基于均匀化理论与上限分析的膨胀土滑坡稳定性分析

Stability analysis of expansive soil landslide based on homogenization theory and upper limit analysis

在膨胀土和滑坡共同作用下,隧道洞口段施工更容易引发地表开裂甚至滑坡等工程灾害,在隧道内采用微型桩群防治滑坡比抗滑桩具有优势。本文基于均匀化理论与上限分析对某高速公路隧道洞口段膨胀土滑坡的稳定性进行计算,并评价微型桩群和削方卸载不同组合方式的处置效果,计算时将微型桩群及桩周土通过均匀化理论等效为符合摩尔库仑强度准则的等效加固体来,以此提高计算效率,最后通过对现场削方+微型桩群加固处置后的滑坡变形监测来验证计算的合理性,得出如下结论:相较于土的强度参数,等效加固体内摩擦角保持不变,黏聚力从26kPa提高到85.36kPa。处置前后的滑坡稳定性评价结果表明,不做处理时,滑坡滑动面从滑坡上方岩土交界面延续到隧道洞口前;仅采用微型桩群加固时,滑坡安全系数在1.17左右,滑动面从岩土交界面延续到隧道洞口后;同时采用微型桩群加固和削方卸载时,滑坡安全系数提高到1.26~1.28,滑动面上缘由土石交界面前移。现场变形监测表明地表变形与深层土体变形均不超过3mm,该措施能保障滑坡的稳定性,同时也验证了计算方法的合理性,可为同类工程提供参考。

Under the forces of expansive soil and landslides,the construction of the tunnel entrance is more likely to cause engineering disasters,such as surface cracking and landslides.The application of micro piles in the tunnel has advantages over anti slide piles.Based on the homogenization theory and upper limit analysis,this study calculates the stability of expansive soil landslide at the entrance of an expressway tunnel,and evaluates the treatment effect of different combinations of micro pile groups and cutting-unloading.In the calculation,to improve the calculation efficiency,the micro pile groups and soil around the piles are equivalent to the plus solid conforming to the Mohr-Coulomb strength criterion based on the homogenization theory.the results then are verified by monitoring the landslide deformation after the cutting and micro pile group reinforcement treatment in the field.This study indicates that compared with the strength parameters of soil,the internal friction angle of equivalent reinforcement remains constant,and the cohesion increases from 26 kPa to 85.36 kPa.The evaluated landslide stability before and after treatment show that the sliding surface of the landslide extends from the rock-soil interface above the landslide to the front of the tunnel portal without treatment;when only using micro pile group reinforcement,the landslide safety factor is about 1.17,and the sliding surface extends from the rock-soil interface to the tunnel portal;when only using both micro pile group reinforcement and cutting-unloading,the safety factor increases from 1.26 to 1.28,and the upper edge of the sliding surface moves forward from the rock-soil interface.The field deformation monitoring shows that the deformation of surface and deep soil are less than 3 mm,which can keep the landslide stable,and also verifies the effectiveness of the calculation method.This study provides beneficial information for similar projects.