加筋垫层承载机理与工程应用研究

【作者】 左广洲；

【导师】 刘毓氚；

【作者基本信息】 福州大学 ， 岩土工程， 2006， 硕士

【摘要】 随着土工合成材料在土木工程领域的推广,以土工合成材料作为筋材的加筋垫层得到广泛的应用,社会经济效益显著。工程实践推动加筋垫层应用水平不断提高,但是加筋垫层加筋机理的理论研究还不完善,远远落后于工程实践,加筋垫层设计和计算还没有一套相对成熟的方法,这将直接影响着加筋垫层的进一步推广应用。本文在国内外加筋垫层研究成果的基础上,在筋材选择和布置、加筋垫层应力扩散角的分布规律、设置加筋垫层的地基的承载性能及加筋地基的工程应用做了较深入的研究,得出了一些有益的结论: 1.在加筋垫层设计中,筋材的长度、间距、层数等对于加筋垫层加筋效果的影响还不是很清楚,加筋垫层的设计往往依靠经验,缺乏必要的理论指导,选择的材料参数过于保守。本文应用有限元研究了设置加筋垫层的地基的承载性能和变形性状,得出了筋材参数(筋材层数、筋材间距、筋材埋深、筋材模量、筋材长度)和砂垫层的性质(砂垫层厚度、砂垫层内摩擦角)对加筋垫层加筋效果的影响规律,研究结果表明筋材参数对加筋垫层加筋效果影响存在最佳值:筋材层数为3层、筋材间距为0.2～0.25的基础宽度、筋材埋深为0.25倍的基础宽度、筋材长度为5倍的基础宽度。2.应力扩散角计算是加筋垫层设计的关键,但是目前应力扩散角的计算理论依据不足,规范计算与工程实际有较大的差距。本文应用基底附加应力反算法推导了应力扩散角的计算公式,然后应用该方法研究了加筋垫层设置参数和筋材参数对加筋垫层应力扩散角的影响规律,研究结果表明,加筋垫层应力扩散角的范围45o～60o,且加筋垫层设置参数和筋材参数都存在最优值,此时对应应力扩散角最大。最后采用正交回归分析法研究了应力扩散角的影响因素,结果表明筋材的间距对加筋垫层应力扩散角影响最大,其次是筋材的埋深,对加筋垫层应力扩散角影响最小的是筋材的长度,并推导了考虑各种影响因素的加筋垫层应力扩散角计算公式,弥补了工程实践中加筋垫层应力扩散角计算的不足。3.本文在总结归纳前人试验研究的基础上,得到了设置加筋垫层的地基的破坏形式,并应用极限平衡理论推导了设置加筋垫层的地基承载力公式。并用本文得到的计算公式与改进的Terzaghi承载力公式、王钊的极限分析法和有限元法进行比较,结果表明本文的计算公式很好地体现了加筋垫层的加筋机理,可为设置加筋垫层的地基承载力设计提供了参考。4.对用加筋垫层处理前后土岩组合地基的变形性状和承载性能进行了研究,更多还原

【Abstract】 With the development of the geosynthetic, geosynthetic has been widely used in civil engineer. With the application of the geosynthetic, the theory research and design method of the geosynthetic reinforcement layer have been improved, but the mechanism research of the geosynthetic reinforcement layer is not perfect, the design and calculation of the geosynthetic reinforcement layer has no mature method, it affects the application of the geosynthetic reinforcement layer widely. Basing on the history research of the predecessor, this paper studied the choise of geosynthetic、the calculation of the stress diffusion angle and the calculation of the bearing capacity of the geosynthetic reinforcement layer, key results of the study can be summaried as follows: 1.In design of the geosynthetic reinforcement layer, the effect of geosynthetic parameters (such as geosynthetic space: h , geosynthetic width : b, the embedded depth of the first geosynthetic: u , total numbers of geosynthetic reinforcement layer: N et al.) has no clarity, the design of the geosynthetic reinforcement layer sometimes depends on experience. This paper studied the bearing capability and deformation property of foundation of the geosynthetic reinforcement layer using finite element analysis, results indicate geosynthetic factors exist optimal value: N=3, h=0.2~0.25B, u=0.25B, b=5B. 2.The calculation of the stress diffusion angle is very important in design of the geosynthetic reinforcement layer, but there is no method in common till now. This paper firstly used additional stress back-analysis and orthogonal regression analysis to acquire the calculation formula of the stress diffusion angle, and then studying geosynthetic parameters and cushion properties on the stress diffusion angle. In addition, through the orthogonal regression analysis, results indicate geosynthetic spacing has a most effect on the stress diffusion angle of the geosynthetic reinforcement layer, secondly the embedded depth of the first geosynthetic, however, geosynthetic width has a slight effect on the stress diffusion angle. 3.This paper concludes the trial research results of the predecessor, gaining the failure form of foundation of the geosynthetic reinforcement layer, then adopting limit equilibrium theory to get the bearing capacity formula of the geosynthetic reinforcement layer, and then comparing the calculation results of the improving Terzaghi bearing capacity formula、limit analysis method of Wang Zhao、the finite element method and the bearing capacity formula of this paper, results indicate the bearing capacity formula of this paper can reflect the geosynthetic mechanism of the geosynthetic reinforcement layer,so this formula can offer theorical guidance for the bearing capacity calculation of foundation of the geosynthetic reinforcement layer. 4.This paper studied the performance of bearing capacity and deformation property of soil-rock composite subgrade improving with the geosynthetic reinforcement layer, results indicate the geosynthetic reinforcement layer can easily deal with soil-rock composite subgrade, improving the stress field and displacement field of the foundation, sharing the stress distribution, decreasing the uneven settlement,improving the performance of bearing capacity of the geosynthetic reinforcement layer.更多还原