共查询到18条相似文献，搜索用时 642 毫秒
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为降低深基坑工程设计与施工风险,对东门口站现场实际水文地质情况进行不同工况的抽水试验,取得场地准确水文地质参数(承压含水层)。该抽水试验指导进行基坑突涌性评价和实际工况运行控制情况,为降水运行提供依据对类似工程的设计、施工及风险控制具有借鉴意义。 相似文献
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长江漫滩地区第四系是一个巨厚的复杂含水体,地下水丰富,对深大基坑施工影响极大。南京梅子洲过江通道连接线及青奥轴线地下交通系统工程位于长江下游漫滩,基坑最大开挖深度为27.5 m。为满足基坑降水设计及施工要求,勘察时选择有代表性的地段布置了3组抽水试验井,对潜水含水层及承压水含水层进行抽水试验,根据试验井类型和边界条件,选用潜水完整井稳定流、承压水完整井稳定流及非稳定流、承压水非完整井稳定流及非稳定流等多种地下水计算模型进行参数计算并综合分析,为设计提供水文地质参数,并实地验证了参数的合理性。 相似文献
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国家大剧院深基坑地下水控制设计及施工技术 总被引：3，自引：0，他引：3
国家大剧院基坑地下水控制是大剧院工程的三大难题之一,也是专家们讨论的焦点。经过水文地质试验和充分论证,确定了地下水控制方案和施工方法,即采用反循环成井工艺施工引渗井,将上层滞水和潜水引渗到第一层承压含水层中消纳,保证第一步基坑开挖至-15 7m;在-15 7m位置采用连续墙阻隔第一层承压水,并使用旋挖钻机在槽内施工降水井,疏干槽内承压含水层并进行越流补给控制,保证基坑开挖至-26m;在歌剧院台仓局部加深部份(-32 5m),采用封闭布设减压井,解决基坑开挖和台仓地下结构施工时基坑突涌的问题;最后采用特殊的封井技术,将井管内高于槽底约10m的承压水头封堵在槽底以下0 5m,安全截断井管,保证了基础施工。 相似文献
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福州轨道交通建设中的岩土工程问题 总被引：1，自引：0，他引：1
由于福州盆地工程地质条件的复杂性以及隧道工程的特殊性,在福州轨道交通建设过程中将遇到大量环境岩土工程问题。主要的环境岩土工程问题有:(1)隧道掘进范围内的承压含水层。承压含水层富水性、透水性强,由于开挖深度大,必须考虑下部承压水的影响,避免产生基坑突涌问题。砂砾卵石层直接覆盖于基岩裂隙热水上,受热水构造带高温热水的直接补给以及热传导,地下轨道交通建设对地热场是否存在影响以及地热对轨道交通的影响需要深入研究。(2)软土的大变形与低强度。导致地基失稳与土体结构强度破坏。(3)深大基坑开挖施工引发的可能灾变。基坑开挖易产生滑塌、流泥、突水(涌)、地表沉陷等问题,必须采取有效的支护措施,避免基坑失稳而影响工程安全及周边环境。对这些环境岩土工程问题,应加强勘察新技术的应用,查明建设场地岩土工程地质条件;采用人工地层冻结法、桩基托换技术进行施工;开发和利用适合本地区岩土条件的新技术、新工艺,如新型桩、新的止水、降水措施等基坑支护新技术,以及采用信息化施工新技术。 相似文献
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上海宝钢集团建设的加热炉区漩流池,其基坑平面形状为直径约25 m的圆形,开挖深度32 m,场地内承压含水层,水头高度43.50 m,采用深井井点降水,最终将建设场地承压含水层地下水位埋深降低到29.28 m以下,避免了基坑突涌破坏,实现了基坑的安全开挖,采用跟踪法降水,最大限度地减少了降水对周边环境的影响。 相似文献
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当基坑需进行非截断条件下的承压含水层降水时,承压水抽降产生的影响范围远大于基坑开挖的影响范围,其对基坑外既有隧道的影响值得重视。进行了承压层减压降水对既有盾构隧道影响的有限元仿真模拟,考虑了既有隧道相对于承压含水层不同位置时,既有隧道周围土体应力场、既有隧道横断面内力和变形。研究结果表明,隧道全部或者大部分位于承压含水层中时,抽水除可引起隧道发生整体隆起或沉降外,还将导致隧道自身产生较大的竖向压缩变形;当隧道全部位于上、下部隔水层时,含水层抽水对其隧道的变形影响不大,但当隧道位于上部隔水层情况下,抽水将会引起隧道产生整体下沉。 相似文献
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多层含水层抽水试验分层止水方法介绍 总被引：2，自引：0，他引：2
前言沙岭子电厂水源地进行水文地质勘测中,由于水源地地下水由潜水、承压水及承压自流水所组成的多层含水层类型。鉴于这样一个多含水层的结构特征,为取得各层含水层的水文地质参数及水位、水温、水质等资料,就必须解决井内、外分层止水进行抽水试验以及井内水位降深观测装置和观测孔的观测管分层安装、分层止水等一系列多工艺问题。 相似文献
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Ye-Shuang Xu Huai-Na Wu Bruce Zhi-Feng Wang Tian-Liang Yang 《Environmental Earth Sciences》2017,76(9):351
Foundation dewatering has become a major cause of land subsidence in Shanghai. The burial depth of foundations in relation to geotechnical construction works is less than 75 m, and the corresponding groundwater includes phreatic, low-pressure artesian, and the first confined aquifers. Based on the geological and hydrogeological conditions beneath Shanghai, methods of dewatering may be divided into three modes and further five patterns according to the insertion depth of the dewatering-retaining system. The most common dewatering mode aims to reduce the water pressure in the confined aquifer by setting the dewatering wells inside the pit, whilst the retaining walls are buried in the confined aquifer and partially cut off the confined aquifer layer. To predict the settlement due to foundation dewatering, numerical models are generally adopted, which are similar to those used to predict land subsidence induced by regional groundwater withdrawal; however, since foundation dewatering is conducted along with the setting of retaining walls and foundation pit excavation, which differs from regional groundwater withdrawal, interactions between the retaining wall-dewatering well, the dewatering-excavation, and dewatering-recharge are important factors affecting the analytical model. Since the grading of the shallow soil layers is different, stratified settlement characteristics of the shallow soil strata and seepage erosion, which results in additional deformation, need to be given particular consideration. 相似文献
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Wang Jianxiu Liu Xiaotian Liu Shaoli Zhu Yanfei Pan Weiqiang Zhou Jie 《Acta Geotechnica》2019,14(1):141-162
