土体蠕变与桩锚耦合作用的土拱效应分析

Analysis of soil arching effect between soil creep and anchored piles coupling

桩锚支护是边坡加固的主要措施之一,从桩间土拱形成机理和土拱轴线形态出发,建立了土拱横截面抗剪切效应下土拱等效简支梁的挠度计算式,诠释了桩间土拱凸向桩后土体的特点。同时考虑了土体粘结力、内摩擦角和锚索拉力水平向分量及其时变特性对桩间土体应力状态的影响,并结合桩间土拱横截面Coulomb剪切准则和土拱横截面静力平衡条件,分别推导了正常土体、抗剪土体、土体蠕变属性和土体蠕变桩锚耦合作用等4种情况的拱轴线方程。比较分析了上述4种情况两相邻桩的最大跨度。结果表明第2种情况两相邻桩的最大跨度值为最大,其次是第4种情况和第3种情况,而第1种情况的跨度值为最小。研究结果验证了理论推导式的有效性,建议抗滑桩加固边坡设计中应以第4种情况进行桩中心距取值。所述结论可为了解桩间土拱蠕变弱化机理、拱轴线时变特征和桩锚工程设计参数取值提供有益参考。

Supporting structure of anchor-pile is one of the most effective measure in slope strengthening. Starting from formation mechanism and form of soil arching between adjacent piles, the calculated formula for the deflection by the influence of stress state , which is considered on the internal friction of soil and anchor cable tension, was built based on the equivalent simple supported beam on soil arch and the characteristic of the soil arch convex to soil behind of piles was explained. The equation on arch axis was solved theoretically combining with Coulomb shear criterion in the condition of static equilibrium in the cross section on soil arching. The four axial line equation of arch were derived for following four conditions of normal soil, anti-shear soil, soil creep and coupling between soil creep and anchored pile. The maximum spans between two adjacent piles for above four conditions were analyzed comparatively. The results show that the maximum span is occurring the second condition, in turn the fourth condi- tion and the third condition, but the span for the first condition is minimum. The results verify the validity of de- rived theoretical formula. It is suggested that the central distance choice of the pile should be based on above fourth condition. The conclusion provides useful reference for soil arch creep weakening mechanism, time-verying charac- teristics of arch axis and choice of value of pile cap engineering design parameters.