广州航空邮件处理中心土洞及桩端软土层处理工艺研究     

王干文 《中国煤炭地质》2008,(8):42-46

广州航空邮件处理中心位于岩溶发育地区,场区内存在大量土洞、溶洞等不良地质现象。该建筑物拟采用静压桩基础。为保证建筑物及场道安全,须对场区土洞进行处理。结合场地具体情况和施工工期要求,首先对大体积土洞进行泵注细石砼骨料充填处理,以消除地面大面积塌陷的危险,消灭压桩机械施工安全隐患,然后开始进行静压桩基础施工,同时在场地允许区域对中小体积土洞、桩端软土层等分别进行泵注砂浆骨料和袖阀注浆处理．以确保洞体密实和保证桩基承载力。通过对处理工艺、处理范围的比较筛选和对质量控制要点、施工技术要点的分析提炼．达到了施工简便、造价合理、安全高效的目的,并采用骨料取芯检测、土体标贯试验和压缩试验、洞体物探等多种检测手段,完全达到了设计要求,取得了良好的工程效果和经济效益。  相似文献   

Chernobyl radiocaesium in a karst system,Marble Cave,Crimea     

A. B. Klimchouk  V. V. Gudzenko 《Environmental Geology》1996,28(3):161-166

 Surface contamination with radioactive caesium introduced into the environment after the accident at the Chernobyl nuclear plant was high enough in the Crimean Mountains to allow using radiocaesium as an indicator of penetration of radioactive contamination into a karst system. Caesium concentrations have been studied in soils above Marble Cave, Tchatyrdag Plateau, in percolation waters and in sediments transported by percolation waters within the cave. Contamination of the daylight surface with ¹³⁷Cs is about 30 kqB m^–2 which is approximately 13 times higher than the density of global fallouts. Besides ¹³⁷Cs, almost all samples showed presence of ¹³⁴Cs with the ¹³⁷Cs/¹³⁴Cs ratio close to that of Chernobyl contaminations. Concentrations of ¹³⁷Cs range from 9 to 15 mBq l^–1 in the present percolation waters in the cave. In sediments related to percolation waters ¹³⁴Cs is detected in some samples besides ¹³⁷Cs, although the effect of ²²⁸Ac is not ruled out. Surprisingly, the highest concentrations of radiocaesium were measured in "old" sediments in the cave's lower series. These sediments are not associated with modern percolation and are represented by a clay/moonmilk alternating sequence deposited in an old dried cave lake. Moonmilk layers have higher caesium content than clay. It is assumed that Chernobyl caesium was transported into the cave with aerosols which were then deposited mainly in areas where condensation occurs. The sampling site is located just in the boundary between two microclimatic zones with a temperature gradient of 0.5  °C. Active condensation processes occur in this area. Caesium was not detected in another similar sampling site (old lake deposits) located within homogeneous microclimatic conditions. If the above interpretation is correct, these results show the geochemical significance of the aerosol-condensation mechanism of mass transport and localisation. Received: 1 June 1995 · Accepted: 4 December 1995  相似文献   

A multivariate statistical and geostatistical study on the geochemistry of allochtonous karst bauxite deposits in Hungary     

Bárdossy  George  Kovács  Ó. 《Natural Resources Research》1995,4(2):138-153

A geochemical evaluation of the Szc-Halimba-Kisld area, Hungary, covering an area of more than 200 km² is presented using different statistical and geostatistical methods. The study area is a representative example of allochtonous karst bauxite accumulation. The three groups of deposits studied here have been explored and mined since 1950. Several thousand boreholes have been drilled, and bauxite cores were analyzed for the five main chemical components. A total of 80,000 pleces of analytical data were processed, followed by a geological examination of borehole logs and of mining excavations.The quantitative geochemical evaluation of the data set led to both geochemical and practical results: The geochemical behavior of the allochtonous, clastic karst bauxite deposits differs essentially from that of the autochtonous and parautochtonous ones, as well as that of the lateritic bauxite deposits. The deposits of the study area can be split into several subsequent geochemical-sedimentological units, each representing an event of bauxite transport and accumulation. Clear regional patterns can be revealed in the composition of these units. The geostatistically measured chemical variability of the geochemical units is rather different, the lowest units showing the smallest variability. The interrelations of the main chemical components are weaker and more irregular in the studied deposits than in the autochtonous lateritic bauxite deposits. Additional local genetic features, such as transport routes, can be delineated by the methods applied. Within each deposit, local changes of chemical composition and of its variability can be determined more precisely. These results can be used in bauxite prospecting and exploration, because areas of high or low bauxite quality can be predicted.  相似文献   

