The Forming Mechanism And Foreast Of Fatalness About Karst Subsidence In Guilin City

Guilin is a well-known city is famous for its beautiful scenery and culture, it located in thesubtropical karst area. the geologic setting is opened and fragile, it is influenced by the humanproject activity and natural environment factor , ground subsidence took place frequently, accordingto statistics, all kinds of subsidence took place more than 280, it caused serious economic losses ,aroused great concern from many people in society, seriously restrict the fast development of theurban construction, threaten the security of people's lives and properties, it is the typical frequentcity of the karst subsidence. Studying the ground subsidence in history and rule of distribution ofspace-time; Finding out the essential feature of ground subsidence; Studying geologicalenvironment, forming terms, development rule and influence factor, Analyzing this formingmechanism of ground subsidence, setting up the geological model of karst subsidence andEstablishing estimation and predictable method about ground subsidence, taking a divisionalpredictable estimation and bring forward a effectively method of prevent and cure to karst groundsubsidence of Guilin; offering a prevent and cure countermeasure effectively to prevents and curesthe karst subsidence of Guilin, instructing the task of prevention and control; Ensuring people'ssafety of life and property, all have a very important theory and realistic meaning.The geological information, engineering of hydrology, environmental geology, groundwaterlong-term observation information, remote sensing is analyzed and including dividing geophysicsto reconnoitre for the information, drilling project , on-the-spot destructiveness draw water test,indoor simulation test, including all kinds of reconnoitre information of geotechnical engineering,this kind of information of urban area of Guilin is collected . at this foundation, we overall analyzedthe meteorological hydrology, topographical ground forming characteristic , stratum lithology,geological structure , groundwater systematic characteristic of Gui Lin, etc. on the basis ofanalyzing a large number of real data, we have also analyzed the relationship of carbonate mineralcomposition in Guilin, chemical compositions and karst development; and analyzed the relationshipof stratum and lithology, carbonate rock group , geological structure and the karst development.The characteristic of corrosion of horizon D and buried depth, vertical and horizontal developmentrule of underground karst and the fill of underground karst were also analyzed. At the last we alsohave a overall statistical analysis to the space-time distributed characteristic of distributed stratumof the karst subsidence and ground form unit of Guilin, etc. The main research include that groundsubsidence was influenced by the ground forms, The Quaternary system soil horizon lithologystructure, The geological structure, The karst development degree of Guilin; Groundwater of Guilinand the Engineering activity of Human especially pumping and draining between groundwater. ByAnalyzing and researching the test about the model of karst ground subsidence, permeate and out ofshape, a critical condition about karst ground subsidence produce. was got Analyzing testing results,summarizing the basic reason and mode about ground subsidence caused by drainning anddumping groundwater. By Analyzing the effects of mechanics of different subside function,forming condition and mechanism of origin cause of formation of subsidence in the karst region ofGuilin. Was provided all kinds of characteristic of predicted methods. According to that wasanalyzed ground subsidence be caused by complicated geological environment and influence factorthat more producing and the characteristic that restrain from each other, by the way of usingsubsidence influence factors and multiple goal second fuzzy decision method geological calamitydangers of Guilin city and countermeasures was put forwarded karst ground subsidence was welladopted. Effective preventions , curing methods. There are some very important reality anddirective significances in effectively preventing and curing the karst subsidence geological calamityof Gui Lin . in this thesis following achievement here. â… . Basic type and characteristic of the karst subsidence in Gui Lin is found out. Groundsubsidence have the characteristics of obvious space-time. It's space-time distribution has the groupquality, directional quality and equidistant quality. It closely related to power degree of humanproject activity, the distribution of subsidenced point have the characteristics of weakening fromurban area to periphery, time distribution has the characteristics that seasonality , periodicity andfrequentness of subsidencing in recent years aggravating year by year, it also has the rules ofsuccession , many issue , intermission and such as being suddenly to subsidence in Guilin karst area.Base rock lithology has a obvious control function to subsidence distribution, the limestonesubsidence of D3r firstly developed, secondly is dolostone of C1y. The most of subsidencesdeveloped in the areas of smaller than 5 meters in the thickness of soil layer, which werecharacteristics