Analysis And Evaluation On Main Engineering Geological Problems Of Some Airport In Guizhou

In China the karst areas distributed widely.The complexity of karst foundation caused a lot of problems on airport construction.Especially in the mountains of southwest China,such as Yunnan,Guizhou,Chongqing,the large scale topographies increases the difficulty of projects and easier to induces krast collapse,slope failure and foundation uneven settlement.So study the main engineering geological problems karst airports makes a difference on airports construction.Based on previous research,relying on original data of engineering geological mapping,drilling,geophysical and field testing,combined with laboratory soil test results,this paper identified engineering geological background,analyzed main engineering geological problems and achieved the following results.(1)The study area located eastern of Sichuan Yunnan meridional structural zone,northern of Nanling EW tending structural zone,which was the secondary regional planation surface.The tectonic unit was the complex area composed of the Guizhou and Guangxi platform syncline’s secondary tectonic units,eastern edge of eastern Yunnan Depression,and left wing of western Guizhou epsilon-type structure.(2)According to he topography and geotechnical structural characteristics,this field region can be divided into three engineering geological zoning which were platform colliculus ridge spinal,ditch source and slope,and trough valley.After analyzed the characteristics of each area comprehensively,the author suggest the two main engineering geological problems were karst stability,high fill slope stability.(3)The field located in position of orientation tableland which was groundwater supply district.Bedrock mainly consisted of limestone and dolomite with highly fractures and poor integrity.These are favorable factors for karst development.Generally,the karst shape is mainly vertical and the growth is from medium to strong degree,strong growth mainly.(4)The karst on surface registers as funnel,sink hole,shaft,soil cave,depression,and clint,solution groove and channel,etc.While the growth underground is mainly composed of karst cave,strong corrosion belt and soil cave.The encountered holes rate of geological drilling is 23.59% and the karst rate is 5.99%.The advantage direction of karst is same to preferred structure planes.(5)Karst stability is mainly controlled by various factors such as lithology,occurrence,physical properties of rock and soil,the strength of tectonism and fractures,groundwater’s storage and migration characteristics,geometry,burial and filling condition of underground caves,and the size of overlying load,and so on.Two methods,civilian airport survey specification and estimating the safety thickness of caves’ roof,were used for semi-quantitative evaluation of karst stability in the field.The result of former is 5 caves with a rate of 21% are unstable while the latter is 7 and29%.The same rate of these two methods is 75%.(6)After calculated the stability factors of three typical high fill slopes in the field,the result suggest that when the slope ratio is 1:2,all of them are stable under natural condition,unstable under earthquake condition and some unstable under storm condition.(7)The author made a numerical simulation analysis with FLAC software on Zhijiadagou high fill slope.The result shows that various parts of this slope have a certain degree change on stress and displacement,especially in the original terrain with larger thickness.