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On Defects and Disaster-causing Factors in Tunnelling in Salt Rocks
(1 Key Laboratory of Transportation Tunnel Engineering of Ministry of Education, Southwest Jiaotong University, Chengdu 610031;2 The Second Engineering Company CREGC, Chengdu 610073)
Abstract The Friendship tunnel on China-Laos railway is located in salt rocks, where very serious tunnel defects are encountered during construction. Therefore, it is of great significance to study the causes of the defects for the subsequent construction. In view of this, the investigation is carried out at the Friendship tunnel site to reveal construction defects and deeply study the disaster-causing factors by means of on-site sampling, indoor test, on-site monitoring and theoretical analysis, etc. It is found that lining cracks and excessive deformations are caused by water solubility and expansibility of salt rocks; tunnel collapse, cavity, corrosion and crystallization are caused by water solubility and corrosivity of salt rocks. Invert heave is caused by uneven settlement, salt recrystallization and rheology of weak surrounding rocks. Mechanical properties and water solubility of salt rocks, salt rock percentage, underground water composition and content in excavation section are main reasons for construction disasters of salt rock tunnel. Such combined measures as strengthening drainage, using multi-layer waterproofing structure, optimizing building materials, increasing structural corrosion resistance and implementing double-layer initial support and base replacement can be used as important measures for rapid and safe construction of salt rock tunnels.
Abstract：
The Friendship tunnel on China-Laos railway is located in salt rocks, where very serious tunnel defects are encountered during construction. Therefore, it is of great significance to study the causes of the defects for the subsequent construction. In view of this, the investigation is carried out at the Friendship tunnel site to reveal construction defects and deeply study the disaster-causing factors by means of on-site sampling, indoor test, on-site monitoring and theoretical analysis, etc. It is found that lining cracks and excessive deformations are caused by water solubility and expansibility of salt rocks; tunnel collapse, cavity, corrosion and crystallization are caused by water solubility and corrosivity of salt rocks. Invert heave is caused by uneven settlement, salt recrystallization and rheology of weak surrounding rocks. Mechanical properties and water solubility of salt rocks, salt rock percentage, underground water composition and content in excavation section are main reasons for construction disasters of salt rock tunnel. Such combined measures as strengthening drainage, using multi-layer waterproofing structure, optimizing building materials, increasing structural corrosion resistance and implementing double-layer initial support and base replacement can be used as important measures for rapid and safe construction of salt rock tunnels.
WANG Zhijie1 LI Jinyi1 DENG Yuhang1 DU Yiwen1 ZHOU Ping1 BAI Xiaoke2 LI Fenggang2
.On Defects and Disaster-causing Factors in Tunnelling in Salt Rocks[J] MODERN TUNNELLING TECHNOLOGY, 2021,V58(5): 46-55
2021, Vol. 58 