Hydrology and hydrogeology of Sakaryabaşı Karstic springs, Çifteler, Turkey     

G. Günay 《Environmental Geology》2006,51(2):229-240

The Sakarya River is one of the largest rivers in Turkey and is fed mainly from Sakaryabaşı springs. The Sakaryabaşı springs are located in the Central Anatolia and issue from confined/semi-confined karst having a thermal component and therefore, having quite different hydrogeological characteristics as compared to the Taurus Karst region, a typical example of the Mediterranean type of karst. The karstic carbonate rocks that form the groundwater reservoir are overlain by a thick semi-pervious overburden of mainly clastics of Neogene age. Tectonics is the major factor controlling the occurrence of the karst springs in the area where topography is rather flat. This study aimed at explaining the occurrence and movement of the karst groundwater within the system by use of hydrogeological, chemical, and isotopic tools. Isotopic composition of the waters revealed that all waters in the region are of meteoric origin and the thermal component is due to deep circulation. The catchment area of the hydrogeological system extends to the south and groundwater movement is towards the outlets, which are in a depression along a major fault. The movement of the groundwater, based on analysis of remotely sensed images, is controlled mainly by structural elements.  相似文献   

Soil quality changes in land degradation as indicated by soil chemical, biochemical and microbiological properties in a karst area of southwest Guizhou, China   总被引：7，自引：0，他引：7  

Pingjiu Zhang  Lianqing Li  Genxing Pan  Jingchen Ren 《Environmental Geology》2006,51(4):609-619

Not only the nutritional status and biological activity but also the soil ecological functioning or soil health has been impacted profoundly by land degradation in the karst area of southwest China where the karst ecosystems are generally considered as extremely vulnerable to land degradation under intensified land-use changes. The objectives of this study are to elucidate the changes in overall soil quality by a holistic approach of soil nutritional, biological activity, and soil health indicators in the karst area as impacted by intense cultivation and vegetation degradation. Topsoil samples were collected on selected eco-tesserae in a sequence of land degradation in a karst area of southwest Guizhou in 2004. The soil nutrient pools of organic carbon (C_org), extractable extracellular carbon (C_ext), total soil nitrogen (N_t), alkali-hydrolyzable nitrogen (N_ah), total phosphorus (P_t), available phosphorus (P_a) were analyzed by wet soil chemistry. The soil biological properties were studied by means of measurements of microbial biomass carbon (both by fumigation–extraction, FE-C_mic, and by calculation from substrate-incubation respiration, SIR-C_mic) of respiration [respiration without addition of substrates, basal respiration (BR), and potential respiration (PR) with substrate-incubation] and of soil enzyme activities (invertase, urease, and alkaline phosphatase). Soil health status was assessed by simple indices of C_mic/C_org and BR/C_mic in conjunction with bacterial community structures determined by polymerase chain reaction and denaturing gradient gel electrophoresis. While the nutritional pool parameters, such as C_org and C_ext, described basically the changes in soil life-supporting capacity with cultivation interference and vegetation declined, those parameters of biological activity such as FE-C_mic, SIR, and SIR-C_mic as well as bacterial community structures measured by molecular method evidenced well the changes in soil functioning for ecosystem health with the land degradation.  相似文献   

Karst groundwater protection in the Kupa River catchment area and sustainable development   总被引：1，自引：0，他引：1  

B. Biondić  R. Biondić  S. Kapelj 《Environmental Geology》2006,49(6):828-839

One of the most significant water resources in the Republic of Croatia is the catchment area of the Kupa River, located in the region bordering the Republic of Slovenia. About 88% of the total amount of water in this catchment originates in Croatia and just 12% from Slovenia; therefore, the largest part of the catchment area (about 1000 km²) is on the Croatian side of the border. It is a typical karst area of the Dinarides with aquifers characterized by a relatively rapid water exchange, high groundwater flow velocities and aquifers open to human impact from the surface. Consequently, the aquifers are highly vulnerable and at risk. Due to the availability of large quantities of high-quality spring water (about 6 m³/s), the entire area has a strategic importance within the context of any future development strategy pertaining to the western part of Croatia. The catchment area on the Croatian side was investigated using a wide range of research methods that included a classical hydrogeological approach, the detailed hydrologic calculation of water balance to the hydrogeochemical analyses and modelling. The objective was to determine protection zones and protection measures for the whole area. The difficulties are increased due to the fact that the karst catchment area is crossed by major traffic corridors, oil pipelines and a railway and that many settlements and a highly developed wood industry are present. The combination of protecting water resources with adequate prevention measures and necessary remedial activities that should satisfy the very strict requirements necessary for the protection of the karst aquifers while still allowing for present and future human activities is difficult – but not impossible – to achieve. One good example is the present highway with a closed dewatering system and waste water treatment before the water passes into the karst underground system.  相似文献   

The vulnerability of karst springs—a case study of the Hubelj spring (SW Slovenia)   总被引：3，自引：0，他引：3  

