Geological and hydrogeological environment in Shanghai with geohazards to construction and maintenance of infrastructures

Shanghai Administrative Region (SAR) is located on the deltaic deposit of the Yangtze River. The bed rock under SAR is generally buried in the depth of 200 m to 300 m except for several massifs, where the bed rock is exposed to the ground surface. The Quaternary deposit in Shanghai is soft sediment. The variation of palaeoclimate influenced the sea level and resulted in a very complicated sedimentary environment. The Quaternary deposit in SAR is composed of an alternated multi-aquifer-aquitard system (MAAS). The groundwater system is composed of one artesian aquifer and five confined aquifer layers with very high groundwater pressure head. The MAAS was formed mainly within the warm geological era updated to 2.6 million years ago. Between two aquifers, there is an aquitard which is composed of soft clayey soil formed mainly within the cold era. The aquitards are composed of very soft clayey silt with very high compressibility and humus content. The humus material was transformed into methane gas under a long-term geological process. With the development of economy, the infrastructures were (or are being) constructed in the top shallow soft clayey deposit, aquifer I and aquifer II. In SAR, the following geohazards occurred or possibly occur during the construction and maintenance of infrastructures: i) quicksand and piping hazards; ii) pumping-induced hazards and recharge-cutoff hazards; iii) long-term settlement due to the seasonal fluctuation of groundwater level; and iv) geohazards of methane gas.     

The impact of groundwater on the excavation of tunnels in two different hydrogeological settings in central Italy

To double the capacity of the Orte?CFalconara railway line (central Italy), the Santa Croce tunnel was constructed (1985?C1995), which runs between the Nera Montoro and Narni stations. In the same period, to double the capacity of the Ancona?CBari railway line, the Moro, Cintioni, S. Giovanni and Diavolo tunnels were constructed between the Ortona and Casalbordino stations. The high likelihood of intercepting a significant volume of groundwater in calcareous rocks of the Santa Croce tunnel led to a shift in the layout of the tunnel, which allowed construction of the tunnel by more rapid and less expensive means. Groundwater along the Moro tunnel layout, in a sandy aquifer, has been drained by the excavation of a preliminary tunnel, which allowed a discharge of up to 0.080?m³/s. In the S. Giovanni and Diavolo tunnels, a particular hydrogeological setting was found to exist in the form of lens-shaped bodies of fine grey sand-and-silt aquitards intercalated between the bottom muddy-sandy deposits (very low permeability) and the sandy aquifer; this caused sudden groundwater inflow and tunnel collapse. The S. Giovanni tunnnel, excavation was completed using the HydroShield system, whereas in the Diavolo tunnel, a well-point system was adopted, which avoided any environmental hazards.     

广东大亚湾海洋地质环境与潜在地质灾害

大亚湾是国家重点开发的海湾，通过对其大量实测资料的综合分析和研究表明，大亚湾有9种底质类型，除沿岸及岛屿周围颗粒较粗外，湾内浅海区主要为粘土质粉砂和粉砂质粘土，工程地质条件较好。大亚湾目前底质总体污染较小，以轻微污染为主，但湾内水体交换能力差，污染易而治理难，应倍加保护。大亚湾潜在地质灾害包括活动性地质灾害因素和限制性地质条件，主要有海岸侵蚀、沙波、断层、不规则埋藏基岩、埋藏脊、航道沟、异常堆积区和陡坎等。     

GIS-based hydrogeological databases and groundwater modelling

Reliability and validity of groundwater analysis strongly depend on the availability of large volumes of high-quality data. Putting all data into a coherent and logical structure supported by a computing environment helps ensure validity and availability and provides a powerful tool for hydrogeological studies. A hydrogeological geographic information system (GIS) database that offers facilities for groundwater-vulnerability analysis and hydrogeological modelling has been designed in Belgium for the Walloon region. Data from five river basins, chosen for their contrasting hydrogeological characteristics, have been included in the database, and a set of applications that have been developed now allow further advances. Interest is growing in the potential for integrating GIS technology and groundwater simulation models. A "loose-coupling" tool was created between the spatial-database scheme and the groundwater numerical model interface GMS (Groundwater Modelling System). Following time and spatial queries, the hydrogeological data stored in the database can be easily used within different groundwater numerical models. Electronic Publication     

Calculation of groundwater head distribution with a close barrier during excavation dewatering in confined aquifer

When pumping is conducted in confined aquifer inside excavation pit(waterproof curtain),the direction of the groundwater seepage outside the excavation changes from horizontal to vertical owing to the existence of the curtain barrier.There is no analytical calculation method for the groundwater head distribution induced by dewatering inside excavation.This paper first analyses the mechanism of the blocking effects from a close barrier in confined aquifer.Then,a simple equation based on analytical solution is proposed to calculate groundwater heads inside and outside of the excavation pit with waterproof curtain(hereafter refer to close barrier)in a confined aquifer.The distribution of groundwater head is derived according to two conditions:(i)pumping with a constant water head,and(ii)pumping with a constant flow rate.The proposed calculation equation is verified by both numerical simulation and experimental results.The comparisons demonstrate that the proposed model can be applied in engineering practice of excavation.     

