Tunnels located in cold regions are vulnerable to frost damage resulting from the special atmosphere, which directly threatens the safety of the tunnel structure and operation. Frost problems of tunnels in cold regions have not been fundamentally resolved. This paper reviews design theory and the frost mitigation techniques currently used in the design, construction and maintenance of cold region tunnels. The depths of freezing and thawing and frost heaving force are the key indexes of design theory. Insulation is the main design technology used to prevent frost heaving and thawing, and the active heating technology has also been applied in practice. In construction, reducing the heat of hydration and blasting by specific winter construction techniques can prevent tunnel freeze–thaw damages. In operation, the restoration of drainage systems, the reinforcement of structures and the reinstallation of freezing-prevention systems are effective measures to treat frost problems. Finally, some constructive suggestions and opinions are put forward to improve the service performance of tunnels.
Large deformation of surrounding rock makes the internal space of a tunnel cannot meet the requirements of normal use after support, even leads to the instability of surrounding rock and destruction of the tunnel structure. In order to optimize the parameters of the primary support to control the deformation of surrounding rock, field tests and numerical simulations are carried out. Based on the engineering geological conditions and the deformation monitoring data of surrounding rock, four important creep parameters of the improved Burgers model are inversed by numerical simulation, considering the creep of surrounding rock in tunnel construction. The results show that it is feasible to use tunnel crown settlement as a control indicator to determine the thickness of shotcrete. Short rock bolts are preferentially used in the tunnel arches, and a combination of long and short rock bolts should be used on the sidewall to control the large deformation of surrounding rock. When the excavation method of upper-lower bench is used in the single-track railway with a relatively large high-span ratio, the horizontal convergence monitoring points of the upper bench are recommended to be set 0.8-0.9 times the height of the upper bench from the tunnel arch crown, and those of the lower bench are recommended to be set 0.6-0.7 times the total height of the upper-lower bench from the tunnel arch crown.
It is necessary to set up slagging well to facilitate slagging and improve construction efficiency during the construction of tunnel shaft inverse well method. Due to the geological condition of the shaft and human factors, the slag chute is easily blocked and the construction period is affected. The conventional dredging method has some problems such as low efficiency, complicated process and long time limit. In this paper, based on Yunnan province Taihe Sumie to Lincang highway tunnel shaft engineering, put forward a way to use two strands in a certain distance between wire rope clamp, two of the same height of the steel wire rope clip through the switch assembly structure of the hinge connection, can be efficient and convenient to dredge the well construction shaft sneak slag well jam problem, as a reference for other similar projects.
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