| The geological and environmental conditions in the southwestern mountainous areas are complex,and the geological environmental issues in urban areas are prominent.Many old urban areas have insufficient intensity of land use and urgently require quality improvement and upgrading under the requirements of new urbanization development.The old town area of Dafang County in Guizhou Province is built on an ancient landslide accumulation body,which has been continuously creeping and deforming since the end of the 19th century.On the one hand,there is the rapid development of towns under the background of land shortage,and on the other hand,the landslide deformation has caused house cracking,ground deformation,and social panic.What is the risk of urban areas on ancient landslides?Does the new urbanization construction have security guarantees?How to efficiently use limited land resources?These are the real problems that urgently need to be answered in the old town area of Dafang County.This study analyzes the mechanism of the geological and environmental system in the southwestern mountainous areas of China and urban development,proposes a theoretical method for evaluating the carrying capacity of the geological environment in southwestern mountainous areas,and pilot tests the method in the development and utilization planning of the old town area of Dafang County and the new urbanization construction,which has important practical significance and theoretical value.Based on the above research background,this study focuses on the key scientific problem of"theoretical method for evaluating the carrying capacity of the geological environment in southwestern mountainous urban areas,"takes the old town area of Dafang County as the research area,and carries out a comprehensive urban geological survey.Using a combination of environmental geology,urban geology,ecological geology,hydrogeochemistry,and numerical simulation techniques,the study investigates the geological environmental issues and carrying capacity evaluation method in southwestern mountainous urban areas,the deformation law of the ancient landslide accumulation body in the old town area of Dafang County,and the geological environmental carrying capacity evaluation of the old town area of Dafang County.The study uses a multi-barrel combination model that characterizes carrying capacity,risk,capacity,and suitability relationships to quantitatively analyze the geological environmental carrying capacity of the old town area of Dafang County and draw up optimized distribution proposal maps for different functional land use.The research results can provide reference for the evaluation of the carrying capacity of the geological environment in southwestern mountainous urban areas and the national land-use functional zoning.The main research results of this thesis are as follows:Study on the geological environment of urban areas in Southwest Mountainous Area(1)The Southwest Mountainous Area is located in the transitional zone between the first and second terraces of China,with strong new tectonic movements dominated by intermittent uplift movements,forming multi-level terrace landscapes.Cities and towns are distributed on various types of terraces.Statistical results for 400 cities and towns in the three southwestern provinces(Yunnan,Guizhou,and Sichuan)show that55%of the cities are on flat terraces,40%on river valley terraces,and 5%on slope plateau terraces.(2)The zoning of the geological environment in the Southwest Mountainous Area mainly involves four categories:the unstable zone of the regional crust,the plateau and canyon area,the karst rocky desert area,and the mineral resource-rich area.The main geological environmental problems of urban areas in the unstable zone of the regional crust are landslides,collapses,debris flows,soil liquefaction,and dammed lakes induced by earthquakes.The main geological environmental problems of urban areas in the plateau and canyon area are landslides,collapses,and debris flow disasters.The main geological environmental problems of urban areas in the karst rocky desert area are desertification,collapses,karst subsidence,landslides,and structural water shortages.The main geological environmental problems of urban areas in the mineral resource-rich area are geological disasters induced by mining activities and soil and water pollution caused by mining pits.(3)The core of the new urbanization is to promote the urbanization construction based on county towns,and to create livable,resilient,and smart cities.The geological environmental problems faced by the new urbanization in the Southwest Mountainous Area mainly include landslides,collapses,debris flows,karst subsidence,foundation instability,desertification,soil and water pollution,scarce land resources,structural water shortages,soil erosion,ecological environment deterioration.Theoretical methods for evaluating the geological environmental carrying capacity of urban areas in the Southwest Mountainous Area(1)The evaluation factors of the geological environment in the Southwest Mountainous Area are divided into four categories:spatial,resources,environment,and disasters.Spatial factors have a moderate correlation with resource,environmental,and disaster factors.Water resources,arable land resources,and geological relic resources in resource factors have a strong correlation with other factors,and have a strong restrictive effect on spatial and environmental factors.Landslides,debris flows,and floods in disaster factors have a strong correlation with other factors,and have a strong restrictive effect on other factors,and have a bidirectional restrictive effect on spatial factors.Ecological factors in environmental factors also have a significant restrictive effect on other factors.