随着城市建设的发展,深基础工程越来越多,往往需要采用井点降水进行基础施工。因此,如何防止降水对周围建筑物的危害问题已日益引起人们的重视。一、降水产生的沉降及其危害 1.产生沉降的原因在软土中进行井点降水时,其影响半径范围内的土层中的孔隙水不断减少,地下水位下降,造成土层中间向上的水头压力减小,土层原来的压力平衡状态被破坏。由于地下水位下降,土层中的粘性土含水量减少,产生固结而大大压缩;土层中的含水砂层水的浮托力减小而被压密。这样,粘性土大量的压缩和砂层的压密的叠加,反映在地面上 With the development of urban construction, there are more and more deep foundation projects and it is often necessary to use well-point precipitation for basic construction. Therefore, the problem of how to prevent precipitation from harming surrounding buildings has increasingly attracted people’s attention. 1. Settlement and damage caused by precipitation 1. Causes of sedimentation When well-point precipitation is performed in soft soil, the pore water in the soil layer within the radius of influence is continuously reduced, the groundwater level is decreased, and the middle layer of soil is upward. As the head pressure decreases, the original pressure balance of the soil layer is destroyed. Due to the drop of the groundwater level, the water content of clay soil in the soil layer is reduced, resulting in consolidation and greatly compressed; the floating sand force of the water-bearing sand layer in the soil layer is reduced and compacted. In this way, the superposition of cohesive soil and the compaction of sand layers are reflected on the ground.