非线性大应变固结理论与试验研究

发布时间：2018-01-22 18:53

本文关键词： 宁波软黏土杭州软黏土非线性大应变固结指数渗流模型次固结效应非饱和土宏观试验微观试验真空预压数值模拟　出处：《浙江大学》2015年博士论文　论文类型：学位论文

【摘要】：上世纪20年代Terzaghi创立了固结理论,一个世纪以来固结理论一直是土力学领域的基本课题之一。为了使固结理论与实际情况更为接近,众多学者逐步摒弃Terzaghi的若干假设,发展了大应变固结理论、非Darcy固结理论、非饱和土固结理论等理论分支,大大地丰富了固结理论体系。另一方面,深厚软黏土层广泛分布于我国沿河、沿江和沿海地区。岩土工程师们发现软黏土地基会引起显著的地表变形。显然,对于软土地基上的工程,传统的小应变假设不再适用,应采用大应变假定。大应变固结理论已发展数十年,但目前尚未全面考虑非线性压缩、非线性渗流、非Darcy渗流、次固结效应、非饱和等因素。本文通过理论和试验研究,对软黏土地基的大应变固结问题进行了深入的探讨,主要工作有： (1)开展了三维大应变控制方程组的建立和简化工作。基于平衡方程、本构方程、几何方程、有效应力原理、Darcy定律和渗流连续方程,在Euler坐标下推导了三维大应变固结控制方程组。之后分别在三维、二维和一维情况下将该固结控制方程组进行简化,将多维问题与一维问题联系起来。 (2)考虑非线性压缩和渗流,进行大应变固结理论的研究工作。开展宁波软土室内试验,得到渗透系数及有效应力与孔隙比的非线性关系。考虑非线性压缩和渗流,提出非线性大应变控制方程。根据试验参数对准确考虑自重影响的非线性大应变固结问题进行研究,将超静孔压计算结果和Gibson方程解进行比较。之后对简化考虑自重影响的非线性大应变固结问题进行研究,将超静孔压计算结果和Gibson方程解、Terzaghi方程解进行比较。 (3)对非线性大应变固结中的渗透指数、水力梯度、土体自重影响开展进一步的研究工作。根据宁波、上海和杭州软土已有的试验数据,总结出适合不同软土渗透指数和初始孔隙比的经验关系式。之后研究了非线性大应变固结过程中的水力梯度变化,着重研究荷载大小和土层深度对水力梯度变化的影响。总结出水力梯度的变化规律,并与试验结果比较。将水力梯度变化曲线划分为五个阶段,并应用该划分方法解释固结过程中不同类型孔隙水的运移。此后,研究不同土体自重考虑方法对大应变固结的影响,比较不同外荷载下和不同土层厚度时不同方法的计算结果,最后对不同方法的适用性进行评价。 (4)考虑指数渗流模型,开展非线性大应变固结理论的研究工作。对杭州软土开展室内试验,得到非线性压缩和渗流的表达式。之后考虑指数渗流模型、非线性压缩和渗流,改进了已有的大应变固结理论并推导得到控制方程。基于室内试验结果,分析了不同渗流指数对超静孔压、沉降、固结度计算结果的影响。 (5)考虑次固结效应,进行非线性大应变固结理论的研究工作。开展杭州软土室内试验,得到次固结系数等计算参数。基于对次固结效应的若干假设,改进了已有大应变固结理论中的渗流连续方程。考虑非线性压缩和渗流,推导得到了控制方程。基于试验所得参数,采用以上方法以及两种已有方法分析算例。比较不同方法的超静孔压计算结果,并将不同方法的沉降计算结果与实测结果进行比较。 (6)开展非饱和土大应变固结理论的初步研究工作。将非饱和土受荷后的变形过程分为瞬时压缩阶段和固结变形阶段。在固结变形阶段考虑几何非线性,根据土体应力平衡方程,孔隙流体流动平衡方程和孔隙水流动平衡方程,应用Bishop非饱和土有效应力原理以及Fredlund—Xing土水特征曲线模型,推导了非饱和土大应变固结控制方程组。 (7)开展杭州软黏土宏观-微观双尺度试验研究。对有代表性的原状土样开展了X射线能谱试验、X射线衍射试验、压汞试验、扫描电镜试验,观察天然土样内的孔隙尺寸分布和微观形貌。之后进行了一维普通固结和流变固结试验,并针对不同固结程度的土样开展了压汞试验和扫描电镜试验,对土样的宏观特和微观力学特性进行探讨。 (8)根据江苏省连云港市某真空预压工程,对塑料排水板地基进行三维固结数值模拟。首先基于考虑长、短排水板的三维模型,计算不同工况并分析长、短塑料排水板对软土地基排水固结的影响。之后建立了不考虑排水板的三维模型,变化该模型处理区各土层的渗透系数进行多次计算,逐步逼近考虑长、短排水板的沉降计算结果,得到处理区土体的等效渗透系数。最后建立大场地的三维模型,将等效渗透系数应用于该模型中,并将沉降计算结果与实测结果进行比较。
[Abstract]:In 20s Terzaghi founded a century of consolidation theory, consolidation theory is one of the basic topics in the field of soil mechanics. In order to make the theory of consolidation and much closer to the actual situation, some scholars gradually abandoned the hypothesis of Terzaghi, the development of the large strain consolidation theory, non Darcy consolidation theory, consolidation theory of unsaturated soils. The theory of branch, has greatly enriched the theory of consolidation system. On the other hand, the deep soft clay is widely distributed in our country along the river, along the Yangtze River and the coastal area. Geotechnical engineers have found that soft clay will cause significant surface deformation. Obviously, for the soft soil foundation engineering, the traditional assumption of no small strain for the strain assumption. Large strain consolidation theory has been developed for decades, but has yet to fully consider the nonlinear compression, nonlinear seepage, non Darcy flow, secondary consolidation effect, non saturation and other factors. Through theoretical and experimental research, the problem of large strain consolidation of soft clay foundation is discussed in this paper.
(1) the establishment of 3D large strain control equations and simplify the work. Based on the equilibrium equation, constitutive equation, geometric equation, effective stress principle, Darcy's law and the continuity equation of seepage in Euler coordinates derived 3D large strain consolidation equations. Then in 3D, 2D and 1D case the consolidation equations are simplified, linked with one-dimensional multi-dimensional problems.
(2) considering the nonlinear compression and seepage, research work is carried out. The large strain consolidation theory of soft soil in Ningbo by indoor test, the permeability coefficient and the effective non-linear relation between stress and void ratio. Considering the nonlinear compression and seepage, the nonlinear large strain control equation. According to the study of nonlinear large strain consolidation problem of test parameters considering the accurate effect of weight, the excess pore pressure through the comparison of the calculated results and solutions of the Gibson equation. After the study of simplified nonlinear large strain consolidation of the weight, the pore pressure calculation results and Gibson equation, compare the solutions of Terzaghi equation.
