| Karstareas in SouthwestChina are extensively developed,and the hydrogeological conditions of the project are complicated.The engineering safety problems caused by karst development emerge in an endless stream,which has a great influence on the safety of the construction of the project.It is of great significance to find out the distribution and development law of the karst and to find ways to govern the situation according to local conditions.Based on the investigation and study of Longdongbao Airport expansion project,this paper analyzes and studies the hydrogeological structure of the field area through the field investigation of the topographic features,stratigraphic structure,regional hydrology,regional tectonics,surface and underground karst distribution characteristics of Longdongbao Airport Characteristics,the use of mathematical statistics analysis method to explore the law of karst development and its main control factors,analysis of the airport construction may bring the hydrogeological problems,and put forward the measures and recommendations.The main conclusions are as follows:(1)On the distribution characteristics of karst,the study area is located in the watershed,the karst form is vertical,the overall development is moderate,and the local fault affects the belt strongly.The surface karst is mainly distributed in depressions,karst caves,karst troughs,dissolved troughs and stone teeth,karst funnels and sinkholes.The underground karst is mainly composed of pipe gap,fissure karst cave,dissolution fracture zone and soil cave.On the plane,the karst development degree is higher,the area distributes in the northeast end and the south end of the study area,and the middle area is relatively weak.The karst depressions and sinkholes are arranged in a linear and beaded direction,and the most developed areas are the karst cave and the residual hill area.There are concentrated distribution zones of karst caves,and the strong dissolution and fault zones are banded along the fault passing zone.Vertically,the karst development is characterized by layered distribution,and the karst caves and erosion zones at the height of 1040 m to 1060 m are most developed,and gradually decrease to both sides.(2)Criteria with reference to the existing strength of karst development,statistics based on the area of karst surface density,maximum flow rate,drilling hole rate in spring,karst line rate,put forward the division standard of the strength of Guiyang Longdongbao karst regions,and study area of karst development intensity zoning;(3)Karst development has the following laws: the karst development has directional,karst development is multi-layered,karst development is inherited and it has a tendency toward deep development.The direction of karst is selective for strata,tectonic and geomorphic units,karst study area showed along the lithology boundary development regional tectonic line and development regularity of karst development direction,in addition to also controlled by tectonic joints and fracture;karst development of a multi aspect is multilayer the karst individual form,the study area karst development space elevation is mainly concentrated in 1040 m ~ 1060 m and 1080 m ~ 1120 m two elevation range.At the same time,two or three karst caves were revealed at different elevations in XK332,XK501 and other boreholes.On the other hand,they were reflected in the vertical zonation of underground karst.Study area a large number of drilling revealed an underground karst development degree decreases with the depth increase.From shallow to deep.From cave fracture to transition,has the obvious vertical zonation of karst development;the inheritance and the deep features: The valley area is sheathed in the depression,depression in stacked sinkholes,karst funnel phenomenon,reflect the inheritance and to the depth of point;at the same time,due to the different period of erosion groundwater erosion datum change,cave area pipeline underground river,karst springs in order to adapt to this change as a result of multilayer karst,karst development is to reflect the depth of the straight;the statistics of karst in elevation,the elevation of 1095 m above and below 1120 m range in the karst cave is fractured karst more strongly.Because the development of karst cave is caused by the continuous seepage of surface water,it shows that the study area is in karst development stage,and the karst fissure and pipe gap karst are transforming into cave type cave,which has the trend of deep development;At the same time,the artificial coal-fired heating activities accelerated the formation of acid rain,never exacerbated the dissolution of carbonate rocks,making the regional negative karst topography continue to develop,and become the main controlling factor of karst development in the region.(4)by analyzing the control factors of karst development in the study area,the main controlling factors of karst development are as follows: formation lithology,topography,groundwater chemistry,hydrodynamic conditions and geological structure.Lithology and occurrence control degree of the karst development,performance for the karst northeast runway limestone formation phenomenon is obvious,while the central and Western dolomite karst formation is weak;the effects of topography in the karst development area,the terrain is relatively steep its mountain area,karst in surface morphology,the terrain is relatively flat.Karst area,surface and underground forms are more developed,while in the low-lying Valley(the northern runway)area,karst is developed,and the karst valley,the surface morphology of large scale;development scale and direction of the influence of karst geological structure,surface and underground karst is along the tectonic line is very well developed,and has a certain the direction of karst depressions and karst funnel long axis and Bo Yang Ping fault strike is basically the same,underground cave also has along the tectonic line to send The characteristic of groundwater development is that groundwater affects the development intensity of karst,and shows that the surface water in the northern end of the runway is easy to concentrate and collect lots,and the ground surface and underground karst are very developed.(5)based on the area of solution of hydrogeological condition analysis summary,combined with the characteristics of karst,the study area of engineering area three main karst hydrogeological problems: uneven settlement of foundation,the problem of karst collapses high fill slope instability problems.(6)according to the intensity of karst development in the study area,combined with the main parts of karst engineering geological problems,the hydrogeological division of the karst engineering is carried out in the flying area:The karst development region and the weak soil distribute widely in the northern and southern parts of the flying area;The karst area in the middle part of the flying area develops moderately and the soft soil distributes less area;Theslope area.For different partition regions.According to karst phenomena,karst engineering problems and karst water problems,different treatment measures and suggestions are put forward. |
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