高地应力深切河谷形变应力场及线路问题初探
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摘要
为研究高地应力作用下河谷深切卸荷、岩体强风化的地质环境对拟建川藏铁路的影响,利用ABAQUS对高地应力背景场由河流深切卸荷下的河谷形变—应力场特征进行数值模拟研究;考虑到岩体的宏观力学性能受到卸荷回弹变形的影响而急剧减小,利用场变量实现力学参数随卸荷动态变化,对比分析河谷形变—应力场特征;针对印度板块挤压欧亚大陆板块使河谷两岸地应力值存在差异的情况,模拟主、被动盘的差异卸荷。结果表明:自重应力与40 MPa构造应力同时作用下的卸荷回弹值可达仅计自重应力场的3～6倍,出现由陡、缓倾面构成的"X"状共轭结构面,工程开挖下边坡岩体容易沿陡倾面崩塌,沿缓倾面滑移。将卸荷前后岩体偏应力比值k作为评价岩体受到卸荷影响程度的标准,高地应力作用下谷坡水平深度方向的k值介于1.5～2.5,地应力的量值对岩体卸荷程度有很大影响;较之不考虑岩体力学性质劣化情况,岩体塑性区范围将扩展,裂隙向谷坡上部延伸,坡体稳定性进一步下降;高地应力作用的河谷主动岸,坡面塑性区明显存在"X"状潜在滑移面,而被动岸仅有单向缓倾滑移面,主动岸对开挖扰动的抵抗力更低。据此提出相应的灾害预防措施的建议,为拟建进藏道路的区域工程地质选线提供参考。
In order to investigate the influence of unloading of the surface due to a river's cutting down and weathering of rock mass under high geostress on the planned Sichuan-Tibet railway,numerical simulations of deformation and stress field of deep-incised valley under high geostress were implemented with ABAQUS.Field variables were used to realize the dynamic change of mechanical parameters of rock mass under the influence of unloading deformation,the deformation and stress field of valley were also analyzed.A numerical model that boundary conditions on both sides are different was built according to the fact that Indian plate is extruding to Eurasian plate.The results show that the unloading displacement of rock mass under 40 MPa tectonic stress combined with self-weight stress was 3 to 6 times larger than that due to self-weight stress,and conjugated structural planes appeared in valley side-slope,which are composed of steep inclined and gently inclined planes,and imply an instable mode of collapse and slip in excavation.As an index to evaluate the unloading effect of rock mass,deviatoric stress ratio k was taken to describe the difference of initial and post unloading.The k in horizontal direction of valley under high geostress is 1.5 to 2.5,which means that the geostress plays an important role in valley unloading.Compared with the condition that do not consider the weakness of mechanical properties,the stability of the slope further decreased,the plastic area increased and the fracture extended to the top of the slope.The conjugated structural planes appeared on the bank under high geostress,while the other bank only has gently inclined slip planes.The bank under high geostress appears lower resistance to the excavation disturbance.Some disaster prevention suggestions and some references for route selection in deep-incised valley under high geostress are put forward.
In order to investigate the influence of unloading of the surface due to a river's cutting down and weathering of rock mass under high geostress on the planned Sichuan-Tibet railway,numerical simulations of deformation and stress field of deep-incised valley under high geostress were implemented with ABAQUS.Field variables were used to realize the dynamic change of mechanical parameters of rock mass under the influence of unloading deformation,the deformation and stress field of valley were also analyzed.A numerical model that boundary conditions on both sides are different was built according to the fact that Indian plate is extruding to Eurasian plate.The results show that the unloading displacement of rock mass under 40 MPa tectonic stress combined with self-weight stress was 3 to 6 times larger than that due to self-weight stress,and conjugated structural planes appeared in valley side-slope,which are composed of steep inclined and gently inclined planes,and imply an instable mode of collapse and slip in excavation.As an index to evaluate the unloading effect of rock mass,deviatoric stress ratio k was taken to describe the difference of initial and post unloading.The k in horizontal direction of valley under high geostress is 1.5 to 2.5,which means that the geostress plays an important role in valley unloading.Compared with the condition that do not consider the weakness of mechanical properties,the stability of the slope further decreased,the plastic area increased and the fracture extended to the top of the slope.The conjugated structural planes appeared on the bank under high geostress,while the other bank only has gently inclined slip planes.The bank under high geostress appears lower resistance to the excavation disturbance.Some disaster prevention suggestions and some references for route selection in deep-incised valley under high geostress are put forward.
