不同方式处理后软土地基侧向变形规律

高速公路建设期侧向位移的控制是评价路基变形的重要依据。依据四川省遂-资(遂宁至资阳)高速公路软基沉降变形观测的数据,通过对现场监测资料的分析,分别探讨西南地区软土路基经塑料排水板(PVD)、碎石桩处理后,路基侧向变形y与深度z,最大侧向变形增量△ym与地表沉降增量△SD,平均侧向变形量Sy与地表沉降量Sf的变化规律。研究表明,(1)根据Boussinesq解答和实测数据得到路堤荷载作用面积下变形y随着深度z大致呈"S"形变化,近地表变化剧烈,随荷载增加最大侧向位移深度基本保持不变,土体最大侧向变形深度与路堤填筑高度无关,与土性有关;(2)经PVD处理后的软基在填筑期、预压期均有大量侧向位移发生,各占总位移量的50%,最大侧向位移深度在距离地表1.0~1.5 m处;(3)经碎石桩处理后软基侧向位移在填筑期已完成总位移量的75%~80%,总位移量明显小于PVD处理后软基侧向位移量,最大侧向位移深度在距离地表2.5~3.5 m处;(4)PVD处理软基在固结阶段△ym/△SD、Sy/Sf分别为0.15~0.30和0.10~0.20,大于填筑前期2~4倍,而碎石桩处理软基固结阶段△ym/△SD、Sy/Sf分别为0.10~0.15和0.03~0.05,各个阶段变化相当。

塑料排水板处理软基侧向变形规律及预测模型

探讨西南地区软土路基经塑料排水板方式处理后,路基侧向变形的规律。基于四川省遂一资高速公路软土路基沉降变形监测的数据,对土体侧向变形随深度、侧向变形随时间的变化规律进行统计分析,并根据其变化特征,分别提出相应的预测模型。研究表明:(1)在路堤填筑过程中侧向水平位移近地表处(0.15~0.3倍软基厚度)侧向位移变化剧烈;(2)侧向水平位移随时间存在3种变化关系:填筑前期为△y_m=△S_D,路堤填筑从临界填筑高度到设计填筑高度的过程为△y_m=0.15△S_D,填筑完成后为△y_m=0.3△S_D。最大侧向水平位移随时间大致呈"S"形曲线分布;(3)根据侧向水平位移随深度变化特点、侧向水平位移随时间变化特点,分别提出y(z)=ae^(-λz)(bsinλz+ccosλz)、y(t)=a/(1+e^(b-c·t·r))模型进行预测,预测结果与实测数据较为吻合。

Side force formation mechanism and change law of TBM center cutter

The center cutter of a hard rock tunnel boring machine(TBM) is installed on the cutterhead at a small radius and thus bears complex side force.Given this fact,the formation mechanism and change law of the side force suffered by the center cutter were studied.Based on the rock shear failure criterion in combination with the lateral rolling width,a model for predicting the average side force was set up.Besides,a numerical analysis model of the rock fragmentation of the center cutter was established,and the instantaneous load changing features were investigated.Results shows that the inner side of the center cutter can form lateral rolling annulus in rock during the rotary cutting process.The smaller the installation radius is,the greater the cutter side force will be.In a working condition,the side force of the innermost center cutter is 11.66 k N,while it decreases sharply when installation radius increases.Variation tends to be gentle when installation radius is larger than 500 mm,and the side force of the outermost center cutter is reduced to 0.74 k N.