考慮應力主軸變化下各向異性砂土靜動力特性試驗研究
發(fā)布時間：2019-07-03 20:13
【摘要】：在路堤、邊坡等工程中,地基土單元在固結(jié)過程中不僅主應力大小會發(fā)生改變,大主應力軸方向也會發(fā)生偏轉(zhuǎn),這種涉及應力主軸偏轉(zhuǎn)的各向異性“傾斜”固結(jié)一方面使得砂土顆粒重新排列,進而產(chǎn)生應力誘發(fā)各向異性,另一方面會導致土體形成不同的初始固結(jié)應力狀態(tài),包括初始豎向偏應力以及初始扭剪應力。在這種復雜的初始固結(jié)應力狀態(tài)條件下,當土體進一步承受波浪荷載、交通荷載等涉及主應力軸旋轉(zhuǎn)的復雜應力路徑時,土體表現(xiàn)出來的變形和強度特性將變得更加復雜。因而,在實驗室模擬土體的復雜初始固結(jié)應力條件,并進一步開展涉及應力主軸變化的復雜應力路徑下靜動力試驗研究,對于建立涉及應力主軸變化這種復雜應力條件下各向異性固結(jié)土體的變形規(guī)律和本構(gòu)模型具有十分重要的試驗指導意義。本文利用空心圓柱扭剪儀針對各向同性固結(jié)和各向異性“傾斜”固結(jié)飽和砂土進行了一系列涉及應力主軸變化的復雜應力路徑下靜動力排水試驗研究。主要開展了以下工作研究：(1)分別針對各向同性固結(jié)和各向異性“傾斜”固結(jié)飽和砂土試樣進行了一系列排水靜力剪切試驗,對比分析了制樣過程形成的固有各向異性以及“傾斜”固結(jié)誘發(fā)的各向異性對土體應力應變關系、峰值剪切強度、割線模量、剪脹關系、非共軸等靜力特性的影響,并建立了“傾斜”固結(jié)條件下增量峰值應力比和初始割線模量與固結(jié)主應力方向角和剪切主應力增量角度差值之間關系。(2)通過對不同固結(jié)條件和主應力方向下剪切過程中體應變發(fā)展的對比分析,得到了獨立于剪切主應力方向和固結(jié)條件的統(tǒng)一相位轉(zhuǎn)換應力比(q/p)phase；結(jié)合應力應變非共軸發(fā)展規(guī)律,研究了非共軸對剪脹關系的影響,并通過引入非共軸因子修正了非共軸度造成的剪脹曲線與Rowe直線型剪脹曲線的偏差。(3)針對各向同性固結(jié)條件下主應力軸旋轉(zhuǎn)試驗,分析了應力比對體應變發(fā)展模式的影響,得到了與靜力剪切試驗一致的相位轉(zhuǎn)換應力比(q/p)phase,當應力比低于相位轉(zhuǎn)換應力比時,主應力軸旋轉(zhuǎn)過程中體應變表現(xiàn)為體縮變形,反之為體脹變形。另一方面,通過引入非共軸因子分析了主應力軸旋轉(zhuǎn)過程中非共軸對剪脹關系的影響。(4)針對各向異性“傾斜”固結(jié)條件下主應力軸連續(xù)旋轉(zhuǎn)試驗,分析了固結(jié)誘發(fā)各向異性對主應力軸連續(xù)旋轉(zhuǎn)過程中應變分量發(fā)展以及應變流動過程中表現(xiàn)出的應變增量大小發(fā)展和非共軸演變規(guī)律的影響；發(fā)現(xiàn)了主應力軸旋轉(zhuǎn)周期內(nèi)最大非共軸角度可以通過應變增量峰值對應的旋轉(zhuǎn)角度與試樣最薄弱方向(70。)之間的滯后角度進行度量。研究了旋轉(zhuǎn)圈數(shù)對體應變發(fā)展模式的影響,隨著旋轉(zhuǎn)圈數(shù)增加,試樣相對密實度不斷增大,砂土試樣從中密向密實狀態(tài)轉(zhuǎn)變,從而導致從第5圈開始在局部旋轉(zhuǎn)范圍內(nèi)出現(xiàn)體脹變形,而且體脹范圍也隨著旋轉(zhuǎn)圈數(shù)增加而不斷擴大。(5)針對低路堤下地基土單元涉及應力主軸偏轉(zhuǎn)的各向異性“傾斜”固結(jié)條件下的動力循環(huán)排水試驗,研究了“傾斜”固結(jié)過程中形成的不同初始固結(jié)應力狀態(tài),包括初始豎向偏應力qvo和初始扭剪應τ0,對動力循環(huán)過程中豎向永久變形的影響。試驗結(jié)果表明,第一圈永久豎向應變與初始豎向偏應力大小呈線性增長的關系,而與初始扭剪應力基本無關；在qv075kPa,τ0OkPa條件下,初始豎向偏應力和初始扭剪應力都會加速前期豎向永久變形的累積,但當qv0≤75kPa,永久豎向應變平均增長率基本保持恒定,幾乎不受初始豎向偏應力的影響；在Barksdale提出的對數(shù)模型的基礎上,建立了考慮初始豎向偏應力和初始扭剪應力綜合影響的永久豎向累積修正模型。(6)“傾斜”固結(jié)中形成的不同初始固結(jié)應力狀態(tài)對動力循環(huán)過程中體應變發(fā)展的影響表明,存在一個臨界初始豎向偏應力qv0=75kPa,將循環(huán)加載過程中體應變發(fā)展分為體脹和體縮兩種模式；初始扭剪應力的存在會使得土體在動力循環(huán)中產(chǎn)生體脹趨勢,而且體脹量隨著初始扭剪應力的增大而增大。綜合考慮初始豎向偏應力和初始扭剪應力作用時,在(σz-σθ)-2σzθ建立了以K0固結(jié)點為起點與水平軸夾角為2(α△σc)CCL的臨界固結(jié)線CCL (Critical Consolidated Line),當α△σc(α△σc)CCL時后續(xù)動力循環(huán)過程中表現(xiàn)為體縮變形,反之為體脹變形。(7)針對K0固結(jié)飽和砂土進行了一系列交通荷載“心臟型”動力循環(huán)應力路徑以及不考慮主應力軸旋轉(zhuǎn)效應的普通動力循環(huán)應力路徑試驗的對比研究,揭示了交通荷載引起的主應力軸旋轉(zhuǎn)會加速豎向變形的累積以及減弱豎向回彈模量,并且且隨著循環(huán)應力比增大,主應力軸旋轉(zhuǎn)對豎向變形特性影響更加明顯,最后Uzan回彈模量的基礎上通過引入扭剪循環(huán)應力比CSRt,提出了能反映主應力軸旋轉(zhuǎn)的豎向回彈模量修正公式。
[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).
【學位授予單位】：浙江大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TU441
本文編號：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).
【學位授予單位】：浙江大學
【學位級別】：博士
【學位授予年份】：2015
【分類號】：TU441
【參考文獻】
相關期刊論文 前1條
1 范留明,李寧,丁衛(wèi)華;數(shù)字圖像偽彩色增強方法在巖土CT圖像分析中的應用[J];巖石力學與工程學報;2004年13期
，本文編號：2509634
本文鏈接：http://sikaile.net/jingjilunwen/jianzhujingjilunwen/2509634.html
最近更新
教材專著