(2)A method for evaluating the geological environmental carrying capacity of urban areas based on the multi-barrel model is proposed.When considering the correlation and restrictive effects among different geological environmental factors,the correlation barrel theory of geological environmental factors is adopted.When studying the relationship between environmental governance projects and risk tolerance in geological environmental carrying capacity,the geological environmental risk barrel model is used.For the study of the relationship between the carrying capacity of resource and environmental factors and resource guarantee level,environmental capacity,and environmental risk,the resource and environmental barrel model is used.When considering the relationship between spatial carriers and population,the barrel model of geological environmental suitability for different functional land uses is adopted.The carrying capacity is evaluated through risk,environmental capacity,and suitability,etc.Deformation characteristics and risk assessment of the slope body in the old town area of Dafang County(1)The landslide in the old town area of Dafang County occurred around30700±170 BP.Currently,the slope body is generally stable,but in areas with thick cover layers and steep slopes,it is in a state of basic stability-undesirable stability.The slope continues to deform,with a surface deformation rate of about 14mm/year in the strong deformation zone,a displacement deformation rate of 70—92mm/year at a depth of 5m,and a displacement deformation rate of 52—71mm/year at a depth of12m.The influence of three factors,excavation of foundation pit,precipitation,and building loading,on the deformation rate in the strong deformation zone is:building loading>excavation of foundation pit>groundwater level.(2)The slope risk assessment of the old town area of Dafang County shows that the safe area accounts for 4.2%,the relatively safe area accounts for 53.5%,the relatively dangerous area accounts for 30.6%,and the threatened area accounts for11.7%.The areas with high vulnerability of buildings are mainly distributed in the northeast area where the houses are made of wood.Most of the buildings in the urban area have low risk,and high-risk areas are distributed in the southern part of the urban area,which is related to the high vulnerability of buildings and the high risk of slope deformation.Water resources and groundwater environmental capacity assessment in the old town area of Dafang County(1)Dafang County has an annual available water resources of 423 million cubic meters,which can meet the demand for water resources for urban development.The water supply in the central urban area is 77,400 cubic meters per day,which can meet the water supply demand for the maximum daily water consumption of 63,000 cubic meters in 2035.The county has a high degree of water resources security,but there is a structural shortage of water.(2)The results of groundwater environmental capacity assessment show that the high-capacity area is 1.77km~2,accounting for 22%;the general capacity area is3.33km~2,accounting for 42%;the low capacity area is 2.69km~2,accounting for 34%;and the overloaded area is 0.17km~2,accounting for 2%.The overall water environment capacity is good.Land suitability assessment for construction in the old town area of Dafang County(1)The results of the geological environmental suitability assessment for residential land in the old town area of Dafang County show that the unsuitable area is1.31km~2,accounting for 16.5%,the area with poor suitability is 1.40km~2,accounting for 17.6%,the area with relatively suitability is 2.39km~2,accounting for 30.1%,and the unsuitable area is 2.85km~2,accounting for 35.8%.(2)The results of the suitability evaluation of commercial land geological environment in the old town area of Dafang County show that the unsuitable area is0.90km~2,accounting for 11.3%,the areas with poor suitability are 2.47km~2,accounting for 31.0%,the areas with relatively suitable suitability are 4.42km~2,accounting for55.5%,and the unsuitable area is 0.17km~2,accounting for 2.1%.Most of the old town area in Dafang County is suitable for residential and commercial land planning.Evaluation of geological environment carrying capacity in the old town area of Dafang County(1)Based on the"short board effect"of a barrel,the geological environment carrying capacity of the old town area of Dafang County was characterized by the comprehensive results of construction land,total building area,and population,which is 134,400 people.Currently,the old town area has a population of approximately91,400 people,and the future population is expected to be between 130,000 and140,000,with a surplus carrying capacity of 40,000 to 50,000 and significant room for population growth.(2)Areas I and II are located in a zone with relatively high instability of landslide deposits.Future plans will include the formation of luxury fragrant park and Dafang cultural ecological axis,with a suggestion to mainly build low-rise buildings.Future buildings in Area III will mainly consist of multi-story buildings.Currently,Areas IV and V mainly have single-story or low-rise buildings and are relatively easy to transform as part of the old town renovation.The main buildings in the VI district are mainly medium and low-rise buildings,forming a tourist resort accommodation area.For areas VII,Ⅷ,IX,and X,it is recommended to build mainly multi-story buildings with appropriate high-rise buildings interspersed.Area XI is the current new building area of Dafang,and mainly consists of residential land with multi-story buildings.This article has formed a theoretical method suitable for the evaluation of geological environment carrying capacity in southwestern mountainous urban areas,which has been applied in the renovation plan of the old town area of Dafang County,and has reference value for similar urban planning and construction.The innovations of this article are mainly reflected in:(1)Based on the traditional barrel model,a multi-barrel combination model is proposed,which characterizes the relationship between carrying capacity,risk,capacity,and suitability by combining barrel boards(geological environmental elements),drainage valves(disaster-bearing bodies),solutions(water and soil environments),and color codes(suitability levels).A quantitative analytical method is proposed,combined with the renovation example of the old town area of Dafang County.(2)Based on the creep law of old landslides,an improved constitutive creep model is proposed,and a risk evaluation and quantification model method for engineering construction and operation is formed by simulating excavation of building foundation pits,precipitation,and building loading in the renovation of the old town area. |
PDF Full Text Request