侧向预压增量法解析土压力
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摘要
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。
In deep foundation pit, soil wedge is assumed in an active state of limit equilibrium under the gravity effect of side wall. Anchors or other supports produce pressure to the wedge slip surface, thus intergranular stress, shear stress, friction and shear strength prevent the slope sliding. When digging deeper, soil can still maintain the state described above. Theoretical derivation was carried out according to this concept and More-Coulomb strength theory: the relationship between shear stress strength increment and the principal stress increment was obtained. And accordingly, the formulas of the maximum and minor principal stress increment and the internal stress distribution of soil wedge were obtained. The analytic formula for pit wall vertical depth with the lateral pressure and the foundation pit top load was established, which is suitable for generalized nonlinear strength criterion in soil test, and stress circle with shear stress envelope was drawn. Nonlinear internal force analysis method was provided. Compared with the current earth pressure calculation model, this method is material saving and has obvious economic benefit.
引文
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