西安地铁四号线沿线长安地裂缝研究
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摘要
采用地面调查、钻探和槽探等方法,对临潼—长安断裂带内西安地铁四号线沿线的长安地裂缝进行了研究。钻探剖面显示,在地面高程变化梯度最大处附近存在地裂缝异常,异常两侧的古土壤标志层出现明显错断。对其中一处异常进行了大型探槽开挖,探槽两侧壁剖面显示:地裂缝带由1条主缝和数条次缝组成;主缝走向平行于临潼—长安断裂,南东盘相对下降,倾向南东,与临潼—长安断裂倾向相反,倾角80°~85°;主缝错断古土壤层1.1m,相对于上升盘,地裂缝下降盘地层厚度变大。研究结果表明,长安地裂缝发育在特定的构造地貌部位,即临潼—长安断裂带内"梁洼"地貌黄土梁南侧高程变化梯度最大处附近,由构造活动引起,具有正断层性质和生长断层性质,与西安地裂缝具有相同的构造特征。
Chang'an ground fissures along the fourth metro line of Xi'an city inside the Lintong-Chang'an fault zone were studied by ground survey,drilling exploration and trench investigation.Two drilling profiles show that the fissure abnormities may occur at topographic place with the maximum elevation gradient and the paleosol stratum beside the two sides of abnormities have obviously vertical drops.The excavation of one large-scale trench reveals following facts:(1) the fissure zone is composed of one major fracture and several junior cracks and the major fracture is well developed and parallels to Lintong—Chang'an fault zone;(2) the southeastern wall of the major fracture is relatively declined and inclined to the southeastern with dip of 80°~85°,which is opposite to the Lintong—Chang'an fault;(3) the palaeosol layer of two sidewalls is dislocated with 1.1m displacement and the downthrown side stratums of major fracture are thicker than those of the uplifted side.The investigation and research results show that Chang'an ground fissures develop in particular loess landform area inside the Lintong—Chang'an fault zone and emerge near the place with the maximum elevation gradient in the southern side of loess swale and induced by deep tectonic activity.Similar to Xi'an ground fissures according to the fault style and developing mode,Chang'an ground fissures appear as the characteristics of both normal fault and growth fault in general.
引文
[1]李永善.西安地裂缝[M].北京:地震出版社,1986
    [2]刘国昌.西安的地裂缝[J].长安大学学报:地球科学版,1986,8(4):9-22(Liu Guochang