名山组泥岩顺层边坡原位直剪试验及开挖模拟

In-situ Direct Shear Test and Excavation Simulation of MudstoneBedding Slope in Mingshan Formation

为研究川西名山组泥岩顺层边坡在坡脚开挖后的卸荷特征,通过原位直剪试验获取了名山组泥岩的岩体破坏及强度特征,并进一步采用有限元模拟分析了坡脚开挖后顺层边坡的卸荷松动特征。结果表明:名山组泥岩的剪切破坏可分为弹性受荷阶段、裂缝发展阶段和剪切面贯通后阶段;岩体结构面强度显著低于岩石,且强度曲线特征受上覆荷载影响较大;岩石的应变软化特征较结构面更为显著,剪切面贯通后强度急剧衰减,且降幅远高于结构面;坡脚开挖卸荷后,顺层边坡的卸荷松动区主要分布于基覆界面、风化界面和临空面附近的岩层层面处,卸荷深度与切层厚度线性正相关;设计采用的边坡防护方案能有效控制位移及应力,桩前土体开挖时需注意信息化施工。

In order to study the unloading characteristics of mudstone bedding slope of Mingshan Formation in western Sichuan after excavation at the foot of slope,the failure and strength characteristics of mudstone in Mingshan Formation were obtained by in-situ direct shear test,and the unloading and loosening characteristics of bedding slope after excavation at the foot of slope were further analyzed by finite element simulation.The results show that the shear failure of mudstone in Mingshan Formation can be divided into elastic loading stage,fracture development stage and post-shear surface penetration stage.The strength of rock mass structural plane is significantly lower than that of rock,and the characteristics of strength curve are greatly affected by overlying load.The strain softening characteristics of rock are more significant than that of structural plane.The strength of shear plane decreases sharply after penetration,and the decrease is much higher than that of structural plane.After excavation and unloading at the foot of the slope,the unloading loose zone of the bedding slope is mainly distributed at the rock layer near the base-cover interface,weathering interface and free surface.The unloading depth is linearly positively correlated with the thickness of the cut layer.The slope protection scheme adopted in the design can effectively control the displacement and stress.Information construction should be paid attention to when excavating the soil in front of the pile.