基于强度折减法的浅变质岩风化层边坡稳定性研究
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摘要
边坡稳定分析的方法很多,传统上主要采用极限平衡分析方法。近年来,引入了强度折减法,强度折减法是结合有限元或有限差分等数值计算方法来实现边坡稳定性分析的。采用有限差分强度折减法进行边坡稳定分析,能直接得到安全系数和最危险滑动面,并且能得到边坡的应力场分布,还可以描述边坡的失稳过程。
以浅变质岩风化层边坡为研究对象,基于FLAG-3D软件,结合有限差分强度折减理论,对浅变质岩风化层边坡进行了稳定性分析。
分析研究了浅变质岩风化层边坡的工程特性;对现有的边坡失稳判据进行了分析对比,选定计算收敛判据作为失稳判据,并利用FLAG-3D软件编译相应的程序来实现强度折减法,求解边坡安全系数并搜索最危险滑动面;选取了一个均质边坡和一个非均质边坡作为算例,运用自编强度折减法程序进行边坡稳定分析,验证了本文算法的适用性;基于均质边坡算例,简单分析了计算网格划分和内摩擦角、粘聚力、弹性模量、泊松比等参数对边坡安全系数计算值的影响;运用本文分析方法对某浅变质岩风化层边坡稳定性进行了分析。得出以下主要结论:
(1)浅变质岩风化层边坡岩体的物理力学性质差,强度低,坡体内构造面、小断层发育,风化后形成软弱带,导致浅变质岩风化层边坡自身稳定性差。在降雨、坡体开挖等因素的影响下,浅变质岩风化层边坡极易发生边坡失稳。
(2)建立计算模型时要合理的划分计算网格。当网格划分密度较低时,边坡的安全系数随网格密度的增加而减小,且变化较大;当网格划分密度较高后,边坡的安全系数随网格密度的增加而引起的变化较小。网格密度过低会影响计算精度,而过高的网格密度则会消耗过多的计算时间,因此一般要通过试算来确定合理的网格密度。
(3)在相同的计算条件下,内摩擦角φ对安全系数计算值的影响较大,粘聚力c次之,弹性模量E和泊松比μ对边坡的安全系数计算值几乎没有影响。
(4)本文基于FLAG-3D软件的自编强度折减法计算程序具有一定的适用性,可以较为准确地确定边坡的安全系数和最危险滑动面的位置。
There are many methods for the slope stability analysis, the limiting equilibrium method is mainly used traditionally, the strength reduction method which analyses slope stability with finite element or finite difference method is introduced these years. According to the strength reduction method with finite difference , the factor of safety and the most dangerous slip surface can be obtained directly, the stress field and the process of destabilization can be shown too.
This paper takes the slightly weathered rock as subject investigated, and uses the strength reduction method with finite difference based on FLAC-3D software to analyse the stability of slightly weathered rock slope.
This paper researches the engineering characteristic of the slightly weathered rock slope, analyses the existing criterions of destabilization and takes the convergence criterion. This paper makes a program based on FLAC-3D software to carry out the strength reduction method, and gets the factor of safety and the most dangerous slip surface according to it. This paper takes one homogeneous slope and one heterogeneous slope as examples to test the self-orgnizing strength reduction method which is mentioned above. Based on the homogeneous slope, it simply analyses the influence to the factor of safety of the mesh, internal friction angle, cohesive strength, Young's modulus and Poisson's ratio. Finally it analyses an instance of the slightly weathered rock slope by the self-orgnizing strength reduction method. The conclusions are as follows:
(1) Because of bad physical mechanical property of rock mass, low strength, so many structural planes and minor faults which leads to weak strip after weathered, the homeostasis of the slightly weathered rock slope is serious. With the influence of external factors such as rainfall, engineering projects and unreasonable job practicees, it's very easy to be unstable.
(2) The mesh should be ploted reasonably in the process of model building. When the mesh density is low, the factor of safety reduces greatly with the increase of mesh density, when the mesh density is high, the factor of safety changes little with the increase of mesh density. The precision of calculation will not be nice if the mesh density is too low, contrarily it will cost too much time to calculate if the mesh density is too high. So it's normally need to confirm the reasonable mesh density according to pilot calculation.
