多因素作用下植被对岸坡稳定影响的试验及数值模拟研究

发布时间：2018-04-08 22:16

本文选题：植被　切入点：渗透破坏　出处：《天津大学》2015年博士论文

【摘要】：内河航道土质岸坡常年受渗流、船行波和降雨的作用,其稳定性受到威胁。为了防止岸坡失稳现象的发生,维护通航安全,必须对危险岸坡采取治理措施,以提高其稳定性。而植被护坡作为一项兼顾岸坡加固及环境保护的工程技术,在近几十年间被广泛应用于岸坡整治工程。对于多因素作用下植被对岸坡稳定影响的研究,目前的研究成果尚未涉及根系对岸坡浅层稳定影响的判别以及船行波作用下草根加筋土动力特性研究。此外,渗透对土体结构性破坏的影响、船行波作用下岸坡的强度折减以及植被覆盖对降雨工况下岸坡稳定影响的相关分析也是不完善的。本文采用土工试验与数值模拟相结合的手法,对植被护坡前后航道土质岸坡在渗流、船行波和降雨作用下的稳定性进行分析研究。内容如下:(1)开展原状素土和重塑素土的三轴渗透剪切试验,研究渗透破坏对土体有效应力强度指标的影响,得出渗流作用后土体内摩擦角不变,粘聚力降低。在此基础上,本文通过莫尔-库仑准则将此破坏作用以“等效围压降低”的形式量化表述。此外,还推导出以指数函数的形式来表征渗透工况下的有效应力强度随水力坡降变化的公式。(2)开展重塑草根加筋土的三轴渗透剪切试验,研究根系的存在对土体渗透性和强度的影响,并推导出考虑渗流对草根加筋土强度破坏影响范围的计算公式。(3)开展重塑素土和重塑草根加筋土的动三轴试验,研究其孔压和残余应变随循环次数增长的变化规律。通过对比得出根系在抵抗动力破坏的过程中发挥的作用是降低循环荷载作用过程中孔压的增长和残余应变的累积。此外,推导出循环后草根加筋土的抗剪强度折减率随动应力比变化的公式。(4)在试验的基础上建立了考虑渗透破坏对土体有效应力强度影响的修正Duncan-Chang本构模型,并以危险滑动区能量积分变化来作为岸坡整体失稳判别准则。此外,针对草本植被根系作用深度较浅而对岸坡整体稳定性基本无影响的特点,提出以岸坡表层植被根系作用区的变形能量总和作为判断根系作用的指标。该研究对全面分析岸坡在渗流作用下的整体及局部稳定性提供了理论依据。(5)结合试验得出的素土与草根加筋土的抗剪强度折减率随动应力比的变化公式,通过对软件二次开发,建立了岸坡不同区域内土体抗剪强度指标的弱化模型。此外,提出以岸坡表面最大位移突变作为船行波作用下的岸坡失稳判别准则,从而计算出岸坡在不同船行波荷载作用下所产生的不同的失稳模式。从而对分析船行波作用下草本植被保护岸坡在抵抗动力荷载破坏方面的研究提供了理论依据。(6)建立了全面考虑坡面流冲刷强度与植被覆盖影响的降雨工况下植被对岸坡稳定影响的数值分析模型,提出以岸坡发生圆弧滑动失稳之前表层塑性区的发展来表征降雨对岸坡稳定的影响。(7)利用本文提出的多因素作用下植被对岸坡稳定影响的分析方法,进一步分别对不同渗流、船行波和降雨工况作用下的内河航道土质岸坡进行稳定性分析,得出:根系在抵抗渗流对岸坡表层变形扰动方面起到了作用;船行波作用后岸坡会在水位线附近和坡脚产生大变形,所以需要着重对这两个区域加强生态和工程保护措施;随植被覆盖率的降低和降雨时间的延长,表层破坏的范围加大,所以需要对岸坡表层塑性破坏区域加强生态及工程保护措施。
[Abstract]:Inland waterway perennial soil slope seepage, rainfall and ship wave function, its stability is threatened. In order to prevent the occurrence of slope instability, maintaining the safety of navigation, we must take measures on bank risk, to improve its stability. And the slope vegetation as a both slope reinforcement and environmental protection engineering in in recent years has been widely used in slope remediation projects. For the study of multiple factors affecting the vegetation on the slope stability, the results of the present study does not involve root Slope Shallow stability discrimination and ship waves of grassroots reinforced soil dynamic characteristics research. In addition, osmotic effect on soil structural damage to the ship. The traveling wave effect of strength reduction and the bank under the vegetation coverage analysis of the impact on the slope stability under the condition of rainfall is not perfect. This paper uses soil test and numerical model The combination of tactics, the vegetation and the waterways in the soil slope seepage, analyze the stability of the ship wave and the effect of rainfall. The contents are as follows: (1) shear test three axial penetration undisturbed soil and remolded in soil, study the seepage failure impact effect on soil strength index, the seepage after the action of the internal friction angle of soil constant, cohesive strength reduced. On this basis, the Mohr Coulomb criterion will damage to the "quantitative form of equivalent confining pressure to reduce the statement. In addition, is derived in the form of exponential function to characterize the permeability of effective stress intensity changes with the hydraulic gradient formula under the condition of. (2) shear tests of three axis penetration to carry out remodeling of grassroots reinforced soil, influence study of root on soil permeability and strength, and deduces the seepage of grass-roots strength of reinforced soil damage influence scope Formula (3). Three triaxial test is carried out to reshape the soil and remodeling of grassroots reinforced soil, the variation of pore pressure and residual strain of research with the number of cycles of growth. By comparing the root plays in the process of dynamic damage resistance effect is reduced accumulation of cyclic loading process of pore pressure and growth the residual strain. In addition, the shear strength reduction rate with dynamic stress ratio formula is derived. After GRS (4) on the basis of experiments considering seepage damage constitutive models of modified Duncan-Chang effective stress intensity effect on soil was established, and the energy of dangerous sliding area integral change as the overall slope instability criterion. In addition, according to the characteristics of herbaceous vegetation root depth is shallow and has no effect on the overall stability of slope, the slope surface is proposed to root zone and the total deformation energy As a judge of root index. The research provides a theoretical basis for the comprehensive analysis of slope under seepage action of the overall and local stability. (5) the shear strength reduction rate changes with the formula of dynamic stress ratio with experimental results for soil and GRS, through the two development software. The weakening model of shear strength index of soil slope in different areas. In addition, the maximum displacement of slope surface under the action of mutation as the ship wave slope instability criterion to calculate the slope generated under different load under different ship wave instability mode. Thus the slope vegetation protection of ship wave under the effect of the herbs in the dynamic load resistance provides a theoretical basis for the destruction of the study. (6) the establishment of a comprehensive consideration of the vegetation on the slope stability influence of overland flow erosion intensity and vegetation cover affects rainfall conditions The numerical analysis model, proposed effects of instability before development of the plastic zone surface to characterize the rainfall on the slope stability of slope with circular slip occurred. (7) using the analysis method of influence of vegetation on the slope stability under the action of multiple factors, further respectively on the different seepage flow effect of ship wave and rainfall condition the inland waterway soil slope stability analysis, the seepage on the slope surface of root in resistance to deformation disturbance plays a role of slope; will produce large deformation in the water near the line and slope ship wave action, so the need to focus on ecological and engineering protection measures of the two areas to strengthen; with the vegetation coverage rate and reduce the rainfall time prolonged, the increase range of surface damage, so the slope surface plastic damage area to strengthen ecological and engineering protection measures.

【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：U617

【相似文献】