Research On Vertical Assessment Of Underground Space Development And Utilization In Changchun City Based On GIS Platform

With the rapid growth of populations and economies,cities are expanding not only outward but also upward.However,due to the dense density of population and limited land resources,urban development is facing many problems,such as human-land conflict,traffic congestion and environmental pollution,so people are beginning to pay attention to the potential of underground space.However,the exploitation of subterranean space is an irreversible project,and blind exploitation may lead to waste and geological disasters.Before exploiting underground space,vertical assessment is a prerequisite and foundation for scientific and reasonable development and exploitation of underground space.Based on the reference of previous research on underground space exploitation,this paper proposes an assessment method for the suitability of underground space exploitation by combining random forest algorithm and GIS platform.According to the data available in Changchun,we analyze the factors influencing the exploitation of subterranean space in Changchun city,and establish an assessment indicators structure in seven dimensions:topographic geomorphology,engineering geology,hydrogeology,adverse geology,human activities,ecological protection,and socio-economic value.The GIS platform was used to process the spatial data,and the random forest algorithm was used to assess and obtain the evaluation results of the appropriateness of underground space development and exploitation in Changchun city.Based on the evaluation of the suitability of underground space exploitation,the capacity assessment model of underground space resources was used to evaluate the capacity of underground space available for reasonable exploitation,and the GOACD software was used for three-dimensional modeling to obtain the assessment results of the capacity of underground space available for reasonable exploitation in the study area.The depth of 50 meters below the surface of Changchun urban area is the object of this study,which is divided into shallow(0～-15 meters),sub-shallow(-15～-30meters)and sub-depth(-30～-50 meters).According to the evaluation results of the appropriateness of underground space exploitation,it is divided into four levels:suitable area(levelΙ),more suitable area(levelΙΙ),poorly suitable area(levelΙΙΙ)and unsuitable area(levelΙV).The assessment results show that:the shallow underground space is mainly of grade I～II,which accounts for 56.35%,and the main constraints are fracture,collapse,ground collapse,surface water body,population density and traffic condition;the sub-shallow underground space accounts for 70.29%of grade I～II,and water-richness,fracture and population density are the limiting factors;in the evaluation of the suitability of the sub-depth layer,grade I～II accounts for 76.54%,of which water-richness and fractures are the limiting factors.According to the assessment of the capacity available for reasonable exploration and use of underground space in Changchun city,the capacity of reasonably exploitable shallow subterranean space is 5.191 billion m~3,and if the calculation is based on 5m story height,the shallow subterranean space can be used to provide 1.038billion m~2 of floor space;the capacity of sub-shallow underground space available for rational exploitation is 6.476 billion m~3,and sub-shallow underground space can be used to provide 1.295 billion m~2 of floor space;the capacity of sub-deep subterranean space that can be reasonably exploited is 7.052 billion m~3,and 1.410 billion m~2 of construction area can be provided by using sub-deep subterranean space,so the available area of underground space is very huge.The assessment of the appropriateness of underground space exploitation in Changchun city and the capacity of rational exploitation of underground space is carried out,and the results can provide reference for the preparation of underground space exploitation planning.