(3) on the permeability index, nonlinear large strain consolidation of hydraulic gradient, soil gravity affect the further research work. According to the test data of Shanghai and Ningbo, the soft soil in Hangzhou, summed up the different soft soil permeability index and initial void ratio. The empirical relationship of hydraulic gradient change process of nonlinear the influence of strain consolidation, focuses on the change of hydraulic gradient load and soil depth. Summed up the changes of the hydraulic gradient, and compared with the experimental results. The hydraulic gradient change curve is divided into five stages, the migration of different types of pore water and the application of the classification method of interpretation in the process of consolidation. Then, study the different considering the soil weight method for large strain consolidation, the calculation results of different methods are compared under different load and different soil thickness, finally apply to different methods Evaluation of sex.
(4) index to carry out research work flow model considering nonlinear large strain consolidation theory. To carry out laboratory tests of Hangzhou soft soil, obtained the nonlinear compression and seepage. After considering the exponential seepage model, nonlinear compression and seepage, improved the existing large strain consolidation theory and derive control equation based on the indoor test. Analysis of the different index of seepage, pore pressure, settlement, the effect of degree of consolidation.
(5) considering the secondary consolidation effect, the research work carried out nonlinear large strain consolidation theory of soft soil in Hangzhou. To carry out laboratory tests, the calculated parameters of the coefficient of secondary consolidation. Some assumptions on the secondary consolidation effect based on improved continuous seepage equation has a large strain consolidation theory. Considering the nonlinear compression and seepage are deduced the control equation. The parameters from the tests based on the above method and two kinds of existing methods analysis examples. The comparison of different methods of pore pressure and settlement calculation results, different methods of calculation results and the measured results were compared.
(6) to carry out the work of non large strain consolidation theory of saturated soil. The deformation process of saturated soil under loading is divided into instantaneous compression stage and consolidation deformation stage. In the stage of consolidation deformation considering geometric nonlinearity, according to the soil stress balance equation, pore fluid flow balance equation and pore water flow balance equation, application Bishop principle of effective stress of unsaturated soil and Fredlund - Xing model of soil water characteristic curve of unsaturated soil is deduced, large strain consolidation equations.
(7) to carry out the Hangzhou soft clay macro micro dual scale experiment. The undisturbed soil samples representative of the developed X ray energy spectrum test, X ray diffraction test, mercury injection test and SEM test, observation of pore size distribution in the natural soil and morphology. After the ordinary one-dimensional consolidation and the rheological consolidation test, and according to the different soil consolidation degree to carry out the mercury injection test and SEM test, macro and micro mechanical properties of soil are discussed.
(8) according to the Jiangsu city in Lianyungang Province, a project of vacuum preloading consolidation numerical 3D simulation of plastic drainage plate foundation. Based on the three-dimensional model considering the long, short drains, calculation and analysis of different conditions of long, short of plastic drainage plate on the drainage consolidation of soft soil foundation. After the establishment of the 3D model is not considered drainage plate, variation of permeability coefficient in the model of the soil treatment area to calculate, gradually approaching the settlement results considering the long, short drains calculation, equivalent treatment soil permeability coefficient. Finally the establishment of three-dimensional model of large field, the equivalent permeability coefficient is applied to the model, and the calculation results and the settlement the measured results were compared.

【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TU447

【相似文献】