Study On Karst Spatial Differentiation In The Anticline Of Mingyuexia Gorge Based On Hydrologic Network Control

Carbonate rocks are widely distributed in China.Karst development usually presents spatial heterogeneity due to the differences in tectonic lithology,topography and geomorphology,hydrological conditions and other factors.As a result,engineering construction in karst areas is often faced with many geological disasters and ecological environment problems that cannot be predicted scientifically,such as karst inrush,reservoir leakage,groundwater level decline,karst collapse and so on.Caused serious casualties and economic losses.The carbonate rocks in the isolated fold belt of Eastern Sichuan show a unique pattern of groundwater circulation and karst development under the action of non-dissolvable rock.The ability to control groundwater circulation is different in different cut depth,which affects the depth and intensity of karst development.The relationship between the development of karst and the cutting depth of river valley in Eastern Sichuan was analyzed.It provides theoretical support for the future transportation corridor construction in Eastern Sichuan.This paper takes the anticline of the moon gorge as the research object.The hydrogeology and experimental data of the Eastern Sichuan and the Mingyue gorge anticline were collected.It discussed the groundwater runoff pattern and groundwater circulation pattern under the control of different discharge datum level in the Mingyuexia anticline.To establish the development model of underground karst space.Finally,based on the study of the characteristics of karst spatial differentiation,the groundwater circulation and the development of underground karst in the southern section of the Mingyuexia anticline was studied.The following conclusions are drawn from the above research:?1?Under the background of spacer type of geological structure,on the basis of anticline zone gully cutting depth discharge of underground water,can be divided into horizontal type shallow cut valleys,horizontal type deep valleys,throughout the valley drain datum.The horizontal shallow cut and deep gully control the shallow circulation of karst groundwater,and the deep circulation of karst groundwater is controlled through the shallow gully.?2?Karst is mainly developed in the Jialing formation and the Leikou formation in the Mingyuexia anticline.The karst development is the strongest in the southern part.In the middle section,the karst is moderately developed,and the number of karst rock outcrops,depressions and sinkholes is relatively small,but the number of karst caves and springs is similar to that of the southern section.The karst development in the northern section is weak,and there are less development in the depressions,the sinkhole and the spring point.In general,the karst development is strongest in the southern section,moderate in the middle section and weak in the northern section.?3?The groundwater runoff was divided into three sections:south,middle and north,according to the difference of the development density and cutting depth of the cross-cutting gully in Mingyuexia anticline.The northern section is far away from the through-river valley,and mainly consists of shallow horizontal drainage ditches.In the middle section,karst groundwater mainly drains into deep horizontal gullies.Between deep gullies,a small number of shallow branch gullies drain into local groundwater runoff.The southern section is mainly controlled by the Yulinhe river through the river valley,the south of the village is mainly to the Yulinhe drainage,in addition to the north by the Yulinhe runoff drainage,there are some shallow groundwater to the horizontal drainage.?4?On the plane of the mingyue gorge anticline,the law of karst differentiation is characterized by horizontal and vertical differentiation.The results show that the karst differentiation of Permian strata in anticlinal uplift is an alternating process of weak-strong-weak,while the karst differentiation of Triassic strata from the core to the two wings is a process of strong-weak.The vertical karst differentiation characteristics are shown as the cutting depth of different hydrological network types from shallow to deep.The strength of karstification is usually from strong to weak.?5?The development modes of karst caves in the Mingyuexia anticline and the Eastern Sichuan fold belt can be roughly divided into multiple karst development modes,double karst development modes and single karst development modes.The development pattern of multiple karst caves is that the karst caves on the steep cliffs on both sides of the river valley have multiple layers of karst caves in vertical direction,and the vertical underground river system also shows the development of multiple steps.The development mode of double karst cave is shown as the transverse deep gully,which controls the underground karst development by controlling the groundwater runoff on the one wing of the anticline and the nuclear part.The single karst cave development model shows:the underground karst development controlled by transverse shallow cut gully can adapt to the lower cut of gully,with obvious timeliness,and the basic performance is the water-filled karst cave.?6?The groundwater circulation in the south section of the Mingyuexia gorge anticline is controlled by the transverse shallow cut gullies of the through-river valley.The karstification degree of the solvable rock stratum is shown as T₁j>T₂l>T₁f³>P₂c>T₁f¹,among which the Jialing river formation T₁j²?T₁j⁴>T₁j³?T₁j¹.The form of karst geomorphologic assemblage has gradually changed from karstic mountains in the anticlinal uplifted area to shallow hills and depressions.There are five layers of karst development zones in the southern section of the Mingyuexia anticline,which is above 180-250m,300-350m,480-540m,650-700m and 800m respectively.