土工格栅黏性土界面特性的拉拔试验分析

作者简介：肖成志(1976),男,博士, 副教授，主要从事土工合成材料及其加筋结构特性方面的研究,(Email)。摘要：筋土界面特性是影响加筋土结构性能的重要因素之一，利用中型拉拔模型试验分析了界面正应力和黏性土含水量对格栅黏性土界面相互作用特性的影响，试验结果表明黏性土含水量对格栅极限抗拔力、界面黏聚力和摩擦系数影响明显。不同界面正应力下格栅极限抗拔力在含水量较小时差别显著，随着黏性土含水量增加，格栅极限抗拔力和界面摩擦系数呈现减少趋势，而筋土界面间黏聚力先增大后减小，且当含水量达到塑限含水量时，三者均趋于稳定。格栅抗拔力位移曲线均经历线性和非线性增加以及拉拔极限阶段，并随含水量增加，抗拔力位移曲线由线性增长向极限状态发展的中间阶段逐渐缩短。在拉拔最大载荷下持续一段时间后卸载，发现格栅的横肋应变有增大的趋势，而纵肋应变呈现减小的趋势。

关键词：土工格栅; 筋土界面特性; 拉拔试验; 黏性土

中图分类号：TU476文献标志码：A文章编号：16744764（2012）03004705

Pullouttest Analysis on Properties of Interface between Geogrid and Clay

XIAO Chengzhi1, FENG Xiaojing2

(1. Technology and Research Center of Civil Engineering, Hebei Province, Hebei University of Technology, Tianjin 300132, P.R.China;

2. Traffic & Transportation school, Dalian JiaoTong University, Dalian 116028, P.R.China)

Abstract:The interface interaction between geogrid and soil is one of the key issues on geosyntheticreinforced soil structures. Comparative analysis of properties of geogridclay interface under the different normal stresses and water contents of clay were conducted by mediumsized pullout tests. The results show that ultimate pullout force of geogrid, interfacial cohesion and frictional coefficient are significantly affected by water content of clay. Ultimate pullout force of geogrid tends to be remarkably different when subjecting to different normal stresses at a lower water content. And frictional coefficient of interface decreases with the increase of water content, and interfacial cohesion has a tendency to increase followed by decrease with the increase of water content. Moreover, aforementioned three parameters can keep constant when water content is close to value at plasticity limit. The curves of load and displacement possess three stages: linear increase, nonlinear increase and ultimate pullout. As water content increases, the interval nonlinear changing stage is not conspicuous. Furthermore, it is found that geogrid strains in transversal ribs tend to increase but to reduce in longitudinal ribs when last level load is kept for given hours and then followed by unloading pullout force.

Key words:geogrid; geogridsoil interface properties; pullouttest; clay

筋土界面相互作用特性研究一直是加筋土领域内的热点之一。研究人员借助直剪或拉拔试验对具有较大内摩擦角和良好排水性能的粒状土与筋材间的界面作用机理进行了研究。如Schlosser等［1］首先采用三轴直剪试验研究金属条加筋砂土。随后，国内外针对筋材填料的界面作用特性的试验研究主要涉及的为砂土和碎石土，筋材主要是土工织物或土工格栅［25］，这些试验结果表明筋材抗拔阻力主要由筋土界面摩阻力和土对格栅横肋的阻力构成，且筋材变形较小时界面摩擦力即达到峰值，进而随格栅变形的增大，其横肋阻力逐渐增加并最终承担大部分格栅加筋承载拉力。近些年来，随着加筋结构广泛用于公路软基处理、港口岸墙和堤坝等加固结构中，而且一些实际工程受地域条件限制，采用黏性土作为回填料的加筋土结构工程日益增多。因此，研究筋材与黏性土之间的界面相互作用特性就显得尤为重要。Bergado［6］试验指出钢制格栅在风化黏土中的抗拔性能主要受筋材的横肋影响。Collin［7］现场试验指出当黏性土中含水量变大时，筋土界面黏结效果明显下降。Mohiuddin［8］通过室内和现场拉拔试验分析了筋材在黏性土体中的抗拔机理，筋材抗拔力受界面法向荷载力与筋材长度的影响明显。Murad等［9］基于室内、外拉拔试验得出适当控制黏性土回填料的含水量时，黏性土与筋材之间也能提供合适的抗拔阻力。张波［10］、冯晓静［11］基于拉拔试验指出，采用黏性土为填料时筋土剪切性能不良且水稳定性较差，当采用高液限黏性土为回填料时，应降低接触面设计强度指标。本文拟通过中型拉拔仪详细分析黏性土含水量和界面法向应力对格栅黏性土界面相互作用的影响。〖=D(〗肖成志，等：土工格栅黏性土界面特性的拉拔试验分析〖=〗1格栅黏性土界面特性的拉拔试验