<<
[an error occurred while processing this directive] | [an error occurred while processing this directive] >>
Characteristics and Influencing Factors of Segment Cracking of LargeDiameter River-Crossing Shield Tunnelling in Composite Rock Strata
(1 School of Civil Engineering, Central South University, Changsha 410075;2 National Engineering Laboratory for High Speed Railway Construction, Changsha 410075)
Abstract The construction of shield tunnels in composite rock strata is vulnerable to cause segment cracking dis?
eases, which has a serious effect on the operation and long-term safety. Based on a large-diameter river-crossing shield tunnel project, field investigations are carried out on the segment cracking during the construction phase. The typical cracking modes and distribution laws are summarized. Three typical rock strata, namely full-face highly weathered conglomerate, full-face middle weathered conglomerate, and their composite stratum are selected to explore the influence of seven key construction parameters on the segment cracking, such as rock condition and advancing speed etc. The results show that segment cracking diseases are composed of longitudinal joint cracking, circumferential joint cracking, corner cracking, bolt hole cracking, segment cracking and segment ring offset. The joint crack accounts for the largest proportion, mainly locating at the crown and its adjacent range of 45°. The joint cracking mechanism is the tensile/compressive failure induced by local stress concentration under uneven joint surface and eccentric jack/erector force. The rock strata conditions are negatively related to the segment cracking, the higher the rock grade, the fewer the cracks. The soft-hard composite stratum is more vulnerable to cause segment cracking,compared to homogeneous rock stratum. Higher advancing speed, larger thrust force, lower synchronous grouting volume and their data discreteness are primary influence factors of the occurrence of segment cracks. A proper and stable cutterhead torque value is beneficial to reduce the occurrence of segment cracks.
Abstract：
The construction of shield tunnels in composite rock strata is vulnerable to cause segment cracking dis?
eases, which has a serious effect on the operation and long-term safety. Based on a large-diameter river-crossing shield tunnel project, field investigations are carried out on the segment cracking during the construction phase. The typical cracking modes and distribution laws are summarized. Three typical rock strata, namely full-face highly weathered conglomerate, full-face middle weathered conglomerate, and their composite stratum are selected to explore the influence of seven key construction parameters on the segment cracking, such as rock condition and advancing speed etc. The results show that segment cracking diseases are composed of longitudinal joint cracking, circumferential joint cracking, corner cracking, bolt hole cracking, segment cracking and segment ring offset. The joint crack accounts for the largest proportion, mainly locating at the crown and its adjacent range of 45°. The joint cracking mechanism is the tensile/compressive failure induced by local stress concentration under uneven joint surface and eccentric jack/erector force. The rock strata conditions are negatively related to the segment cracking, the higher the rock grade, the fewer the cracks. The soft-hard composite stratum is more vulnerable to cause segment cracking,compared to homogeneous rock stratum. Higher advancing speed, larger thrust force, lower synchronous grouting volume and their data discreteness are primary influence factors of the occurrence of segment cracks. A proper and stable cutterhead torque value is beneficial to reduce the occurrence of segment cracks.
GONG Chenjie1 YANG Junsheng1 FU Jinyang1,
2
.Characteristics and Influencing Factors of Segment Cracking of LargeDiameter River-Crossing Shield Tunnelling in Composite Rock Strata[J] MODERN TUNNELLING TECHNOLOGY, 2020,V57(5): 30-42
2020, Vol. 57 