【作者】 汤斌；

【导师】 陈晓平；

【作者基本信息】 武汉大学 ， 岩土工程， 2004， 博士

【摘要】 土体变形的时间效应对于土体的力学属性有重大影响。土体在压缩的过程中,同时包含了固结和蠕变两个过程,是固结和蠕变的耦合过程。 根据国内外研究动态和工程实际的需要,本文在总结前人研究成果的基础上,对武汉地区典型的软土固结蠕变耦合性状进行了室内试验研究和理论分析。探讨了软土固结蠕变室内试验的方法;总结了武汉地区典型的软土固结蠕变变形规律;拟合了武汉地区典型的软土固结蠕变变形的经验公式;建立了实用的非线性弹性粘性固结蠕变模型;推导了非线性弹性粘性固结蠕变模型的有限元方程;在TDBC-95程序的基础上,运用FORTRAN语言改编了有限元计算程序;并用一个工程例子验证了理论的正确性及程序的可行性、适用性。 本文主要结论包括: 1、软土的固结蠕变性状可以通过改装的直接剪切仪和三轴压缩仪以及一维固结仪进行试验研究。武汉地区典型的软土单向压缩试验和三轴固结蠕变试验成果表明,应变与时间的关系曲线具有相似性。在应力水平较低的情况下,表现出衰减蠕变,蠕变量随着时间的增长最后趋向于某一个定值。在应力水平较高时,会发生非衰减蠕变。应力水平越高,蠕变变形越明显。 2、进一步的试验研究与成果分析表明,三轴固结蠕变试验中试样的偏应力～应变等时关系曲线在低应力水平作用下,近似是一些直线,而当应力水平较高时,近似为一簇折线;单向压缩试验中试样的竖向应力～应变等时关系曲线在低应力水平作用下,近似是一些抛物线,而当应力水平较高时,近似为一簇直线。它们都呈现出的相同规律是:试样的应力～应变等时曲线近似为一簇折线或直线,土体的变形为非线性;应力水平越高,应力～应变等时关系曲线越往应变轴靠近,蠕变变形越明显。 3、蠕变可以在排水与不排水两种条件下发生。在低应力水平作用下,排水条件下试样的变形值远远大于不排水条件下试样的变形值。随着荷载级数的增加,不排水条件下试样的变形速率逐渐大于排水条件下试样的变形速率,且最终呈现出不排水条件下试样的变形值超过排水条件下试样的变形值的情况。在相同排水条件下,试样的蠕变性状随着初始含水率及荷载级数的不同而不同。在初始含水率相同的条件下,试样的蠕变性状随排水条件及荷载而发生变化。更多还原

