【作者】 陈华；

【导师】 赵有明； 张玉芳；

【作者基本信息】 中国铁道科学研究院 ， 岩土工程， 2011， 博士

【摘要】 加筋土挡墙具有重力式挡墙无法比拟的优点,从发展初期就受到普遍关注,并成为研究的热点,在工程中得到了广泛的应用。上世纪70年代以来,随着土工合成材料的飞速发展,土工合成材料(尤其是土工格栅)加筋土支挡结构已成为国内外公认最具有发展前景的轻型支挡结构之一。目前,对于单极高度低于10m的土工格栅加筋土挡墙,有关规范都已作了详细的说明,其设计理论及方法都相对成熟,但是对于近年来不断出现的高度大于10m的土工格栅加筋土挡墙,由于相关研究不足,至今还没有成熟可靠的理论支持,绝大多数工程实践还停留在参照类似工程的基础上,理论研究却落后于工程实践,无法满足工程实践的需要。基于上述考虑,为解决山区公路加筋土挡墙设计、施工中存在的问题,本文以云南思小高速公路2个包裹式土工格栅加筋土挡墙试验点(K63+785和K63+795)、水麻高速公路2个面板式土工格栅加筋土挡墙试验点(K68+698和K68+798)和2个复合式土工格栅加筋土挡墙试验点(K69+150和K69+150)为依托,开展了3种常用形式的土工格栅加筋土挡墙现场原型试验及有限元数值模拟分析,深入研究了土工格栅加筋土挡墙的力学特性和工作机理,其主要研究内容及结论如下:1)土工格栅加筋土挡墙墙底垂直压力大小及分布的现场试验规律(1)包裹式和面板式土工格栅加筋土挡墙墙底垂直压力实测值近似均匀分布,普遍大于γ·H值;(2)复合式土工格栅加筋土挡墙墙底垂直压力实测值大都大于γ·H值,呈现近墙趾处大于远墙趾处的非均匀分布特点,这一现象可能与重力式挡墙的强支挡作用有关;(3)“准运营”阶段的墙底垂直压力观测值普遍保持稳定,说明墙底压力的形成与调整主要在施工阶段完成;(4)针对基底垂直压力实测值大于γ·H值的结果,建议:设计高于10m的加筋土高挡墙时,基底垂直压力应乘以增大修正系数K,K=1.2~1.4,以保证地基容许应力有足够的安全储备。2)土工格栅加筋土挡墙筋材变形的现场试验规律(1)随着填土高度的增加,3种形式的土工格栅加筋土挡墙各层筋材变形均呈双峰不均分布,揭示了挡墙存在潜在破裂面;(2)雨季期间,各层筋材变形增加较大(由于土体饱水及部分土体压实度不均产生沉降),在设计、施工中应加以考虑,避免造成不利影响;(3)工后观测阶段筋材变形随时间迁移而逐渐减小,并且很快趋于稳定,表明加筋土高挡墙的最不利工况发生在施工阶段末期,即发生在加筋体填筑施工完毕、形成完整路基体系前;(4)包裹式和面板式加筋土挡墙各层格栅实测最大拉力值均大于设计值,中部的格栅实测值比设计值大40至50%,说明现行规范关于土工合成材料综合折减系数大于5、抗拔安全系数大于1.3的规定是非常必要的。3)土工格栅加筋土挡墙潜在破裂面形式(1)包裹式土工格栅加筋土挡墙潜在破裂面与库仑直线破裂面形状大致相似,只是破坏土楔体的面积增大了;(2)面板式土工格栅加筋土挡墙实测潜在破裂面与0.3H破裂面和经典朗肯法破裂面形状相近,但位置略有差异;(3)复合式土工格栅加筋土挡墙存在2个潜在破裂面,上面一级加筋土挡墙潜在破裂面符合对数螺旋分布,下面一级加筋土挡墙潜在破裂面比较复杂,形式上与0.3H破裂面和库仑直线理论破裂面都不相符,形状、位置主要受试验墙前置重力式挡墙和加筋体的组合影响。4)土工格栅加筋土挡墙有限元数值模拟分析结论选取水麻高速公路的2个面板式土工格栅加筋土挡墙K68+698和K68+798试验点,采用有限元强度折减法进行了数值模拟计算分析,得到以下几点认识:(1)有限元计算得到的面板式土工格栅加筋土挡墙基底垂直应力值与实测的基底垂直应力值大小及规律上基本上一致,均比相应的γ·H偏大,并呈现出近似均匀分布的特点;(2)有限元计算得到的土工格栅拉力和现场实测值基本吻合;(3)有限元计算得到的面板式土工格栅加筋土挡墙最大拉力点位置连线(潜在破裂面)与实测接近,形式上与0.3H破裂面相似;(4)敏感度分析表明,筋土界面强度指标、加筋长度对加筋土挡墙的安全系数及滑面的确定影响较大。本文所进行的研究为交通部西部交通建设科技项目《山区支挡结构的研究》课题高轻型支挡结构研究的重要部分之一。本文分析了土工格栅加筋土挡墙应用发展及开展原型试验研究的选题原因,介绍了现场原型试验方案,分析了原型试验数据成果,研究了土工格栅加筋土挡墙墙底垂直压力分布、筋材拉力和变形规律、挡墙破裂面形状,揭示了土工格栅加筋土挡墙力学特性。研究成果为今后土工格栅加筋土挡墙工程的设计、施工、研究提供技术支持,对进一步完善高大土工格栅加筋土挡墙理论和编制相应的标准、规范提供良好的支撑。通过开展研究,首次在高速公路上与建设同步全面开展了三种常用形式的高大土工格栅加筋土挡墙原型试验研究,原型试验和试验工点建设均取得了成功。通过大型原型试验的成果分析,指出了土工格栅加筋挡墙的破裂面形状、基底压应力的分布和加筋材最大拉力值与国内外以往研究的相同与不同之处,丰富和发展土工格栅加筋土挡墙技术。更多还原