Multi-aquifer pumping test to determine cutoff wall length for groundwater flow control during site excavation in Tokyo, Japan

Multi-aquifer pumping tests, using a multi-screen pumping well and multi-level piezometers, were carried out for groundwater flow control in a large-scale excavation site in Tokyo, Japan. The site was underlain by multi-layered confined aquifers. In the tests, pumping was carried out using a multi-aquifer pumping well in which a screen depth was chosen arbitrarily. Changes in groundwater pressure heads in each aquifer were measured at each screen position of the multi-aquifer pumping well. Hydraulic conductivity (K) and specific storage (S _s) of not only aquifers, but also for low permeability layers between the aquifers, were estimated using the Cooper-Jacob method, and calibrated by a finite element method (FEM) groundwater model. Four different cutoff wall lengths were assumed for final excavation depth, and correlations among wall length, pumping discharge and drawdown at the back of the cutoff wall were obtained from simulations using the K and S _s parameters in the FEM model. Then, the most suitable wall length was selected based on the simulated correlations considering environmental condition, construction period and cost of the cutoff wall.     

深基坑开挖环境效应的控制对策研究

本文提出了深基坑开挖的环境效应的控制对策，强调要面向问题进行了降水设计及护坡设计。     

Hydrogeochemical environment of aquifer groundwater in Shanghai and potential hazards to underground infrastructures

Natural Hazards - The Quaternary deposit in the Shanghai region is composed of a layered multi-aquifer-aquitard system (MAAS). The MAAS was formed mainly during the warm geological era over 2.6...     

天津市地质灾害-气象预报预警方法探讨

天津市蓟县山区面积727km2,以中低山和低山丘陵地貌形态为主,在强降雨和持续降雨条件下发生泥石流、滑坡等地质灾害的可能性客观存在。历史上地质灾害已给当地造成了一定的人员伤亡及财产损失。为了加强突发性地质灾害预防工作,提高人民群众的防灾意识,天津市2004年开始开展地质灾害-气象预报预警工作,取得了一定的效果。针对天津市山区面积较小、地质灾害事件较少的特点,目前常用的地貌分析———临界降雨量模型判据法具有一定的局限性,预报成功率较低。在区域性地质灾害-气象预报预警工作的基础上,开展单点泥石流灾害气象预报预警工作非常必要。对容易发生泥石流灾害的主要沟谷,通过现场调查可以获取沟谷的形态特征参数(沟谷的高差、纵坡的坡度、沟长、流域面积等)。以临界降雨量为变量因子,对每个监测沟谷建立泥石流灾害气象预警预报模型,可以很大程度提高预报的针对性。模型需要在实践中不断检验和完善,逐步提高预报的准确率。     

Evaluation of groundwater potential and eco-geological environment quality in Sanjiang Plain of Heilongjiang Province

Sanjiang Plain of Heilongjiang Province has become an important commodity grain base in our country after the construction of more than a century. Groundwater is the main water source for industrial and agricultural production and daily life in the area. With the large-scale development and construction in this area, there are a series of ecological and environmental geological problems, such as the reduction of groundwater resources, which seriously restricts the sustainable development of local agriculture and society as well as economy. Based on the characteristics of three-dimensional flowof groundwater in Sanjiang Plain, this paper adopts the simulation software Visual MODFLOW to evaluate groundwater exploitation potential. The results show that overall there is a certain exploitation potential of Sanjiang Plain groundwater but it is unevenly distributed, and overdraft phenomenon exists in seven farms such as Baoquanling and Chuangye. Based on analytic hierarchy process, the evaluation result of eco-geological environment quality in Sanjiang Plain shows that 94.5% of the region features good geological environment quality, medium stability and medium bearing capacity. The study can provide geological evidence for optimal allocation of water resources, land planning and regulation, and the high and stable yield of the commodity grain base in Sanjiang Plain.     

Global hydrogeological systems and groundwater of the Pacific segment of the Earth

The paper presents the main results of almost half-century-long theoretical and applied studies by the late K.P. Karavanov dedicated to hydrogeological systems of continents and the oceanic floor as well as to the regional hydrogeology of the Pacific segment of the Earth. This research is not yet over; it is being developed by his followers and serves as a basis for the further study of the subsurface hydrosphere on land and the sea and ocean floor.     

鄂尔多斯白垩系地下水盆地湖眼的形成及其水文地质意义

在鄂尔多斯盆地北部沙漠高原区,部分湖盆的边部发育有数量不等的"湖眼"."湖眼"是分布在湖盆边部的特殊的泉,通过对湖眼的野外调查和物质成分分析,总结了湖眼的分布、结构、动态变化和物质组成特征.研究结果表明,湖眼泥浆来自湖盆底泥,其水分可来自不同循环深度的地下水;湖眼的动态变化可以反映地下水的循环深度;湖眼的分布和动态变化对于研究地下水的排泄方式具有一定的水文地质意义.     

