考虑应力主轴变化下各向异性砂土静动力特性试验研究
发布时间：2019-07-03 20:13
【摘要】：在路堤、边坡等工程中,地基土单元在固结过程中不仅主应力大小会发生改变,大主应力轴方向也会发生偏转,这种涉及应力主轴偏转的各向异性“倾斜”固结一方面使得砂土颗粒重新排列,进而产生应力诱发各向异性,另一方面会导致土体形成不同的初始固结应力状态,包括初始竖向偏应力以及初始扭剪应力。在这种复杂的初始固结应力状态条件下,当土体进一步承受波浪荷载、交通荷载等涉及主应力轴旋转的复杂应力路径时,土体表现出来的变形和强度特性将变得更加复杂。因而,在实验室模拟土体的复杂初始固结应力条件,并进一步开展涉及应力主轴变化的复杂应力路径下静动力试验研究,对于建立涉及应力主轴变化这种复杂应力条件下各向异性固结土体的变形规律和本构模型具有十分重要的试验指导意义。本文利用空心圆柱扭剪仪针对各向同性固结和各向异性“倾斜”固结饱和砂土进行了一系列涉及应力主轴变化的复杂应力路径下静动力排水试验研究。主要开展了以下工作研究：(1)分别针对各向同性固结和各向异性“倾斜”固结饱和砂土试样进行了一系列排水静力剪切试验,对比分析了制样过程形成的固有各向异性以及“倾斜”固结诱发的各向异性对土体应力应变关系、峰值剪切强度、割线模量、剪胀关系、非共轴等静力特性的影响,并建立了“倾斜”固结条件下增量峰值应力比和初始割线模量与固结主应力方向角和剪切主应力增量角度差值之间关系。(2)通过对不同固结条件和主应力方向下剪切过程中体应变发展的对比分析,得到了独立于剪切主应力方向和固结条件的统一相位转换应力比(q/p)phase；结合应力应变非共轴发展规律,研究了非共轴对剪胀关系的影响,并通过引入非共轴因子修正了非共轴度造成的剪胀曲线与Rowe直线型剪胀曲线的偏差。(3)针对各向同性固结条件下主应力轴旋转试验,分析了应力比对体应变发展模式的影响,得到了与静力剪切试验一致的相位转换应力比(q/p)phase,当应力比低于相位转换应力比时,主应力轴旋转过程中体应变表现为体缩变形,反之为体胀变形。另一方面,通过引入非共轴因子分析了主应力轴旋转过程中非共轴对剪胀关系的影响。(4)针对各向异性“倾斜”固结条件下主应力轴连续旋转试验,分析了固结诱发各向异性对主应力轴连续旋转过程中应变分量发展以及应变流动过程中表现出的应变增量大小发展和非共轴演变规律的影响；发现了主应力轴旋转周期内最大非共轴角度可以通过应变增量峰值对应的旋转角度与试样最薄弱方向(70。)之间的滞后角度进行度量。研究了旋转圈数对体应变发展模式的影响,随着旋转圈数增加,试样相对密实度不断增大,砂土试样从中密向密实状态转变,从而导致从第5圈开始在局部旋转范围内出现体胀变形,而且体胀范围也随着旋转圈数增加而不断扩大。(5)针对低路堤下地基土单元涉及应力主轴偏转的各向异性“倾斜”固结条件下的动力循环排水试验,研究了“倾斜”固结过程中形成的不同初始固结应力状态,包括初始竖向偏应力qvo和初始扭剪应τ0,对动力循环过程中竖向永久变形的影响。试验结果表明,第一圈永久竖向应变与初始竖向偏应力大小呈线性增长的关系,而与初始扭剪应力基本无关；在qv075kPa,τ0OkPa条件下,初始竖向偏应力和初始扭剪应力都会加速前期竖向永久变形的累积,但当qv0≤75kPa,永久竖向应变平均增长率基本保持恒定,几乎不受初始竖向偏应力的影响；在Barksdale提出的对数模型的基础上,建立了考虑初始竖向偏应力和初始扭剪应力综合影响的永久竖向累积修正模型。(6)“倾斜”固结中形成的不同初始固结应力状态对动力循环过程中体应变发展的影响表明,存在一个临界初始竖向偏应力qv0=75kPa,将循环加载过程中体应变发展分为体胀和体缩两种模式；初始扭剪应力的存在会使得土体在动力循环中产生体胀趋势,而且体胀量随着初始扭剪应力的增大而增大。综合考虑初始竖向偏应力和初始扭剪应力作用时,在(σz-σθ)-2σzθ建立了以K0固结点为起点与水平轴夹角为2(α△σc)CCL的临界固结线CCL (Critical Consolidated Line),当α△σc(α△σc)CCL时后续动力循环过程中表现为体缩变形,反之为体胀变形。(7)针对K0固结饱和砂土进行了一系列交通荷载“心脏型”动力循环应力路径以及不考虑主应力轴旋转效应的普通动力循环应力路径试验的对比研究,揭示了交通荷载引起的主应力轴旋转会加速竖向变形的累积以及减弱竖向回弹模量,并且且随着循环应力比增大,主应力轴旋转对竖向变形特性影响更加明显,最后Uzan回弹模量的基础上通过引入扭剪循环应力比CSRt,提出了能反映主应力轴旋转的竖向回弹模量修正公式。
[Abstract]:in that construction of the embankment, side slope and the like, the foundation soil unit not only changes the principal stress in the consolidation process, but also the direction of the large principal stress axis is deflected, The stress-induced anisotropy, on the other hand, can lead to the formation of different initial consolidation stress states, including initial vertical bias and initial torsional shear stress. In this complex initial consolidation stress state, when the soil body is further subjected to the complex stress path of wave load, traffic load and the like related to the rotation of the principal stress axis, the deformation and strength characteristics of the soil body will become more complex. Therefore, in the laboratory, the complex initial consolidation stress condition of the soil body is simulated, and the static dynamic test research is further carried out under the complex stress path which relates to the change of the stress principal axis, It is of great significance to establish the deformation law and the constitutive model of the anisotropic consolidation soil under the complex stress condition involving the change of the stress principal axis. In this paper, a series of static and dynamic water drainage tests are carried out for isotropic consolidation and anisotropic "tilt" consolidation saturated sand by a hollow cylindrical torsion shear. The following work is mainly carried out: (1) a series of drainage static shear tests are carried out for the isotropic consolidation and the anisotropic "tilt"-consolidated saturated sand sample, The influence of the intrinsic anisotropy of the sample preparation process and the anisotropy on the stress and strain of the soil, the peak shear strength, the secant modulus, the shear expansion relation, the non-coaxial and other static characteristics is compared and analyzed. The relationship between the increment peak stress ratio and the initial secant modulus and the angle of the consolidation principal stress direction and the increment angle of the shear principal stress is established. (2) The unified phase transition stress ratio (q/ p) phase independent of the direction of the shear principal stress and the consolidation condition is obtained by the contrast analysis of the body strain development in the shear process under the different consolidation conditions and the principal stress direction, and the stress-strain non-coaxial