深圳典型潜水地层地铁车站基坑降水引起水位变化机理的试验研究

以深圳某地铁车站基坑工程为背景,进行基坑不完整井降水模型试验。结果表明:在降水条件相同的情况下,由于绕渗作用的影响,基坑内降水有效影响深度大于基坑外;由于群井效应的影响,基坑内双井降水有效影响深度大于单井降水;在地连墙深度范围内,基坑外土层中孔隙水压变化值随深度的增加而增大,基坑内不完整井降水引起基坑外降水曲线为"先下凹再上凸"型。基于巴布什金潜水层完整井和不完整井涌水量理论计算公式,推导不完整井降水有效影响深度计算公式。基于模型试验数据,通过曲线拟合得到基坑外降水曲线方程。以实际基坑工程为案例,将采用理论计算公式计算得到的基坑内不完整井降水有效影响深度和基坑外降水曲线与数值模拟结果进行对比,发现有效影响深度误差较小,降水曲线基本吻合,从而验证了理论计算公式的正确性和合理性。

A Modified DRASTIC Approach to Shallow Groundwater Vulnerability in the West Lake Watershed in Hangzhou, China

The quality of shallow groundwater in the West Lake watershed wasinvestigated form March to July 2000. Integrating with BlacklandGRASS GIS system, the DRASTIC model was used to compile the ground-water vulnerability map. A land use factor was added to the DRASTICmodel and the modified model (LDRASTIC0 increased the accuracy ofprediction form 26.9/100 to 51.3/100. The vulnerability map showedthat the lowly, moderately and highly susceptible area predictedoccupied about 11.6/100, 70.9/100 and 17.5/100 of the wholewatershed, respectively. Compared with the observed values of nitrateand electric conductivity, the LDRASTIC index improved the Pearsoncorrelation coefficients form -0.010 to 0.237 and 0.380 to 0.503;Both the improved coefficients were significant at the 0.01 level.The modified DRASTIC analysis showed a Great potential as a screeningtool for policy decision-making in groundwater management.

注浆固结技术在热力隧道穿越富水流沙地层中的应用

在北京市亮马河热力管线穿越东四环东风北桥的施工过程中受到路下现状管线的限制,热力管线需穿越粉细沙滞水、潜水地层,为了防止开挖面粉细沙发生坍塌、流沙和液化失稳的情况,保证东风北桥及其路面结构的稳定,采取了泥水平衡顶管和隧道两种敷设方式并对地层采取注浆固化技术,从而保证了热力管线的安全穿越。加固手段采用双重管深孔注浆,灌浆材料以水玻璃和磷酸为主剂,结果表明所应用的工艺技术达到了预期效果。