Water level is decreased during foundation pit excavation to avoid water inrush under confined water pressure. Cut-off wall is often used as waterproof curtain to partially cut off the dewatered aquifer. When a foundation pit is located in a built-up area and the underlying confined aquifer is not cut off, the drawdown must be minimized outside the pit to avoid land subsidence in buildings and pipelines. The coupling effect of the cut-off wall and pumping well is used to control the drawdown outside the foundation pit. However, the coupling mechanism is not intuitively well understood because of the limitations of existing experimental methods. In this study, transparent soil was introduced to model the coupling mechanism in the physical model test. High-purity fused silica and mixed paraffin oil were used as skeleton and fluid to simulate the confined aquifer and groundwater. Industrial solid dye and paraffin oil were used as tracers. A camera was used to collect flow information. Tests were performed for the combinations of cut-off wall and partially penetrating pumping wells. The insertion depth ratio of the cut-off wall most effectively influenced the drawdown. The layout of the pumping wells in horizontal direction influenced water level distribution and flow rate. The optimal depth of the pumping wells was 1–5 m above the bottom of the cut-off wall, and the optimal horizontal distance between the cut-off wall and the pumping wells was 25% of the pit width. Non-Darcy flow was observed within the range of 0–10 m around the bottom of the cut-off wall. These results were significant in understanding the cut-off wall and pumping well coupling effect on foundation pit dewatering.
相似文献13.
In terms of controlling groundwater in deep foundation pit projects, the usual methods include increasing the curtain depth, reducing the amount of pumped groundwater, and implementing integrated control, in order to reduce the drawdown and land subsidence outside pits. In dewatering design for confined water, factors including drawdown requirements, the thickness of aquifers, the depth of dewatering wells and the depth of cutoff curtains have to be considered comprehensively and numerical simulations are generally conducted for calculation and analysis. Longyang Road Station on Shanghai Metro Line 18 is taken as the case study subject in this paper, a groundwater seepage model is developed according to the on-site engineering geological conditions and hydrogeological conditions, the excavation depth of the foundation pit as well as the design depth of the enclosure, hydrogeological parameters are determined via the pumping test, and the foundation pit dewatering is simulated by means of the three-dimensional finite difference method, which produces numerical results that consistent with real monitoring data as to the groundwater table. Besides, the drawdown and the land subsidence both inside and outside the pit caused by foundation pit dewatering are calculated and analyzed for various curtain depths. This study reveals that the drawdown and the land subsidence change faster near the curtain with the increase in the curtain depth, and the gradient of drawdown and land subsidence changes dwindles beyond certain depths. In this project, the curtain depth of 47/49 m is adopted, and a drawdown-land subsidence verification test is completed given hanging curtains before the excavation. The result turns out that the real measurements basically match the calculation results from the numerical simulation, and by increasing the depth of curtains, the land subsidence resulting from dewatering is effectively controlled. 相似文献
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In terms of controlling groundwater in deep foundation pit projects, the usual methods include increasing the curtain depth, reducing the amount of pumped groundwater, and implementing integrated control, in order to reduce the drawdown and land subsidence outside pits. In dewatering design for confined water, factors including drawdown requirements, the thickness of aquifers, the depth of dewatering wells and the depth of cutoff curtains have to be considered comprehensively and numerical simulations are generally conducted for calculation and analysis. Longyang Road Station on Shanghai Metro Line 18 is taken as the case study subject in this paper, a groundwater seepage model is developed according to the on-site engineering geological conditions and hydrogeological conditions, the excavation depth of the foundation pit as well as the design depth of the enclosure, hydrogeological parameters are determined via the pumping test, and the foundation pit dewatering is simulated by means of the three-dimensional finite difference method, which produces numerical