抽水条件下拉张型地裂缝开展过程的数值模拟研究
|
摘要
虽然地裂缝已经成为一种重要的城市地质灾害,但由于地裂缝难以直接观察的特点以及土体变形的复杂性,使得人们对地裂缝的研究大多还停留在对已知地裂缝进行定性的现场勘察和灾害评估。破坏力学的发展使人们很自然的想到利用已有的破坏力学对地裂缝进行模拟和预测,并已取得一定的成果。本文遵循这一思路,引入了破坏力学数值模拟的理论和方法,摈弃了传统的连续体力学分析方法、材料强度理论以及土体脆性破坏的假设,在常规有限单元法的基础上加入基于弥散裂缝模型的钝化断裂带模型,结合裂缝开展的张开度COD和能量释放率作为单元的断裂判据,对土体中拉张型裂缝的动态发展进行模拟,所建立的模型通过已有实验研究成果进行了验证,并对三种常见地质条件下拉张型地裂缝的形成和发展进行了模拟和分析,讨论了不同条件下拉张型地裂缝的形成机制、分布特点及其对土体变形的进一一步影响。
本文的研究表明,利用钝化断裂带模型的方法对土体Ⅰ型开裂过程进行数值模拟是可行的,对实验尺度土样的模拟结果以及对拉张型地裂缝的模拟结果都与实际观测基本相符：模拟过程中,拉张型地裂缝大多形成于浅部土体并竖直向下发展,大多数情况下地裂缝处通常形成明显的水平位移差和相对较小的竖直位移差,说明地裂缝两侧产生了较大的水平张开度和较小的垂向错动,然而在有先期断层存在的情况下,断裂面的重新开裂会产生较为显著的垂向错动,虽然由此带来的剪应力影响有待进一步研究,但也由此可推测随着裂缝开展深度的增加,拉张型地裂缝也有可能产生与先期断层相似的作用,使得其破坏模式从早期的拉张型逐渐向拉张-剪切型转变。
Earth fissures have already become a kind of significant urban geo-hazards. Due to the difficulties in observing soil fissuring and the complexity of soil deformation, current researches on earth fissures are still largely limited to qualitative field surveys and hazard evaluation to some existing fissures. With the development of failure mechanics, it naturally occurs for people to use failure mechanics to simulate earth fissures, and some achievements have been reached. Based on the previous studies, this paper did not use the method and strength theory of traditional continuum mechanics and the assumption of brittle failure of soil, but applied theories and methods of failure mechanics to the simulation of soil cracking, Based on a conventional finite element method program, Crack Band Model, which is developed from Smeared Crack Model, is built to simulate the whole process of soil cracking, with the Crack Opening Displacement (COD) and energy release rate used as the fracture criterion to describe the dynamic propagation of fissures. Then the model has been preliminarily validated by comparing the simulation results to the data acquired from an existing experiment. Finally, tensile-induced earth fissures triggered by groundwater extraction under three kinds of geological conditions have been simulated and analyzed. For each geological condition, the mechanism and the distribution of tensile earth fissuring and the influence of the occurred fissures on further soil deformation are explained.
It is shown that the CBM is a feasible approach for simulating model I crack initiation and propagation in soil, which has been examined by the data from laboratory tests and the field observations of initiation and propagation of tensile-induced earth fissures. Most simulated fissures are initiated at the ground surface and propagate downwards, with significant horizontal and relatively small vertical displacement gradient, which means a great fissure aperture and a rather small vertical offset. However, a greater vertical offset is observed on a fissure formed at a pre-fault. Although the influence of shear strain on earth fissures is currently ignored, it can also be inferred that with the depth of fissure growing greater, the tensile-induce fissure may play a similar role as a pre-fault in the soil layer, which may lead to a change of failure model from pure tension to tension-shear.
