不同类型冻土中隧道隔热保温层铺设方式的选择

Option of Laying Position of Insulation Layer for Tunnel in Frost Region

寒区隧道工程中,铺设隔热保温层可以减轻隧道冻害。隔热保温层的铺设位置不同,起到的隔热或保温效果也不同。采用有限元计算法对不同类型冻土中隔热保温层表面铺设、夹层铺设以及离壁式铺设下的围岩温度场进行了模拟,从隔热保温效果方面对3种隔热保温层铺设方式进行了对比。季节冻土受洞内与外界气温的双重影响,铺设隔热保温层无法阻止围岩冻融循环的产生;多年冻土中隔热保温层夹层铺设以及表面铺设隔热效果相差不大,但夹层铺设时,隔热保温材料遇水以及受挤压后隔热保温效果将降低,应优先采用表面铺设方式。非冻土中隔热保温层离壁式铺设的防冻效果最好,当无法采用离壁式铺设时,将隔热保温层铺设在二衬表面的防冻效果要好于隔热保温层夹层铺设,但应对拱脚位置处的防排水系统进行保温处理。

Insulation layer is widely used to prevent tunnels from being frozen. Different laying position of insu- lation layer makes different temperature change of surrounding rock. The finite element method was used to calculate temperature field of sun＇ounding rock. There were 3 types of insulation applied： insulation on the surface, insulation between two linings and insulation off the wall surface. It is found that ： to seasonally frozen ground through which the tunnel passes, it＇ s useless to lay insulation layer to protect surrounding rock from being frozen due to dual effect of the temperature both from tunnel inside and outside; to permafrost, laying the insulation layer on the surface of the secondary lining has a similar insulation effect with laying the insulation layer between primary support and secondary lining, but heat insulation material become easy to failure when it is laid between two layers of lining due to extrusion and invasion of water, so laying insulation layer on the surfaee of the seeondary lining is the better ehoice; to non-fro- zen ground, separating the insulation layer from lining ＇ s surface has the best insulation effect, while laying the insu- lation layer on the surface of the secondary lining has a better insulation effeet than laying the insulation layer between primary support and secondary lining. But the drainage system at tunnel foundation should be insulated.