多年冻土区公路隧道融化圈计算方法
Calculation method of thawing circle for highway tunnel in permafrost regions

为得到多年冻土区公路隧道围岩温度场和融化圈的发展规律,建立了围岩融化圈的计算方法,对融化圈深度和围岩温度的计算值与实测值进行了对比,采用有限元法分析了支护对融化圈的影响。分析结果表明:围岩温度平均误差不超过0.6 ℃,融化圈深度误差不超过10%,计算值与实测值吻合较好; 每延迟1 d施作喷射混凝土,融化圈深度增大10 cm,喷射混凝土厚度每增加5 cm,融化圈深度增加约10 cm; 一次模筑混凝土入模温度为15 ℃时的融化圈深度比入模温度为5 ℃时大了约10 cm; 当保温板厚度从5 cm增加到20 cm时,融化圈深度减小2/3,保温板及二次模筑混凝土水化热对融化圈深度有较大影响; 洞内风速为3.0 m？s-1时的融化圈深度比洞内风速为1.0 m？s-1时减小了10～20 cm; 施作喷射混凝土30、60、90、120 d后,洞内气温为8 ℃时的融化圈深度为洞内气温为2 ℃时的1.25、1.31、1.35、1.40倍。可见,洞内气温宜控制在3 ℃～5 ℃,围岩开挖后应尽早施作支护,宜选用低热或中热水泥以降低混凝土释放的水化热。
In order to obtain the temperature field of surrounding rock and the development law of thawing circle for highway tunnel in permafrost regions, the calculation method of thawing circle for surrounding rock was established, the calculated values and measured values of thawing circle depth and surrounding rock temperature were compared, and the finite element method was adopted to analyze the influence of support on the thawing circle. Analysis result shows that the average error of surrounding rock temperature is no more than 0.6 ℃, the error of thawing circle depth is no more than 10%, so the calculated value has better accordance with the measured value. When the time of operating shotcrete delays 1 d, the thawing circle depth increases by 10 cm. When the thickness of shotcrete increases by 5 cm, the thawing circle depth increases by about 10 cm. The thawing circle depth with molding temperature of 15 ℃ for the first molding concrete increases by about 10 cm compared to the molding temperature of 5 ℃. When the thickness of insulation board increases from 5 cm to 20 cm, the thawing circle depth decreases by 2/3. The insulation board and the hydration heat of secondary molding concrete have big influence on the thawing circle depth. The thawing circle depth with wind speed of 3.0 m？s-1 in hole decreases by 10-20 cm compared to wind speed of 1.0 m？s-1 in hole. 30, 60, 90, 120 d after shotcrete being operated, the thawing circle depths at air temperature of 8 ℃ in hole are 1.25, 1.31, 1.35, 1.40 times of thawing circle depths at air temperature of 2 ℃ in hole respectively. Obviously, air temperature in hole should be controlled at 3 ℃-5 ℃, the support should be operated as early as possible after surrounding rock excavation, and low heat or medium heat cement should be used to decrease the hydration heat released by concrete. 12 tabs, 11 figs, 31 refs