饱和软黄土地层降水及引起周边环境沉降特点 ---以西安地铁5号线为例

以西安地铁5号线某区间工程为背景,根据现场施工过程情况及监测数据,研究了饱和软黄土地层的降水特性及其引起周边环境沉降特点。研究结果:饱和软黄土地层工程性质差,施工风险高,地下水处理是施工首要条件,降水是处理饱和软黄土的重要手段;饱和软黄土地层降水影响范围大,周边环境沉降较大,平均每降水1 m,约产生10 mm沉降;降水突变影响区内地层累计沉降及差异沉降均较大,但非降水突变影响区呈整体性、均匀性沉降,差异沉降较小;降水前期,临近建筑物沉降速率大于地面沉降速率;饱和软黄土地层的失水固节持续时间较长,其主要失水固节沉降时间一般大于1. 5个月。

The Characteristics of Dewatering in Saturated Soft Loessial Strata and Settlement of Surroundings Caused by it ---Take Xi"an Metro Line 5 as an Example

According to the construction process and monitoring data of an interval tunnel in Xi"an Metro Line 5, this paper mostly studies the characteristics of dewatering in saturated soft loessial areas and its impact on the settlement of the surroundings. The results show that the saturated soft loess has poor engineering properties and high risks of construction. So the primary condition of construction is to deal with the groundwater, and dewatering is an important means to deal with saturated soft loess. The rainfall in saturated soft loessial areas has broad influence and causes large settlement of surrounding environment. Every 1 meter of rainfall produces about 10 millimeters of subsidence. Abrupt dewatering change can largely affected the accumulative and differential settlement of stratum in the area. While the areas without abrupt change of dewatering presents holistic and uniform settlement, and the differential settlement is small. In the early stage of dewatering, the settlement rate of adjacent buildings is greater than that of the surface land. The duration of water loss and consolidation joints in saturated soft loess is longer, and the settlement time of main water loss and consolidation joints is generally more than 1.5 months.