引文
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[17]贾善坡,陈卫忠,杨建平,等.基于修正Mohr-Coulomb准则的弹塑性本构模型及其数值实施[J].岩土力学,2010,31(7):2052-2058.
[18]哈秋舲.加载岩体力学与卸荷岩体力学[J].岩土工程学报,1998,20(1):114.
[19]谭成轩,张鹏,郑汉淮,等.雅砻江锦屏一级水电站坝址区实测地应力与重大工程地质问题分析[J].工程地质学报,2007,16(2):162-168.
[2]黄润秋,张倬元,王士天.中国西南地区地壳浅表层动力学过程及其工程环境效应研究[M].成都:四川大学出版社,2001.
[3]黄润秋.中国西南岩石高边坡的主要特征及其演化[J].地球科学进展,2005,20(3):292-297.
[4]徐嘉谟,李晓,韩贝传.成岩地质体的初始应变能状态及其对开挖引起位移场的影响[J].岩石力学与工程学报,2006,25(12):2467-2474.
[5]HAN B C,XU J M.Application of a memory model“consolidated stress”to rock mechanics[J].Scientia Geological sini-ca,1998,7:277-283.
[6]READ R S.20 years of excavation response studies at AECL's underground research laboratory[J].International Journalof Rock Mechanics&Mining Sciences,2004,41(8):1251-1275.
[7]哈秋舲,李建林,张永兴,等.长江三峡工程节理岩体卸荷非线性岩体力学[M].北京:中国建筑工业出版社,1998.
[8]刘国霖.陡高边坡节理岩体卸荷力学的物理基础[J].武汉水利大学学报,2000,22(3):185-190.
[9]李建林.卸荷岩体力学[M].北京:中国水利水电出版社,2003.
[10]胡斌,张倬元,陶连金.某深切峡谷区地应力场的变化特征分析[J].世界地震工程,2001,17(2):110-115.
[11]周济芳,李建林,杨学堂,等.影响卸荷岩体力学特性的因素及力学参数研究[J].灾害与防治工程,2004,25(1):50-54.
[12]李晓春,陈剑平.小湾水电站边坡卸荷作用及裂隙成因研究[J].自然灾害学报,2005,14(2):103-107.
[13]晏长根,林峰,吴法权,等.岩体扰动深度估算的应力场方法[J].长安大学学报,2011,31(4):68-72.
[14]张向东,刘严,孙闯,等.软岩隧道开挖方法数值模拟分析[J].广西大学学报:自然科学版,2010,35(1):73-77.
[15]赵德军,陈洪德,吴德超.雅砻江锦屏一级水电站左岸深部裂缝成因机制探讨[J].水文地质工程地质,2011,38(6):102-107.
[16]费康,张建伟.ABAQUS在岩土工程中的应用[M].北京:中国水利水电出版社,2010:67-68.
[17]贾善坡,陈卫忠,杨建平,等.基于修正Mohr-Coulomb准则的弹塑性本构模型及其数值实施[J].岩土力学,2010,31(7):2052-2058.
[18]哈秋舲.加载岩体力学与卸荷岩体力学[J].岩土工程学报,1998,20(1):114.
[19]谭成轩,张鹏,郑汉淮,等.雅砻江锦屏一级水电站坝址区实测地应力与重大工程地质问题分析[J].工程地质学报,2007,16(2):162-168.
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