This paper is the result of urban geological survey engineering.
Objectives This paper aimed at investigating solutions of eco−geological security issues caused by rising groundwater level due to the utilization of underground space in valley cities in cold and arid regions, such as soil salinization in farmland ecological zone and building damage in urban ecological zone.
Methods On the basis of relevant data collection, geological drilling, geotechnical engineering test, pumping test and eco−geological observation were carried out. The genetic mechanism of eco−geological security risk was analyzed by using hydrogeological and other theoretical methods.
Results The geological security risk assessment approaches for 3 types of ecosystems, including human habitation, farmland, forest−grass, were proposed, and the evaluation index system and standards were established. The eco−geological security risk in Ledu District of Haidong city were evaluated. The results showed that, under the current situation of underground space utilization, the high−risk areas were mainly distributed in mouth areas of Yinsheng Gully, Gangzi Gully, Fengdui Gully and other high−rise building urban areas influenced by groundwater; the medium−risk areas were mainly distributed in the low−lying areas of grade I and II terraces. Under the scenario of building an underground railway along the bank of Huangshui River, the high−risk and medium−risk areas would be expanded compared with the current situation of underground space.
Conclusions The proposed three evaluation approaches for eco−geological security risk were proven to be effective. Both scenarios would induce the geological security risk for all three ecosystems, with the latter scenario posing higher risks and wider impacts. The key areas should be monitored periodically, and techniques such as groundwater drainage be used to prevent risks.
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