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2016 Vol. 4, No. 4

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Building a scientific and ecological earth–on an important field of geo-science: Geo-environment and construction engineering effect
LU Yao-ru, ZHANG Wei, LIU Qi, YANG Min, ZHANG Feng-e
2016, 4(4): 259-278.
Abstract(270) PDF(465)
This paper explores the 12 aspects of geo-environment and construction engineering, including the earth evolution, the structure of geological bodies, the comprehensive utilization of resources, the geo-environmental effect, the engineering construction, the sustainable development and, etc. This paper presents that the good environment could only be created through the conservation and efficient utilization of resources, the joint efforts of disaster prevention and mitigation, as well as the avoidance of adverse environmental effect caused by human activities. This paper concludes that, to build a scientific and ecological earth, the development laws of geo-science must be learnt.
A discussion of up-flow springs
ZHOU Xun, WANG Xiao-cui, CAO Qin, LONG Mi, ZHENG Yu-hui, GUO Juan, SHEN Xiao-wei, ZHANG Yu-qi, TA Ming-ming, CUI Xiang-fei
2016, 4(4): 279-283.
Abstract(339) PDF(1027)
Based on their genesis, springs are commonly classified as depression spring, contact spring, overflow spring and fault spring, etc. In addition, a kind of springs, i.e., up-flow spring, can be found in the field. An aquifer is overlain by poorly-permeable unconsolidated sediments or relatively impervious formations. If the hydraulic head of the aquifer is higher than the land surface, groundwater may flow up to the ground surface through the local portion of the overlying aquicludes where the permeability is relatively good, and emerges as an up-flow spring. The common characteristics of an up-flow spring are discussed and summarized in this paper, and some examples of the up-flow springs are also given. Up-flow springs can flow up through local permeable zones in the overlying aquicludes rather than permeable faults. Although they cannot be found as frequently as depression springs, contact springs, overflow springs and fault springs etc., yet up-flow springs may occur in the form of normal-temperature springs, hot springs and salt springs.
Statistical characteristics of heavy metals content in groundwater and their interrelationships in a certain antimony mine area
YU Kai-ning, LI Jian, LI Hui, CHEN Kang, LV Bing-xu, ZHAO Long-hui
2016, 4(4): 284-292.
Abstract(336) PDF(1088)
In recent years, most of domestic and foreign researches about heavy metal pollutions of metal mine mainly focus on water, soil and plants on the surface. There is lack of researches about heavy metal pollution in groundwater of metal mine. In this research, a certain antimony mine area is selected as a typical study area. Also, the study about statistical characteristics of heavy metals in groundwater has been carried out. Furthermore, the interrelationships have been preliminarily discussed through related analysis, such as relevant analysis, cluster analysis and principle component analysis. The results show that: the excessive elements in groundwater of study area are Sb, As, Pb, Se, and Ni. The average mass concentration of Sb, As, and Pb is higher than that of drinking water standards (GB5749-2006). The concentration of most heavy metals in dry season is lower than or equal to that in wet season for groundwater. Zn is the only metal in groundwater showing a different pattern, the concentration of which in dry season is higher than that in wet season. Under the impacts of stratum leaching and absorption effect, the concentration of heavy metals (except Pb and Ba) in groundwater are lower than or equal to that in surface water. As and Se, the two heavy metals have a significant positive correlation, which shows the two elements might have gone through similar environmental geochemical effect. Also, the connection among Zn, Hg, Pb, and Mn is not obvious; therefore, the sources of those elements are quite different. In addition, the elements of Se and As have obvious positive interrelationship with elements of CO32- and F-. Also, the Pb has significant positive correlation with PO43-, H2SiO3 and oxygen consumption. The results of cluster analysis show that 9 different heavy metals in the study area can be divided into 3 categories: Zn, Cd, Mn, Hg, Cu, and Cr belong to the first category, Se and As belong to the second one, and the last category is Pb. Also, the principle component analysis divides 6 heavy metals (Zn, As, Hg, Pb, Mn, and Se) into 4 different principle components, which can be utilized to assess heavy metals pollution situations in groundwater. The reliability of this method is higher than 91%. Moreover, the research provides theory basis and models for establishing evaluation index system and exploring the evaluation method of heavy mental pollution in groundwater.