北山预选区公婆泉形成的地质、水文地质条件分析

公婆泉是我国高放废物处置库场址北山预选区众多泉中少有的淡水泉,该泉水的成因问题与处置库场址选择具有一定的关系。通过前人资料的分析,结合水文地质调查工作,探讨了该泉的成因,认为该泉是一个受潜水补给的下降泉。泉水的补给来源是位于该泉西南部的驼马滩盆地古近系一新近系下覆基岩古风化壳地下水,其水质良好、水量丰富,流向北东,经公婆泉丘陵一带后,在沟谷侵蚀含水层处溢出,形成公婆泉。     

塔里木盆地区域地下水环境同位素特征及其意义

以大量水环境同位素样品测试结果为依据,对塔里木盆地的区域水环境同位素特征进行了分析,得出了一些有意义的认识:(1)塔里木盆地不同14C年龄的地下水的δD、δ18O值差异不明显,反映了水资源形成区在最后冰期和冰后期气温相差不大,推测是由于新构造运动使山体隆升,同一位置因高程变化产生的气温变化弥合了气候的变化,这一特征使我们难以运用δD-δ18O关系区别古水(冰期)与现代水(冰后期)。(2)在δD-δ18O关系图上,沿大气降水线可把盆地内主要河流及其补给形成的地下水大致圈定在3个域内,这3个域的区别不是大气环流作用的结果,而是河流源区山脉高程效应的反映。(3)与西北内陆盆地其他大型河流比较,阿克苏河流域下游承压自流水的14C年龄小得多,这是由阿克苏河径流量大、下游为河槽洼地、不完全具备山前倾斜平原水文地质特征等决定的。阿克苏河下游承压水水循环交替迅速,开发潜力较大,在西北内流盆地中是一个特例。(4)塔克拉玛干沙漠第四系松散层地下水主要是从盆地南缘侧向补给的,在沙漠腹地由深部向浅部顶托排泄。盆地内深层油田水处于高度封闭的滞留状态,与上部松散沉积层地下水之间基本没有联系。     

复杂环境下基坑开挖监测与分析

旧城改造中由于周围环境复杂,基坑开挖对土层产生扰动,并引起围护结构的变形,有可能造成基坑失稳。以复杂环境下基坑开挖为例,讨论了基坑开挖监测方案,分析了现场监测结果,并指导现场施工开挖,确保了围护结构本身和周围环境的安全,信息化施工取得良好效果。     

Electrical geophysical and hydrogeological investigations of groundwater aquifers in Ruseifa municipal landfill, Jordan

The effect of the Ruseifa municipal landfill on the shallow groundwater aquifers in the area was investigated in two separate sites. The first one was not used since 1994, whereas the other is still being used for dumping. Fourteen electrical resistivity soundings were performed to detect the leachate and its effect on the quality of the groundwater. Results indicated that the solid waste thickness of the landfill was ranged from 3 to 20 m with resistivity value less than 10 Ω m. Based on the resistivity decreases of values less than 5 Ω m, the leachate was detected in the landfill sites at depths ranged from 10 to 50 m. However, the flow direction of the leachate at depth ranging 10–20 m in the terminated site was toward north, whereas the flow direction of the leachate in the site still used for dumping was toward east–northeast which causes the major source of groundwater pollution.     

岩溶水文地质环境地质信息管理系统构建与实现

为服务地质调查数据管理需求,基于GIS平台,构建了岩溶地区水文地质环境地质信息管理系统,按标准对调查数据、空间数据进行集成整合,实现了岩溶数据资料信息的数字化、可视化、动态化管理。其系统主要功能模块包括调查数据管理模块、空间数据管理模块、数据核查管理模块、钻孔柱状图管理模块、基础数据管理模块、系统数据管理模块。      

天津滨海新区围海造陆对沿海低地浅层地下水环境的影响

天津滨海新区被提到国家总体发展战略后,随着经济持续发展、城市化进程不断加速及产业转移,进行了大规模围海造陆,在拓展土地空间的同时,也造成了相当多的环境问题。利用滨海新区由陆到海的3条水文地质剖面获取的地下水动态变化监测数据和土壤含盐量测试结果,开展了围海造陆对沿海低地浅层地下水环境的影响研究。结果显示:1受围海造陆影响,对应的沿海低地浅层水位已经出现由陆到海逐渐增高的现象,造成地下水位反向倾斜,阻碍了地下水径流和排泄;2由陆到海浅表土壤全盐量出现逐渐增高的特征,在浅层地下水反向径流作用下,东部区域大量的盐分将被携带至沿海低地,使沿海低地盐渍化程度加重,严重影响到湿地保护和生态建设;3围海造陆对海岸带生态环境的影响是一个长期缓慢的过程,应持续监测近岸海域和陆域沿海低地生态环境的变化情况,以便提出合理的修复建议。     

Geological and hydrogeological reconstruction of the main aquifers of the Maltese islands

Hydrogeology Journal - Geological and hydrogeological conceptualizations of the five main aquifers of Malta were performed by means of characterization of the groundwater bodies’ geometries...