(3) With the same computational condition, internal friction angle influences the calculation of factor of safety greately, cohesive strength takes second place, Young's modulus and Poisson's ratio influences the calculation of factor of safety hardly.
(4) The self-orgnizing strength reduction method based on FLAC-3D software in this paper is applicable, it can get reasonable factor of safety and the most dangerous slip surface.
以浅变质岩风化层边坡为研究对象,基于FLAG-3D软件,结合有限差分强度折减理论,对浅变质岩风化层边坡进行了稳定性分析。
分析研究了浅变质岩风化层边坡的工程特性;对现有的边坡失稳判据进行了分析对比,选定计算收敛判据作为失稳判据,并利用FLAG-3D软件编译相应的程序来实现强度折减法,求解边坡安全系数并搜索最危险滑动面;选取了一个均质边坡和一个非均质边坡作为算例,运用自编强度折减法程序进行边坡稳定分析,验证了本文算法的适用性;基于均质边坡算例,简单分析了计算网格划分和内摩擦角、粘聚力、弹性模量、泊松比等参数对边坡安全系数计算值的影响;运用本文分析方法对某浅变质岩风化层边坡稳定性进行了分析。得出以下主要结论:
(1)浅变质岩风化层边坡岩体的物理力学性质差,强度低,坡体内构造面、小断层发育,风化后形成软弱带,导致浅变质岩风化层边坡自身稳定性差。在降雨、坡体开挖等因素的影响下,浅变质岩风化层边坡极易发生边坡失稳。
(2)建立计算模型时要合理的划分计算网格。当网格划分密度较低时,边坡的安全系数随网格密度的增加而减小,且变化较大;当网格划分密度较高后,边坡的安全系数随网格密度的增加而引起的变化较小。网格密度过低会影响计算精度,而过高的网格密度则会消耗过多的计算时间,因此一般要通过试算来确定合理的网格密度。
(3)在相同的计算条件下,内摩擦角φ对安全系数计算值的影响较大,粘聚力c次之,弹性模量E和泊松比μ对边坡的安全系数计算值几乎没有影响。
(4)本文基于FLAG-3D软件的自编强度折减法计算程序具有一定的适用性,可以较为准确地确定边坡的安全系数和最危险滑动面的位置。
There are many methods for the slope stability analysis, the limiting equilibrium method is mainly used traditionally, the strength reduction method which analyses slope stability with finite element or finite difference method is introduced these years. According to the strength reduction method with finite difference , the factor of safety and the most dangerous slip surface can be obtained directly, the stress field and the process of destabilization can be shown too.
This paper takes the slightly weathered rock as subject investigated, and uses the strength reduction method with finite difference based on FLAC-3D software to analyse the stability of slightly weathered rock slope.
This paper researches the engineering characteristic of the slightly weathered rock slope, analyses the existing criterions of destabilization and takes the convergence criterion. This paper makes a program based on FLAC-3D software to carry out the strength reduction method, and gets the factor of safety and the most dangerous slip surface according to it. This paper takes one homogeneous slope and one heterogeneous slope as examples to test the self-orgnizing strength reduction method which is mentioned above. Based on the homogeneous slope, it simply analyses the influence to the factor of safety of the mesh, internal friction angle, cohesive strength, Young's modulus and Poisson's ratio. Finally it analyses an instance of the slightly weathered rock slope by the self-orgnizing strength reduction method. The conclusions are as follows:
(1) Because of bad physical mechanical property of rock mass, low strength, so many structural planes and minor faults which leads to weak strip after weathered, the homeostasis of the slightly weathered rock slope is serious. With the influence of external factors such as rainfall, engineering projects and unreasonable job practicees, it's very easy to be unstable.
(2) The mesh should be ploted reasonably in the process of model building. When the mesh density is low, the factor of safety reduces greatly with the increase of mesh density, when the mesh density is high, the factor of safety changes little with the increase of mesh density. The precision of calculation will not be nice if the mesh density is too low, contrarily it will cost too much time to calculate if the mesh density is too high. So it's normally need to confirm the reasonable mesh density according to pilot calculation.
(3) With the same computational condition, internal friction angle influences the calculation of factor of safety greately, cohesive strength takes second place, Young's modulus and Poisson's ratio influences the calculation of factor of safety hardly.
(4) The self-orgnizing strength reduction method based on FLAC-3D software in this paper is applicable, it can get reasonable factor of safety and the most dangerous slip surface.
