【作者】 蒋建清；

【导师】 杨果林；

【作者基本信息】 中南大学 ， 土木工程， 2010， 博士

【摘要】 红层软岩主要是指侏罗纪到新近纪的陆相红色岩系,岩性为泥岩、砂岩、泥质砂岩、砂质泥岩、粉砂岩等,俗称红砂岩粗粒土,在我国分布广泛。区域性分布的红砂岩粗粒土在路基工程中得到了大量应用,但是红砂岩粗粒土填方路堤开裂、稳定性不佳及不均匀沉降等病害一直是普遍和突出的问题,给行车舒适性和安全性造成了极不利的影响。因此,红砂岩粗粒土加固处治技术是红层地区软岩填料应用于路基工程的关键之一。针对上述问题,本文依托湖南省交通厅科技项目“高速公路新型加筋土结构技术研究与示范工程”(200612)、湖南省教育厅科研项目“高速公路加筋土路堤力学行为与设计方法的研究”(08C199)等科研课题,结合湖南省湘潭至衡阳高速公路加筋红砂岩粗粒土路堤的建设,采用现场试验、室内试验、理论分析和数值模拟等方法,开展红砂岩粗粒土加筋路堤挡墙力学机理及地震稳定性的研究。主要进行了以下几个方面的工作：(1)针对湘南红层软岩填料,在湖南潭衡西线高速公路上进行红砂岩路堤大尺度原位推剪试验,分析红砂岩粗粒土在推剪力作用下的变形特性、力学特性以及破坏特征,得到红砂岩粗粒土原位推剪试样三维滑动面的简化处理方法。并以极限平衡为理论基础,推导在考虑三维滑动面时路堤填料强度参数计算公式,获得红砂岩粗粒土的强度指标。(2)采用格宾网和高强土工格栅等加强红层软岩填料,针对格宾网和土工格栅加筋红砂岩粗粒土,分别制备不同加筋层数、不同压实度和不同含水量的试样,进行一系列大三轴试验。主要研究加筋红砂岩粗粒土强度和应力-应变特性,分析红砂岩加筋粗粒土的宏观力学机理,并引入强度比参数分析加筋效果,探讨土的含水量和压实度、加筋层数等对加筋红砂岩粗粒土力学特性和变形的影响。将格宾网与土工格栅加筋效果进行对比,优选红砂岩粗粒土加筋加固方案。(3)以PFC3D程序和离散颗粒流理论为研究平台、利用FISH语言编程进行二次开发,建立格宾网加筋红砂岩粗粒土颗粒流数值模型,以大三轴试验、筋材拉伸试验及拉拔试验等为基础,校正颗粒流模型的细观力学参数。在此基础上,研究加筋红砂岩粗粒土细观加筋机理和细观力学特性,分析围压和加筋层数等对其细观力学特性的影响,并获得不同应变阶段加筋红砂岩粗粒土颗粒位移场分布特性和内部剪切带发展规律,为从本质上认识红砂岩粗粒土加筋加固机理提供了方法。(4)针对潭衡西线格宾加筋红砂岩粗粒土挡墙试验段,在现场布置各种测试元器件,进行比较系统的监测,得到格宾加筋红砂岩粗粒土挡墙墙面变形、墙后土压力分布、格宾网拉筋变形等规律。以FLAC3D为研究工具,建立格宾石笼面墙、土、格宾网、及接触面的三维耦合数值模型,对影响挡墙受力和变形的主要参数进行数值仿真与优化分析,提出红砂岩粗粒土路堤格宾加筋处治设计时要考虑的控制因素及可供设计和施工参考的资料。(5)利用FLAC3D动力分析模块,进行格宾加筋红砂岩粗粒土挡墙抗震性能数值分析,通过室内拉拔试验和模型墙抗震试验结果校正数值模型参数。给出格宾加筋红砂岩粗粒土挡墙在地震作用下的动力响应规律(加速度时程、位移时程、破坏模式等),系统分析结构材料参数以及地震动参数变化对挡墙动力响应的影响,提出格宾加筋红砂岩粗粒土挡墙抗震设计位移控制标准、地震加速度系数取值方法以及不同抗震设防区格宾网合理竖向间距。(6)基于不同形状的简化破裂面,将挡墙加筋体划分成一定数量水平土条,针对不同模量加筋材料,提出地震作用下加筋土挡墙内部稳定性设计的水平条分方法,推导筋材拉力和所需筋材长度的计算公式,并分析填土内摩擦角、地震加速度系数对筋材拉力及所需筋材长度的影响。为加筋土挡墙抗震设计提供了方法。(7)考虑加筋对路堤抗侧刚度的影响及筋材与土体间的摩擦力,提出将加筋路堤简化为一个由弹簧、阻尼器、筋—土摩擦片相连接的竖向多质点体系。基于达朗贝尔原理,推导水平地震作用下加筋路堤多质点体系的动力方程,将动力方程所代表的动力学系统用状态空间予以描述,最后基于SIMULINK仿真平台建立动力方程的求解模型,得到加筋路堤地震反应结果。为加筋路堤地震反应预估提供了简化方法。更多还原

