上海地区土体静止侧压力系数的试验研究

静止侧压力系数K_0是进行地下结构设计时必不可少的参数,准确确定K_0系数具有重要的工程意义。依托上海深隧工程,采用三轴仪开展K_0固结试验,研究不同加、卸载路径下土体K_0系数的变化规律,分析了几种常见的静止侧压力系数确定方法的适用性,并根据试验结果得到了新的预测公式。结果表明:(1)深部黏性土的K_0值在0.30～0.45之间,且与土层的先期固结压力成正比;(2)在取土引起的应力释放到再加载的过程中,部分试样的K_0值先减小至低于正常固结值,再增大并逐渐稳定;(3)采用经验公式估算K_0值时,土体内摩擦角宜采用正常固结时的有效峰值内摩擦角。

Experimental Study on Static Lateral Pressure Coefficient of Soil in Shanghai Area

Static lateral pressure coefficient K0 is an essential parameter in the design of underground structures. It is of great engineering significance to accurately determine the coefficient K0. Relying on a deep tunnel project in Shanghai, the K0 consolidation test is carried out by triaxial apparatus, and the change laws of K0 coefficient of soil under different loading and unloading paths are studied. The applicability of several common methods for determining the static lateral pressure coefficient is analyzed. Besides, the new prediction formula is established based on the test results. The results show that: (1) the K0 value of the deep clayed soil is between 0.30 and 0.45, and is proportional to the pre-consolidation pressure of soil layer; (2) The K0 value of some samples first decreases to lower than the normal consolidation value, then increases and gradually stabilizes during the process of stress release and reloading caused by soil borrowing; (3) the effective peak internal friction angle under the normal consolidation condition is recommended when estimating the value of K0 by using the empirical formulas.