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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。
The vacuum preloading reinforcement method has been widely used as a soft clay reinforcement technology. However, it is not very reasonable to apply the currently used construction technology (vacuum action surface at the surface) to reinforce the dredger fill. It leads to high investment, long construction period and so on. We believe that a more reasonable approach is to move the vacuum effect surface deep. This article describes the model tests conducted with the same soil material under the same test conditions. The test compares the reinforcement effect of the vacuum action surface at the bottom and top of the specimen. In addition, the effect of the distance between the drain pipes on the reinforcement effect was also compared. In the test, the vacuum process in the sand mat, the vacuum suction in the sludge, the time course of the sedimentation and the water output were determined. The changes in the moisture content before and after the test and the distribution of the shear strength of the cross plate were also measured. Axis Shear Tests determine changes in soil properties. In order to make a quantitative comparison, this paper starts from the basic principles of soil mechanics, and introduces parameters such as the coefficient of consolidation, the effective stress growth coefficient, and the ratio of excess pore pressure coefficient. Tests show that after the vacuum action surface moves to the bottom, a good reinforcement effect will be achieved. In addition, the spacing of vacuum drains can have a significant effect on the reinforcement effect.