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Analysis of Temporal and Spatial Variation Law of Crystalline Materials and Water Environment and Crystallization Path of the Tunnel Drainage System in Calcium-bearing Surrounding Rocks
(1. School of Civil Engineering, Chang′an University, Xi′an 710061; 2. School of Highway, Chang′an University, Xi′an 710061;3. CCCC Third Harbor Engineering Co., Ltd., Shanghai 472299)
Abstract By testing the samples collected from the crystalline materials and water environment of 7 tunnels in cal? cium-bearing surrounding rocks, the temporal and spatial variation law and characteristics of crystalline minerals,water quality and ion concentration have been analyzed, the drainage crystallization path model has been built, the calcium source and carbon source of crystallization have been identified, and the suggestions for prevention and control of the problems are offered. As the results suggest, depending on their forms, the crystalline materials in the drainage system of mountain tunnels can be classified into soft flocculent material, powdery blocky material and hard stony material. The three types of materials have different forms and hardness values and their generative processes are consistent. The forms of crystalline materials are useful in selecting the methods for solving crystallization. The water quality parameters and ion concentration show clearly uniform spatial pattern; the shotcrete initial support has the most obvious impact on the water environment; after water permeating through shotcrete initial support, the pH value, total dissolved solids (TDS) , Ca2+, Na+, K+ and CO32- concentrations in the water increase signifi? cantly, while the HCO3- concentration decreases significantly; the increase and decrease of Ca2+ concentration will reveal the current condition and history of initial support cracking, SO42- is not involved in the crystallization related reactions, and its concentration is helpful for determining whether the surrounding rock water environment has changed. In the crystallization path, the carbon source of crystalline materials is from biological residue, respiration of plant root system and dissolution of carbonate, while the calcium source is from calcium dissolution and precipitation of calcium-bearing surrounding rock and the dissolution of hydration products of initial support concrete.
Abstract：
By testing the samples collected from the crystalline materials and water environment of 7 tunnels in cal? cium-bearing surrounding rocks, the temporal and spatial variation law and characteristics of crystalline minerals,water quality and ion concentration have been analyzed, the drainage crystallization path model has been built, the calcium source and carbon source of crystallization have been identified, and the suggestions for prevention and control of the problems are offered. As the results suggest, depending on their forms, the crystalline materials in the drainage system of mountain tunnels can be classified into soft flocculent material, powdery blocky material and hard stony material. The three types of materials have different forms and hardness values and their generative processes are consistent. The forms of crystalline materials are useful in selecting the methods for solving crystallization. The water quality parameters and ion concentration show clearly uniform spatial pattern; the shotcrete initial support has the most obvious impact on the water environment; after water permeating through shotcrete initial support, the pH value, total dissolved solids (TDS) , Ca2+, Na+, K+ and CO32- concentrations in the water increase signifi? cantly, while the HCO3- concentration decreases significantly; the increase and decrease of Ca2+ concentration will reveal the current condition and history of initial support cracking, SO42- is not involved in the crystallization related reactions, and its concentration is helpful for determining whether the surrounding rock water environment has changed. In the crystallization path, the carbon source of crystalline materials is from biological residue, respiration of plant root system and dissolution of carbonate, while the calcium source is from calcium dissolution and precipitation of calcium-bearing surrounding rock and the dissolution of hydration products of initial support concrete.
LIU Yuyang1 XI Longlong1 LAI Hongpeng2 ZHAO Yongbin3 SUN Weixing3 JIA Neng1
.Analysis of Temporal and Spatial Variation Law of Crystalline Materials and Water Environment and Crystallization Path of the Tunnel Drainage System in Calcium-bearing Surrounding Rocks[J] MODERN TUNNELLING TECHNOLOGY, 2023,V60(3): 217-226
2023, Vol. 60 