干湿效应下崩岗岩土不均匀沉降变形规律与崩壁崩坍机制

Mechanism of effects of wetting-drying on nonuniform settlement and caved wall collapse in slope disintegration erosion area

发育于花岗岩出露区崩岗岩土受干湿效应影响显著,导致崩壁坍塌和工程设施受损。通过崩解和快速固结试验,采用6种干湿水平研究干湿路径、固结压力对崩壁岩土相对变形率的影响。结果显示,脱湿过程中裂隙性是影响相对变形率主要因素,而在增湿过程中基质吸力、崩解性、土壤质地则共同决定了不同压力下相对变形率高低。当超过平均先期固结压力103.06 kPa后,相对变形率随固结压力增加而增大;压缩系数与初始含水率呈指数递增关系,初始含水率超过25%后压缩系数剧增;红土层①的压缩系数变化幅度最广(0.15~0.62 MPa-1),均值最大(0.31 MPa-1)。从干湿效应导致的不均匀沉降角度揭示了崩壁崩坍机制,并讨论了崩岗区水保工程和监测设施不均匀沉降防治原则。其结论可为崩岗防治,工程设施维护提供一定科学依据。

Effect of wetting-drying on soils derived from granite is significant;and it causes collapse of caved walls or damage of engineering facilities. Slaking test and consolidation test with 6 wetting-drying level treatments are performed to identify effects of wetting-drying paths and consolidation pressures on relative deformation ratio. The results show that crack is the main reason for the relative deformation ratio at dehumidifying stages, while relative deformation ratio depended on matric suction, slaking property, and soil texture at humidifying stages. Relative deformation ratio increased with consolidation pressures especially in excess of preconsolidation pressure of 103.06 kPa. The relationship between coefficient of compressibility and initial water content conformed to an exponential function, and coefficient of compressibility increased rapidly with the initial water contents beyond 25%. Laterite layer ① had the most range of compressibility coefficient (0.15-0.62 MPa-1) with the average value of 0.31 MPa-1. The mechanism of caved wall collapse also is revealed from non-uniform settlement due to wetting-drying effect. Some countermeasures of engineering facilities in disintegration erosion area against nonuniform settlement are discussed. The obtained results could offer references to engineering maintenance and slope disintegration erosion control.