风积沙环境下高等级公路冻土块石路基降温性能分析

Analysis on the cooling performance properties of block-stone embankment in permafrost regions under the scenario of aeolian-sand

青藏高原脆弱的生态系统以及人类工程活动,加剧了青藏工程走廊线性工程两侧沙漠化、荒漠化发展趋势,尤其冻土块石路基面临日益严重的风积沙灾害问题。以多年冻土区高等级公路块石路基为研究对象,采用数值模拟分析风积沙环境下封闭块石路基的降温性能和长期热稳定性。结果表明:风积沙堆积对封闭块石路基下部土层冻土温度的影响程度高于冻土上限,1.0 m湿沙工况降低冻土温度,0.2 m干沙则增大冻土温度。升温背景下,随年平均气温增加风沙堆积对路基冻土上限影响程度增强,干沙增大冻土融化深度,湿沙抬升冻土上限。随冻土含冰量减小,路基中心冻土上限对气候升温敏感性增加,风沙堆积影响减弱。气候升温和风沙堆积条件下,在年平均气温低于-5.5℃时,宽幅沥青路面封闭块石路基能够满足降温要求,使人为冻土上限保持在块石层内。研究成果可为风沙危害区多年冻土块石路基的病害治理和拟建青藏高速公路块石路基设计提供科学依据。

The fragile ecosystems and human engineering activities in the Tibetan Plateau aggravate the desertification along the linear engineering of Qinghai-Tibet Engineering Corridor. Therefore block-stone embankment in permafrost regions faces increasing severe aeolian sand hazard. In this paper,cooling performance and long-time thermal stability of block-stone embankment with high-grade pavement under the scenario of aeolian sand were analyzed. The results showed that permafrost temperature is more easy to be affected by accumulation of aeolian sand for closed block-stone embankment by comparing the permafrost table under the center of permafrost embankment. Wet sand of 1. 0 m depth can reduce permafrost temperature,while dry sand of 0. 2 m depth can rise permafrost temperature. Permafrost temperature is more sensitive to water content of sand as compared with the sand deposit depth. Under the circumstance of climate warming,the impact of sand deposit on permafrost table of embankment will weaken with the mean annual air temperature decreasing. The dry sand increases the thawed depth of permafrost,and the wet sand raises permafrost table. Permafrost table beneath the center of embankment is more sensitive and the impact of accumulation of sand weakens together with the decrease of ice content of permafrost. When the mean annual air temperature is lower than-5. 5 ℃,closed block-stone embankment for high-grade highway could keep artificial permafrost table within the rock layer in the condition of climate warming and aeolian sand deposit.