本文的研究表明,利用钝化断裂带模型的方法对土体Ⅰ型开裂过程进行数值模拟是可行的,对实验尺度土样的模拟结果以及对拉张型地裂缝的模拟结果都与实际观测基本相符：模拟过程中,拉张型地裂缝大多形成于浅部土体并竖直向下发展,大多数情况下地裂缝处通常形成明显的水平位移差和相对较小的竖直位移差,说明地裂缝两侧产生了较大的水平张开度和较小的垂向错动,然而在有先期断层存在的情况下,断裂面的重新开裂会产生较为显著的垂向错动,虽然由此带来的剪应力影响有待进一步研究,但也由此可推测随着裂缝开展深度的增加,拉张型地裂缝也有可能产生与先期断层相似的作用,使得其破坏模式从早期的拉张型逐渐向拉张-剪切型转变。
Earth fissures have already become a kind of significant urban geo-hazards. Due to the difficulties in observing soil fissuring and the complexity of soil deformation, current researches on earth fissures are still largely limited to qualitative field surveys and hazard evaluation to some existing fissures. With the development of failure mechanics, it naturally occurs for people to use failure mechanics to simulate earth fissures, and some achievements have been reached. Based on the previous studies, this paper did not use the method and strength theory of traditional continuum mechanics and the assumption of brittle failure of soil, but applied theories and methods of failure mechanics to the simulation of soil cracking, Based on a conventional finite element method program, Crack Band Model, which is developed from Smeared Crack Model, is built to simulate the whole process of soil cracking, with the Crack Opening Displacement (COD) and energy release rate used as the fracture criterion to describe the dynamic propagation of fissures. Then the model has been preliminarily validated by comparing the simulation results to the data acquired from an existing experiment. Finally, tensile-induced earth fissures triggered by groundwater extraction under three kinds of geological conditions have been simulated and analyzed. For each geological condition, the mechanism and the distribution of tensile earth fissuring and the influence of the occurred fissures on further soil deformation are explained.
It is shown that the CBM is a feasible approach for simulating model I crack initiation and propagation in soil, which has been examined by the data from laboratory tests and the field observations of initiation and propagation of tensile-induced earth fissures. Most simulated fissures are initiated at the ground surface and propagate downwards, with significant horizontal and relatively small vertical displacement gradient, which means a great fissure aperture and a rather small vertical offset. However, a greater vertical offset is observed on a fissure formed at a pre-fault. Although the influence of shear strain on earth fissures is currently ignored, it can also be inferred that with the depth of fissure growing greater, the tensile-induce fissure may play a similar role as a pre-fault in the soil layer, which may lead to a change of failure model from pure tension to tension-shear.
引文
[1]耿大玉,李忠生.中美两国的地裂缝灾害[J].地震学报,2000,(04)：433-441+448
[2]王哲成,张云.地下水超采引起的地裂缝灾害的研究进展[J].水文地质工程地质,2012,39(2)：88-93
[3]王光亚,施斌,王晓梅,吴曙亮,武健强.江阴南部地面沉降及地裂缝研究[J].水文地质工程地质,2009,(02)：117-122
[4]HOLZER T L, PAMPEYAN E H. Earth fissures and localized differnetial subsidence [J]. Water Resources Research,1981,17(01):223-227
[5]JACHENS R C, HOLZER T L. Differential compaction mechanism for earth fissures near Casa Grande, Arizona [J]. Bulletin of the Geological Society of America,1982,93(10):998-1012
