衡水地区地裂缝空间发育特征与地下水位降深关系

Exploitation of Deep Groundwater with Relevant Issues of Earth Fissures at Hengshui Area in North China

通过浅层地震法及高密度电阻率法物探对河北衡水地区最近发现的3条地裂缝调查,探明了地裂缝地下发育深度、宽度、倾向等,发现地裂缝在地表与地下发育特征有明显不同:地表以一条地裂缝存在,在地下深处则以裂缝带发育,裂缝带两侧裂缝埋深不同,地下裂缝形态表现为上窄下宽。对该地区深层钻探、水文地质和多年地下水开采等资料分析表明,该地区的地裂缝是地质历史时期地质构造活动产物,开采深层地下水等资源则是促使地裂缝发展的主要原因。通过对不同地点地裂缝发育深度与近36年以来地下水水位降深的关系分析,结果显示:不同地区地裂缝发育深度与相应深层地下水水位降深呈线性关系。研究成果对地裂缝机理研究及预防开采深层地下水对地质环境的影响具有指导作用。

The earth fissure is one of the geological hazards in North China Plain. It is developing continually in recent years. More than 573 Earth fissures have been found since 1995. From 1995 to 2005 in fissures were found in one area of North China Plain. Earth fissures directly lead to cultivated land tion system leakage, house and hydraulic facilities damages as well as pollution of groundwater. It Hengshui, 4 new cracking, irriganot only seriously threatens human being, economy construction in cities and villages, but also brings countless damage and hidden danger to descendants. Therefore, the study of Earth fissure attracts great attention of concerned experts. We found three-Earth fissures that had been developing in recent years around the depression cone of groundwater in Hengshui area：①. Nanzhangjiacun village at Shenxian County in November, 2003 ;②. Nanqinglin village of Wuyi County -Hanguan village at Fucheng County in June, 1995;③. Shuipo village of Jianguo town at Gucheng County in May, 2002. The result of geophysical prospecting work shows that Earth fissures are developing obviously in different way on the Earth surface and underground in depth, width, etc. The earth fissure on the Earth surface is wider in the upper part and is narrower with the depth. Reversely, the earth fissures of underground are narrower in the upper part and is wider with depth. Ground fissures are usually developed as a fissure zone underground in the Hengshui area with its width of 10-38m and depth of burial of 60-120m. The geophysical prospecting shows the dip of axes for underground fissure zone to the steep, 75 -88 . The terminal fissures of the same fissures zone are different in depth burial. Usually the difference in vertical depth is about 10-30m. The earth fissures that we can see on the earth surface are only the seriously active part in the earth fissure zone. They may be wider and longer with effects on the human activities. Even the other side may become active. The investigation shows, on one hand, earth fissures in the Hengshui area is consistent extending along the geotectonic directions. On the other hand, the earth fissures are all distributed close to the juncture between the accumulation at the channel belt and the interchannel zone around subsidence basin of different soil masses. Analysis indicates that the geotectonic movements are the direct reason to form some hidden fissure plane in the soil mass or the hidden earth fissures. The different origins of the soil mass provide the favourable conditions for the sures development. ground fissures development. Datum of deep layer drilling , deep groundwater exploration, local hydrogeological condition, drawdown of deep and shallow water exploration in recent 35 years and earth fissures development of different areas proved better correlation with exploration drawdown of deep groundwater than with exploration drawdown of shallow groundwater and the ground fissures developed are deeper than drawdown of groundwater. This is closely related to the deeper groundwater depression cone, geothermal exploitation and oil exploitation, etc. To sum up, the earth fissures are usually developed around the depression cone of groundwater as a fissure zone underground in the Hengshui area. It is the result of geological tectonic activities of different periods, tectonic activity form hidden earth fissures. And exploitation of ground water is also the main reason that caused land subsidence and earth fissures developing in hard soil area in North China. It will be guidance for research mechanism of earth fissure and for preventing the effect that exploiting deep groundwater acted on geological environment.