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膨胀土地基条件下建筑物沉降变形特点及控制方法研究
Study of Settlememnt Characteristics and Control Measures on Structures Built on Expansible Foundation Soil
摘要
膨胀土形成于第四纪上更新世Q3及其以前,是以蒙脱石或蒙脱石-伊利石为主要矿物成分的高塑性黏土。黏粒含量高,自由膨胀率大于等于40%。吸水膨胀、失水收缩是它的一个主要特点,由于气候条件的变化、季节的更替,建筑物的地基土不断地产生上、下的胀缩变形,从而导致建筑物或构筑物的上、下往复运动甚至开裂和损坏,且不易修复。本文将从膨胀土的特性出发,结合膨胀性土建筑地基变形计算理论研究现状,以对膨胀性土胀缩变形机理和变形条件研究成果为基础,采用理论分析方法,通过对膨胀土的胀缩变形及其影响因素的分析来研究膨胀性地基条件下建筑物沉降变形的发生发展过程和沉降变形的特点,从而得出对此条件下建筑物沉降变形的控制技术和工程措施。本文通过对膨胀土地基上建筑物的破坏特征情况的分析,总结出膨胀土地基上建筑物破坏裂缝的类型及产生的原因,为膨胀土上建筑物的合理设计提出了减少胀缩变形的预防措施;在上述各项分析和研究的基础上,本文介绍了膨胀土地区建筑物的设计措施、并从加固机理、适用范围与施工技术方面,结合膨胀土工程性质的多年研究成果与我国大量工程实践的应用效果,介绍了膨胀土地基的几种主要处理方法,以及膨胀土地基上的建筑物由于地基的胀缩变形引起建筑物的开裂破坏时的控制方法。
Abstract
Expansible soil was believed to have been formed during Pleistocene period of Quarternary System or earlier times. It consists of montmorillonite and/or montmorillonite-illite and normally falls into high plasticity soil category. The expansibe soil is characterised by a high clay content, with a free swelling rate of 40% or greater; it swells when soaked with water and shrinks if moisture loss occurs. The change in soil moisture is subjected to alternating of seasons, which may lead to the swelling and contracting of foudnation soil and therefore may create structural damages to the buildings/structures under a periodical movements. Such damage is substantial and difficult to repair. The paper was based on properties of expansible soil, current settlement analysis theory, mechanism of soil swelling and contracting, and research results on conditions of deformation. A theortical method was adopted during the study, in which the factors influencing soil swelling and contracting properties were analysed to study the process and features of settlement developed in building foundations with expansible soil. The counter-measures were therefore proposed to control the settlement. The paper also conducted an analysis on features of structural damages caused by expansible soil. The types and causes of the cracking on structures were discussed and preventing measures were also proposed. Based on the various analyses and studies, the paper addressed the design and treatment measures for expansible soil. Several commonly used foudnation treatment measures and deformation/cracking control methods for expansible soil were introduced based on foudnation improvement theory, construction technique, years of research results on expansible soil engineering properties, and numbers of engineering practice.
工程实践证明:这些措施都是行之有效的。这些都为膨胀土地基的治理提供了科学的依据。
The measures proposed were proven to be valid and effective during the engineering application. It provided a scientific grounds for treatment of foundations with expansible soil.
关键词:膨胀土,地基胀缩变形,变形量计算,变形分析,工程措施
Keywords: Expansible soil, swelling and contracting of foudnation soil, deformation estimate, deformation analysis, engineering counter-measures |
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