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Study on the Cracking Mechanism of Subsea Shield Tunnel Segments under the Dual Mechanical Action of Loading and Corrosive Expansion
(1. Department of Geotechnical Engineering, College of Civil Engineering, Tongji University, Shanghai 200092; 2. China Railway First Survey and Design Institute Group Co., Ltd., Xi'an 710043; 3. School of Civil Engineering, Beijing Jiaotong University, Beijing 100044)
Abstract The cracking caused by the corrosive expansion of shield tunnel segments in the marine corrosion envi? ronment is a major threat affecting the safe serviceability of a tunnel. Attention should be paid to the combined action of lining stress arising out of water and soil pressure and additional stress arising out of rebar corrosion. Based on the extended finite element method (XFEM), a corrosive-expansion-induced cracking analysis model for the subsea shield tunnel was built to reflect this dual stress action, and the corrosive expansion-induced cracking behaviors and mechanical mechanism of lining rings during its service were studied. The results showed that the corrosive expansion-induced cracking behaviors in different positions of lining rings were significantly affected by the original lining stress of segments; two haunches on the outer ring and the crown and arch bottom on the inner ring were located in the tensile stress concentration zone of lining rings, and the tensile stress caused by water and soil pressure is the major factor affecting lining cracking, while the effect of corrosive expansion was relatively small, and these cracks were characterized by early cracking, rapid extension and cracking perpendicular to the protection layer; two haunches on the inner ring and the crown and arch bottom on the outer ring were the compressive stress concentration zone of lining rings, and its cracking arising out of the relatively high compressive strength of concrete was mainly dependent on the tensile stress caused by corrosive expansion of rebars. Rebar corrosion had to last long enough to transform the surrounding concrete from being compressed to being tensioned and finally cause cracking, and these cracks were characterized by late cracking, slow extension and cracking parallel to the protective layer; arch shoulder and foot were in the status of stress transition, and cracks obliquely intersected the protective layer.
Abstract：
The cracking caused by the corrosive expansion of shield tunnel segments in the marine corrosion envi? ronment is a major threat affecting the safe serviceability of a tunnel. Attention should be paid to the combined action of lining stress arising out of water and soil pressure and additional stress arising out of rebar corrosion. Based on the extended finite element method (XFEM), a corrosive-expansion-induced cracking analysis model for the subsea shield tunnel was built to reflect this dual stress action, and the corrosive expansion-induced cracking behaviors and mechanical mechanism of lining rings during its service were studied. The results showed that the corrosive expansion-induced cracking behaviors in different positions of lining rings were significantly affected by the original lining stress of segments; two haunches on the outer ring and the crown and arch bottom on the inner ring were located in the tensile stress concentration zone of lining rings, and the tensile stress caused by water and soil pressure is the major factor affecting lining cracking, while the effect of corrosive expansion was relatively small, and these cracks were characterized by early cracking, rapid extension and cracking perpendicular to the protection layer; two haunches on the inner ring and the crown and arch bottom on the outer ring were the compressive stress concentration zone of lining rings, and its cracking arising out of the relatively high compressive strength of concrete was mainly dependent on the tensile stress caused by corrosive expansion of rebars. Rebar corrosion had to last long enough to transform the surrounding concrete from being compressed to being tensioned and finally cause cracking, and these cracks were characterized by late cracking, slow extension and cracking parallel to the protective layer; arch shoulder and foot were in the status of stress transition, and cracks obliquely intersected the protective layer.
QIAN Yuan1 XU Chong2 LIU Xiaorui2 HUANG Meng3
.Study on the Cracking Mechanism of Subsea Shield Tunnel Segments under the Dual Mechanical Action of Loading and Corrosive Expansion[J] MODERN TUNNELLING TECHNOLOGY, 2023,V60(3): 102-111
2023, Vol. 60 