Characterizing seepage behavior of weakly cemented filling fault fracture zone

HUANG Zhen; WANG Zhenpeng; GU Qixiong; ZHANG Xiaojun; XU Hanhua; WU Yufan; LIN Yuanshen

doi:10.13225/j.cnki.jccs.2024.1381

Abstract：Water inrush accidents caused by weakly cemented filling fault fracture zone often occur under mining disturb-ance and groundwater seepage,posing a great threat to deep resource exploitation.The characteristics of cemented filling within the fault fracture zone directly control fluid migration and the formation of seepage channels.Identifying its impact on the seepage characteristics of fault fracture zones is of great importance in revealing the mechanism of water inrush from faults.Therefore,triaxial seepage tests were conducted on fault fracture zones with different Talbot function power exponent n values.CT scanning was used to analyze the microstructural changes of the fault fracture zone before and after seepage,and numerical simulations based on CT scanning data were conducted to study the seepage characteristics within weakly cemented filled fault fracture zones.The research results indicate that confining pressure affects permeability by altering the structure of fault fracture zones.The increase in confining pressure leads to the compression of pores and frac-tures within the fault fracture zone,and the permeability coefficient of weakly cemented filled fault fracture zones de-creases with increasing confining pressure.The internal connectivity and permeability of the fault fracture zone is better and higher with the higher of the Talbot function power exponent n and rock content.Conversely,the porosity and pore connectivity of the fault fracture zone is lower with the lower value of the Talbot function power exponent n.Groundwa-ter seepage will reduce the spherical pores inside the fault fracture zone and increase the flat pores,leading to the gradual formation of seepage channels.Moreover,the changes in the azimuth and inclination angles of pores within the fault frac-ture zone can reflect alterations in the internal seepage pathways.Under the action of groundwater seepage,dominant seepage channels will gradually form between the skeletons of fault fracture zones,leading to the formation of water in-rush channels.The Talbot function power exponent n value has a significant impact on the water inflow of water inrush through the fault fracture zone.The water inflow of water inrush exhibits a trend of first increasing and then decreasing with the increase in the Talbot function power exponent n value.