【作者】 陈晓斌；

【导师】 张家生； 安关峰；

【作者基本信息】 中南大学 ， 道路与铁道工程， 2007， 博士

【摘要】 由于土石混填粗粒土具有良好的工程性质以及取材广泛,在湖南省高速公路路基工程中大量应用,其中红砂岩粗粒土最为常见,但是红砂岩填土路基路段存在较多与长期沉降相关的路面结构病害。针对上述存在的问题,论文结合湖南省交通科技项目“高速公路路基沉降及其对路面的影响”研究课题,以湖南省红砂岩地区高速公路红砂岩粗粒土路基填料为研究对象,研制了低应力状态下的粗粒土大型三轴流变试验仪,采用室内试验、现场试验和数值计算方法,对土石混填粗粒土路堤的流变工程性质进行了研究,主要研究内容及研究结论如下:(1)以湖南省内分布广泛的红砂岩土石混填路基填料为研究对象,进行了试验研究和理论分析。对干的红砂岩粗粒土及饱水的红砂岩粗粒土进行了压缩试验、剪切试验和压缩流变试验研究,并针对每组试验进行了试验前后土样的级配分选试验。试验研究说明红砂岩粗粒土符合路基填筑的技术要求,是红砂岩地区修建道路时最常用的路堤填料。水对红砂岩粗粒土的颗粒破碎效应影响比较大,如在流变试验中饱水土样的颗粒破碎率B_r=0.247大于干土样的B_r=0.118,饱水土样颗粒破碎率B_g=145.04,红砂岩粗粒土干土样颗粒破碎率B_g=88.44;水对红砂岩粗粒土颗粒破碎起到促进作用。受力状态明显影响红砂岩粗粒土的颗粒破碎效应和土体变形,试验研究发现流变试验的颗粒破碎效应系数＞压缩试验中的颗粒破碎效应系数＞剪切试验中的破碎效应系数。如干的红砂岩粗粒土土样中,压缩流变试验的B_r=0.118＞压缩试验的B_r=0.085＞剪切试验的Br=0.048。颗粒破碎效应试验研究认为红砂岩粗粒土流变机理主要在两个方面:红砂岩粗粒土粗颗粒的破碎效应和红砂岩粗粒土中细颗粒移动填充效应,两者共同作用使得土体发生流变。红砂岩粗粒土的流变过程可以划分为三个阶段。流变过程中水和应力状态是影响流变进程的最关键的因素。(2)针对道路工程领域中路基土体围压力的特点,研制了一套用于土石混填粗粒土路基填料流变试验的大型三轴流变试验仪(GSRT),在道路工程领域率先引进土石混填粗粒土路基填料大型三轴流变试验仪。GSRT流变仪可以进行常规粗粒土三轴试验和粗粒土三轴流变试验,GSRT流变仪所接受的试验土样尺寸为Φ=300mm,H=600mm,可直接进行最大粒径d=60mm粗粒土路基填料的流变试验。粗粒土路堤填料大型三轴流变试验仪(GSRT)压力室部件采用SZ30-4型三轴试验仪的压力室部件。GSRT流变仪轴向压力由气液平衡储能器提供,GSRT流变仪最大轴向压力为3.0MPa,采用无级调压。GSRT流变仪围压力,由水头压力提供,试验围压力分为50kPa、100kPa、150kPa、200kPa等4级。GSRT流变仪的研制,对于开展道路工程领域土石混填粗粒土路基填料的流变性质研究提供了可行的试验设备,丰富了道路工程领域土工试验设备。(3)以怀新高速公路K20+240里程高填路堤红砂岩粗粒土路堤填料为研究对象,在研制的GSRT粗粒土大型三轴流变试验仪上进行了试验研究。试验分析表明,应力状态,主要是应力水平和围压的大小对红砂岩粗粒土路堤填料蠕变性质影响明显,不同应力水平下,有着不同的流变特征。较小的应力水平时(S=0.1)时,蠕变曲线表现为只有弹性变形,粘滞变形可以忽略不计,认为土样在这样的应力水平下只有瞬时的弹性变形;中等应力水平时(0.2＜S≤0.6),试验蠕变曲线表现为线性粘弹性流变特征;较高的应力差值下(0.8＜S)的蠕变曲线出现了加速流变阶段,蠕变变形不收敛。尤其是当应力水平为S=0.1时,蠕变曲线很早就出现加速阶段,土体朝破坏趋势发展,大应力状态下土体进入塑性屈服阶段,土体表现为非线性粘塑性变形特征。基于红砂岩土石混合粗粒土路基填料的非线性流变特征,提出了一个基于二次多项式核函数的粘塑性体(N),用于描述粗粒土非线性粘塑性变形。将该粘塑性体与Burgers流变模型串联,建立了6元件改进的Burgers流变模型,并采用模式搜索与非线性最小二乘法确定了改进的Burgers流变模型参数。采用FLAC5.0所提供的二次开发程序接口,编写了建立的改进的Burgers流变模型计算程序。对怀新高速公路K18+160和K20+240两个红砂岩土石混填粗粒土高填路堤的流变沉降进行了计算,并将数值计算结果与实测结果进行了对比,对比结果表明数值计算值与实测值比较吻合,验证了改进的Burgers流变模型及其参数的合理性。嵌入FLAC5.0的改进的Burgers本构模型数值计算程序为土石混填粗粒土路堤长期沉降计算提供了工具。更多还原