Thermal stresses analysis of casing string used in enhanced geothermal systems wells
ZHANG Pei-feng
2016, 4(4): 293-300.
Abstract(309) PDF(1760)
In the enhanced geothermal systems wells, casing temperature variation produces casing thermal stresses, resulting in casing uplift or bucking. When the induced thermal stresses exceed casing material’s yield strength, the casing deforms and collapses. The traditional casing design standard only considers the influence of temperature variation on casing material’s yield strength. Actually, for commonly used grades of steel pipe, casing’s material properties-such as yield strength, coefficient of thermal expansion, and modulus of elasticity change with temperature variation. In this paper, the modified thermal stress equation is given. Examples show that the allowable temperature of the material grade N80’s casing is only 164 ℃, which is much lower than that of the traditional design standard. The effective method to improve the casing pipe’s allowable temperature is pre-stressed cementing technology. Pre-stressed cementing includes pre-tension stress cementing and pre-pressure stress cementing. This paper focuses on the design method of full casing pre-tension stress cementing and the ground anchor full casing string pre-tension cementing construction process.
Groundwater resources in karst area in Southern China and sustainable utilization pattern
XIA Ri-yuan
2016, 4(4): 301-309.
Abstract(392) PDF(640)
Occurrence conditions of groundwater in southern karst area are complicated. The water-bearing media in the karst have multiplicity, and the groundwater is hosted in holes, gaps, seams, pipes and caves. The karst water shows heterogeneity where fast and slow flow coexist, and the Darcy and non-Darcy flow coexist, and the liquid flow, the gas flow and solid flow coexist. The evaluation and investigation indicates that the mineable resource of karst groundwater is about 53.44 billion m3/y, and the current exploitation quantity is merely 6.565 billion m3/year. The exploitation and utilization potential is gigantic. In the region there are altogether 2 763 karst subterranean rivers with a total length of 12 687 km. The dry season runoff volume equals to 47 billion m3/year. At present the exploitation is only 10%. Four effective utilization models of karst groundwater resources have been put forward. (1) The karst hills-depression zone formed the surface-underground united reservoir. By digging tunnels, water diversion irrigation and generating electricity, the ecological economy is developed. (2) In the deep-cut peak cluster depression area, by using the high-part Epikarst spring and constructing the regulation and storage water tank, the stereo ecological agriculture is developed. (3) In the karst peak forest plain and hilly-gully area, the pump-type underground regulating reservoir is constructed and the water-saving ecological agriculture is strengthened. (4) In the fault basin region with the surrounding groundwater runoff belting beam backwater, the water resources are jointly controlled to develop a fruit crop base within the basin.
Study on engineering-hydrogeological problems of hydroelectric project
XU Mo, ZHANG Qiang, KANG Xiao-bing, ZHANG Shi-shu, QI Ji-hong, YANG Yan-na, GUO Jian
2016, 4(4): 310-319.
Abstract(194) PDF(1664)
Engineering-hydrogeological problems arise from the interaction between engineering activities and geological environment, in which rock-soil mass and groundwater are especially important constituents. However, up-to-date research on them is relatively dispersive and simple due to their complexity and lack of comprehensive and systematic study methods. Starting from geological analysis of mechanism to geological model based on geological regularities, the paper predicts the tendency of geological evolvement and puts forward proper measures to solve problems. In this paper, elevated water-sensitive structure in rock-soil mass, which mainly causes engineering hydrogeological problems, and problems in hydropower is discussed based on unique construction in Chinese Western hydropower projects. Engineering hydrogeological problems are reservoir induced earthquakes leakage from reservoir bottom in karst, stability of high slope at reservoir banks, sliding of dam foundation and dam abutment, and confined water at key positions which are introduced and determined by using water-sensitive factors (or structure) according to special hydrogeological conditions.
