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以沪渝高速公路湖北段平缓反倾红砂岩为研究对象,在平缓反倾红砂岩高陡边坡中岩体易软化崩解。自然冲侵蚀形成的高陡山体卸荷变形可达几十毫米至近百毫米,卸荷变形破裂方向与构造节理重叠,使节理裂隙变宽,贯通性提高,为高陡坡体提供了顺坡向陡直破裂面。加之公路切坡卸荷变形和坡体软化变形,岩体软化后的变形模量下降约80%,卸荷变形和软化变形各有数毫米的变形量,与自然坡体卸荷重叠,使坡体变形进一步加大,使红砂岩坡体潜在不稳定性增大。同时地下水作用使卸荷裂隙充填一定高度的静水压力,还使岩体产生软化,岩块软化系数一般在0.3~0.7,导致岩体强度显著下降,30～40 m高的静水压力可使边坡的稳定性系数从开挖前的5.56降至1.96,开挖后从2.77降至1.07,这两方面的作用可使切坡后较稳定的反倾坡体变化到极限平衡状态,甚至失稳状态。因此,施工中要特别注意切坡后的即时加固,并采取措施防止卸荷裂隙中地下水聚积,减少地下水对坡体的软化。
Taking the flat anti-dip-red sandstone in Hubei section of Hu-Yu Expressway as the research object, the rock mass is easy to soften and disintegrate in the steep slope with gentle anti-dip red sandstone. Natural erosion erosion formed by high mountain steep unloading deformation up to tens of millimeters to nearly 100 millimeters, the direction of unloading deformation and structural overlap overlap, so that joint fissures broaden and improve the continuity for the high steep slope slope provides a steep slope Straight rupture surface. Coupled with the unloading of road cutting and slope softening deformation, the deformation modulus of rock mass after softening decreased by about 80%, unloading deformation and softening deformation of several millimeters of deformation, and natural slope unloading overlapping, so that slope Deformation further increased, red sandstone slope potential instability increases. At the same time, the groundwater can fill the unloading fissures with a hydrostatic pressure at a certain height and soften the rock mass. The softening coefficient of the rock mass is generally between 0.3 and 0.7, resulting in a significant decrease of the rock mass strength. The hydrostatic pressure of 30-40 m can make the slope The stability coefficient decreased from 5.56 before excavation to 1.96 and from 2.77 to 1.07 after excavation. These two effects can make the more stable anti-slope body after cutting slope change to the limit equilibrium state or even the unstable state . Therefore, special attention should be paid to the immediate reinforcement after slope cutting in construction and measures should be taken to prevent the groundwater from accumulating in the unloading cracks to reduce the softening of the slope body by groundwater.