Suitability evaluation of utilizing urban underground space in the karst area in Gui'an New Area
In recent years,with the continuous acceleration of urbanization in China,the development and utilization of ground space and aboveground space have gradually become saturated,and various"urban diseases"such as traffic congestion,land resource shortage,ground noise are increasingly severe.Therefore,reasonable development and utilization of urban underground space is of practical significance to alleviate the scarcity of urban resources,improve environmental conditions,and enhance the quality of residents'life.Located in a typical karst mountainous area on the plateau of central Guizhou,Gui'an New Area not only faces common problems in its urban development such as insufficient land for human due to the unique karst landform of this area,but also faces many engineering geological problems such as karst collapse,mud and water inrush during the development and utilization of underground space.At present,the utilization of urban karst underground space in Gui'an New Area is still in the early stage of planning and implementation.It is necessary to investigate the structural characteristics of underground space,explore and demonstrate the methods applicable to evaluate the suitability of utilizing underground space in karst areas before the large-scale development of underground space.Based on the planning of constructing urban underground space in Gui'an New Area,this study takes the ecological new town in Gui'an New Area as an example.According to different karst hydrogeological units(water-bearing media),it proposes a conceptual model for underground space utilization through comprehensive geological surveys,engineering surveys,and groundwater dynamic monitoring.This study also establishes a suitability evaluation system and method for utilizing underground space according to different zones and layers with groundwater system units.The suitability evaluation of underground space utilization in typical karst areas has been conducted by using the ArcGIS platform,and targeted suggestions have been proposed.The research results indicate as follows,(1)For the utilization of semi-underground space,14.97％of the space may fall into the grade of very high suitability,21.14％of high suitability,22.36％of low suitability,and 41.52％of very low suitability.Due to the degree of terrain undulation and rock fragmentation of the strata,the unsuitable area for utilization in semi-underground space is mainly concentrated in the fault zone and the area at relatively low elevations.In the areas with high levels of engineering excavation and subway construction,the availability of semi-underground space is also relatively low.For the utilization of shallow underground space,10.54％of the space may fall into the grade of very high suitability,33.52％of high suitability,33.28％of low suitability,and 23.66％of very low suitability.Shallow underground space mainly falls into the utilization grades of low and very low suitability because it is generally affected by geological structure,stratigraphic lithology,surface water system,karst development degree,and human excavation.The area with high suitability for utilization is located in a small part on the east side of the high-speed railway station,but it is controlled by the karst groundwater system.Consequently,this area is difficult to be utilized and the excavation is likely to change the groundwater flow field,which can cause problems such as karst water gushing,mud bursting,or karst collapse.For the utilization of sub-shallow underground space,27.3％of the space may fall into the grade of very high suitability,16.64％of high suitability,26.45％of low suitability,and 29.6％of very low suitability.The grades for the use of sub-shallow underground space mainly fall into low and very low suitability(totaling 56.05％).The utilization of sub-shallow underground space is greatly influenced by the development level and structure of groundwater and karst,but is not closely related to the engineering construction and utilization of semi-underground space.The utilization of underground space is significantly controlled by the construction of shallow subways and other engineering projects.Overall,the geological environment conditions of sub-shallow layer are slightly poor,and the rock mass in the structural and karst development areas is broken,which increases the difficulty and cost of underground engineering construction.To prevent environmental geological problems like the water inflow of foundation pit and karst collapses,it is recommended to take reasonable measures such as the foundation pit enclosure during underground engineering construction.(2)The establishment of evaluation method based on the units of groundwater system and the ArcGIS platform is convenient and practical,and the reliability of evaluation results have been verified.(3)The underground space in karst areas is significantly constrained by factors such as karst collapses,geological structures,karst pipeline development,and conditions of groundwater recharge and drainage.Before the development and utilization of underground space in karst areas,it is recommended to accurately delineate the groundwater system,investigate groundwater dynamics,take precautions to geological disasters such as water inrush and karst collapse,conduct suitability evaluations,comprehensively analyze the types of underground space utilization and limiting factors,and clarify karst hydrogeological conditions.For areas with low suitability,reasonable planning or preliminary engineering treatment should be carried out to obtain ecological,economic,and environmental benefits in a coordinated way.Under the premise of scientifically protecting underground space resources and the ecological environment,the maximization of development and utilization benefits should be achieved.The evaluation results are significant for the guidance of constructing Gui'an Station,Metro line S1,and the surrounding underground comprehensive pipe galleries in Gui'an New Area.The results are also of practical significance for promotion of the scientific development and utilization of underground space,protection of resources and ecological environment,and prevention and control of geological disasters in karst areas.
Gui'an New Areakarst areaurban underground spacesuitability evaluation
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