干湿循环下红砂岩强度衰减规律及工程应用

Strength attenuation law and engineering application of red sandstone with the action of dry-wet cycles

干湿循环作用下红砂岩岩体强度衰减是导致红砂岩边坡失稳的重要原因.针对这一现象,选取湖南省某在建高速公路具有代表性的红砂岩,采用烘干-浸泡的方式模拟岩石及结构面干湿循环过程,对干湿循环作用下红砂岩岩体抗劈裂强度及抗剪强度进行试验.试验结果表明,随着干湿循环作用次数的增加,岩石抗劈裂强度降低了55.7%,内摩擦角及粘聚力分别降低了75.6%及25.9%,结构面内摩擦角及粘聚力分别降低了72.7%及23.4%;结构面抗剪切强度远远小于岩体抗剪切强度,这是影响边坡稳定性的主要因素.运用试验结果对实际边坡进行安全系数计算,发现干湿循环作用下边坡安全系数降低了约60%.

An important reason leading to the red sandstone slope instability is that the rock and structural plane strength decay under the action of dry-wet cycles.A representative red sandstone and structural plane of a under-construction freeway in Hunan Province was selected to study the strength attenuation law and engineering application of red sandstone.In order to simulate the process of rock and structural plane dry-wet cycles,the experiment was conducted with the mode of soaking and drying.The results show that with times increase of dry-wet cycles,the attenuation degree of anti-splitting strength,cohesive force and internal friction angle of rock are 55.7%,75.6% and 25.9% respectively.The attenuation degree of cohesive force and internal friction angle of structural plane are 72.7% and 23.4%.The influence of dry-wet cycles on cohesive force is greater than internal friction angle.In addition,as the main influence factor of slope stability,the shearing strength of the structural is far lower than the shearing strength of the rock.Using test results,through the calculation of slope safety factor,it is found that the attenuation degree of safety factor is 60% with the action of dry-wet cycles.