Study On Engineering Geological Environment And Construction Suitability Of Xiong’an New Area

As an important national strategy,the construction of the Xiong’an New Area is of great strategic significance to the integrated development of Beijing,Tianjin and Hebei.The development and construction of Xiong’an New Area,which is a new ecological city,is restricted by engineering and environmental geology.Therefore,conducting research on the suitability of urban construction with full knowledge of engineering and environmental geology of Xiong’an New Area helps reduce or even avoid geological problems caused by engineering construction,greatly facilitates and maintains the coordination between urban environment and development,and provides scientific support and guidance for urban planning and construction.This paper analyzed the engineering and geological environmental conditions of the study area based on the collection and analysis of basic geological data of the New Area,geological survey,drilling and geophysical prospecting.Then,the paper identified the marker strata of Quaternary stratigraphy in Xiong’an New Area by means of lithofacies palaeogeography,climatic stratigraphy,luminescence dating,carbon-14 dating,grain size analysis,magnetic susceptibility testing and chromatic aberration testing.Furthermore,the paper divided the Quaternary engineering geological strata of Xiong’an New Area according to the lithologic assemblage and variation of boreholes.With the above-mentioned work,a 3D geological model of Xiong’an New Area with a depth of fewer than 100 meters was established based on the geological information of 496 boreholes.By analyzing factors that affect the suitability of urban construction,and planning and corresponding regulations of the New Area,a comprehensive evaluation system of suitability for engineering construction at different depths of Xiong’an New Area was developed.Then,the weight was identified by the entropy weight-analytic hierarchy process,and the suitability for engineering construction in different depths of the Xiong’an New Area was evaluated.Finally,with evaluation results,the paper delved into the potential above-ground and underground integrated development and construction mode,and presented suggestions for the overall planning of the New Area.The main research results are as follows:(1)Division of engineering geological strata.Based on the temporal and spatial distribution of special sedimentary rock layers,rock assemblage,the recorded environment of Xiong’an New Area,and the theory of climate stratigraphy,this paper examined the tricky issue of fine division and correlation of Quaternary strata in stable subsidence areas of plain of eastern China and proposed that the stratigraphic cycle of global climate change that reflects the periodic changes of cold and warm climate can be used as the basic unit for fine division and correlation of Quaternary stratigraphic regions in North China Plain.Furthermore,in this study,the climatic transition events were determined,the stratigraphic age framework was established,and the stratigraphic stratification marks of the Quaternary were identified.Then,the Xiong’an New Area with a depth of fewer than 100 meters was divided into 18 engineering geological strata and 87 sub-strata in accordance with the lithologic assemblage and variation of boreholes.(2)Construction of 3D geological model.The engineering and geological environment database was established based on data from basic geology,Quaternary geology,hydrogeology,engineering geology,environmental geology,remote sensing geology,geophysical exploration and geochemistry.According to the division of engineering geological strata,the geological information of 496 engineering geological boreholes in Xiong’an New Area,a 3D geological model of Xiong’an New Area with 1770km ~2and at the depth of fewer than 100m was constructed to reflect the spatial distribution of different engineering geological strata in Xiong’an New Area and their correlations.(3)Establishment of a comprehensive evaluation system for the suitability of engineering construction at different depths above-ground and underground of Xiong’an New Area.The factors affecting the suitability of Xiong’an New Area construction were evaluated by different parts.By examining engineering geological conditions affecting the urban construction of the New Area,five first-class evaluation indexes and ten second-class evaluation indexes were identified,including foundation soil conditions,hydrogeological conditions,environmental geological problems,site stability and available resources of underground space.Then,a comprehensive evaluation system for the suitability of engineering construction of above-ground,shallow underground,sub-deep underground and deep underground of Xiong’an New Area was developed.(4)Comprehensive evaluation of suitability of engineering construction at different depths above and below ground in the Xiong’an New Area.By employing the entropy weight-analytic hierarchy process,the comprehensive weight of each evaluation factor was identified.Then,with cloud theory,the paper proposed an evaluation model that helps examine the suitability of the above-ground,shallow underground,sub-deep underground and deep underground of Xiong’an New Area.(5)Based on the comprehensive evaluation of the engineering construction suitability of Xiong’an New Area,this study delved into the integrated development and construction mode of above-ground and underground space,and presented suggestions for the overall planning and construction of the New Area.It is proposed that efforts should be made to coordinate the above-ground and underground spaces so as to improve the intensity of layered and multifunctional development and utilization of underground space.More consideration should be given to the prevention and control of land subsidence,and enhanced regulation of groundwater and the study of water leakage in Baiyangdian Lake should be conducted.Furthermore,an effective groundwater management and control system shall be put in place to prevent land subsidence,ground fissures or anti-floating problems of buildings caused by the large rise and fall of groundwater.To maximize benefits,minimize negative impacts,and seek development while ensuring prevention,and by taking underground space development,water system and ecological landscape construction,flood control and flood discharge into consideration,the existing pits and ponds shall be fully planned and used to create a city with lucid waters and lush mountains.