贵州贵定尖山营特大桥基础异常升降成因探讨
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摘要
尖山营特大桥桥墩每年均出现雨季抬升,旱季沉降的异常现象。本文针对桥墩异常升降问题,采用野外地质调绘、现场监测、钻探、物探以及室内试验等方法相结合,分析造成尖山营特大桥墩体异常升降的主要原因。通过现场地质调绘和钻孔岩芯发育情况获取研究区地质构造分布,分析构造作用对异常升降的影响;基于天然音频大地电法勘探与对研究区地表水出露情况的勘察,研究承压水的赋存情况;将钻孔岩芯进行室内膨胀特性试验,研究了桥址区地基岩土体的吸水膨胀特性对桥墩升降的潜在作用。结果表明:排除地质构造和承压水原因,引起桥墩异常升降的主要原因是膨胀岩土体与地下水物理化学反应带动上部结构抬升及沉降引起的。桥址区二叠系吴家坪组(P2w)地层岩土体的膨胀力试验预估值在3～59 MPa之间,上部总荷载1. 38～13. 5 MPa,膨胀力大于上部结构重力载荷;原状膨胀岩试样在1. 05 MPa的轴压作用下吸水,存在0. 35%的膨胀应变,结合已有研究可确定130 m厚的膨胀性地层可造成上部结构抬升45. 5mm。二叠系吴家坪组(P2w)地层的吸水膨胀、失水收缩性能,与地下水的补给与排泄相结合,是引发桥墩异常升降的主要原因。
Jianshanying bridge is a control station on the newly-built high-speed railway line from Guiyang to Guangzhou. This paper combined the methods of field geological survey, field monitoring, drilling,geophysical exploration and laboratory test to analyze the main reasons for the abnormal lifting of the great bridge piers. The geological structure distribution in the study area was obtained by geological mapping and drilling core development. The developmental state of groundwater in the bridge site is deduced from the survey of surface water and audio magnetotelluric exploration( AMT). Indoor expansion tests of drill core were carried out to study the water-absorbing expansion characteristics of the foundation rock soil in the bridge site area. The results show that excluding the reasons of geological structure and groundwater in the confined aquifer,the superstructure rises and falls due to the physical and chemical reaction between expansive rock mass and groundwater. The Permian Wujiaping formation( P2 w) in the bridge site area has the potential swelling force estimated to be between 3 MPa and 59 MPa,which is much greater than the structural loads( ranging from 1. 38 MPa to 13. 5 MPa). Under the action of axial pressure of 1. 05 MPa,the undisturbed expansive rock sample absorbs water and has an expansion strain of 0. 35%. Combined with the existing studies,it is found that the expansion formation 130 m thick can cause the uplift of the superstructure of 45. 5 mm. Therefore,the Permian Wujiaping formation( P2 w) is mainly responsible for the abnormal rise and fall of the bridge piers due to its water absorption expansion and water loss shrinkage,combined with groundwater recharge and discharge.
Jianshanying bridge is a control station on the newly-built high-speed railway line from Guiyang to Guangzhou. This paper combined the methods of field geological survey, field monitoring, drilling,geophysical exploration and laboratory test to analyze the main reasons for the abnormal lifting of the great bridge piers. The geological structure distribution in the study area was obtained by geological mapping and drilling core development. The developmental state of groundwater in the bridge site is deduced from the survey of surface water and audio magnetotelluric exploration( AMT). Indoor expansion tests of drill core were carried out to study the water-absorbing expansion characteristics of the foundation rock soil in the bridge site area. The results show that excluding the reasons of geological structure and groundwater in the confined aquifer,the superstructure rises and falls due to the physical and chemical reaction between expansive rock mass and groundwater. The Permian Wujiaping formation( P2 w) in the bridge site area has the potential swelling force estimated to be between 3 MPa and 59 MPa,which is much greater than the structural loads( ranging from 1. 38 MPa to 13. 5 MPa). Under the action of axial pressure of 1. 05 MPa,the undisturbed expansive rock sample absorbs water and has an expansion strain of 0. 35%. Combined with the existing studies,it is found that the expansion formation 130 m thick can cause the uplift of the superstructure of 45. 5 mm. Therefore,the Permian Wujiaping formation( P2 w) is mainly responsible for the abnormal rise and fall of the bridge piers due to its water absorption expansion and water loss shrinkage,combined with groundwater recharge and discharge.