results that consistent with real monitoring data as to the groundwater table. Besides, the drawdown and the land subsidence both inside and outside the pit caused by foundation pit dewatering are calculated and analyzed for various curtain depths. This study reveals that the drawdown and the land subsidence change faster near the curtain with the increase in the curtain depth, and the gradient of drawdown and land subsidence changes dwindles beyond certain depths. In this project, the curtain depth of 47/49 m is adopted, and a drawdown-land subsidence verification test is completed given hanging curtains before the excavation. The result turns out that the real measurements basically match the calculation results from the numerical simulation, and by increasing the depth of curtains, the land subsidence resulting from dewatering is effectively controlled. 相似文献
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Yong-Xia Wu Hai-Min Lyu Jack Shuilong Shen Arul Arulrajah 《Environmental Earth Sciences》2018,77(10):392
This paper discusses the geological and hydrogeological features of Quaternary deposits in Tianjin as well as the geohazards related to groundwater hydrology in this region. The soft soil deposits, comprising silt, sand, silty clay and clay, are composed of four aquifer groups. In the first aquifer group, one phreatic aquifer and two confined aquifers have relationships with underground construction in the urban area. These three aquifers are separated by two aquitards and collectively form a multi-aquifer system. During geotechnical construction, potential geohazards present are related to the groundwater, which include water-in-rushing, quicksand and piping hazards. To prevent the aforementioned geohazards, dewatering is conducted; however, groundwater pumping may result in large settlements of the surrounding ground. To reduce pumping-induced settlement, the dewatering–waterproofing system has been adopted. According to the characteristics of the subsoil, excavation depth and the surrounding environment, the dewatering system can be divided into five patterns. In the first four patterns, when pumping is conducted in the excavation pit, the groundwater head in the adjacent aquifers outside the pit decreases due to the leakage effect of the aquitards located between the aquifers. In the fifth pattern, waterproof curtain has cut off the aquifers completely and dewatering in the pit cannot result in settlement around excavation pit. To avoid geohazards related to groundwater hydrology, countermeasures recommended include construction of an effective waterproof curtain, selection of a reasonable excavation dewatering pattern and withdrawal of required groundwater. 相似文献
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地下工程建设中不可避免地遇到地下水的控制问题,正确的水文地质参数是准确预测基坑涌水量进而进行地下水控制的前提.文章以郑州地铁5号线经开第八大街站的现场抽水试验为基础,通过1个抽水试验孔、2个观测孔进行了 3个不同水位降深的抽水试验,以更精确地确定含水层的水文地质参数,为深基坑地下水控制设计和施工提供重要的基础数据,对类... 相似文献
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Numerical study of dewatering in a large deep foundation pit 总被引：2，自引：1，他引：1
Jianxiu Wang Bo Feng Haipeng Yu Taiping Guo Guangyun Yang Junwu Tang 《Environmental Earth Sciences》2013,69(3):863-872
During foundation pit excavation, groundwater is often the most important factor that affects pit stability. Dewatering is widely used in pit excavation to avoid uplift of excavation floors due to high water pressure. The characteristics of seepage in small-scale deep foundation pits of high-rise buildings or in the long narrow foundation pits of subway stations have been extensively investigated. However, the characteristics of seepage in large-scale deep excavations have not been studied. This paper investigates the large deep excavation of the buildings in Oriental Fisherman’s Wharf. The total area of the construction site is 33,917 m2. Single-well and group-well field pumping tests were performed and a numerical simulation by 3D finite difference method (FDM) was carried out. The simulation used results from the field pumping tests. The permeability parameters of the confined aquifer were then revised, based upon comparisons of simulation and observation results. Subsequently, dewatering schemes were simulated by FDM forward analysis. The simulation results show that dewatering schemes can minimize seepage and uplift in large excavation pits, though settlement outside the pit may need treatment measures. 相似文献