عنوان مقاله [English]
Excavation and segment installation is simultaneous in D.S.TBM tunneling. Segmental quality control in production phase (in factory) and accuracy and rapidity of segment installation in implementation phase are considered amongst main advantages of segmental lining application in mechanized tunneling. But inherent defects of segments and stepping and spalling after installation decrease concrete lining quality. Recognition of cause and mechanism of segment defects is an important factor in quality improvement of precast concrete lining. In this paper, lining installation quality and causes of concrete damages have been studied using Tehran-Karaj water conveyance tunnel (lot II) site data.
During segment installation some damages such as stepping and spalling might occur. There are different influencing factors, which can be categorized as manufacturing and installation related damages. In order to study the type and the cause of segment damages which were installed in different location of a ring, about ten thousand rings were analyzed in Tehran-Karaj water conveyance tunnel (lot II) with 14 km length, excavated by D.S.TBM.
Methodology and Approaches
Lining installation quality of this tunnel was studied using statistical approach. The effective parameters on segment damages classified in ground situation, tunnel alignment, machine parameters, concert characterizations, thrust of the jacks, tail shield situation, quality of installation and other parameters. In this tunnel, each concrete ring consists of 5+1 key universal segment that was assessed based on survey deviance, eccentric thrust jacks and accuracy of segment installation on amount and size of defects.
Results and Conclusions
This approach shows that minimum and maximum spalling occurs in key segment and its contiguous segments, respectively. In addition, stepping in key contiguous segments are more than other type of segments. Comparing segment installation condition and survey deviance in curve alignments shows a great reduction in installation quality and increase in number of stepping and spalling area.