| The water seepage disease caused by fractures is the most common and serious type of disease in grotto temples.It is characterized by narrow water channels,complex crack networks,and weak seepage phenomena,making it a key and difficult point for disease detection and prevention.Therefore,the study of fractured channels and seepage mechanisms is particularly important and plays a role in the prevention and control of water seepage diseases in stone cultural relics.The paper is funded by the special task of"Protection and Utilization of Cultural Heritage"under the National Key Research and Development Program"Monitoring,Early Warning,and Prevention of Major Natural Disasters."The research focuses on the"Study of Fissure Flow Paths and Evaluation in Grotto Rock Mass"and selects the northern section of the Buddha Bay in Dazu Beishan Rock Carvings as the research scope.Qualitative and quantitative analyses of the water seepage characteristics are conducted through field investigations,which clarify the harm caused by seepage to the stone carvings from physical,chemical,and biological perspective.The regional geological and hydrogeological conditions are analyzed and generalized to establish a hydrogeological conceptual model.The rainfall infiltration supply,drainage channel discharge,and carving area seepage amount are quantitatively analyzed.91 fractures data are collected through field surveys of the standing wall.Statistical analysis and grouping fitting are conducted to obtain the distribution form,average diameter,average aperture,standard deviation,and volume density of the dominant fracture groups.A three-dimensional fissure network model is established using the Monte Carlo random simulation method.Furthermore,it can simulate the water seepage laws in the rock carvings.The seepage mechanism is qualitatively and quantitatively revealed.The main conclusions are as follows:（1）In the Buddha Bay North section of Dazu Beishan Rock Carvings,49 areas with water seepage were found.Based on the amount of water and the cause,the water seepage characteristics are divided into five types:dampness,immersion,water droplets,dripping,and flowing water.Among them,there are 25 dampness areas,21immersion areas,2 water droplet areas,1 dripping area and 1 wet area.There is an area with S<1000 cm2,14 areas with 1000 cm2<S≤10000 cm2,16 areas with 10000cm2<S≤20000 cm2,and 18 areas with S>20000 cm2.The harm caused by water seepage to the rock carvings mainly includes physical,chemical,and biological effects.The groundwater types are porous water in the Quaternary loose rock layer and fractured bedrock water.The main source of groundwater supply is atmospheric precipitation.The water chemistry type is HCO3-Ca·Mg type water.The water-containing media in the rock carving area are generalized as the covering layer water-containing body and sandstone fracture water-containing body.The covering layer water-containing body was analyzed using the equivalent continuous medium for seepage analysis,and the sandstone fracture water-containing body is analyzed using a discrete fracture network for seepage analysis.The main boundary conditions include impermeable boundaries,flow boundaries,and discharge boundaries.The infiltration coefficient of the covering layer is determined to be 0.30,and the permeability coefficient of the sandstone fracture medium is calculated using the cubic law.Based on field surveys,the drainage area in the research area is 5330.60 m2,and the flow rate at the drainage channel outlet is 0.05L/s.The total amount of surface water and groundwater in the rock carving area is5365.78 m3,the amount of rainfall infiltration is 1609.73 m3,the drainage channel outlet is 1576.80 m3,and the amount of water seepage in the carving area is 32.93 m3.（2）Based on the measurement of the standing wall of the statue in the northern section of the Buddha Bay of the Dazu Beishan Rock Carvings,91 fractures were obtained,mainly characterized by low ductility,extremely strong permeability,and high-angle fracture.Four dominant groups are obtained,and the central attitude of the fracture distribution is 199.690°∠80.615°,305.290°∠78.798°,217.330°∠15.368°,and 55.979°∠65.515°,respectively.The attitudes of the four crack groups are all well fitted by the Fisher distribution.According to the Anderson-Darling goodness-of-fit statistic,the distribution forms of the measured crack lengths and widths for each group is determined,and they all conform to the lognormal distribution.Based on the statistical window method,the average radius,radius standard deviation,average width,width standard deviation,and volume density values of each group of cracks are calculated and analyzed.The average radius is distributed between 1.216 m and 2.751m and the radius standard deviations is distributed between 0.493 m and 1.437 m.The average widths is distributed between 18.447 mm and 26.550 mm and the width standard deviations is distributed between 49.322 mm and 66.984 mm.The volume densities is distributed between 0.0112 m-3 and 0.0130 m-3.（3）DFNWORKS is used to simulate the seepage law in the stone carving area.The model generated a total of 6823267 grids and 3350854 Voronoi control bodies,and obtain a steady-state flow solution.The maximum flow velocity at the statue wall of the stone carving area is 0.1 m/s,and the total hydraulic head value at each point is distributed between 5.2 m and 15 m.After the water infiltrated from the upper cover layer of the stone carving area,it diffuses downward through the fracture network and seeped out.The flow velocity gradually increases from east to west,and the fractures with larger inclination angles have higher flow velocities,serving as the main leakage channels.The fractures with smaller inclination angles have lower flow velocities,which play a role in dispersing the direction of water flow and expanding the range of seepage.As a result,the distribution range of seepage diseases on the statue wall is expanded.The simulation obtain a seepage flow rate of 9.8×10-7 m3/s and an annual seepage volume of 30.91 m3.The simulation results are reasonable compared with the actual results. |
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