微型抗滑桩双排单桩与组合桩抗滑特性研究

RESEARCH ON ANTI-SLIDING CHARACTERISTICS OF SINGLE DOUBLE-ROW AND COMPOSITE ANTI-SLIDE MICROPILES

通过3组大型模型试验,研究微型抗滑桩双排单桩与组合桩在加固边坡时的抗滑特性。边坡位移监测结果表明,微型抗滑桩能提供较大的抗滑力,降低变形速率,对边坡有较好的加固效果;组合桩加固效果更佳,较单桩抗滑力提高6.8%。桩体破坏有3种形式:桩体弯曲、桩土脱空、桩体断裂;双排单桩裂纹倾角较大,为65.7°,呈弯–拉破坏;组合桩裂纹倾角为33.9°,呈拉–剪破坏;后桩裂纹宽度较前桩大。双排单桩桩体自由段土压力沿桩身呈"S"型分布;后桩承受土压力大于前桩,前后桩最大土压力之比为0.53∶1～0.50∶1;桩前滑面层位存在桩土脱空区,土压力最大值在滑移面上10%桩长附近;桩体嵌固段土压力在下滑力较小时呈倒三角形分布;当土压力较大时呈矩形分布。组合桩由于连梁作用,前桩桩顶产生较大的正弯矩,桩身最大负弯矩出现在滑面附近,前后桩最大负弯矩之比为0.67∶1～0.80∶1。

The anti-sliding characteristics of single double-row and composite anti-slide micropiles are studied through three model experiments. The monitoring results of slope displacement indicate that： （1） micropiles can provide relatively bigger sliding resistance and decrease deformation rates; and it has obvious slope reinforcement effect. （2） Comparing with single double-row micropiles, composite micropiles have better reinforcement effect and the sliding resistance increases by 6.8%. There are three failure models namely bending failure of the pile body, disengaging between pile and soil and the fracture failure of piles. The crack angle of single double-row piles, with bending-tensile failure, is bigger value of 65.7~, while the value of composite piles is 33.9~, with bending-shearing failure. And the backward piles＇ cracks are more obvious than the forward piles. The soil pressure acting on the free section of single double-row pile body is ＂S＂ shaped distribution. The backward piles bear bigger soil pressure owing to directly contacting loads; meanwhile, the ratios of the maximum of soil pressure between the forward piles and backward piles are 0.53 ： 1 - 0.50 ： 1. As a result of the empty area between the pile and soil, the maximum of soil pressure distributes in 10% of the length of the pile above the sliding surface. The sliding resistance below sliding surface is inverted with triangular distribution under small pushing force and presents rectangular distribution under big pushing force. Due to the effect of coupling beam, the positive bending moment produced at the top of the forward piles is bigger; and the maximum negative moment appears around the sliding surface. The ratio of maximum negative bending moments between the backward piles and the forward piles is 0.67 ： 1 - 0.80 ： 1.