厚风积砂覆盖地层立井井壁竖直附加力与井壁结构

采用物理试验方法,初步开展饱和砂与井壁混凝土界面竖向剪切试验,获得了界面竖向抗剪强度指标;基于数值计算,进一步研究厚风积砂覆盖地层立井井壁竖直附加力的变化规律。结果表明:风积砂地层中,井壁竖直附加力随深度的增加呈现出非线性增长规律,并在风积砂含水层与基岩交界面附近达到极值;进入基岩段后,竖直附加力部分由基岩分担,附加力急剧减小。在厚度超过100 m的风积砂地层中,随着含水层水位的不断下降(如超过20 m),传统的双层复合井壁结构在竖直附加力等作用下,于基岩交界面附近可能出现井壁破裂灾害,应采用适应地层沉降的可缩井壁结构限制竖直附加力的增长。

Vertical additional force and structure of shaft lining in thick aeolian sand strata

Through physical experiment and numerical calculation, the vertical shear test between sat-urated sand and shaft concrete interface was preliminarily studied, and some interface shear strength parameters were obtained. The variation of vertical additional force on shaft lining in thick aeolian sand strata was further studied through numerical calculation. Research results have shown that 1) The verti-cal additional force presents nonlinear growth rule as the depth in aeolian sand strata increases, and the maximum vertical additional force appears near the interface between aeolian sand and bedrock; and 2) After entering the bedrock, vertical additional force rapidly decreases because of bedrock force-sharing effect. In more than 100 meters depth of aeolian sand, as water level of aeolian sand aquifer declines (such as decline more than 20 meters), traditional double layer shaft lining can be ruptured near the in-terface between aeolian sand and bedrock under the action of vertical additional force. Therefore, the compressible shaft lining structure should be adopted to limit the increase of vertical additional force in thick aeolian sand strata.