【Abstract】 Because of its incomparable advantages, reinforced soil retaining wall is widely used in the projects. With the rapid development of geosynthetics, geosynthetics (geogrid especial) retaining wall is one of light supporting constructure that has been the most prospective since 1970s.At present, the theory and application of the geogrid reinforced soil retaining wall(H<10m) are reliable. However, the theory and application of the geogrid reinforced soil retaining wall(H>10m) are very unreliable. So, a large number of geogrid reinforced soil retaining walls(H>10m) are designed with reference to the similar projects, instead of the reliable design method.Considering the reasons mentioned above and to solve the problems during the design and construction of highways in the mountain areas, this paper aims to study the mechanical behavior of the geogrid reinforced soil retaining walls. This study is conducted through the field test and the numerical simulation by finite element method. The main contents and conclusions in this paper are:1)The experimental results on the vertical basal pressure of the geogrid reinforced soil retaining wall(1)The measured normal stresses at the basement of the wrapping and panel geogrid reinforced soil retaining walls are nearly uniformly distributed and they are larger than the value ofγ·H.(2)The measured normal stresses at the basement of the compound geogrid reinforced soil retaining walls (with concrete rigid face) are larger than the value ofγ·H and they are not uniformly distributed. It is observed that the normal stress is larger near the toe of the retaining wall. This may be due to the strong supporting effect of the gravity retaining wall.(3)The measured normal stresses at the basement of the geogrid reinforced soil retaining walls remain stable at the stage of“quasi-operation”. This illustrates that the formation and variation of the normal stresses are almost completed at the construction stage. (4)As the measured normal stresses at the basement of the geogrid reinforced soil retaining walls are larger thanγ·H, it is suggested that the calculated normal stresses at the basement should be enlarged by K (K= 1.2-1.4) when the height of the wall is larger than 10 m. This is to ensure the bearing capacity is high enough.2)The experimental results on the geosynthetics deformation of the geogrid reinforced soil retaining wall(1)With the increment of the height of the earth fill, the deformation of the geogrid inside the retaining walls is not uniform (looks like a double-peak). This implies a potential failure surface exists inside the retaining wall.(2)During the rainy season, the·deformation of the geogrid inside the retaining walls is quite large (due to the soil settlement by saturation and nonuniform compression). This should be considered during the design and construction to prevent unfavorable effects.(3)After the construction, the·deformation of the geogrid inside the retaining walls is becoming smaller with time and tends to be stable. This illustrates the most unfavorable condition for the high geogrid reinforced soil retaining walls occurs at the end of the construction (i.e., the subgrade is formed and the filling project is completed).(4)The measured largest tension force of the geogrid inside the wrapping and panel geogrid reinforced soil retaining walls is larger than the designed value. The one in the central part is larger than the designed value by 40%-50%. Thus the code is reasonable and necessary to take a material reduction factor (>5) and to maintain a high safety factor (>1.3).3)The potential failure surface of the geogrid reinforced soil retaining walls(1)The potential failure surface of the wrapping geogrid reinforced soil retaining walls is similar to the theoretical prediction by the Coulomb method. The only difference is the area of the soil wedge.(2)The measured failure surface of the panel geogrid reinforced soil retaining walls is similar to the theoretical prediction by the“0.3H”method and the classic Rankine’s method(3)There are two potential failure surfaces in compound geogrid reinforced soil retaining.The above one is consistent with the distribution of the number of spiral,and the below one is alittle complicated. It is quite different from the theoretical prediction by the “0.3H”method and the Coulomb method.The shape and location are mainly affected by combination of retaining walls and reinforced soil.4)The FEM results of the geogrid reinforced soil retaining wall Two panel geogrid reinforced soil retaining walls at the K68+698 and K68+798 of the Shui-Ma Highway are investigated by the field testing. Also, numerical simulations are conducted by the strength reduction finite element method and some conclusions can be given as follows:(1)The calculated and measured normal stresses at the basement are consistent. Both of them are larger than and uniformly distributed.(2)The calculated tensional force of the geogrid is almost consistent to the measured value in the field testing.(3)The simulated potential failure surface of the panel geogrid reinforced soil retaining walls is close to the real measured result and similar to the theoretical prediction by the“0.3H”method.(4)According to sensitivity analysis by FEM, the intensity index and the geosynthetics length have more influence over the stability factor of the geogrid reinforced soil retaining wall.This study is a key component of the research for the project of the west traffic construction <The study of supporting constructure in mountainous areas>. This pape introduced the applying of geogrid reinforced soil retaining walls and the topics reason for doing prototype test research The main works include:introducing the site prototype test plan,analyzing the data results,studying the vertical pressure distribution,reinforced soil’s pull,deformation & the failure surface’s shape ,and revealling the mechanical properties. With this research,the construction of the high geogrid reinforced soil retaining walls and the prototype test,which are synchronized with project’s construction on the highway,get success first.The research results point out the accordance or difference with the studied conclusion of the failure surfaces’s shape, pressure distribution and the biggest pull of geogrid reinforced soil retaining walls at home and abroad,enrich and develop the technology of the geogrid reinforced soil retaining walls greatly. The research results are useful to the later design,construction and study,and to perfect the theory and the design standard of the geogrid reinforced soil retaining wall.更多还原