引文
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[14]肖东升.贵州区域地壳稳定性及地震危险性分析[D].成都:西南交通大学,2002.[XIAO D S.Analysis of regional crustal stability and seismic risk probability in Guizhou Province[D]. Chengdu:Southwest Jiaotong University,2002.(in Chinese)]
[15]田洋,赵小明,牛志军,等.鄂西南利川二叠纪吴家坪组硅质岩成因及沉积环境[J].沉积学报,2013,31(4):590-599.[TIAN Y,ZHAO X M,NIU Z J, et al. Petrogenesis and sedimentary environment of Permian Wujiaping formation siliceous rocks in Lichuan,Southwestern Hubei[J]. Acta Sedimentologica Sinica,2013,31(4):590-599.(in Chinese)]
[16]李振嵩.硅碱活性碳酸盐岩开挖骨料试验分析及应用[J].人民珠江,2018,39(4):85-88.[LI Z S. Test analysis and application of carbonatite excavation aggregates with Alkali-Silica reactivity[J]. Pearl River,2018,39(4):85-88.(in Chinese)]
[17]中华人民共和国地质矿产部.大地电磁测法技术规程:DZ/T0173-1997[S].北京:中国标准出版社, 1997.[Ministry of Geology and Mineral Resources of the People’s Republic of China.Technical specification for magnetotelluric survey:DZ/T0173-1997[S]. Beijing:China Standard Press,1997.(in Chinese)]
[18]文江泉,韩会增.膨胀岩的判别与分类初探[J].铁路工程学报,1996(2):231-236.[WEN J Q,HAN H Z. Preliminary study of distinguishing and classifying on swell rock[J]. Journal of Railway Engineering Society,1996(2):231-236.(in Chinese)]
[19]孙小明,武雄,何满朝,等.强膨胀性软岩的判别与分级标准[J].岩石力学与工程学报,2005,24(1):128-132.[SUN X M,WU X,HE M C,et al. Differentiation and grade criterion of strong swelling soft rock[J]. Chinese Journal of Rock Mechanics and Engineering,2005,24(1):128-132.(in Chinese)]
[20]吴光,赵志明,王金淑,等.一种岩体膨胀应力测试仪:中国,ZL201720378268. 8[P]. 2017-04-12.[WU G,ZHAO Z M,WANG J S,et al. The utility model relates to a rock mass expansion stress testing instrument. China,ZL201720378268. 8[P].2017-04-12.(in Chinese)]
[21]王炳忠,王起才,张戎令,等.上覆荷载和厚度对原状膨胀土膨胀量的影响分析[J].铁道标准设计,2018,62(2):72-75.[WANG B Z,WANG Q C,ZHANG R L,et al. The effect of upper load and thickness on the expansion of undisturbed expansive soil[J]. Railway Standard Design,2018,62(2):72-75.(in Chinese)]
[2] El-GARHY B M,WRAY W K,YOUSSEF A A.Using soil diffusion to design raft foundation on expansive soils[C]//Geotechnical Special Publication,2000,99:586-601.
[3]范臻辉.膨胀土地基胀缩特性及桩—土相互作用研究[D].长沙:中南大学.[FAN Z H. Research on swelling-shrinking characteristic and pile-soil interaction of expansive soil foundation[D].Changsha:Central South University,2007.(in Chinese)]
[4] ALONSO E E,RAMON A. Heave of a railway bridge induced by gypsum crystal growth:field observations[J]. Géotechnique,2013,63(9):707-719.
[5] EINSTEIN H H. Tunnelling in difficult groundSwelling behaviour and identification of swelling rocks[J]. Rock Mechanics and Rock Engineering,1996,29(3):113-124.
[6] GENNARO M,ABDOLREZA O,SIAVASH Z,et al.Performance of a pier group foundation in swelling rock[J]. Geotechnical&Geological Engineering,2017,35(1):91-109.
[7] XIAO H,ZHANG C,WANG Y,et al. Pile-Soil Interaction in expansive soil foundation:analytical solution and numerical simulation[J]. International Journal of Geomechanics,2011,11(3):159-166.
