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研究在干湿循环和集中降水条件下甘肃古浪砂岩泥岩互层顺层边坡的崩塌机制,对于砂岩此类边坡的崩塌治理具有重要意义。崩塌机制可概括为在干湿循环作用下软层泥岩反复胀缩,致硬层砂岩产生节理并贯通;在集中降雨影响下泥岩崩解致砂岩悬空,极限平衡打破则形成倾覆崩塌或滑动崩塌。基于室内侧限膨胀试验和直剪试验,考虑泥岩遇水膨胀和软化共同作用,建立膨胀性顺层边坡的砂岩抗裂、倾覆和滑动稳定力学模型,推导相应的抗裂系数、倾覆和滑动稳定系数计算公式,并在实际工程中进行了应用与验证。研究表明:(1)在含水率阈值范围内,泥岩的抗剪强度随着含水率的增加而增大,吸水膨胀所产生的膨胀力对抗剪强度起主要作用;当含水率超过阈值,则抗剪强度随着含水率的增加而减小,此时泥岩吸水致抗剪强度参数c,φ值降低对抗剪强度起主要作用。(2)悬空砂岩抗裂系数与砂岩岩层厚度的平方成正比,与下层泥岩的膨胀力成反比,与下层泥岩风化深度的平方成反比。(3)悬空砂岩的滑动稳定系数与岩层厚度成反比,与w d w(d-d)/d成正比,砂岩岩层倾角呈负相关关系,与抗剪强度参数c,φ呈正相关关系。
It is important to study the collapse mechanism of the bedding bedding slope of Gulang sandstone in Gansu under the conditions of wet-dry circulation and concentrated rainfall. Collapse mechanism can be summarized as repeated expansion and contraction of soft mudstone under wetting and drying cycles, resulting in joint formation and penetration of hard sandstone; under the influence of concentrated rainfall, the sandstone is dilapidated by the collapse of mudstone and is overthrown or slipped by limit equilibrium. Based on the lateral expansion test and the direct shear test, the mechanical model of anti-cracking, overturning and sliding stability of sandstone with expansive bedding slope is established, and the corresponding anti-cracking coefficient, overturning and sliding Stability coefficient calculation formula, and in the actual project has been applied and verified. The results show that: (1) Within the range of water content, the shear strength of mudstone increases with the increase of water content, and the swelling force caused by water swelling plays a major role in shear strength; when the water content exceeds the threshold, The shear strength decreases with the increase of water content. At this time, the decrease of the shear strength parameters c and φ due to the absorption of mudstone plays a major role in the shear strength. (2) The coefficient of anti-cracking of suspended sandstone is proportional to the square of the thickness of sandstone, inversely proportional to the swelling force of the lower mudstone and inversely proportional to the square of the depth of the lower mudstone. (3) The sliding stability coefficient of suspended sandstone is inversely proportional to the thickness of the rock, which is in direct proportion to w d w (d-d) / d. The dip angle of sandstone is negatively correlated and has a positive correlation with the shear strength parameters c and φ.