Permafrost

Experimental Study on the Influence of Paving Location and Diameter
on the Cooling Effect of Ballast Embankment
Xiao-zu Xu 1 ,Bin-xiang Sun 1 ,Qi Liu 1 ,Shuang-jie Wang 2 , Jin-zhao Zhang 2
(1.Department of Civil Engineering, Shaoxing College of Arts and Sciences, 312000, China;
2.The First Highway Survey & Design Institute of Communications, Xian, 710068,China)
Abstract: To study the influence of paving location and diameter on the cooling effect of
ballast embankment, the one dimensional tests were carried out on the three materials of ballast,
cobble and sandy gravel with single, compound and mixed structures in an insulated box of 50
cm in length and width and 65cm in height under the periodic fluctuation of air temperature at
the top of the specimen. Results show that for single structure, the natural convection is
appeared respectively in the ballast with the diameter of 2-4cm, 4-6cm, 6-8cm and in the cobble
with diameter of 10-15cm,among with the ballast with diameter of 4-6 cm provides the best
cooling effect. For the compound and mixed structures, the cooling effects are weakened. The
mean temperature of ballast is deceased with increasing its thickness. To use the mechanism of
natural convection sufficiently we suggest that the ballast with diameter of 4-6 cm could be
used as filling material for the embankment in permafrost regions and the paving location
should be at the top of the embankment. The compound and mixed structures of different
materials, such as ballast, cobble and sandy gravel, should not be used in permafrost regions.
Key words: diameter of ballast, paving location, embankment, cooling effect
The elementary study on the chain-styled mechanism and the new-typed
method to the chain breakage of the water leakage hazard in Kunlun
mountain tunnel
Xue-fu Zhang 1,2
(1. School of Civil Engineering and Architecture, Chongqing Jiaotong University, Chongqing 400074,
China;2. State Key Laboratory of Frozen Soil Engineering, Cold & Arid Regions Environmental and
Engineering Research Institute, Chinese Academy of Sciences, Gansu Lanzhou 730000,China)
Abstract:The hazard of the water leakage is the most familiar one in the several hazards in the
cold region tunnels. This hazard could bring on other hazards, such as frost heave, because the
water leakage is frost in spring, autumn or winter. In this paper, after the geologic status and the
design general situation of Kunlun mountain tunnel in Qing-Tibet railway are represented, the
hazards of water leakage of the tunnel are introduced by the time step based on the measured
data in-situ. From the viewpoint of the chain-styled rule, the chain-styled mechanisms of the
water leakage hazard in Kunlun mountain tunnel are open out. According to the principle to the
chain breakage and the chain-styled mechanisms of the water leakage hazard, a new-typed
method to the chain breakage, using the ripped-stone method, is presented based on the
principle of protecting the frozen soil layer from thawing. The design of the ripped-stone is
made, and matters needing attention during designing and constructing the ripped-stone are put
forward. So the new analysis method and the new prevention and cure measure are offered for
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