Evaluation of the effectiveness of an alternative to control groundwater inflow during a deep excavation into confined a
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ORIGINAL ARTICLE
Evaluation of the effectiveness of an alternative to control groundwater inflow during a deep excavation into confined aquifers Chengyong Cao1 · Chenghua Shi2 · Linghui Liu2 · Jianwen Liu2 Received: 18 July 2020 / Accepted: 14 October 2020 / Published online: 31 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract This paper presents a case study of groundwater control for a deep excavation into confined aquifers in Fuzhou, China. Field pumping tests were first carried out prior to the excavation to investigate the groundwater conditions at the site and as well as to evaluate the feasibility of previous designed dewatering systems (34 m diaphragm walls together with pumping wells). The results showed that under the condition of previous dewatering systems it would have been extremely difficult to safely lower the water level inside the excavation. A co-working scenario of partially penetrating curtains and horizontal waterproof curtain with jet grouting was then proposed to control groundwater inflows. Additional water-tightness assessment tests (WAT) were then performed that allowed to confirm the efficiency of the proposed method. From the feedbacks of WAT, this proposed scenario not only successfully lowered the water lever inside the excavation below the excavation bottom (maximum drawdown up to 14.9 m), but also it minimized the drawdown outside the excavation (less than 0.2 m). Furthermore, an approach was proposed to approximately estimate the hydraulic conductivity of the jet-grouting at the real site from the result of WAT. The hydraulic conductivity of jet-grouted soil is three orders of magnitude lower than that of the original sediments. Keywords Deep excavation · Confined aquifers · Groundwater control · Jet grouting · Water-tightness assessment test
Introduction In recent years, with the sustained and rapid development of the national economy in China, urban underground space development and utilization is getting more and more Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12665-020-09253-3) contains supplementary material, which is available to authorized users. * Chenghua Shi [email protected] * Linghui Liu [email protected] Chengyong Cao [email protected] Jianwen Liu [email protected] 1
College of Civil and Transportation Engineering, Shenzhen University, Shenzhen 518060, China
School of Civil Engineering, Central South University, Changsha 410075, China
2
attention in large and medium-sized cities. The construction of urban railway systems (metros) in urban areas has been recognized as one of the most effective way to relieve the problems of high-density development and traffic congestion. The metro stations are an important part of an urban rail transit network, but during construction they often have to encounter such complicated and difficult situations as poor ground conditions, large groundwater inflows, and densely constructed subsurface urban infrastructure. In general, grou
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