of more larger of the thickness of soil layer, the more small subsidenced frequency.The most of subsidence happened in the clay of unary and the area of silty clay. Subsidence ismainly distributed in peak forest plain and terrace. The development of subsidencing is seasonal,more than 90% of the man-made subsidence are caused by drawing. â…¡. Carried on a systematic research on engineering geology environmental terms ofsubsidence forming in Guilin, the corresponding map was also worked out, the controlled factors ofsubsidence was analyzed in depth, this offered the systematic foundation geological information forurban planning, engineering construction, prevent and cure subsidence for Guilin city. â…¢.The relationship between basement rock and ground subsidence was studied, conclusionthat karst development degree in level and vertical is asymmetrical was got. On the flat, the karstdevelopment degree is strengthened gradually from the peak cluster, peak forest plain to theisolated peak plain, from two sides of the east and west to Li river valley, the karst developmentform is from pipeline to netted, underground river system developed; on the vertical, karstdevelopment presented the trend of weaken from shallow to the deep; the faster of Karstdevelopment, be easier to subside, the bigger of subsidence density, the bigger of the scale. â…£. Through analyzing the geological structure of Guilin, it was discovered, that the geologicalstructure development of district has some characteristics of distance nature, zonation and Vunbalanced. Draw a conclusion, that the karst of Guilin mainly took place in the nuclear departmentof fold, incline end, raised end and faulted zone, etc. especially developing mostly in the faultedzone of EW, NE, NW orientaion and the confluent position of every group of fracture. â…¤. We have systematically studied the essential feature of the groundwater of Guilin, andmainly researched these factors that influence the ground subsidence, include groundwater variety,fluctuate frequency of groundwater, strong groundwater runoff, groundwater surface and basalsurface distant, etc. It was analyzed that the relationship of groundwater table fluctuating, throughsuffosion, vacuum suck corrode , change rock soil body physics mechanics nature causing karstground subsidence; especially the relationship of pumping and draining groundwater changing it'sdynamic characteristic due to soil hole development to bring out karst ground subsidence. It drawthe conclusion that the subsidence of 80% more than take place in the strong groundwater runoffshed in Guilin. This offered a scientific basis for predicting and preventing ground subsidence, aswell as correctly dealing with and utilize the groundwater resources. â…¥. By researching the model test about karst ground subsidence, the data about permeate andout of shape test, then the critical condition of karst ground subsidence was produced subsidedcritical pressure of binary and binary above structure soil layer district is 20KPa, Subsided criticalpressure of unitary soil layer district is 40KPa. It offers a scientific quantitive basis for probing intokarst subside mechanism, it was controlled factor, and the subsidence of predicting and preventingand cure. Analyze the production of destructive dumping test, summarized that draining offgroundwater cased the basic reasons and models of ground subsidence. It was also explored that theinfluencing coverage and degree that due to artificial function to subsidence. We considered thatkarst subsidence was due to geological environment naturally mainly, artificial function exerts ainfluence to subsidence often through changing natural environmental factors, it only play abringing out and promoting function. â…¦. Forming environment and developing rule that karst subsidence of Guilin wassystematically researched. Inner links and rules between many kinds of environmental conditionsand karst subsidence was revealed, the karst subsidence was mainly controlled by the geologicalstructure, karst, soil layer nature and groundwater, especially was controlled by constructionobviously. it is Consider that producing karst subsidence is a result of a comprehensive function ofmany kinds of factors work together. The primary conditions about producing karst subsidence ofGuilin, Cap rock of a certain thickness, external effort, especially activity of groundwater. Karstcave interspace is the passway for groundwater moving rock, soil of material, it is also foundationof producing karst subsidence. The touching off factors about producing subsidence is variouskinds of efforts of nature and human project (groundwater activity, earthquake force , top loadstrength , vibration strength ,etc.). The most active and important dynamical factor in the formingprocess is the change of Water table level, range of changing, frequency and water dynamicalcharacteristic. Karst cave interplace, which was formed from the groundwater long term corrosionfunction to the soluble rock offered the essential condition. The karst mainly distributed along thelocation of the strong development of karst, The karst develop mainly along horizon of carbonaterock more pure, rupture broken cingulum, fold axis department and the tangent cingulum of soluble...