Physical model test on the effect of different anchoring methods on the mechanical and deformation characteristics of anchored slide-resistant piles
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摘要:
锚索抗滑桩是滑坡的主要支护结构之一。目前, 软硬相间地层条件下锚索抗滑桩的受力与变形特征尚缺乏系统研究。以软硬相间地层为地质背景, 基于自主研发的柔性测斜仪和自动加载系统, 构建了锚索抗滑桩加固滑坡物理模型试验系统, 开展了锚索抗滑桩加固滑坡的物理模型试验, 揭示了推力不断增加过程中抗滑桩、锚索和滑体的变形与受力特征, 对比研究了布锚方式对桩-锚受力与变形的影响规律, 通过数值模拟的方法分析了软硬相间地层对锚索抗滑桩的影响机理, 并以双锚点抗滑桩为例进行了理论分析。研究结果表明: ①在滑坡-锚索抗滑桩体系中, 桩身各点位移和滑体深部位移均随桩身深度的增加而减小, 滑体后部位移速率大于中部, 且滑体位移速率大于桩身位移速率; ②单锚点抗滑桩的桩-锚推力分担比经历了4个阶段的变化, 趋于稳定时桩-锚推力分担比约为9∶1, 锚索拉力作用下桩身弯矩呈"S"型分布, 正负弯矩非对称; ③锚固角度越大, 锚索拉力的增速越大, 不同锚固角度对桩身内力值的影响主要体现在受荷段; ④多锚点抗滑桩结构的锚索分担更多的推力, 与单锚点抗滑桩相比, 双锚点与三锚点抗滑桩的最大桩身弯矩分别减小了22.41%和40.55%;⑤与均质地层相比, 软硬相间地层中软、硬岩交界面处基岩应力发生突变, 不同软岩厚度比和桩底是否嵌入硬岩, 均对锚索拉力和桩-岩之间的相互作用有不同程度的影响; 其次, 双锚点抗滑桩内力的理论值与试验结果较为接近。本研究成果可为软硬相间地层中锚索抗滑桩加固滑坡工程的优化设计提供依据。
Abstract:Anchored slide-resistant piles are one of the main supporting structures for landslides. To date, there is still a lack of systematic studies on the characteristics of the mechanics and deformation of anchored slide-resistant piles in weak-hard interbedded strata. This study taking weak-hard interbedded strata as the geological background, based on the self-developed flexible inclinometer and automatic loading system, the test system was constructed. Model tests of landslides reinforced by anchored slide-resistant piles were conducted, and the force and deformation characteristics of piles, anchor cables, and sliding mass were revealed in the process of increasing loading force. The influence of the layout of anchor cables on the force and deformation of the pile-anchor was analyzed. The influence mechanism of the stratum with weak-hard interbedded rock on the anchored slide-resistant piles was analyzed by numerical simulation. In addition, the theoretical analysis was carried out by taking the double-anchored pile as an example. The results show that: ① in the landslide-pile-anchor system, the deep displacement of the pile and sliding mass decreases with increasing pile depth, the growth rate of the rear is greater than that of the middle in the sliding mass, and the growth rate of the sliding mass is greater than that of the pile. ② The thrust sharing ratio of the pile-anchor undergoes four stages, which is approximately 9∶1 when it becomes stable. Meanwhile, the bending moment of the pile is distributed in an "S" shape under the action of the anchor cable tension, and the positive and negative bending moments are asymmetrical. ③ The growth rate of the anchor cable tension increases with the increase in the anchoring angle, and the influence of different anchoring angles on the internal force of the pile is mainly reflected in the loaded section. ④ The multianchored pile structure can share more thrust than the single-anchored pile, and the maximal bending moment values of the double-anchored pile and triple-anchored pile are reduced by 22.41% and 40.55%, respectively. ⑤ Compared with the homogeneous stratum, the stress of the bedrock at the interface between a weak and hard rock in the weak-hard interbedded stratum changes abruptly, and the thickness ratios of the weak rock and whether the pile bottom is embedded in hard rock all affect the axial force of the anchor cable and the pile-rock interaction to varying degrees.Meanwhile, the theoretical value for the internal force of the double-anchored pile is closer to the test result. The study results of this paper can provide evidence for the optimal design of projects for landslides reinforced by anchored slide-resistant piles in weak-hard interbedded strata.
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图 20 不同基岩组合中抗滑桩嵌固段基岩应力分布图(a~f对应表 2中工况a~f)
Figure 20. Stress contour map of the rock on the side of the embedded section in different bedrock combinations
图 21 不同模型中嵌固段桩前与桩后基岩应力分布曲线(a~f对应表 2中工况a~f)
Figure 21. Stress distribution curve of rock on both sides of the embedded section of pile in different bedrock combinations
表 1 材料的相似比和力学参数
Table 1. Similar ratio and mechanical parameters of materials
名称 密度/(g·cm-3) 弹性模量/GPa 黏聚力/kPa 内摩擦角/(°) 抗拉强度/MPa 相似比 1 100 1 1 100 滑体 1.97 0.018 26.08 11.65 / 软岩 2.16 0.15 39.1 16.3 / 硬岩 2.21 0.45 110.5 30.0 / 表 2 锚索拉力统计(数值模拟结果)
Table 2. Statistical analysis of the axial force of the anchor cable(numerical simulation results)
工况 a.软硬相间(w=1/3) b.全软岩 c.全硬岩 d.软硬相间(w=1/2) e.软硬相间(w=1/4) f.上硬下软(w= 2/3) 锚索拉力值/N 152 195 141 157 143 178 基岩顶部应力最大值/kPa -213 -176 -248 -191 -218 -242 桩底后侧应力最大值/kPa -99 -111 -52 -105 -90 -110 最大弯矩值/(N·m) 182 221 162 203 164 210 表 3 计算参数统计(双锚点抗滑桩)
Table 3. Statistical for calculation parameters(double-anchored pile)
名称 参数值 名称 参数值 名称 参数值 H 0.66 m l1 0.40 m R2 2.8×103 kPa L 0.16 m l2 0.35 m E 3×105 kPa h1 0.45 m s1 0.65 m K1 1.21×104 kN/m3 h2 0.21 m s2 0.55 m K2 1.02×104 kN/m3 a 0.05 m Eg 1.3×103 kPa K3 1.21×104 kN/m3 b 0.075 m As 2.83×10-5 m2 / / θ 30° R1 6.6×103 kPa / / 注:H为桩长;L为桩间距;h1为桩身受荷段长度;h2为桩身嵌固段长度;a×b为桩截面尺寸;E为桩身弹性模量;Ki为第i层岩性的水平地基系数,通过与岩石抗压强度的拟合公式进行换算[1];Eg为锚索弹性模量;As为锚索截面积;li为第i排锚索锚点至滑面的距离;si为第i排锚索自由段长度,θ为锚索锚固角度; R1,R2分别为硬岩和软岩单轴抗压强度 -
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