Study on design optimization of a crushed stone layer with shading
board placed on a railway embankment on warm permafrost
Guoyu Li
a,
⁎
, Ning Li
a,b
, Jiamei Kang
b
, Fujun Niu
a
,
Wenbing Yu
a
, Lei Shi
a
, Guiquan Bi
a
a
State Key Laboratory of Frozen Soil Engineering, CAREERI, Chinese Academy of Science, Lanzhou, Gansu 730000, China
b
Institute of Geotechnical Engineering, Xi'an University of Technology, Xi'an, Shanxi 710048, China
Received 9 October 2007; accepted 16 November 2007
Abstract
Under the impact of potential climate warming and human engineering activities, the Embankment with Crushed Stone Slope
Protection (ECSSP) needs further countermeasures to protect the underlying permafrost along the Qinghai–Tibet railway in warm
(−1 to 0 °C) permafrost regions according to the observed in situ data. In this paper, a new strengthening countermeasure, the
Embankment with Shading Board and Crushed Stone Slope Protection (ESBCSSP), is proposed to cool the foundation soil and to
protect the warm permafrost. The crushed stone layers placed on the side slopes of the embankment have an apparent “thermal
semi-conductor” effect by intensive natural convection of pore air in the winter and a “heat shield” effect in the summer. The
shading boards erected on crushed stone slope protection can shade the ground surface from the sun to lower its surface
temperature, and can keep snow from covering the crushed stone layer in the winter, which can enhance the cooling effect of the
crushed stone layer. Based on the processes of natural convective and conductive heat transfer in porous media, systemic numerical
tests were performed to study the cooling effect of the ESBCSSP, and to propose the reasonable range in thickness, height and grain
size of the crushed stone slope protection.
© 2007 Elsevier B.V. All rights reserved.
Keywords: Warm permafrost; Crushed stone slope protection; Shading board; Qinghai–Tibet railway; Climate warming; Design optimization
1. Introduction
Coarse stones are widespread on slopes in many
periglacial environments. They can act as “thermal semi-
conductor”, lowering the ground temperature and causing
permafrost to form. This phenomenon is why crushed
stones have been used in many engineering projects to
keep the underlying permafrost from thawing (Cheng
et al., 2007). Sun et al. (2004) studied the cooling effect
of the Embankment with Crushed Stone Slope Protection
(ECSSP) in situ along the Qinghai–Tibet railway by ob-
serving ground temperature data (see Fig. 1). They found
that the mean annual ground temperature under the
crushed stone layer with coarse particle diameters of 40–
50 cm was lower than that under a similar layer with finer
particle diameter of 5–8cm.Yu et al. (2003) conducted
some laboratory model tests to study the cooling effect of
the crushed stone layer. The experimental results showed
Available online at www.sciencedirect.com
Cold Regions Science and Technology 54 (2008) 36 – 43
www.elsevier.com/locate/coldregions
⁎
Corresponding author. Tel.: +86 931 4967290; fax: +86 931
8271054.
E-mail address: guoyuli@lzb.ac.cn (G. Li).
0165-232X/$ - see front matter © 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.coldregions.2007.11.004