Interactions between benzotriazole and corncob biochars pyrolyzed at different temperature
XING Chen, YU Cheng-long, BI Er-ping, DAI Jin-e
2016, 4(4): 320-327.
Abstract(155) PDF(691)
The sorption of ionizable benzotriazole (BTA) to corncob biochars pyrolyzed at different temperature (i.e., 300 oC, 500 oC and 800 oC) was investigated in this study. Biochars produced at higher temperature showed higher surface area, micropore volume and aromaticity. Consequently, the sorption of BTA changed from absorption to adsorption for biochars pyrolyzed at 300 oC and 800 oC, respectively. Solution pH affected speciation of BTA and surface charge properties of biochars. For BTA0, H-bond, partition and micropore filling are dominant sorption mechanisms. For BTA-, it is suggested that negative charge-assisted H-bond plays an important role in sorption. Corncob biochar pyrolyzed at high temperature (e.g., 800 oC) showed the highest sorption affinity for BTA. Ca2+ in solution enhanced BTA- and BTA0 sorption through cation-bridge and surface complexation.
Krypton-85 dating of shallow aquifer in Hebei Plain
ZHANG Xiang-yang, CHEN Zong-yu, YANG Guo-min, TU Le-yi, HU Shui-ming
2016, 4(4): 328-332.
Abstract(179) PDF(1097)
The inert gas radioactive isotope 85Kr (with a half-life of 10.74 years), due to its stable physical and chemical properties, is an ideal tracer for shallow groundwater dating. In such a dating application, first the dissolved gas is extracted from groundwater in the field, then krypton is separated from the gas sample, and finally the isotopic abundance 85Kr/Kr will be determined by an ATTA instrument. According to the atmospheric input curve of 85Kr, the 85Kr age of groundwater is determined. We conducted 85Kr analysis in three wells in Zhengding County on the plains in front of the Taihang Mountains, and made a comparison with tritium (3H) method.
Dynamic assessment of pollution risk of groundwater source area in Northern China
LIU Shu-yuan, WANG Hong-qi
2016, 4(4): 333-343.
Abstract(238) PDF(929)
Based on the dynamic analysis and research of pollution risk of groundwater sources, this paper creates the dynamic assessment method of pollution risk of groundwater source area under the theory of “source-pathway-receptor”, and applies this method to one typical fissure karst groundwater source area in northern China. Following the 30-year petroleum pollutant migration simulation and pollution risk assessment of groundwater source area, this study finds that the very high risk zone is mainly located in Q Petrochemical Company and the surrounding area and the area adjacent to River Z. Within this period of thirty years, the pollution risk of groundwater source area has showed a dynamic trend that features an inverted “V” shape. The ratio of very high risk zone to the total area will be 18.1%, 17.47% and 16.62% during the tenth year, the twentieth year and the thirtieth year separately, and will reach the highest level of 19.45% during the fifteenth year. Meanwhile, the vertical migration distance of pollutant centre concentration changed from the surface soil at the outset to the deepest point of about 250 meters underground during the tenth year. The results of this risk assessment indicate the dynamic feature of pollution risk. The dilution, degradation and migration of petroleum pollutants in groundwater system contribute to an ultimate decline in pollution risk.
Simulation of groundwater level recovery in abandoned mines, Fengfeng coalfield, China
MA Luan, WANG Guang-cai, SHI Zhe-ming, GUO Yu-ying, XU Qing-yu, HUANG Xu-juan
2016, 4(4): 344-353.