【Abstract】 Granular soil is used widely as highway embankment fillings in Hunan province, for its good engineering properties and extensive distribution, especially Redstone granular soil. However, the engineering practice shows that much pavement structure damage was caused by long-term rheological deformation. To solve this problem, the subject-Research on Highway Embankment Settlement with Affection on Pavement Structure was put forward by Hunan province Communication Science and Technology Development Fun. The main contents of this doctoral dissertation are the research results of this subject. In order to study the rheological properties of red stone granular soil, a series of rheological experiments were executed on the newly developed large tri-axial rheological apparatus. Laboratory experiment, in-situ tests and numerical calculation methods were synthetically adopted to analyze the soil-stone granular soil embankments’ rheological deformation, and the main research contents and conclusions are as follows:（1） Sample tests of Redstone granular soil embankment fillings are carried out, and soil samples include dry Redstone granular soil and wet one. Experiments are consisted of compression test, direct simple shearing tests, and confining leash compressing rheological tests. In order to study the grain component percentage’s changes, the sieve analysis tests for each soil samples are also carried out after these tests. The grain crushing effects of the red sandstone granular soil were studied under different stress types （compression stress, shearing stress）, different load time （e.g. rheology test）, and different humidity conditions （dry and wet）. The tests showed that water had important effects on coarse grain crushing and final rheological values of red sandstone granular soil. For example, in the compression rheological tests, the average grain crushing rate （B_g） of wet soil samples was 145.04, while, the dry soil sample one was 88.44; the final rheological strain value of the wet soil sample was about 15.5%, while the dry soil sample one was about 9.86%. And, the tests showed that stress conditions also have great effects on coarse grain crushing rate of red sandstone granular soil. The average coarse grain crushing rate （B_g=49.14） in the confining leash compressing tests is smaller than the average coarse grain crushing rate （B_g=88.44） in rheological tests and bigger than the average coarse grain crushing rate （B_g=49.14） in the direct simple shearing tests.Through the tests studies and theory analysis, the rheological mechanism of the red sandstone granular soil was generalized as the coarse grain’s crushing effects and the fine grain’s filling effects. The rheological procedure of the red sandstone granular soil could be divided into three phases, in which water and stress conditions were two critical factors affecting rheology process.（2） According to the characteristic of fillings pressure in road embankments, a large tri-axial rheological apparatus （GSRT） are developed to study the rheological properties of granular soil fillings. This GSRT have four main parts, including the constant confining pressure providing part, the constant axial pressure providing part, confining pressure cell and soil sample cell, testing data measurement part. The axial pressure in GSRT is provided by the oil-gas energy depositing vessel’s pressure oil with less than 5% axial pressure fluctuation during rheological tests procedure. The cell confining pressure in GSRT is provided by water head pressure in tube which could keep longtime constant during the rheological tests procedure. The confining pressure cell and soil sample cell in GSRT were directly adapted from the common large tri-axial apparatus’s （SZ30-4） with the dimension （Φ=300mm, h=600mm）. The axial force, the axial strain, the confining pressure, the volumetric strain, the drained water volume and the pore water pressure of the soil sample are measured. The common tri-axial tests and the tri-axial rheological tests of granular soil can be expediently executed on GSRT. The technical parameters of GSRT are as below: The constant axial pressure range with stepless free adjustment: 0～3.0MPa; The confining pressure range with four level adjustment: 50kPa, 100kPa, 150kPa, 200kPa; The granular soil samples with the large dimension （Φ=300mm, h=600mm） and large diameter grain (the maximum diameter of the grain, d_max=60mm) in the soil sample. This large triaxial rheological apparatus （GSRT） was firstly applied in road engineering research domain to study the granular soil embankment fillings in China. The development of GSRT presented the good testing tool for the granular soil embankment fillings’ rheological properties and richen the soil test apparatus.（3） To study the rheological properties of granular soil embankment fillings, red stone granular soil samples were experimented on the GSRT, which were taken from the k20+240 embankment in Huaixin highway construction site.The experiment results showed that the stress condition, especially the principal stress level is the critical influencing factor of the rheological deformation properties. There were different rheological properties of the creep curves under different principal stress level. Under the low principal stress level （S=0.1）, the granular soil showed the elastic properties, and there was no obvious rheological deformation. Under the principal stress level （0.2<S<0.6）, creep curves showed the linear viscoelastic rheological properties. The linear viscoelastic rheological model （Burgers） could describe the linear rheological properties well. However, under the principal stress level （0.8<S） creep curves showed the non-linear viscous plastic rheological properties. Especially, under the principal stress level （S=1.0）, the accelerating rheological phase of creep curves occurred at an early time, and soil had a trend of failure. The Burgers rheological model can describe the linear rheological properties including the attenuation creep phase and steady state creep phase well, but can not describe the non-linear rheological properties, especially, the accelerated creep phase.Based on the nonlinear viscous plastic deformation properties of red sandstone granular soil embankment fillings, a new viscous plastic rehological component （N rehological component） is established on quadratic rehological core equation. To put this N rehological component and Burgers rehological model in series, a modified Burgers rehological model with 6 elements was set up, and the parameters of this modified model are identified by the non-linear model searching least square algorithm.The program of modified Burgers model was developed and applied in numerical calculation by the advanced implements in FLAC5.0, then the rehological deformation of K18+560 and K20+240 soil-stone granular soil embankments was calculated with it. The comparison of calculative deformation data and the surveyed deformation data showed that there was a good agreement between the calculative deformation and surveyed deformation. So the modified Burgers model enclosed in FLAC5.0 and parameters in this model were feasible. The modified Burgers model enclosed in FLAC5.0 offered a referenced tool for the rehological deformation calculation of highway soil-stone granular soil embankments.更多还原