[6]BOLING J K. Earth-fissure movements in south-central Arizona, U.S.A, Wallingford, ROYAUME-UNI, F,1986 [C]. International Association of Hydrological Sciences,
[7]HOLZER T L. Ground failure caused by groundwater withdrawal from unconsolidated sediments-United States [M]. Wallingford, ROYAUME-UNI:International Association of Hydrological Sciences,1986
[8]WOLFF R G. Relationship between horizontal strain near a well and reverse water level fluctuation [J]. Water Resources Research,1970,6(6):1721-1728
[9]LOFGREN B E. Significant Role of Seepage Stresses in Compressible Aquifer Systems [J]. Eos, Transactions, American Geophysical Union,1971,52(11):832
[10]HELM D C. Hydraulic Forces that Play a Role in Generation Fissures at Depth [J]. Bulletin of the International Association of Engineering Geology,1994,31:293-302
[11]ROTHENBURG L. Horizontal ground movements due to water abstraction and formation of earth fissures [J]. International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts, 1996,33(8):239-249
[12]王庆良,刘玉海,陈志新,王文萍.抽水引起的含水层应变—地裂缝活动新机理[J].工程地质学报,2002,10(1)：46-51
[13]SHENG Z P, HELM D C, LI J. Mechanisms of earth fissuring caused by groundwater withdrawal [J]. Environmental and Engineering Geoscience,2003,9(4):351-362
[14]伍洲云,余勤,张云.苏锡常地区地裂缝形成过程[J].水文地质工程地质,2003,30(1)：67-73
[15]BUDHU M. Mechanics of earth fissures using the Mohr-Coulomb failure criterion [J]. Environmental and Engineering Geoscience,2008,14(4):281-295
[16]ZHANG Y, XUE Y Q, WU J C, YU J, WEI Z X, LI Q F. Land subsidence and earth fissures due to groundwater withdrawal in the Southern Yangtse Delta, China [J]. Environmental Geology,2008, 55(4):751-762
[17]BURBEY T J, CARRE N-FREYRE D, CERCA M, GALLOWAY DEVIN L, SILVA-CORONA J J. Mechanisms for earth fissure formation in heavily pumped basins [J].IAHS-AISH publication,2010,339(8):3-8
[18]TUCKWELL G W. The control of stress history and flaw distribution on the evolution of polygonal fracture networks [J]. Journal of Structural Geology,2003,25(8):1241-1250
[19]易学发,苏刚,王卫东,唐俊昌.用数值模拟研究西安地裂缝[J].水文地质工程地质,1999,26(005)：33-36
[20]石玉玲,门玉明,彭建兵,黄强兵,刘洪佳,陈立伟.西安城区地裂缝破裂扩展的数值模拟[J].水文地质工程地质,2008,(6)：56-60
[21]陈立伟.地裂缝扩展机理研究[D].西安；长安大学,2007
[22]李全明,张丙印,于玉贞,王建国.土石坝水力劈裂发生过程的有限元数值模拟[J].岩士工程学报,2007,29(2)：212-217
[23]喻葭临.土中剪切带扩展机理研究和扩展过程模拟[D].北京；清华大学,2009
[24]丁金粟,刁玉椿,孙亚平.击实粘粘性土断裂韧度性质研究[J].水利学报,1990,21(07)：55-60
[25]范天佑.断裂理论基础[M].北京：科学出版社,2003
[26]GRIFFITH A A. The phenomena of rupture and flow in solids [J]. Philosophical Transactions of the Royal Society of London Series A, Mathematical and Physical Sciences,1921,221:163-198
[27]葛修润,任建喜,蒲毅彬,马巍,孙红.岩土损伤力学宏细观试验研究[M].北京：科学出版社,2004
[28]易顺民,朱珍德.裂隙岩体损伤力学导论[M].北京：科学出版社,2005
[29]DUGDALE D S. Yielding of steel sheets containing slits [J]. Journal of the Mechanics and Physics of Solids,1960,8(2):100-104
[30]黄克智,余寿文.弹塑性断裂力学[M].北京：清华大学出版社,1985
[31]HANSON J A, HARDIN B O, MAHBOUB K. Fracture toughness of compacted cohesive soils using ring test [J]. Journal of Geotechnical Engineering,1994,120(5):872-891
[32]王俊杰,朱骏高.击实粘性土断裂韧度KIC的试验研究[J].岩石力学与工程学报,2005,24(21)：47-52
[33]BAZANT Z P, OH B H. Crack band theory for fracture of concrete [J]. Materials a structures,1983, 16(3):155-177
[34]WANG J J, ZHU J G, CHIU C F, ZHANG H. Experimental study on fracture toughness and tensile strength of a clay [J]. Engineering geology,2007,94(1-2):65-75