[8]李国和,荆志东,许再良.京沪高速铁路沿线地面沉降与地下水位变化关系探讨[J].水文地质工程地质,2008,35(6):90-94.[LI G H,JING Z D,XU Z L. A discussion of the correlation between land subsidence and groundwater level variation along the Jinghu high speed railway[J]. Hydrogeology&Engineering Geology,2008,35(6):90-94.(in Chinese)]
[9]雷坤超,陈蓓蓓,宫辉力,等.基于PS-InSAR技术的天津地面沉降研究[J].水文地质工程地质,2013,40(6):106-111.[LEI K C,CHEN B B,GONG H L,et al. Detection of land subsidence in Tianjin based on PS-InSAR technology[J].Hydrogeology&Engineering Geology,2013,40(6):106-111.(in Chinese)]
[10]李莎,成建梅,宫辉力.基于变渗透系数的地下水开采-地面沉降三维模拟研究[J].水文地质工程地质,2018,45(3):14-21.[LI S,CHENG J M,GONG H L. Three dimensional simulation of groundwater exploitation and land subsidence based on variable permeability[J]. Hydrogeology&Engineering Geology,2018,45(3):14-21.(in Chinese)].
[11]贵州省地质局.贵州主要构造体系[M].贵阳:贵州人民出版社, 1980.[Geological Bureau of Guizhou Province. Guizhou’s main tectonic system[M]. Guiyang:Guizhou People Press,1980.(in Chinese)]
[12]何邵麟,陈智.贵州地壳表层构造地球化学分区及其意义[J].贵州地质,2002,19(3):148-154.[HE S L,CHEN Z. The zoning of surface tectonic geochemistry in Guizhou and its significance[J].Guizhou Geology,2002,19(3):148-154.(in Chinese)]
[13]郭金城.贵州主要活动构造体系与地震[J].贵州科学,1993,11(3):18-23.[GUO J C. The principal active tectonic systems in Guizhou and earthquakes[J]. Guizhou Science,1993,11(3):18-23.(in Chinese)]
[14]肖东升.贵州区域地壳稳定性及地震危险性分析[D].成都:西南交通大学,2002.[XIAO D S.Analysis of regional crustal stability and seismic risk probability in Guizhou Province[D]. Chengdu:Southwest Jiaotong University,2002.(in Chinese)]
[15]田洋,赵小明,牛志军,等.鄂西南利川二叠纪吴家坪组硅质岩成因及沉积环境[J].沉积学报,2013,31(4):590-599.[TIAN Y,ZHAO X M,NIU Z J, et al. Petrogenesis and sedimentary environment of Permian Wujiaping formation siliceous rocks in Lichuan,Southwestern Hubei[J]. Acta Sedimentologica Sinica,2013,31(4):590-599.(in Chinese)]
[16]李振嵩.硅碱活性碳酸盐岩开挖骨料试验分析及应用[J].人民珠江,2018,39(4):85-88.[LI Z S. Test analysis and application of carbonatite excavation aggregates with Alkali-Silica reactivity[J]. Pearl River,2018,39(4):85-88.(in Chinese)]
[17]中华人民共和国地质矿产部.大地电磁测法技术规程:DZ/T0173-1997[S].北京:中国标准出版社, 1997.[Ministry of Geology and Mineral Resources of the People’s Republic of China.Technical specification for magnetotelluric survey:DZ/T0173-1997[S]. Beijing:China Standard Press,1997.(in Chinese)]
[18]文江泉,韩会增.膨胀岩的判别与分类初探[J].铁路工程学报,1996(2):231-236.[WEN J Q,HAN H Z. Preliminary study of distinguishing and classifying on swell rock[J]. Journal of Railway Engineering Society,1996(2):231-236.(in Chinese)]
[19]孙小明,武雄,何满朝,等.强膨胀性软岩的判别与分级标准[J].岩石力学与工程学报,2005,24(1):128-132.[SUN X M,WU X,HE M C,et al. Differentiation and grade criterion of strong swelling soft rock[J]. Chinese Journal of Rock Mechanics and Engineering,2005,24(1):128-132.(in Chinese)]
[20]吴光,赵志明,王金淑,等.一种岩体膨胀应力测试仪:中国,ZL201720378268. 8[P]. 2017-04-12.[WU G,ZHAO Z M,WANG J S,et al. The utility model relates to a rock mass expansion stress testing instrument. China,ZL201720378268. 8[P].2017-04-12.(in Chinese)]
[21]王炳忠,王起才,张戎令,等.上覆荷载和厚度对原状膨胀土膨胀量的影响分析[J].铁道标准设计,2018,62(2):72-75.[WANG B Z,WANG Q C,ZHANG R L,et al. The effect of upper load and thickness on the expansion of undisturbed expansive soil[J]. Railway Standard Design,2018,62(2):72-75.(in Chinese)]