下基坑侧壁直立深度解析公式,它可适用于土工试验广义折线性强度理论,并绘以应力圆剪切包线几何图式,给出非线性内力分析方法。与当前土压力作用模式对比可明显增加基坑挖深。
As the pit digs deeper, the wedge sloping slope will be at active limit equilibrium (downward slip) under the weight of the side soil. In this state, the pre-pressure exerted on the side wall by the anchor rod or branch top is transmitted to the slip surface of the earth wedge. The compressive stress, shearing stress and frictional shear strength increment generated between the soil particles can balance the pre-pressure Slide down. When you continue to dig deep to make it again in the above state. Based on this concept and deduced from the theory of Mohr effect and Coulomb strength, the formula between the increase of shear strength and the increment of principal stress leads to the formula of the increment of magnitude of principal compressive stress. The internal stress distribution of deep excavation wedge in foundation pit is given. The analytical formula of vertical depth of side wall of foundation pit under lateral preloading and vertical load on foundation pit is established. It can be applied to generalized linear fracture strength theory in geotechnical test. Painted by stress circle cutting envelope geometry, given nonlinear internal force analysis. Contrasting with the current mode of earth pressure, the excavation depth can be obviously increased.