[35]HILLERBORG A, MOD ER M, PETERSSON P E. Analysis of crack formation and crack growth in concrete by means of fracture mechanics and finite elements [J]. Cement and Concrete Research,1976, 6(6):773-781
[36]RASHID Y R. Ultimate strength analysis of prestressed concrete pressure vessels [J]. Nuclear Engineering and Design,1968,7(4):334-344
[37]庄茁,柳占立,成斌斌,廖剑晖.扩展有限单元法[M].北京：清华大学出版社,2012
[38]BELYTSCHKO T, BLACK T. Elastic crack growth in finite elements with minimal remeshing [J]. International Journal for Numerical Methods in Engineering,1999,45(5):601-620
[39]黄献海.扩展有限元法计算裂纹问题的研究[J].山西建筑,2008,34(31)：3-4
[40]周元德,张楚汉,会峰.混凝土断裂的三维旋转裂缝模型研究[J].工程力学,2004,21(5)：1-4+82
[41]LI Y J, ZIMMERMAN T. Numerical evaluation of the rotating crack model [J]. Computers and Structures,1998,69(4):487-497
[42]方德平.岩石应变软化的有限元计算[J].华侨大学学报(自然科学版),1991,(02)：177-181
[43]姜庆远,叶燕春,刘宗仁.弥散裂缝模型的应用探讨[J].土木工程学报,2008,41(2)：81-85
[44]ROTS J G. Smeared and discrete representations of localized fracture [J]. International Journal of Fracture,1991,51(1):45-59
[45]张云,薛禹群,吴吉春,蒲晓芳,刘运涛,魏子新,李勤奋.上海第四纪土层邓肯——张模型的参数研究[J].水文地质工程地质,2008,(1)：19-22
[46]HERNANDEZ-MARIN M, BURBEY T J. Controls on initiation and propagation of pumping-induced earth fissures:insights from numerical simulations [J]. Hydrogeology Journal,2010,18(8):1773-1785
[2]王哲成,张云.地下水超采引起的地裂缝灾害的研究进展[J].水文地质工程地质,2012,39(2)：88-93
[3]王光亚,施斌,王晓梅,吴曙亮,武健强.江阴南部地面沉降及地裂缝研究[J].水文地质工程地质,2009,(02)：117-122
[4]HOLZER T L, PAMPEYAN E H. Earth fissures and localized differnetial subsidence [J]. Water Resources Research,1981,17(01):223-227
[5]JACHENS R C, HOLZER T L. Differential compaction mechanism for earth fissures near Casa Grande, Arizona [J]. Bulletin of the Geological Society of America,1982,93(10):998-1012
[6]BOLING J K. Earth-fissure movements in south-central Arizona, U.S.A, Wallingford, ROYAUME-UNI, F,1986 [C]. International Association of Hydrological Sciences,
[7]HOLZER T L. Ground failure caused by groundwater withdrawal from unconsolidated sediments-United States [M]. Wallingford, ROYAUME-UNI:International Association of Hydrological Sciences,1986
[8]WOLFF R G. Relationship between horizontal strain near a well and reverse water level fluctuation [J]. Water Resources Research,1970,6(6):1721-1728
[9]LOFGREN B E. Significant Role of Seepage Stresses in Compressible Aquifer Systems [J]. Eos, Transactions, American Geophysical Union,1971,52(11):832
[10]HELM D C. Hydraulic Forces that Play a Role in Generation Fissures at Depth [J]. Bulletin of the International Association of Engineering Geology,1994,31:293-302
[11]ROTHENBURG L. Horizontal ground movements due to water abstraction and formation of earth fissures [J]. International Journal of Rock Mechanics and Mining Sciences and Geomechanics Abstracts, 1996,33(8):239-249
[12]王庆良,刘玉海,陈志新,王文萍.抽水引起的含水层应变—地裂缝活动新机理[J].工程地质学报,2002,10(1)：46-51
[13]SHENG Z P, HELM D C, LI J. Mechanisms of earth fissuring caused by groundwater withdrawal [J]. Environmental and Engineering Geoscience,2003,9(4):351-362
[14]伍洲云,余勤,张云.苏锡常地区地裂缝形成过程[J].水文地质工程地质,2003,30(1)：67-73
[15]BUDHU M. Mechanics of earth fissures using the Mohr-Coulomb failure criterion [J]. Environmental and Engineering Geoscience,2008,14(4):281-295