development law is combined, The influence of the non-coaxial factor on the shear expansion is studied, and the deviation of the shear expansion curve and the Rowe linear shear expansion curve caused by the non-coaxial factor is corrected by introducing the non-coaxial factor. (3) The influence of the stress ratio on the body strain development mode is analyzed for the stress axis rotation test under the condition of isotropic consolidation, and the phase transition stress ratio (q/ p) phase which is consistent with the static shear test is obtained, and when the stress ratio is lower than the phase conversion stress ratio, The body strain during the rotation of the principal stress axis shows the deformation of the body, and vice versa. On the other hand, by introducing the non-coaxial factor analysis, the influence of the non-coaxial alignment on the shear-expansion relationship during the rotation of the principal stress axis is analyzed. (4) According to the continuous rotation test of principal stress axis under the condition of anisotropic "tilt" consolidation, the influence of consolidation-induced anisotropy on the development of the strain component and the development of the strain increment and the non-coaxial evolution of the strain during the continuous rotation of the principal stress axis is analyzed. It is found that the maximum non-coaxial angle in the rotation period of the principal stress axis can correspond to the weakest direction (70) of the sample by the rotation angle corresponding to the peak value of the strain increment. ) The lag angle between them is measured. The influence of the number of turns on the development mode of the body strain is studied. With the increase of the number of turns, the relative compactness of the sample is increasing, and the sand sample is changed from the dense state to the dense state, resulting in the occurrence of the deformation of the body in the local rotation range from the fifth turn, And the expansion range of the body is also expanded with the increase of the number of turns of the rotation. (5) The initial consolidation stress state formed during the "tilt" consolidation is studied for the dynamic cyclic drainage test under the condition of the anisotropic "tilt" consolidation under the deflection of the stress principal axis for the foundation soil unit under the low embankment, including the initial vertical deflection stress qvo and the initial torsion shear stress q0, The effect of the vertical permanent deformation in the power cycle. The experimental results show that the relationship between the permanent vertical strain of the first ring and the initial vertical partial stress is linearly increased, and is not related to the initial torsional shear stress; at the condition of qv075kPa and 2000OkPa, the initial vertical deflection stress and the initial torsional shear stress can accelerate the accumulation of the vertical permanent deformation in the early stage, However, when qv0 to 75kPa, the average growth rate of the permanent vertical strain is basically kept constant and is almost not affected by the initial vertical bias stress; on the basis of the logarithmic model proposed by Barksdale, a permanent vertical cumulative correction model considering the comprehensive effects of initial vertical partial stress and initial torsional shear stress is established. (6) The influence of different initial consolidation stress state formed in the "tilt" consolidation on the body strain development during the dynamic cycle shows that there is a critical initial vertical partial stress, qv0 = 75kPa, and the body strain development in the cyclic loading process is divided into two modes: The presence of the initial torsional shear stress will cause the body to expand in the power cycle, and the volume of the body will increase with the increase of the initial torsional shear stress. The critical consolidation line CCL (Critical Consolidated Line) with a K0 consolidation point as the starting point and a horizontal axis included angle is set up at a K0 consolidation point when considering the initial vertical partial stress and the initial torsional shear stress. In that follow-up power cycle, the body-contraction deformation is shown in the process of follow-up power cycle, on the contrary, the body is expanded and deformed. (7) A series of traffic load "heart