北京晓幼营板理化岩体结构面强度的原位测试
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摘要
岩体强度很大程度上取决于结构面的强度,板理化岩体尤其如此。通过原位测试直接获得岩体结构面的强度参数对于岩体稳定性分析和工程设计都具有重要意义。为了解板理化岩体板理结构面的强度性质,选择北京房山区晓幼营白云质板理化岩体进行了结构面强度的原位测试研究。鉴于传统岩体原位直剪试验成本高和操作难的情况,在掌握北京地区构造应力资料的基础上,在试验中考虑岩体中板理结构面的产状与构造应力方向的关系,提出了一套利用地应力提供原位试体剪切面法向力的测试分析方法:开挖出不同方向、不同解除状态的3个试体(试坑);试坑中两个平行的解除面与原岩之间形成一定距离的空间,自然构成了施加水平试验荷载的反力框架,从而免除了传统试验中笨重的试验反力装置。由于解除面组合的变化,试体受到的构造应力状态有相应的变化,与试验荷载叠加后在预定剪切面上形成了不同大小法向力和切向力。上述方法免除了笨重的反力装置,取得了一定的实验效果,确定了被测岩体结构面的强度参数:黏聚力c和摩擦角φ,对原位岩体结构面强度测试方法进行了一次有益的新尝试,得到的岩体结构面的强度参数为类似板岩地区大型输电线路塔杆地基设计及岩体稳定性分析提供了参考。
Strength of rock mass is largely determined by the strength of structure planes in the rock mass.This is especially true to platy rock mass.It is significant to get the strength parameters of structure planes in the rock mass directly by in-situ test both for the stability analysis of rock mass and for engineering design.In order to understand the strength property of platy rock mass,in-situ tests for the strength of the structure plane in dolomite platy rock mass at Xiaoyouying in Fangshan District of Beijing are carried out.Traditional in-situ tests will result in a high cost,and bring more difficulties for the shear strength of rock mass.To get rid of the heavy reaction frame,according to the relationship between the attitude of platy planes and the direction of tectonic stress in the rock mass,three test rock blocks,laterally disconnected from their parent rock in different forms,are dug out vertically on the horizontal ground of the test site.Beside two parallel vertical free surfaces,a certain free room is left between test block and its parent rock.This room is just a reaction frame for loading,where a jack and steel pads can be put and horizontal test loads can be applied vertically to the free surface of the test block.This makes the test get rid of cumbersome reaction equipment totally.The state of the tectonic stress in the test block changes with the forms of block disconnection from its parent rock and the varied tectonic stresses in different states,adding upon the stresses caused by horizontal test loads,forms different normal and tangential stresses in the pre-concerted shear plane at last.By means of the test method explained above,and based on the data of the local tectonic stress in Beijing territory,a pretty good result has resulted from the in-situ test for the shear strength(c,φ)of platy planes in the dolomite platy rock mass at Xiaoyouying in Fangshan district of Beijing.The strength parameter will be a helpful reference for the design of extra high voltage network foundation and for the stability analysis of engineering rock masses in mountain areas with similar platy rock mass.
Strength of rock mass is largely determined by the strength of structure planes in the rock mass.This is especially true to platy rock mass.It is significant to get the strength parameters of structure planes in the rock mass directly by in-situ test both for the stability analysis of rock mass and for engineering design.In order to understand the strength property of platy rock mass,in-situ tests for the strength of the structure plane in dolomite platy rock mass at Xiaoyouying in Fangshan District of Beijing are carried out.Traditional in-situ tests will result in a high cost,and bring more difficulties for the shear strength of rock mass.To get rid of the heavy reaction frame,according to the relationship between the attitude of platy planes and the direction of tectonic stress in the rock mass,three test rock blocks,laterally disconnected from their parent rock in different forms,are dug out vertically on the horizontal ground of the test site.Beside two parallel vertical free surfaces,a certain free room is left between test block and its parent rock.This room is just a reaction frame for loading,where a jack and steel pads can be put and horizontal test loads can be applied vertically to the free surface of the test block.This makes the test get rid of cumbersome reaction equipment totally.The state of the tectonic stress in the test block changes with the forms of block disconnection from its parent rock and the varied tectonic stresses in different states,adding upon the stresses caused by horizontal test loads,forms different normal and tangential stresses in the pre-concerted shear plane at last.By means of the test method explained above,and based on the data of the local tectonic stress in Beijing territory,a pretty good result has resulted from the in-situ test for the shear strength(c,φ)of platy planes in the dolomite platy rock mass at Xiaoyouying in Fangshan district of Beijing.The strength parameter will be a helpful reference for the design of extra high voltage network foundation and for the stability analysis of engineering rock masses in mountain areas with similar platy rock mass.
