Comprehensive Exploration And Hydrogeological Characteristics Of The Suspected Collapse Column In The Xinjulong Mine In Shandong Province

In January 2013,in the eight mining area of the Shandong Xinjulong Energy Co.,Ltd,it was found by the three dimensional seismic exploration that there is a geological anomaly with a suspected collapse column in the middle of the Huangtang syncline,which has a strike toward northwest,with a major axis of approximately 296 m,a minor axis of approximately 148 m.Its upper boundary reaches the B layer of the bauxite,the lower reaches the Ordovician limestone.In order to further identify the existence and water-richness as well as the hydraulic connection of the collapse column and aquifers.The electric prospecting work was carried out on the suspected collapse column area on September 2014.The resistivity of the northwestern part of the suspected collapsed column shows anomalous characteristics of low resistivity by a analyzing the electrical profile and the slice diagrams,indicating that the fracture of the region is developed,the rock is broken,the water-richness is better.The resistivity of the southeast part is relatively higher,which indicates that the area of the region is relatively low or the cementation is better,and the water-richness is poor.Based on the electrical and seismic exploration data,it is considered that the electrical characteristics of the suspected collapse column are in good agreement with the characteristics of the reflected waves,and it can be inferred that the collapse column has a higher degree of credibility.In order to find out the properties of the suspected collapse column,especially to judge the scale and hydraulic conductivity of the suspected collapse column,and to evaluate its influence on the tunnel excavation and coal mining in the mining area,an exploration borehole for the suspected collapse column was drilled,and the properties of the suspected collapse column were evaluated.The main geological and hydrogeological achievements of the boreholes were explored,and the possibility and attributes of the suspected collapse columns were analyzed correctly.First of all,from the perspective of 3D seismic exploration data alone,there are indeed the main features of the collapse columns.Similarly,it is difficult to explain from the seismic data that the reflection of the coal seam is basically continuous and this is in contradiction with the huge “collapse column” of the 3D seismic interpretation.Secondly,the thickness and depth of coal seams exposed in the coal seams are normal,and even the B-layered bauxite is normal.The drilling core has no messy bedding,pebble-like filling,calcite and iron infiltration.Only are there normal structuralinfluences or fissure development in the overburden of coal seams,such as cracks and fractures,and there are no traces of collapse columns.The formation revealed by the drilling has in turn effectively explained the anomalies of the 3D seismic and terrestrial electrical methods-shallow formation fractures.Finally,drilling and geological analysis show that the collapse column does not exist and is a “low-speed trap” for the seismic explaration.A comprehensive hydrogeological analysis carried out by the borehole coring and major aquifer pumping tests and the ground-based controlled source audio-magnetotelluric prospecting on the suspected collapse column area.Although the electrical method data indeed show “vertical low-resistance strips”along the “suspected collapse column” in the area,it can be considered that the low resistance zone is caused by the development of fractures and pores in the shallow overburden according to the careful analysis of drilling and exposing.As for the presence of a deep strip,it is caused by the “shadow” of current electrical surveys.The final conclusion is that the hydrogeological characteristics of the area are in line with the basic hydrogeological conditions of the mine.It will not be threatened by the water burst from the collapse column.Excavation along the coal seam will be mainly threatened by “sand aquifer 3r” on the roof and floor of the coal seam.The excavation is designed through the area with waterproof pillars and advanced exploration to ensure safe driving through the area.This result also confirmed the result of this paper.