type" dynamic cyclic stress paths are carried out for the K0 consolidated saturated sand, and the comparison study of the normal dynamic cyclic stress path test which does not take into account the rotation effect of the principal stress axis is carried out, It is revealed that the rotation of principal stress axis caused by traffic load can accelerate the accumulation of vertical deformation and decrease the modulus of vertical resilience, and as the ratio of cyclic stress increases, the influence of principal stress axis rotation on the characteristic of vertical deformation is more obvious. On the basis of the last Uzan elastic modulus, the vertical resilience modulus correction formula that can reflect the rotation of the principal stress axis is put forward by introducing the torsional shear circulation stress ratio (CSRt).
【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】：TU441
本文编号：2509634
[Abstract]:in that construction of the embankment, side slope and the like, the foundation soil unit not only changes the principal stress in the consolidation process, but also the direction of the large principal stress axis is deflected, The stress-induced anisotropy, on the other hand, can lead to the formation of different initial consolidation stress states, including initial vertical bias and initial torsional shear stress. In this complex initial consolidation stress state, when the soil body is further subjected to the complex stress path of wave load, traffic load and the like related to the rotation of the principal stress axis, the deformation and strength characteristics of the soil body will become more complex. Therefore, in the laboratory, the complex initial consolidation stress condition of the soil body is simulated, and the static dynamic test research is further carried out under the complex stress path which relates to the change of the stress principal axis, It is of great significance to establish the deformation law and the constitutive model of the anisotropic consolidation soil under the complex stress condition involving the change of the stress principal axis. In this paper, a series of static and dynamic water drainage tests are carried out for isotropic consolidation and anisotropic "tilt" consolidation saturated sand by a hollow cylindrical torsion shear. The following work is mainly carried out: (1) a series of drainage static shear tests are carried out for the isotropic consolidation and the anisotropic "tilt"-consolidated saturated sand sample, The influence of the intrinsic anisotropy of the sample preparation process and the anisotropy on the stress and strain of the soil, the peak shear strength, the secant modulus, the shear expansion relation, the non-coaxial and other static characteristics is compared and analyzed. The relationship between the increment peak stress ratio and the initial secant modulus and the angle of the consolidation principal stress direction and the increment angle of the shear principal stress is established. (2) The unified phase transition stress ratio (q/ p) phase independent of the direction of the shear principal stress and the consolidation condition is obtained by the contrast analysis of the body strain development in the shear process under the different consolidation conditions and the principal stress direction, and the stress-strain non-coaxial development law is combined, The influence of the non-coaxial factor on the shear expansion is studied, and the deviation of the shear expansion curve and the Rowe linear shear expansion curve caused by the non-coaxial factor is corrected by introducing the non-coaxial factor. (3) The influence of the stress ratio on the body strain development mode is analyzed for the stress axis rotation test under the condition of isotropic consolidation, and the phase transition stress ratio (q/ p) phase which is consistent with the static shear test is obtained, and when the stress ratio is lower than the phase conversion stress ratio, The body strain during the rotation of the principal stress axis shows the deformation of the body, and vice versa. On the other hand, by introducing the non-coaxial factor analysis, the influence of the non-coaxial alignment on the shear-expansion relationship during the rotation of the principal stress axis is analyzed. (4) According to the continuous rotation test of principal stress axis under