[16]ZHANG Y, XUE Y Q, WU J C, YU J, WEI Z X, LI Q F. Land subsidence and earth fissures due to groundwater withdrawal in the Southern Yangtse Delta, China [J]. Environmental Geology,2008, 55(4):751-762
[17]BURBEY T J, CARRE N-FREYRE D, CERCA M, GALLOWAY DEVIN L, SILVA-CORONA J J. Mechanisms for earth fissure formation in heavily pumped basins [J].IAHS-AISH publication,2010,339(8):3-8
[18]TUCKWELL G W. The control of stress history and flaw distribution on the evolution of polygonal fracture networks [J]. Journal of Structural Geology,2003,25(8):1241-1250
[19]易学发,苏刚,王卫东,唐俊昌.用数值模拟研究西安地裂缝[J].水文地质工程地质,1999,26(005)：33-36
[20]石玉玲,门玉明,彭建兵,黄强兵,刘洪佳,陈立伟.西安城区地裂缝破裂扩展的数值模拟[J].水文地质工程地质,2008,(6)：56-60
[21]陈立伟.地裂缝扩展机理研究[D].西安；长安大学,2007
[22]李全明,张丙印,于玉贞,王建国.土石坝水力劈裂发生过程的有限元数值模拟[J].岩士工程学报,2007,29(2)：212-217
[23]喻葭临.土中剪切带扩展机理研究和扩展过程模拟[D].北京；清华大学,2009
[24]丁金粟,刁玉椿,孙亚平.击实粘粘性土断裂韧度性质研究[J].水利学报,1990,21(07)：55-60
[25]范天佑.断裂理论基础[M].北京：科学出版社,2003
[26]GRIFFITH A A. The phenomena of rupture and flow in solids [J]. Philosophical Transactions of the Royal Society of London Series A, Mathematical and Physical Sciences,1921,221:163-198
[27]葛修润,任建喜,蒲毅彬,马巍,孙红.岩土损伤力学宏细观试验研究[M].北京：科学出版社,2004
[28]易顺民,朱珍德.裂隙岩体损伤力学导论[M].北京：科学出版社,2005
[29]DUGDALE D S. Yielding of steel sheets containing slits [J]. Journal of the Mechanics and Physics of Solids,1960,8(2):100-104
[30]黄克智,余寿文.弹塑性断裂力学[M].北京：清华大学出版社,1985
[31]HANSON J A, HARDIN B O, MAHBOUB K. Fracture toughness of compacted cohesive soils using ring test [J]. Journal of Geotechnical Engineering,1994,120(5):872-891
[32]王俊杰,朱骏高.击实粘性土断裂韧度KIC的试验研究[J].岩石力学与工程学报,2005,24(21)：47-52
[33]BAZANT Z P, OH B H. Crack band theory for fracture of concrete [J]. Materials a structures,1983, 16(3):155-177
[34]WANG J J, ZHU J G, CHIU C F, ZHANG H. Experimental study on fracture toughness and tensile strength of a clay [J]. Engineering geology,2007,94(1-2):65-75
[35]HILLERBORG A, MOD ER M, PETERSSON P E. Analysis of crack formation and crack growth in concrete by means of fracture mechanics and finite elements [J]. Cement and Concrete Research,1976, 6(6):773-781
[36]RASHID Y R. Ultimate strength analysis of prestressed concrete pressure vessels [J]. Nuclear Engineering and Design,1968,7(4):334-344
[37]庄茁,柳占立,成斌斌,廖剑晖.扩展有限单元法[M].北京：清华大学出版社,2012
[38]BELYTSCHKO T, BLACK T. Elastic crack growth in finite elements with minimal remeshing [J]. International Journal for Numerical Methods in Engineering,1999,45(5):601-620
[39]黄献海.扩展有限元法计算裂纹问题的研究[J].山西建筑,2008,34(31)：3-4
[40]周元德,张楚汉,会峰.混凝土断裂的三维旋转裂缝模型研究[J].工程力学,2004,21(5)：1-4+82
[41]LI Y J, ZIMMERMAN T. Numerical evaluation of the rotating crack model [J]. Computers and Structures,1998,69(4):487-497
[42]方德平.岩石应变软化的有限元计算[J].华侨大学学报(自然科学版),1991,(02)：177-181
[43]姜庆远,叶燕春,刘宗仁.弥散裂缝模型的应用探讨[J].土木工程学报,2008,41(2)：81-85
[44]ROTS J G. Smeared and discrete representations of localized fracture [J]. International Journal of Fracture,1991,51(1):45-59
[45]张云,薛禹群,吴吉春,蒲晓芳,刘运涛,魏子新,李勤奋.上海第四纪土层邓肯——张模型的参数研究[J].水文地质工程地质,2008,(1)：19-22
[46]HERNANDEZ-MARIN M, BURBEY T J. Controls on initiation and propagation of pumping-induced earth fissures:insights from numerical simulations [J]. Hydrogeology Journal,2010,18(8):1773-1785