振动作用下土钉-粉土界面受力特性模拟试验研究

Simulation test study on shear stress characteristics of soil nail interface in silt under vibration

为研究近接施工产生的振动作用对基坑土钉支护体系土钉受力的不利影响。针对振动作用对土钉与土体界面受力特性的影响问题,开展土钉拉拔界面剪切模拟试验,研究不同土体含水率和上覆压力下,振动作用对钉-土界面剪应力和界面剪切强度的影响规律。振动作用下,钉-土界面剪应力呈现非线性衰减趋势,剪应力越大,衰减量越大;振动初期,界面剪应力降幅较大,随着振动时间增加,界面剪应力降低趋势逐渐收敛;在土体含水率和振动时间相同时,上覆荷载越大,钉-土界面剪应力越大;上覆荷载和振动时间相同时,含水率越大,钉-土界面剪应力越小。振动作用引起土体及钉-土界面扰动损伤,界面摩擦角和黏聚力衰减,界面剪切强度显著降低;较大的上覆荷载使钉土间相互作用加强,有助于降低振动作用的影响;在振动作用下,土体含水率对钉-土界面剪切受力的影响较静力条件下更为显著。研究结果为振动作用下土钉承载力量化计算及土钉类基坑支护安全分析与控制提供支撑。

In order to study the adverse effect of vibration caused by near construction on soil nailing force of foundation pit soil nailing support system.Aiming at the influence of vibration on the mechanical characteristics of soil nail-soil interface,the shear simulation test of soil nail pullout interface was carried out to study the influence of vibration on the shear stress and shear strength of nail-soil interface under different soil moisture content and coating pressure.Under vibration,the shear stress at the nail-soil interface showed a nonlinear attenuation trend.The greater the shear stress,the greater the attenuation.In the early stage of vibration,the interfacial shear stress decreased greatly,and the decreasing trend of interfacial shear stress gradually converged with the increase of vibration time.When the soil moisture content and vibration time are the same,the greater the load,the greater the shear stress of the nail-soil interface;when the load and vibration time are the same,the greater the moisture content,the smaller the shear stress of the nail-soil interface.Vibration causes disturbance damage to the soil and the nail-soil interface,the interface friction angle and cohesion are attenuated,and the interface shear strength is significantly reduced.Under the action of vibration,the influence of soil moisture content on the shear force of the nail-soil interface is more significant than that under static conditions.The research results provide support for the quantitative calculation of soil nailing bearing capacity under the action of vibration and the safety analysis and control of soil nailing foundation pit support.