Vertical soil arch effect analysis and soil pressure calculation behind piles for pile-anchor supporting system
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摘要: 针对桩锚支护桩后竖向土拱效应, 利用土拱力学平衡条件分析了土拱的形成机理、几何特性与其对土体应力分布的影响。采用室内模型试验, 监测得到不同阶段下土体的应力场分布, 通过与现场监测数据和经典理论计算值的比较, 验证竖向土拱的存在。基于竖向土拱效应, 采用斜土层单元法, 推导了桩后土体应力分布表达式, 并与经典理论计算值和模型试验数据进行了对比分析。研究结果表明: 土体自重应力曲线在2层锚杆间发生衰减, 桩侧土压力在锚杆支点处出现相对峰值, 锚杆上部形成了竖向土拱, 对土体应力重分布影响显著。采用考虑竖向土拱效应的斜土层单元法得到的土压力分布规律与室内试验结果一致, 2条曲线同深度处桩侧土压力最大差值不超过15%, 表明利用该方法计算出的土压力具有较高的准确性。Abstract: Aimed at the vertical soil arch effect of pile-anchor retaining structure, the formation mechanism and geometric characteristics of vertical soil arch and its influence on soil stress distribution were analyzed by using the mechanical equilibrium condition of soil arch.In indoor model test, soil stress field distributions at different excavation stages were obtained by monitoring.The existence of vertical soil arch was proved by comparing the test data, the monitoring data and the theoretical values.Based on the vertical soil arch effect, the expressions of soil stress distribution behind pile were derived by adopting the oblique soil element method, and the computed values were analyzed based on the classic theory computation values and the test data.Study result shows that the gravity stress curve of soil attenuates between anchors.There are relative peaks on lateral stress curve at anchor supporting point behind pile.Vertical soil arch appears above the bolts, and has significant effect on soil stress redistribution.The soil pressure distribution law calculated by the oblique soil element method considering vertical soil arch effect is consistent with the test result, the biggest soil pressure difference at the same depth of two curves is less than 15%, which proves that the calculating method of soil pressure is accurate.
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图 17 土压力计算值与实测值比较
Figure 17. Comparison between calculated soil pressures and measured values
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