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在河流下切、斜坡成坡过程中,斜坡应力场不断调整和适应坡体的变化,表浅部岩体在应力变化过程中往坡外发生卸荷,在同一地区岩体卸荷深度应当相差不大。而在西南某水电站相隔仅1.4km上下坝址勘察过程中发现,两坝址岩体卸荷深度却存在较大差异,上坝址岩体卸荷深度在20m以上,最大深度达到90m;下坝址岩体卸荷深度仅为5~20m。,通过现场调查及数值模拟成果表明,上下坝址岩层方位是两坝址岩体卸荷差异的决定性因素,上坝址为顺向坡,岩层走向与边坡走向平行,倾角较陡的岩层形成拉裂面,易于风化营力的侵入,岩体卸荷深度大;下坝址为横向坡,岩层走向与边坡走向近于垂直,岩体强度远大于岩层面的强度,且平行坡向的结构面数量少,岩体卸荷深度在20m以内。
During the process of slope cutting and slope cutting, the slope stress field is continuously adjusted and adapted to the change of the slope body. The unloading of the surface superficial rock mass to the outside of the slope occurs during the stress change. The unloading depth of the rock mass in the same area should be different Big. However, during the survey of upper and lower dam sites of only 1.4km apart from a certain hydropower station in southwest China, it is found that the unloading depth of the two dam sites is quite different. The unloading depth of the upper dam site is above 20m and the maximum depth reaches 90m. Site rock unloading depth of only 5 ~ 20m. The results of field investigation and numerical simulation show that the rock orientation of the upper and lower dam sites is the decisive factor for the difference of the unloading of rock mass between the two dam sites. The upper dam site is a forward slope, and the strike of the rock formation is parallel to the strike of the slope and the steep dip formation Which is easy to weathering and camping. The depth of unloading of rock mass is large. The lower dam site is horizontal slope. The strike of the rock and the direction of slope are close to vertical. The strength of rock mass is much larger than that of rock face, A small number of structural planes, rock unloading depth within 20m.