【作者】 施维成；

【导师】 朱俊高；

【作者基本信息】 河海大学 ， 岩土工程， 2008， 博士

【摘要】 粗粒土是土石坝的主要坝体材料,鉴于目前200甚至300m级高土石坝的修建,对粗粒土在三维应力状态下的强度变形特性以及各向异性特性进行研究已经非常迫切。真三轴试验是进行这方面研究的重要手段,国内外不少学者都曾对砂土及粘土进行过真三轴试验研究,然而由于试验仪器等原因的限制,对于包括砾石料在内的粗粒土,很少有人进行这方面的研究。本文利用河海大学两台真三轴仪分别对砾石料、粗粒土进行了真三轴试验,并在此基础上提出一个粗粒土三维破坏准则及双屈服面三维弹塑性模型。探讨了使用河海大学ZSY-1型真三轴仪对砾石料进行真三轴试验的具体操作方法,并对砾石料试样进行了不同围压下的等σ3等b加载试验,研究了中主应力对砾石料应力应变关系、主应变之间关系及强度参数φ、M的影响。对河海大学最新研制成功的TSW-40型真三轴仪进行调试,考察可能影响试验结果的各种因素,包括:试样端部约束的影响、试样帽与水囊盒之间摩擦的影响、复合加压块及水囊盒的影响。并且对该仪器的变形量测以及应力传感器进行率定。使用TSW-40型真三轴仪对粗粒土进行了一系列真三轴试验,包括:等σ3等b试验、等p等b试验、平面应变试验、单向加荷试验以及等p等q试验。研究了粗粒土在三维应力状态下的变形和强度特性。根据砾石料和粗粒土的真三轴试验结果,提出了一个粗粒土三维破坏准则。推导了该准则的φb~b关系,研究了该准则在π平面上的破坏轨迹形态,并对该准则进行了验证。提出了一个双屈服面三维弹塑性模型,包括弹性部分、屈服函数、硬化准则和塑性势函数;建议了根据常规三轴压缩试验结果确定模型参数的方法;用该模型计算了等σ3等b加载应力路径下的变形,并与粗粒土的真三轴试验结果进行比较,对模型的合理性进行了初步验证;将模型加入三维有限元计算程序,应用于土石坝工程计算,并与邓肯E-B模型进行比较,验证了模型的适用性。更多还原

【Abstract】 Coarse-grained soils are the main materials of earth rockfill dams, and there are many high earth rockfill dams to be built whose height reach 200 even 300 metres, therefore it is urgency to study on the strength and deformation characteristics of coarse-grained soils under three dimensional stress states, as well as the anisotropic characteristics of coarse-grained soils.True triaxial test is an important method to study the response of soils in three dimensional stress states. A lot of true triaxial tests of sand and clay have been performed by researchers inside and outside. However, for coarse-grained soils including gravel, restricted by apparatus etc, few such investigation is done. The two true triaxial apparatuses in Hohai University are used to perform true triaxial tests respectively on fine gravel and coarse-grained soils. And then on the basis of these tests, a new three-dimensional failure criterion and a two-yield-surface elastoplastic model are presented.The specific operating methods of true triaxial tests on fine gravel using the ZSY-1 Type True Triaxial Apparatus in Hohai University are discussed. Subsequently a few of true triaxial tests on fine gravel have been performed, in which bothσ3 and b are invariable. On the basis of the tests, the influences of intermediate principal stress on the stress-strain relationship, relations between the three principal strains and the strength parametersφand M are studied separately.The TSW-40 Type True Triaxial Apparatus in Hohai University which is developed recently has been examined. Several factors which may influence the test results are investigated, mainly including the following three points: the influence of the sample end restriction; the influence of the friction between the sample cap and the water-bag box; the influence of the metal-rubber complex and the water-bag box.Series of true triaxial tests on coarse-grained soils have been performed, includingσ3- and b-constant tests, p- and b-constant tests, plane strain tests, single-direction loading tests and p- and q-constant tests. Deformation and strength characteristics of coarse-grained soils in three dimensional stress states have been studied.Based on the results of true triaxial tests on fine gravel and coarse-grained soils, a new failure criterion is presented and verified. Theφb~b relationship of the failure criterion is deduced, and the shape of the failure locus on theπ-plane is investigated. A two-yield-surface nonassociative elastoplastic model is established, including elastic part, yield functions, hardening rules and plastic potential functions. The model incorporates seven parameters which can all be determined from simple experiments such as conventional triaxial compression tests. The predicted stress-strain curves show that the model is capable of successfully representing the experimental measurements. Additionally, the model has been incorporated in a three-dimensional FEM program for the solution of an earth rockfill dam problem.更多还原