超固结土层垂向形变机理及临界水位控沉分析——以西安南郊钻孔土样研究为例

超固结地层发生地面沉降需要一个大于超固结应力的起始附加应力来驱动。依据有效应力原则,临界水位与超固结应力之间存在线性相关关系,则超固结地层垂向形变机理亦可通过临界水位描述为：当人为开采地下水引起的起始水位降深大于临界水位时,地面沉降将明显发生。西安南郊地质技校钻孔埋深100-300m内土样试验资料分析及计算结果表明：该地层普遍呈现超固结特性;第一、二承压含水组的临界水位值分别为63.44m及73.76m;将“临界水位”作为控制地面沉降与最大限度开采地下水资源的主控指标来考虑,是地面沉降的有效防治措施。

Deformation mechanism of over-consolidation soil and land subsidence controlled by critical water-level

For over-consolidated strata, land subsidence usually occurs under the critical condition that initial additional stress is larger than over-consolidation stress. According to the principle of effective stress, there is linear correlationship between critical water-level and over-consolidation stress, so above deformation mechanism can be described as： land subsidence will take place when initial drawdown exceeds critical water-lever. This paper analyzes test data of soil samples from bore at depth 100 - 300m in south Xi＇an City, and obtains conclusions as follows： almost of all strata have over- consolidation characteristics; critical water-level values of the first and second confined aquifer are 63.44m and 73.76m respectively; critical water-level can be served as main-control index of controlling land subsidence and exploiting groundwater resources at maximum.