真空作用面位置及排水管间距对预压效果的影响

The Influence of Vacuum Location and the Spacing of Drain Well on the Effect of Preloading Improvement

真空预压加固法作为一种软粘土的加固技术已得到广泛的应用。但是,把目前经常采用的施工技术(真空作用面位于地表)用于加固吹填土,就不十分合理。它导致投资高昂、施工期限过长等。我们认为,比较合理的方法是把真空作用面移向深处。本文介绍了以同一种土料,在同样的试验条件下所进行的模型试验,试验中比较了真空作用面位于试样底部及顶部的加固效果。此外,还比较了排水管间距对加固效果的影响。试验中测定了砂垫层内的真空度、淤泥中的真空吸力、沉降及出水量的时间过程线,还测定了试验前后的含水量变化及十字板抗剪强度的分布,并取土做三轴剪切试验测定土特性的变化。为了做出定量的比较,本文从土力学的基本原理出发,引进了固结度系数、有效应力增长系数、超孔隙压力系数比等参数。试验表明,真空作用面移向底部后,会取得较好的加固效果。此外,真空排水管间距对加固效果会有明显的影响。

As a mathod of improvement of soft foundation, the vacuum, preloading method has been widely used, However, the traditional method that vacuum is applicated on the ground surface is not perfect for the dredged marine clay fill. It costs too expeneive and lasts long period. It is considered that the vacuum surface moves down to the deeper level would be better than that on the ground surface, the model tests performed in laboratory with the samo materials and testing condition are introduced in this paper, The improving effect of different vacuum levels and the influence of the spacing of drain well on are compared. The vacuum value in the sandmat and the negative pressure, the settlement and the volume of water output in the peat were measured. The variation of water content, the distribution of the vane strength aloag the depth of clay fill and the triaxiai compression strength after testing are also measured so as to clarify the changes of soil behaviours, according to the fundamental of soil mechanics, some parameters, including the coefficient of consolidation degree, the coefficient of effective stress increment and the coefficient of excess pore pressure are introduced. The results are presented that it would more reasonable when the vacuum surface moves down to the lower level. To shorten the spacing of drain well would have an efficient improvement of soft clay fill.