Recent advances in the application of vertical drains and vacuum preloading in soft soil stabilisation
Recent advances in the application of vertical drains and vacuum preloading in soft soil stabilisation
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发表时间：
2010
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通讯作者：
B. Indraratna
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作者：
B. Indraratna
摘要世界上许多重要的基础设施都是沿着沿着拥挤的海岸带建造的，这些海岸带由高度可压缩和脆弱的土壤组成，直到相当深的地方。软质冲积层和海洋粘土沉积层的承载力非常低，沉降特性过大，对高层建筑和大型商业建筑以及港口和运输基础设施的设计和维护具有明显的影响。在施工前稳定这些软土对于长期和短期稳定性都是至关重要的。仅通过施加超载荷载对软土进行施工前固结通常需要很长时间，除此之外，这些大多数低洼、可渗透且非常厚的粘土沉积物达到90%以上固结所需的荷载可能会在很长一段时间内过高。在成本和效率方面，垂直排水系统结合真空压力和堆载预压已成为一种有吸引力的地基加固方案。该技术通过促进快速径向流动来加速固结，从而在增加有效应力的同时降低超孔隙压力。在过去的15年里，作者和他的同事们开发了许多实验，分析和数值方法，模拟预制垂直排水管（PVDs）和真空预压的力学，包括二维和三维分析，以及更全面的设计方法。这些最新的技术已被应用于澳大利亚和东南亚的各种真实的生活项目。一些新的设计概念包括重叠涂抹区的作用，由于PVD-心轴渗透，孔隙压力预测的基础上椭圆形空腔膨胀理论，和上升和下降的孔隙压力通过预制垂直排水管（PVD）在循环荷载下。这些最新的进展，使超孔隙水压力，横向和垂直位移的稳定地面的预测更准确。这个E.H.戴维斯纪念讲座介绍了通过PVD和真空预压法进行软基加固的理论和实践发展以及突出发现的概述，并应用于澳大利亚，泰国和中国的选定案例研究。
SUMMARY Much of the world’s essential infrastructure is built along congested coastal belts that are composed of highly compressible and weak soils up to significant depths. Soft alluvial and marine clay deposits have very low bearing capacity and excessive settlement characteristics, with obvious design and maintenance implications on tall structures and large commercial buildings, as well as port and transport infrastructure. Stabilising these soft soils before commencing construction is essential for both long term and short term stability. Pre-construction consolidation of soft soils through the application of a surcharge load alone often takes too long, apart from which, the load required to achieve more than 90% consolidation of these mostly low lying, permeable, and very thick clay deposits can be excessively high over a prolonged period. A system of vertical drains combined with vacuum pressure and surcharge preloading has become an attractive ground improvement alternative in terms of both cost and effectiveness. This technique accelerates consolidation by promoting rapid radial flow which decreases the excess pore pressure while increasing the effective stress. Over the past 15 years, the Author and his co-workers have developed numerous experimental, analytical, and numerical approaches that simulate the mechanics of prefabricated vertical drains (PVDs) and vacuum preloading, including two-dimensional and three-dimensional analyses, and more comprehensive design methods. These recent techniques have been applied to various real life projects in Australia and Southeast Asia. Some of the new design concepts include the role of overlapping smear zones due to PVD-mandrel penetration, pore pressure prediction based on the elliptical cavity expansion theory, and the rise and fall of pore pressure via prefabricated vertical drain (PVD) under cyclic loads. These recent advances enable greater accuracy in the prediction of excess pore water pressure, and lateral and vertical displacement of the stabilised ground. This E.H. Davis Memorial Lecture presents an overview of the theoretical and practical developments and salient findings of soft ground improvement via PVD and vacuum preloading, with applications to selected case studies in Australia, Thailand, and China.