引文
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[2]潘家铮.建筑物的抗滑稳定和滑坡分析[M].北京:水利出版社,1980
[3]张天宝.土坡稳定分析和土工建筑物的边坡设计[M].成都:程度科技大学出版社,1987
[4]陈祖煜.土坡稳定分析-原理、方法、程序[M].北京:中国水利水电出版社,2003
[5]赵尚毅,时卫民,郑颖人.边坡稳定分析的有限元法[J]地下空间,2001,21(5):450-454.
[6]姚寿广.边界元数值算法及其工程应用[M].北京:国防工业出版社1995
[7]刘波,韩彦辉编著.FLAC原理、实例与应用指南[M].北京:人民交通出版社,2006.
[8]卓家寿,章青.不连续介质力学问题的界面元法[M].科学出版社,2000
[9]王泳嘉等.离散元法及其在岩土力学中的应用[M].辽宁:东北大学出版社,1991(2)
[10]石根华著,任放等译.块体系统不连续变形数值分析新方法[M].北京:科学出版社,1993
[11]陈菲.强度折减法在滑坡三维稳定性分析中的应用[D].武汉:中国科学院武汉岩土力学研究所.2006
[12]卓家寿,邵国建,陈振雷.工程稳定问题中确定滑塌面、滑向与安全度的干扰能量法[J].水利学报,1997,(7):80-84.
[13]卓家寿,弹塑性力学中的广义变分原理[M],北京:中国水利水电出版社,2002
[14]邵国建,卓家寿,章青.岩体稳定性分析与评价准则研究[J].岩石力学与工程学报,2003,22(5):691-696.
[15]赵进勇.用干扰能量法模拟边坡失稳过程[J].岩土工程学报,2002(3):367-370.
[16]江伟,耿克勤.边坡可靠性分析与评价[J].水利水电技术,1994.3
[17]李文秀.矿山高陡边坡稳定性研究的模糊数学方法[J].长江科学院院报,1996年9月
[18]程相君.神经网络及其应用[M].北京:国防工业出版社,1995
[19]崔政权、李宁编著.边坡工程-理论与实践最新发展[M].中国水利水电出版社,1999
[20]Zienkiewicz O C,Humpheson C,Lewis R W Associated and non-associated visco-plasticity and plasticity in soil mechanics[J].Geotechnique,1975,25(4):671-689.
[21]Duncan J M.State of the art:limit equilibrium and finite-element analysis of slopes[J].Journal of Geotechnical Engineering,ASCE,1996,122(7):577--689.
[22]徐干成,郑颖人.岩土工程中屈服准则应用的研究fJ].岩土工程学报,1990 12(2):93-99
[23]Ugai K.A method of calculation of total factor of safety of slope by elaso-plastic FEM.Soils and Foundation.1989,29(2):190--195
[24]Dawson.E.M.Slope stability analysis by shear strength reduction.Geotechnique,1999,49(6):835-840
[25]Lane.Assessment of stability of slope under drawdown conditions.Journal of Geotechnical and Geoenvinmental Engineering,2000,126(5):443--450
[26]连镇营.强度折减有限元法研究开挖边坡的稳定性[J].岩土工程学报,2001,23(4):407-411
[27]郑颖人,赵尚毅.用有限元强度折减法进行边坡稳定分析[J].中国工程科学,2002,4(10):57-61
[28]张鲁瑜、郑颖人.有限元强度折减系数法计算土坡稳定安全系数的精度研究[J].水利学报,2003,1:21-27
[29]郑颖人、赵尚毅.有限元强度折减法在土坡与岩坡中的应用[J].岩石力学与工程学报,2004,23(19):3381-3388
[30]郑颖人,赵尚毅.有限元强度折减法研究进展[J].后勤工程学院学报,2005,第三期
[31]赵尚毅,郑颖人,时卫民,王敬林.用有限元强度折减法求边坡稳定安全系数[J].岩土工程学报,2002,24(3):333-336
[32]孙伟,龚晓南.土坡稳定分析强度折减有限元法[J].科技通报,2003,19(4):319-322.
[33]栾茂田,武亚军,年廷凯.强度折减有限元法中边坡失稳的塑性区判据及其应用[J].防灾减灾工程学报,2003,23(3):1-7.
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