深层土侧向应力的试验研究及新认识

Experimental studies and new ideas on the lateral stress in soil

在不同试验室利用多种试验仪对河北省衡水、黄骅等地区埋深500 m以内的多个土样,进行了静止侧压力系数K0试验。试验结果表明:土的静止侧压力系数K0并不总为常数,指出了岩土工程中常用静止侧压力系数公式K0=△σ3/△σ1求侧向应力σ3的适用范围与不足,认为该公式用于垂向应力σ1小于200 kPa时浅部土体求得的侧向应力σ3基本适用,用于垂向应力σ1大于200 kPa的深层土求得的侧向应力σ3则存在一定缺陷,可能引起深部土体工程的不安全隐患或事故。指出了不同类型土的侧向压力σ3与垂向应力σ1存在较好的幂函数相关关系,说明了对相同土样不同试验方法测试侧向应力σ3也有差异,总结出正确求得不同深度土体侧向应力σ3的方法。研究成果可为岩土工程施工与研究提供可靠技术参数。

Soil lateral stress σ3 or earth pressure at rest P0 was extensively used in geotechnical engineering designs and calculations. The coefficient of earth pressure at rest k0 were tested with a large number of samples buried above the depth of 500 m in areas, such as Hengshui, Huanghua of Hebei province etc. by using various instruments in different laboratories. It was shown that k0 was not always a constant, it was a variable, indicating the deficiency of the formula K0=△σ3/△σ1 in calculating σ3. This formula was basically applicable to calculate σ3 when the vertical effective stress σ1 was less than 200 kPa in shallow soil, but it was defective when σ1 was larger than 200 kPa, and might cause unsafety and accidence when it was used in deep soil. It was found that there was a good power-law relations between σ3 and σ1 for different soils, and different experimental methods might acquire different results of σ3. Therefore, an improved method was presented to calculate σ3, which could provide reliable data for geotechnical engineering construction and research.