Table of Content

20 June 2006, Volume 12 Issue 2

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Article

Research on the Problems of the Land Subsidence in China

XUE Yu-qun1,ZHANG yun1,YE Shu-jun1,Wu Ji-chun1,WEI Zi-xin2,LI Qin-fen2,YU Jun3

2006, 12(2):  153-160. 

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Abstract:The land subsidence in China can be divided into two types: (1) the subsidence is mainly caused by excessive groundwater withdrawal; (2) the subsidence is caused by groundwater, oil, gas and warm groundwater withdrawal, which is superposed on the neotectonic movement. Not only do the different layers have difference deformation features, but also the same layers in the different location have different deformation features. Even the same layers in the same location have different features in different stage. The corresponding models based on the actual deformation features of the soil should be built in order to simulate the real subsidence condition. The couple of the models and the difference between the vertical and horizontal scales are the problems to be solved for the accurate simulation.

The Status and Prevention Strategy of Land Subsidence in China

HE Qing-cheng, YE Xiao-bin, LI Zhi-ming, LIU Wen-bo

2006, 12(2):  161-168. 

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Based on the detailed analysis on status and problems of land subsidence in most cities in the Changjiang River Delta, the North China Plain, the Guanzhong Plain, the Huabei Plain and the Songnen Plain in China, we propound the guiding idea, principle, staged and final objectives of the land subsidence survey and monitoring, and we also propose the prevention strategy with the respect of the specific situation in China.

A Study on Land Subsidence in Shanghai

LI Qin-fen,WANG Han-mei.

2006, 12(2):  169-178. 

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This paper introduces some new viewpoints getting from the studying on land subsidence of Shanghai in recent years. It also presents some primary achievements obtained in the processes of research on the early forecasting warning system of land subsidence in Shanghai. With consideration of the 11th Five-Year-Plan of land subsidence prevention and cure in Shanghai, this paper points out the existing problems of current studying work which need to be solved urgently, and gives some suggestion on the future study and research direction.

Characteristics of Land Subsidence and its Remedial Proposal in Suzhou-Wuxi-Changzhou Area

Yu Jun1、2,WANG Xiao-mei2,WU Jian-qiang2,XIE Jianbao3

2006, 12(2):  179-184. 

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According to the land subsidence data nvestigated and monitored in Suzhou, Wuxi and Changzhou area in recent years, the current situation, characteristics, formation mechanism of land subsidence and its future trend after groundwater prohibition are systematically analyzed and the countmeasure of land subsidence controlling in future are also suggested.

The Relation between Groundwater Exploitation and Land Subsidence in the Coast Plain of Zhejiang

ZHAO Jian-kang,WU Meng-jie, LIU Si-xiu, SHEN Hui-zhen

2006, 12(2):  185-194. 

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The coast plain in Zhejiang province has subsided Since 1960s. Along with the groundwater exploited constantly, the land subsidence caused a series of harms such as the tide disaster and the waterlogging disaster aggravated ，the city drainage capacity weakened, the river navigable capacity declined，and the farmlands submerged perennially. It may affect national economy sustaining development. According to the dynamic monitoring values of land subsidence and groundwater level and the research results, the history, the status and the rule of land subsidence are summarized. And the advice on prevention and treatment measures of land subsidence was brought forward.

Land Subsidence Survey and Monitoring in the North China Plain

HE Qing－cheng，LIU Wen－bo，LI Zhi－ming

2006, 12(2):  195-209. 

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The North China Plain has witnessed the most excessive pumping of groundwater in the world and covers the largest subsidence area with the most funnels on the planet. The groundwater level of approximately 70,000 square kilometers in this region falls below sea level. Surface subsidence has picked up speed over the last two decades as a result of an increasing demand for groundwater caused by fast economic growth and urbanization, pollution of surface water and the construction of skyscrapers. This paper put forward a series of work programming to monitor and control land subsidence mainly caused by groundwater overdraft in North China Plain. Finally, Some progressed and achievements on basic facilities construction and general study are presented in this paper.

Use of Parallel Simulation Technique in Formulating GroundwaterFlow M odel in Suxichang Area

WANG Xiao-mei1，YU Jun1，ZHU Guo-rong2，WANG Hao-rar2

2006, 12(2):  210-215. 

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The modeling of groundwaterflow in a confined-unconfi ned aquifer of multiple irregular superposed subdomains was documented in the study． Finite element method(FEM)parallel simulation technique(PST)was used for simulation．C++ was conjointly used to edit the modeling codes program，which was run on a message passing interface(MPI)system—parallel virtual machine(PVM)．Through domain decomposition method under the MPI environment，the parallel model computing was then carried out．Finally，actual series of dynamic data of the exploited groundwater in Changzhou and Wuxi were utilized for the FEM parallel、simulation on a two co-jointly mounted Internet computers system.The studies demonstrate that data preparation for the parallel simulation was quite simple，and the results exhibite high data precision．

Carry on the Study of the Data Fusion for the Aquifer Heterogeneity

WU Ji-chun

2006, 12(2):  216-222. 

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The author suggest in this paper that great emphasis should be placed on the study of the data fusion for the aquifer heterogeneity. It is necessary for the study to combine and apply the research results in the correlated subjects. In order to carry on the study of the data fusion for the heterogeneity in the porous aquifer，from easy to hard, the technique of the data fusion which is relatively mature in the military area should be applied firstly. The main research contents and the advanced project of the data fusion study are presented. The preliminary research results are also presented in this paper.

