基于现场波速测试的盾构掘进施工土体扰动区域研究

Study on soil disturbance area under shield tunnelingbased on field shear wave velocity test

依托杭州12号大街提升改造工程,结合与土体扰动关系密切、且易于获取的剪切波速,对盾构穿过的地层进行现场剪切波速测试,获取了穿越前后土层剪切波速剖面图。通过对测试结果的分析,发现波速变动对土体扰动是可行的,并确定了受盾构施工扰动土体的剪切波速变化规律,同时对盾构扰动范围进行了相对明确的划分。结果表明:盾构对上方土体的扰动主要集中在盾构隧道顶部9 m范围内的区域,且距离盾构越近,受扰动程度越大;监测点处的土体受到扰动,其剪切波速表现出先降低,后短暂上升,继而持续下降的变化趋势,反映了盾构掘进过程中土体松动、挤压和沉降等扰动状态及力学特性的变化。

Based on the upgrading project in No.12 Street,Hangzhou,shear wave velocity tests are conducted on the stratum where a shield tunneling machine(STM)passes by and the geological profiles of wave velocity are obtained before and after the STM passes through the building since the shear wave velocity directly represents the stiffness of soil and is easy to obtain.Through the analysis of the test results,it is found that the wave velocity variation is feasible for soil disturbance and the shear wave velocity variation of the soil disturbed by shield construction is determined.At the same time,the shield disturbance range is relatively clearly delineated.The results show that the disturbance of the soil above the shield is mainly concentrated in the area within 9 meters from the top of the shield tunnel,The closer the shield is,the larger the disturbance extent is.The shear wave velocity of the soil at the monitoring point first decreases,then temporarily increases,and finally continuously decreases during the shield crossing,which reflects the changes of the disturbance state and mechanical properties of soil such as loosening,extrusion,and subsidence during the shield tunneling process.