【Abstract】 Red soft rock that mainly belongs to continental red rock series from Jurassic to Neogene is widely distributed in China, simply intitule Red-sandstone granular soil. Its lithology is commonly classified as mudstone, sandstone, shaly sand, sandy mudstone, siltstone, etc. Regionally distributed Red-sandstone granular soil is largely used as embankment fillings. However, the engineering practice shows that Red-sandstone granular soil embankment generally exsists some prominent disadvantages such as poor stability, easily cracking, uneven settlement, etc. It causes negative influences to the driving comfort and safety. Strengthening technology for Red-sandstone granular soil plays a important role in the application of red soft rock fillings to embankment engineering in red beds area. In this paper, therefore, the mechanical behaviors and seismic stability of reinforced Red-sandstone granular soil retaining wall were researched deeply by in-situ tests, laboratory experiments, theoretical analysis and numerical simulations, combining with the construction of reinforced Red-sandstone granular soil embankment in highway from Xiangtan to Hengyang in Hunan province and the following projects:Study on new reinforced structure in Highway and its demonstration engineering supported by Hunan Province Transportation Department Research Project (200612) and Study on mechanical mechanism and design method of reinforced highway embankment supported by Hunan Provincial Department of Education Project (08c199). The main researches had been carried out as follows:(1) Large-scale horizontal push-shear field tests were carried out aiming at red soft rock fillings of southern Hunan province, test sites on Western Tanheng highway of Hunan province. Mechanical characteristics, deformation properties and failure mechanism of Red-sandstone granular soil embankment when acted thrust were analyzed. Simplified method for three-dimensional sliding surface of its field push-shear sample was proposed. Based on the theoretical analysis of three-dimensional thrust-sliding limit equilibrium method, the computation formulas for the large-scale field horizontal push-shear test considering three-dimensional sliding surface was inferred, and the shear strength parameters of red-sandstone granular soil were calculated. (2) Gabion mesh and high strength geogrid were adopted to strengthen red soft rock fillings. A series of large-scale triaxial tests were carried out on gabion mesh and high strength geogrid reinforced Red-sandstone granular soil with different reinforcement layers, different compaction and different water content. Microscopic reinforcement mechanism, strength and stress-strain characteristics of reinforced Red-sandstone granular soil were studied. The effects of reinforcement layers, water content and compaction on stress-strain relationship and strength properties of red-sandstone granular soil were analyzed. The reinforcing effects were evaluated by introducing the strength ratio parameter. Optimization of reinforcement scheme was put forward based on the comparisons between geogrid and gabion mesh reinforced red-sandstone granular soil.(3) Utilizing PFC3D program and discrete particle flow theory, particle numerical model of Red-sandstone granular soil reinforced with gabion meshes was builded by programming secondary development using FISH. The micro-mechanical parameters of the particle model were calibrated according to large-scale triaxial experiments, tensile tests of gabion mesh and pull-out tests. On this basis, reinforcement micro-mechanism and micro-mechanical properties of reinforced Red-sandstone granular soil were studied, the impacts of confining pressure and reinforcement layers on its micro-mechanical properties were also analyzed. Its displacement distribution and shear zone development law were found at different strain levels. All of these provide nature method for understanding reinforcement mechanism of reinforced Red-sandstone granular soil.(4) Comprehensive observations of the test section of reinforced Red-sandstone granular soil retaining wall in western Tanheng highway were accomplished by various testing elements. The distribution pattern such as deformation of the wall face, soil pressure of the wall back, tensile strain of the gabion mesh layers was obtained by the observations. Using FLAC3D program, the three-dimensional coupling numerical model of stone cage wall face, filling, gabion meshes and interfaces was builded to calculate and optimize the stress and strain of the retaining wall in different influencing parameters, and some controlled design parameters of Red-sandstone granular soil embankment reinforced with gabion meshes which should be taken into account were presented. (5) Numerical simulation using dynamic analysis module of finite difference procedure FLAC3D was conducted on a full-scale gabion-reinforced Red-sandstone granular soil retaining wall subjected to horizontal seismic, and the numerical model wall was validated by comparison of the numerical and the measured seismic experimental results. The dynamical responses of the retaining wall which subjected to seismic waves with different amplitude and reinforced with different vertical spacing reinforcements, such as horizontal and vertical displacement, acceleration and failure mode were analyzed. On the basis of the above analysis, some measures and suggestions such as the seismic-induced displacement control standard, the reasonable vertical spacing of the gabion mesh reinforcement in different seismic region, and the calculation formula for earthquake acceleration amplification factor were proposed for the seismic design of gabion-reinforced soil retaining wall.(6) Based on the assumption of deform rupture shape of the wall which is directed toward the extensibility and inextensibility of reinforcements, a limit equilibrium method identified as horizontal slice method was presented to analyze the internal stability of reinforced retaining wall subjected to horizontal and vertical seismic loads. Formulas about the required tensile force and length of reinforcements to maintain the internal stability of the wall were deduced. In this horizontal slice method, the sliding wedge of reinforced retaining wall was divided into a number of horizontal slices. The effects of variation of parameters such as backfill soil friction angle, horizontal and vertical seismic acceleration coefficients on the stability of the reinforced soil wall were studied. It offered practical method for seismic design of reinforced retaining wall.(7) Considering the effects of reinforcements on soil lateral stiffness and reinforcement-soil friction, the reinforced embankment was simplified as a multi-mass system which was connected by springs, dampers, and reinforcement-soil interfaces. Based on the d’alembert theorem, dynamic equation of the multi-mass system under horizontal seismic was deduced. The dynamic system represented by the dynamic equation was expressed by the state space method. According to the state equation, a numerical simulation model was established using SIMULINK so that the dynamic response of reinforced embankment can be obtained. It offered simplified method for earthquake response prediction of reinforced retaining wall.更多还原