引文
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[2]李同录,罗世毅,何剑,等.节理岩体力学参数的选取与应用[J].岩石力学与工程学报,2004,23(13):2182～2186.Li Tonglu,Luo Shiyi,He Jian,et al.Determination and applicationof mechanical parameters for jointed rock masses.Chinese Journalof Rock Mechanics and Engineering,2004,23(13):2182～2186.
[3]刘雄贞.三峡岩体结构面的强度特性及其破坏机制[J].长江科学院院报,1996,13:10～13.Liu Xiongzhen.The strength characters and failure mechanism ofrock discontinuity in Three Gorges.Journal of Yangtze River Scien-tific Research Institute,1996,13:10～13.
[4]刘明维,何沛田,钱志雄,等.岩体结构面抗剪强度参数试验研究[J].重庆建筑,2005,(6):42～46.Liu Mmingwei,He Peitian,Qian Zhixiong,et al.Experimentalstudy on the shear strength of rock discontinuities.Chongqing Ar-chitecture,2005,(6):42～46.
[5]周应华,周德培,杨涛,等.节理岩体抗剪强度参数的实验分析[J].西南交通大学学报,2005,40(1):73～76.Zhou Yinghua,Zhou Depei,Yang Tao,et al.Experimental investi-gation on shear strength parameters of jointed rock mass.Journal ofSouthwest Jiaotong University,2005,40(1):73～76.
[6]中华人民共和国行业标准编写组.工程岩体试验方法标准(GB/T50266-99).北京:中国计划出版社,1999.Professional Standards Compilation Group of People s Republic ofChina.Standard for Tests Method of Engineering Rock Masses(GB/T50266-99).Beijing:China Planning Press,1999.
[7]中华人民共和国行业标准编写组.水利水电工程岩石力学试验规程(SL264-2001)[S].北京:中国水利水电出版社,2001.Professional Standards Compilation Group of People s Republic ofChina.Specifications for rock tests in water conservancy and hy-droelectric engineering(SL264-2001).Beijing:China WaterPower Press,2001.
[8]American Society for Testing and Materials(ASTM)D 4554～2002,Standard Test Method for in Situ Determination of DirectShear Strength of Rock Discontinuities[S].
[9]范景伟,何江达,刘东燕.现场直剪试验中地应力影响的分析[J].成都科技大学学报,1990,(4):27～32,40.Fan Jingwei,He Jiangda,Liu Dongyan.Analysis for influence ofgeostress in the in-situ shear tests.Journal of Chengdu University ofScience and Technology,1990,(4):27～32,40.
[10]张建海,何江达,宋伟.地应力对现场大剪试验的影响[J].四川大学学报(工程科学版).2000,32(3):29～33.Zhang Jianhai,He Jiangda,Song Wei.Influence of geo-stress onin-situ shear test.Journal of Sichuan University(Engineering Sci-ence Edition),2000,32(3):29～33.
[11]北京市地质矿产局.北京市区域地质志[M].北京:地质出版社,1991.Beijing Municipal Bureau of Geology and Mineral Resources.Bei-jing Regional Geology.Beijing:Geological Publishing House,1991.
[12]北京师范大学地理系地质组.北京地质(内部教材)[R].北京:中国地质图书馆,1977.Geology Group of Department of Geography,Beijing Normal Uni-versity.Beijing Geology(Inedited textbook).Beijing:China Geo-logical Library,1977.
[13]孙叶,王宗杰,沈士贞,等.北京八宝山断裂带煤岭弧形断裂附近局部地应力场[C].见:北京市地震地质会战办公室.北京地区岩组分析与地应力场——北京市地震地质会战研究成果汇编(5)(3-2)[R].北京:中国地质图书馆,1982.Sun Ye,Wang Zongjie,Shen Shizhen,et al.Local tectonic stressnear Meiling arc fault of Babaoshan fault zone in Beijing.In:Bei-jing Seismology and Geology Office eds.Rock Group Analysis andTectonic Stress Field in Beijing Region,Compilation of ResearchResults of Beijing Seismology and Geology(5)(3-2).Beijing:China Geological Library,1982.
[14]罗国煜,李生林.工程地质学基础[M].南京:南京大学出版社,1990.Luo Guoyu,Li Shenglin.Foundation of Engineering Geology.Nan-jing:Nanjing University Press,1990.
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