the condition of anisotropic "tilt" consolidation, the influence of consolidation-induced anisotropy on the development of the strain component and the development of the strain increment and the non-coaxial evolution of the strain during the continuous rotation of the principal stress axis is analyzed. It is found that the maximum non-coaxial angle in the rotation period of the principal stress axis can correspond to the weakest direction (70) of the sample by the rotation angle corresponding to the peak value of the strain increment. ) The lag angle between them is measured. The influence of the number of turns on the development mode of the body strain is studied. With the increase of the number of turns, the relative compactness of the sample is increasing, and the sand sample is changed from the dense state to the dense state, resulting in the occurrence of the deformation of the body in the local rotation range from the fifth turn, And the expansion range of the body is also expanded with the increase of the number of turns of the rotation. (5) The initial consolidation stress state formed during the "tilt" consolidation is studied for the dynamic cyclic drainage test under the condition of the anisotropic "tilt" consolidation under the deflection of the stress principal axis for the foundation soil unit under the low embankment, including the initial vertical deflection stress qvo and the initial torsion shear stress q0, The effect of the vertical permanent deformation in the power cycle. The experimental results show that the relationship between the permanent vertical strain of the first ring and the initial vertical partial stress is linearly increased, and is not related to the initial torsional shear stress; at the condition of qv075kPa and 2000OkPa, the initial vertical deflection stress and the initial torsional shear stress can accelerate the accumulation of the vertical permanent deformation in the early stage, However, when qv0 to 75kPa, the average growth rate of the permanent vertical strain is basically kept constant and is almost not affected by the initial vertical bias stress; on the basis of the logarithmic model proposed by Barksdale, a permanent vertical cumulative correction model considering the comprehensive effects of initial vertical partial stress and initial torsional shear stress is established. (6) The influence of different initial consolidation stress state formed in the "tilt" consolidation on the body strain development during the dynamic cycle shows that there is a critical initial vertical partial stress, qv0 = 75kPa, and the body strain development in the cyclic loading process is divided into two modes: The presence of the initial torsional shear stress will cause the body to expand in the power cycle, and the volume of the body will increase with the increase of the initial torsional shear stress. The critical consolidation line CCL (Critical Consolidated Line) with a K0 consolidation point as the starting point and a horizontal axis included angle is set up at a K0 consolidation point when considering the initial vertical partial stress and the initial torsional shear stress. In that follow-up power cycle, the body-contraction deformation is shown in the process of follow-up power cycle, on the contrary, the body is expanded and deformed. (7) A series of traffic load "heart type" dynamic cyclic stress paths are carried out for the K0 consolidated saturated sand, and the comparison study of the normal dynamic cyclic stress path test which does not take into account the rotation effect of the principal stress axis is carried out, It is revealed that the rotation of principal stress axis caused by traffic load can accelerate the accumulation of vertical deformation and decrease the modulus of vertical resilience, and as the ratio of cyclic stress increases, the influence of principal stress axis rotation on the characteristic of vertical deformation is more obvious. On the basis of the last Uzan elastic modulus, the vertical resilience modulus correction formula that can reflect the rotation of the principal stress axis is put forward by introducing the torsional shear circulation stress ratio (CSRt).
【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】：TU441
【参考文献】
相关期刊论文 前1条
1 范留明,李宁,丁卫华;数字图像伪彩色增强方法在岩土CT图像分析中的应用[J];岩石力学与工程学报;2004年13期
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