【Abstract】 The time’s effect of the soil mass’s deformation has great effect on the mechanics property of the soil mass. Being compressed, the deformation of the soil mass includes two processes as consolidation and creep that is coupled processes of consolidation-creep.Basing upon the research trends of the home and abroad and the demands of practical engineering, summarizing the predecessors’ researches, the thesis studied on tests and analyzed on the theory of coupled character of consolidation and creep of the representative soft clay in Wuhan area. The means of indoor test about consolidation and creep of the soft clay was discussed; the rule of deformation about the coupled character of consolidation and creep of the representative soft clay in Wuhan area was summed up; the empirical formula about deformation of consolidation and creep of the representative soft clay in Wuhan area was fitted out; the pragmatic nonlinear elastic-viscous model about consolidation and creep of the representative soft clay in Wuhan area was established; the finite element equation of the pragmatic model was reasoned out; basing on the TDBC-95 program, the finite element calculator program was reprogrammed with the FORTRAN language; moreover, a project instance was given to verify the theory’s and the program’s feasibility and applicability.The main conclusion of the original consists of:1 .The coupled character of consolidation and creep may be studied by the directly shear-test unit and style three axes compression unit that be refit by the ordinary strain-control style directly cut-test unit and strain-control style three axes cut-test unit and one-dimension consolidation set. The results of the one-dimension compression tests and the three-dimension consolidation-creep tests with the representative soft clay in Wuhan area show the relationship curves of time and strain have the similarity. When the stress level is lower, attenuation creep arise, the creep finally inclines to a certain stable value the time increasing. When the stress level is higher, non-attenuation creep is able to happen, the more the stress level is high, the more obvious the displacement of creep.2.The experiment research and outcome analysis show, when the stress level is lower, the isochronous relationship curves of the partial stress—strain are approximately some straight lines; When the stress level is higher, they act as one cluster of broken line approximately in these tests of the three-dimension consolidation-creep. When the stresslevel is lower, the isochronous relationship curves of the vertical stress- strain of the one-dimension compressing consolidation-creep are approximately some paracurves. When the stress level is higher, they act as one cluster of right line approximately. Yet the same regular rule that they wholly expressed out is, the isochronous relationship curves of the stress-strain of specimen are one cluster of broken line either right line approximately, the soft clay creep act as nonlinear creep approximately. If the stress level is high over, these curves overstep in the direction of strain axis being near, the creep deformation is obviously over.3.The creep may occur below two kinds of terms of consolidated-drained and consolidated-undrained. Below the stress level action, the specimen’s deformation value below term of that drains away water is more than the specimen’s deformation value below term consolidated-undrained far away. With the increasing of loading series, the specimen’s deformation rate below the term consolidated-undrained is more than to the specimen’s deformation rate below the term consolidated-drained one by one, and finally present situation of the specimen’s deformation value below the term consolidated-undrained overtake to the specimen’s deformation value below the term consolidated-drained. Below the same term of consolidated-drained or consolidated-undrained, the creep of specimen is difference if the water content and load series is difference. Below the same term of the water content, that the creep of specimen happens the alternation with load series and term of consolidated-drained or consolidated-undrained.4.Below the term of consolidated-drained, the water content of specimen is high over; the deformation value of the specimen is great over. Below the term consolidated-undrained, when the low stress level action, the water content of specimen is high over, the deformation of the specimen is great over, Yet the deformation value adds not half the water content getting higher; when higher stress level action, on the contrary the deformation value of specimen of low water content is greatly.5.By means of research to the pore-pressure together with time’s relationship curves of these tests of three-strain compressing consolidation-creep, we can see that the rule is, inclining to be steady on the partial stress action of each grade. With the stress level increasing, the pore-pressure is also increasing. This illustrates that creep deformation may cause pore-pressure rising below the term of consolidated-undrained. The changes of creep deformation and pore-pressure possess have the sameness rule. In terms ofmechanism, they are aroused by the sluggish effect that the adjacent pellets come into being in the soil mass medium.6. By means of research to drainage volume with time’s relationship curves of these tests of three-strain compressing consolidation-creep, it shows that, on the loads (partial stress) per step action, drainage volume rise continuously with the time increasing. This illustrates that consolidation deformation of soft clay constantly happens in the coupled process of consolidation and creep. Below Stress level action, drainage volume increase much on the moment of loading, and then add slowly, finally hurrying along one by one to steadies. Stress level gets higher later, drainage volume are little, with the time increasing, then add slowly, finally hurrying along one by one to steadies.7. Uniting the test data of consolidation-creep, the fit has been underway to test’s curves of consolidation-creep by the means of the application mathematical statistics and the empirical formula of every the test curve has been obtained. By means of analyzing and investigating empirical formula, the nonlinear elastic-viscous model of consolidation and creep has been established. The model’s flexibility is depicted with Duncan-Chang model of instantaneous elasticity; the model’s viscosity is depicted with Burgers model. Moreover the parameter in Burgers model has been revised. On the basis of consolidation-creep aspect of model and tests data, experience value of parameter in revision’s Burgers theory model was requested out by means of the mathematical statistics.8. The fundamental differential equation of consolidation and creep was built on the basis of coupled model of consolidation and creep. The numeric analysis to the fundamental differential equation was carried by the finite element method. Finite element equation of consolidation and creep of the soil mass with the increment shape expressed was established by the method of weighted residuals. The calculator program of coupled problem of consolidation and creep was recompiled with the FORTRAN language basing on the TDBC-95 program.9. The project instance makes known: The finite element program can be used to analyze the deformation of soft clay ground. Computational solution shows: The finite element program is applicable; the computational solution of the deformation of soft clay ground is still closer to the real situation.更多还原