Abstract(239) PDF(460)
Abandoned mines are of high potential risk as they could be a large underground storage of pollutants (heavy metals and organic wastes, etc.). Various physical, chemical and biological reactions would take place when groundwater flows into underground spaces, which makes abandoned mine a huge potential hazard to groundwater environment. The recovery of groundwater level is one of the key elements controlling the reactions and causing such hazards. This paper simulated groundwater level recovery processes in the abandoned mines, Fengfeng coalfield by using the computer program FEFLOW. The paper integrated the pipe flow model, “three zones” model and groundwater inrush (discharge) model in the simulation of groundwater in the complex laneway-aquifer system. Groundwater flow in the laneway systems was considered pipe flow and described in Bernoulli equation. The water-bearing medium (coal seam roof) overlying the laneway systems was divided into “three zones” composed of the caving zone, fissure zone and bending zone based on the disruption degrees of previous mining. Groundwater in the Ordovician limestone aquifer (bottom of coal seam) flowing into laneway systems was considered a major inrush/recharge source, and its flow rate was calculated by an inrush (discharge) model which was newly developed in this study and incorporated into FEFLOW. The results showed that it would take approximately 95 days for groundwater in abandoned mines to recover to regional groundwater level elevation, and the total amount of water filling up would be about 1.41195×107 m3, which is consistent with the actual data. The study could be of theoretical and practical significance to mitigate abandoned mines’ hazards and improve mine groundwater utilization.
Applications of hydrogeophysics in characterization of subsurface architecture and contaminant plumes
DENG Ya-ping, SHI Xiao-qing, WU Ji-chun
2016, 4(4): 354-366.
Abstract(386) PDF(2001)
Geophysical methods have been applied to a wide range of hydrogeological problems. With improvement in geophysical inversion algorithms and measurement tools, significant achievements have been made in the characterization of subsurface architecture, time-lapse monitoring of hydrogeological process and contaminant plumes delineation. In this paper, we summarize the geophysical methods that are most widely used in hydrogeology including Electrical Resistivity Tomography (ERT), Induced Polarization (IP), Ground Penetrating Radar (GPR) and Electromagnetic Induction (EMI). Three examples including lab and field works are used to demonstrate current application of geophysical methods for characterizing subsurface architecture and contaminant plumes. Though great progress has been made in hydrogeohysics over the last few decades at home and abroad, challenges still remain in practical applications. More recently, hydrogeophysics continues to develop in the areas of establishment of hydrogeophysical models, large-scale architecture characterization, uncertainty analysis, biogeochemical process monitoring and ecosystem science.
Numerical simulation of groundwater and early warnings from the simulated dynamic evolution trend in the plain area of Shenyang, Liaoning Province (P.R. China)
LIU Jun-qiu, XIE Xin-min
2016, 4(4): 367-376.
Abstract(174) PDF(1026)
Groundwater level is the most direct factor reflecting whether groundwater is in a virtuous cycle. It is the most important benchmark for deciding whether a balance can be struck between groundwater discharge and recharge and whether groundwater exploitation will trigger problems pertinent to environment, ecology and environmental geology. According to the borehole and long-term monitoring wells data in the plain area of Shenyang, a numerical groundwater model is established and used to identify and verify the hydrogeological parameters and balanced items of groundwater. Then the concept of red line levels, the control levels of groundwater is proposed, the dynamic evolution trend of groundwater under different scenarios is analyzed and predicted and groundwater alerts are given when groundwater tables are not between the lower limit and the upper limit. Results indicated: (1) The results of identification and verification period fitted well, and the calculation accuracy of balanced items was high; (2) with the implementation of shutting wells, groundwater levels in urban areas of Shenyang would exceed the upper limit water level after 2020 and incur some secondary disasters; (3) under the recommended scenario of water resources allocation, early-warnings for groundwater tables outside the range would occur in the year of 2020, 2023, 2025 respectively for successive wet, normal and dry years. It was imperative to reopen some groundwater sources and enhance real-time supervision and early-warning to prevent the occurrence of potential problems.