考虑淤堵效应的疏浚淤泥真空固结沉降计算

Calculation on the settlement of dredged slurry treated by vacuum preloading method with consideration of clogging effects

疏浚淤泥含水率高、强度极低,真空梯度作用下排水板周围会快速形成致密"土柱",导致排水固结能力迅速下降,即出现淤堵现象。由疏浚淤泥真空固结室内模型试验获得了出水量变化情况和土体含水率、渗透系数的时空分布情况,确定了排水体周围淤堵区的形成时间与范围,提出了考虑时间效应与淤堵效应的真空度传递模式,同时考虑疏浚淤泥土体压缩和渗透的非线性,建立了考虑淤堵效应的固结分析模型,获得了相应的解析解,通过与已有数据和现场试验结果对比验证了该解答的有效性。利用该解析解,分析了真空度传递模式、淤堵系数λ和淤堵比c对沉降的影响。结果表明,淤堵效应明显减缓了沉降速率,也严重降低了疏浚淤泥的最终沉降量。

The dredged slurry has high water content and very low strength.It is generally considered that there will be no smear effect when the PVD is inserted.However,the dense"soil column"will be formed rapidly around the PVD under the vacuum pressure,which will greatly reduce the drainage capacity and fail to consolidate,i.e.clogging.The clogging effect of vacuum preloading on the dredged slurry is studied through laboratory tests.Based on the drainage volume and rate with consolidation time in the test,the formation time and the range of clogging zone are determined by the spatial and temporal distribution of the water content and permeability coefficient of soils.A vacuum transfer mode considering the clogging effect and the time effect is proposed.At the same time,considering the nonlinear relationship between the compressibility and the permeability of soils,an analysis model for analyzing the consolidation considering the clogging effect is established and the corresponding analytical solutions are obtained.The validity of the analytical solution is verified by comparing with the existing data and field test results.The influence of vacuum transfer mode,λand c on the final settlement is analyzed by using the analytical solution in this work.The results show that the clogging effect obviously slows down the settlement rate and greatly reduces the final settlement of dredged slurry.