软土地基渗透性条件对基坑预降水过程中支护墙侧移的影响研究

发布时间：2018-11-26 16:38

【摘要】：最新工程案例表明,在基坑开挖前,现场预降水可引起支护墙发生显著初始侧移。依托工程实测资料,建立并验证了数值分析模型,通过一系列参数分析研究了软土地基渗透性条件对基坑开挖前预降水过程中支护墙侧移的影响规律及机制。结果表明,基坑预降水深度范围内土层渗透系数越大,渗透性各向异性越明显;在相同的预降水时间内,被降水土层中将会发生更大程度的孔隙水压力减小;在更强的墙-土界面总压力重分布下,预降水引起的支护墙侧移更大。预降水过程中支护墙侧移沿深度的分布范围与预降水深度底部及其以下土层渗透性有关,若为渗透性较差的深厚弱透水层,则当预降水深度位置不超过0.5倍该弱透水层厚度位置时,支护墙侧移将主要发生在预降水深度范围内;若为渗透性较好的透水层,预降水引起的支护墙侧移深度范围可能达到该层以下的另一弱透水层单元位置处。另外,当预降水深度底端紧邻透水性较好土层时,再增大预降水深度会引起支护墙发生较大增量的侧移,此时,应严防"超降";当预降水深度底面以下为深厚弱透水层时,再增大预降水深度引起的支护墙侧移增量并不明显。
[Abstract]:The latest engineering cases show that the site pre-dewatering can cause the significant initial lateral displacement of the retaining wall before the excavation of the foundation pit. Based on the measured data of engineering, the numerical analysis model is established and verified. Through a series of parameter analysis, the influence law and mechanism of permeability condition of soft soil foundation on the lateral displacement of retaining wall during pre-dewatering process of foundation pit excavation are studied. The results show that the larger the soil permeability coefficient is, the more obvious the permeability anisotropy is in the pre-dewatering depth range of foundation pit, and the larger pore water pressure will occur in the dewatering soil layer at the same pre-dewatering time. Under the stronger distribution of the total pressure between the wall and the soil interface, the side shift of the retaining wall caused by pre-dewatering is larger. The distribution range of the lateral displacement depth of the retaining wall in the process of pre-dewatering is related to the permeability of the soil layer at the bottom of the pre-dewatering depth and below, if it is a deep and weak permeable layer with poor permeability. When the depth of pre-precipitation is less than 0.5 times of the thickness of the weak permeable layer, the lateral displacement of the retaining wall will mainly occur in the depth range of pre-precipitation. For a permeable layer with good permeability, the depth range of the lateral displacement of the retaining wall caused by pre-precipitation may reach the location of another weak permeable layer unit below the layer. In addition, when the bottom end of the pre-precipitation depth is close to the better permeable soil layer, increasing the pre-precipitation depth will cause a larger increment lateral shift of the retaining wall. At this time, the "overfall" should be strictly prevented. When there is a deep weak permeable layer below the bottom of the pre-precipitation depth, the lateral displacement increment of the retaining wall caused by increasing the pre-precipitation depth is not obvious.
【作者单位】：湖南科技大学岩土工程稳定控制与健康监测湖南省重点实验室;天津大学滨海土木工程结构与安全教育部重点实验室;广西大学工程防灾与结构安全教育部重点实验室;
【基金】：国家自然科学基金项目(No.51308209,No.51578164,No.51708206,No.11602083) 湖南省自然科学基金项目(No.2016JJ6044) 湖南省教育厅项目(No.15C0557)~~
【分类号】：TU753.66

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