Study On Principle Of Tunnel Freeze Injure And Calculation Method Of Frost Force

In high latitude or high elevation cold region, especially means of many years frozen earth region, freeze injure always happens in tunnel when ground water grows. Thus is proved by a lot of practice of construction and transport service of railway and highway tunnel overseas and interiorly. Freeze injure endangers the safety of tunnel structure and transport service directly, causes serious economic loss. However, with vigorous development of economic construction and the policy of development in western part ascertained by degrees in our country, the requirement to basic transportation establishment adds, especially means of consummate transportation wet. Construction of large quantity tunnel in frozen earth can not be avoided. Therefore, how to take efficacious measure to avoid or reduce freeze injure in construction of tunnel in frozen earth is a problem that need to be settled urgently by tunnel workers at present. Carrying out study on principle of tunnel freeze injure and relative prevention and cure technology has major meaning of engineering practice and vast application foreground.On base of study on large quantity phenomena and principle of tunnel freeze injure, That frost force is main reason of tunnel freeze injure is discovered. Temperature, water, surrounding rock, engineering measure are main factors of tunnel freeze injure. Therefore, the key problem in study is frost force of tunnel in frozen earth.At present, the study on calculation method of frost force of tunnel in frozen earth use analysis method for the coupled problem of stress fields, temperature fields and seepage fields. Because of complexity of engineering practice and limitations of mathematics and mechanics method, this study is not practical. In view of this, calculation fomula of frost force of tunnel in frozen earth is put forward first in this paper according to elasticity mechanics theory. At the same time, half-theory and half-experience calculation method of frost force of tunnel in frozen earth is put forward according to elasticity-plasticity mechanics and finite unit theory. This calculation method is numeric analysis method for the coupled problem of deadweight stress fields and temperaturestress fields after determining scope of freezing surrounding rock by testing ground temperature and determining physics and mechanics parameter of freezing and not-freezing surrounding rock by original mechanics testing. This calculation method is realized by large-size finite unit program ANSYS and proved by model experiment.Frost force of tunnel in frozen earth is calculated and analyzed on condition of different scope of freezing surrounding rock and different rate of volume expansion of freezing surrounding rock according to calculation method of elasticity mechanics to frost force. The characteristic curve of frost force and deformation and the change law of frost force is put forward on different conditions. Finite unit model of plane-strain is set up by large-size finite unit program ANSYS according to calculation method of elasticity-plasticity mechanics to frost force. Frost force of tunnel in frozen earth is calculated and analyzed on condition of different installed depth, different scope of freezing surrounding rock and different rate of volume expansion of freezing surrounding rock. The characteristic curve of frost force and deformation and the distribution law of frost force is put forward on different conditions. At the same time, the dividing line of shallow tunnel and depth tunnel in frozen earth is discussed initially.