B. Trček  M. Veselič  J. Pezdič 《Environmental Geology》2006,49(6):865-874

The hydraulic behaviour of the karst aquifer in the Hubelj spring catchment area (SW Slovenia) was studied by using an indirect research method based on natural tracers. The variations of natural tracers (in precipitation and in groundwater) during the storm event made possible the separation of the Hubelj spring storm hydrograph by the three-component separation technique. The results produced information on the aquifer recharge, storage and discharge processes, as well as on the mechanisms that affected them. They verified the so-called epikarst hypothesis presuming that an important part of a karst aquifer recharge reaches rapidly and intensively from the epikarst zone. It was demonstrated that epikarst water could occupy up to 50% of the spring discharge during precipitation events. This phenomenon could have important consequences on protection and management of the problems of karst aquifers, including engineering problems in karst areas. With this respect the results could give way to new engineering ideas.  相似文献   

A new approach for the development and management of brackish karst springs     

Athanasios Maramathas 《Hydrogeology Journal》2006,14(7):1360-1366

A new approach to the method of artificial upraising of the water outlet point, for management and development of brackish karst springs, uses the MODKARST model. Brackish karst springs simulation can be used to estimate the necessary upraising of the spring elevation, so that sea-water intrusion is blocked. The consequent freshwater loss to the sea, due to this upraising, can also be estimated. The method has been applied to the periodically brackish karst Almiros spring at Heraklion of Crete, Greece. The spring simulation showed that the sea-water intrusion could be prevented through an artificial upraising of the water-outlet point, realized by the construction of a dam. The exact upraising has been estimated. Freshwater loss to the sea because of this upraising has also been estimated. The model could also be used as a tool for the management of the spring. For example, it was used to assess management options for the spring during the depletion period of the year 1994. The best scenario for the development of the spring during this period has been estimated.  相似文献   

Quantification of karst aquifer discharge components during storm events through end-member mixing analysis using natural chemistry and stable isotopes as tracers   总被引：1，自引：1，他引：1  

Daniel H. Doctor  E. Calvin Alexander Jr  Metka Petrič  Janja Kogovšek  Janko Urbanc  Sonja Lojen  Willibald Stichler 《Hydrogeology Journal》2006,14(7):1171-1191

Karst aquifer components that contribute to the discharge of a water supply well in the Classical Karst (Kras) region (Italy/Slovenia) were quantitatively estimated during storm events. Results show that water released from storage within the epikarst may comprise as much as two-thirds of conduit flow in a karst aquifer following rainfall. Principal components analysis (PCA) and end-member mixing analysis (EMMA) were performed using major ion chemistry and the stable isotopes of water (δ¹⁸O, δ²H) and of dissolved inorganic carbon (δ¹³C_DIC) to estimate mixing proportions among three sources: (1) allogenic river recharge, (2) autogenic recharge, and (3) an anthropogenic component stored within the epikarst. The sinking river most influences the chemical composition of the water-supply well under low-flow conditions; however, this proportion changes rapidly during recharge events. Autogenic recharge water, released from shallow storage in the epikarst, displaces the river water and is observed at the well within hours after the onset of precipitation. The autogenic recharge end member is the second largest component of the well chemistry, and its contribution increases with higher flow. An anthropogenic component derived from epikarstic storage also impacts the well under conditions of elevated hydraulic head, accounting for the majority of the chemical response at the well during the wettest conditions.  相似文献   

Interpreting tracer breakthrough tailing in a conduit-dominated karstic aquifer   总被引：1，自引：2，他引：1  

N. Massei  H. Q. Wang  M. S. Field  J. P. Dupont  J. Rodet 《Hydrogeology Journal》2006,14(6):849-858

Breakthrough tailing has been observed during dye-tracing recovery tests in the Norville aquifer system (chalk), France. Karst-conduit flow and transport parameters were assessed using two different interpretative methods: the linear graphical method and the Chatwin method (implemented in the Qtracer2 program). The linear graphical method was used to model the observed tailing effects, which was explained by a second smaller delayed breakthrough curve. By comparing the results of tracer-test interpretation for the two methods, it was possible to relate the area of this second curve to the importance of turbulent flow in spring discharge. The more turbulent the flow, the less important the contribution of the second breakthrough curve and the tailing effect. The observed tailing could possibly be controlled by hydrodynamics to a greater extent than usually expected, the tailing effects being mostly attributed to diffusion phenomena. Tailing effects were expected to increase with discharge and the piezometric level, which would have resulted in overpressure in conduits, fissure flooding, etc. Instead, breakthrough tailing tended to disappear with increasing aquifer discharge, which would support the hypothesis of there being mostly hydrodynamic-controlled tailing effects instead of matrix- or fissure-diffusion.An erratum to this article can be found at  相似文献