Degassing Parameter of Carbon Dioxide in Volcanic Rocks of Northern Songliao Basin and Its Significance in Forecasting Geological Resource of carbon Dioxide

Liu De-liang1, Li Zhen-sheng1, Sun Yan2, Tan Ying1, Liu Bo1, Wu Xiao-qi1, Yang Xiaoyong1

2006, 12(2):  223-227. 

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It was usually thought that extrusive rocks were not gas source of carbon dioxide reservoirs, because most of the gas was released directly into atmosphere in the cooling process. Whereas recently some researches indicated that CO2 gas of Changdedong gas reservoir was mainly adsorbing gas in volcanic rocks, and post-release of adsorbing gas was important to form the gas reservoir. In order to evaluate the potential and possibility for adsorbing CO2 gas forming gas reservoirs quantificationally, low-temperature (250℃) degassing experiments of volcanic rocks in northern Songliao basin were done. The amounts of released volatile are 0.0299~0.0790ml/g, and those of CO2 are 0.0218~0.0706 ml/g (0.429~1.387wt％). The relationship of the amounts between volatile and carbon dioxide is positively linear. The main component of volatiles is carbon dioxide, and the secondly is N2, and some associated components are deoxidized gases, such as H2, CO, CH4, as well as fewer amounts of low-carbon alkanes. Both the content in volatile and degassing amount of CO2 have an inverse relation with the content of hydrocarbon. There is a negative correlation between the CO2 degassing amount and SiO2 content of volcanic rocks. Volcanic rocks, particularly the basic ones, can adsorb vast amount of carbon dioxide and act as the major gas source rocks. When forecasting geological resource of carbon dioxide, the amount of volatile of volcanic rocks at 250℃ can be treated as the lower limit of the content of volatile and remnant CO2, while the content of total carbon as the upper limit of the amount of degassing CO2.

pH variation as indicator for the reaction between arsenite and bsorbents

YE Ying, JI Shan-shan, WU Dai-dai, ZHANG Wei-rui

2006, 12(2):  228-233. 

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Three types of absorbents, ferric hydroxide, Mg-Al layered double oxide (Mg-Al-LDO) and Mg-Fe layered double oxide (Mg-Fe-LDO) were studied for their absorption on arsenite. Initial pH value of NaAsO2 solution is 9.71. After ferric hydroxide being added, the pH variation with time can be divided into 3 stages: in the first 6 minutes, pH increased from 9.71 to 10.36, which indicated that OH- from the solid phase was released into the solution; during the 7 to 40 minutes, pH changed only a little between 10.36-10.34, which indicated that the absorption of ferric hydroxide on AsO2- reached dynamic equilibrium; after 40 minutes, pH value decreased continuously to 9.72 at the 360th minute, which was caused by the condensation reaction between arsenite and the absorbent, H+ was released as a result. During the absorption of Mg-Al-LDO on arsenite, pH values increased with time continuously, this is because that Mg-Al-LDO takes anions from the solution to recover the crystal structure of its precursor, in this reaction hydroxyl is formed. It is found that Mg-Fe-LDO has double absorption effects on arsenite as shown by ferric hydroxide and Mg-Al-LDO, for that its pH-time curve is between the two absorbents. The absorption capacity of ferric hydroxide on arsenite changed a little with temperature, from 69.7mg/g at 25℃ to 73.7mg/g at 90℃. Absorption capacity of Mg-Al-LDO and Mg-Fe-LDO increased apparently when the medium was heated, from 62.4mg/g and 82.5mg/g at 25℃, to 114.9mg/g and 199.0mg/g at 90℃ respectively. Ascending absorption capacity of Mg-Al-LDO and Mg-Fe-LDO on arsenite at 90℃ is quite possibly because that the competition from carbonic anion on arsenite is suppressed by heating, which expelled dissolved CO2 from the solution.

Laboratory Test for Soil Deformation Property in Solutions with Various pH Values

ZHANG Xin-gui，YI Nian-ping，WU Heng

2006, 12(2):  242-248. 

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In the research aspect of water-soil chemical interaction, more emphasis was put on the polluted water, which is under the extreme state. Unfortunately, much less studies were conducted for the soilmass stability in urban regions, which is under the ordinary state at normal temperatures, pressures and chronic change of hydrological environment. Mini-scale structure of soil plays an important role in soilmass stability, and in formation of land subsidence and soil holes in natural condition. The fracture of soil structure takes place by invalidation of the joints fetween grains and aggregates. From the view point of water-soil chemical interaction and based on mini-scale structure of soil, the authors studied the macro-deformation properties in solutions with various pH values, conducted correlative laboratory test and proved the fact that mini-scale structure is the main locations where the water-soil chemical interaction takes place

Zircon REE and Th, U Characteristics of Metamorphic Rocks from the Dabie Mountains

NI Tao1,2,CHEN Dao-gong1,JIN Ping2

2006, 12(2):  249-258. 

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Micro-scale in situ REE analyses of zircon cores and rims have been carried out for eclogites from Xindian, Shuanghe, Huangzhen and jadeite quartzite from Shuanghe, Dabie Mountains. Combining with the CL internal structure and U-Pb to the metamorphic zircon dating, during we studied the zircon REE composition change from the protolith inherited zircon the ultra-high pressure metamorphism. The results show that the inherited core and metamorphic rim have quite different REE contents. It depends on how metamorphic zircon forms, overgrowth or recrystallization of protolith zircon. In general, the metamorphic zircon rims have lower REE contents compared with the protolith cores, especially in HREE. The metamorphic rims also have lower Th/U ratio than that of the cores. Detailed comparative study on REE and Th/U ratio of inherited zircon cores and metamorphic zircon rims may provide important information on forming process of metamorphic zircons and physico-chemical environment when it forms