Field observation of the thermal disturbance and freezeback processes of cast-in-place pile foundations in warm permafrost regions

The bearing capacity of pile foundations is affected by the temperature of the frozen soil around pile foundations.The construction process and the hydration heat of cast-in-place(CIP)pile foundations affect the thermal stability of permafrost.In this paper,temperature data from inside multiple CIP piles,borehole observations of ground thermal status adjacent to the foundations and local weather stations were monitored in warm permafrost regions to study the thermal influence process of CIP pile foundations.The following conclusions are drawn from the field observation data.(1)The early temperature change process of different CIP piles is different,and the differences gradually diminish over time.(2)The initial concrete temperature is linearly related with the air temperature,net radiation and wind speed within 1 h before the completion of concrete pouring;the contributions of the air temperature,net radiation,and wind speed to the initial concrete temperature are 51.9%,20.3%and 27.9%,respectively.(3)The outer boundary of the thermal disturbance annulus is approximately 2 m away from the pile center.It took more than 224 days for the soil around the CIP piles to return to the natural permafrost temperature at the study site.

我国铁路风沙防护体系的研究进展

风沙是沙漠和干旱地区基础设施设计、建设和应用中面临的主要问题之一,更是影响沙区铁路安全运营和使用性能的限制因素。治理风沙病害必须防和治同时进行,采用既防风又防沙的措施,才能达到防护目的。在现有的科学和技术基础上提供一个较为全面的概述,总结了目前治沙取得的成果和存在的问题,展望了治沙工程的发展趋势。从单一措施的阻沙和固沙原理论证出整个防护体系的治沙原理,从而优化防护体系、合理布局,实现理想的治沙效果,保证铁路的高效运行。

青藏铁路格拉段某断面冻土路基病害及防治措施分析

气候变暖的背景下,青藏铁路冻土路基稳定性面临严峻挑战,主要表现为路基出现沉降、开裂等病害。本文通过分析青藏铁路多年冻土区K1496+750路基断面地质条件,对本断面路基沉降产生原因进行分析,并通过分析长周期的变形监测数据,讨论了路基采取块石护坡和热棒等防护措施的作用效果,为多年冻土区路基病害防治提供借鉴。