Permafrost

esonance (NMR) method.
Results indicate that the increase in temperature and salinity (unfrozen water content)
causes a significant loss of strength. The dependence of yield stress, peak stress, initial modulus
and hardening modulus on salinity can be expressed as simple exponential law. The strength of
frozen silty is the most sensitive to the change of salinity among the three type of soil, and then
that of silty clay and clay. Comparing with NaCl, the effect of salinity of Na2SO4 on the strength
of frozen soil is not quite obvious.
The law of the effect of salinity on the strength of frozen soil can be explained by the law
of the effect of salinity on the unfrozen water content of frozen soil. The change of salinity
behaves the strongest effect on unfrozen water content of frozen silty among the three type of
soil. The effect of salinity of Na2SO4 on unfrozen water content of frozen soil is not quite
obvious comparing with that of NaCl. The unfrozen water content even decrease with the
increase of salinity at some temperature and salinity of Na2SO4.
The failure mode of frozen unsaturated soil is brittle type at some dry weight condition.
When the total water content exceeds saturate water content almost all samples behave ductile
mode But brittle failure mode is only observed at low temperature and high water content.
Therefore the unfrozen water content also affects the failure mode of frozen unsaturated soil.
The strength of frozen soil decreases with the increase of unfrozen water content and this
relation can be expressed as a power law. At the condition of same dry weight, the strength of
frozen soil increases with the increase of ice content in frozen soil. The unfrozen water content
affects the mechanical behavior of soil-ice interface, hence, the mechanical properties of frozen
soil. As a consequence, unfrozen water content provides an excellent means for express
mechanical properties in term of such variables as temperature, salinity and surface area.
Key words: frozen fine-grained soil, saline, unfrozen water, strength.
68
The research status and prospect of frozen protection technology
in Heilongjiang province
Xiang-min Qu
(Heilongjiang provincal hydraulic research institute)
Abstract: The total area of Heilongjiang province is 454 thousand ha, and the plantation area is
9265 thousand km 2 , and distributes four water systems including the Heilongjiang river,
songhuajiang river, wusulijiang and suifenhe in Heilongjiang province. The cold environment
bring up many problem for the water conservancy, the frozen destroy of hydraulic structure
induced by the soil frost heaving spread all over. Through the research over 30 years, obtained
tremendous achievements in the theory of engineering frozen soil and the technology of frozen
protection, solved many problems primarily occurred in the construction of water conservancy.
This paper summarized briefly the research status of frozen protection technology of water
conservancy in Heilongjiang province, and make a prospect of the research of frozen protection
technology in Heilongjiang province, based on the present theory status、methods of research on
engineering frozen soil and the development level of new material.
Keywords: engineering frozen soil, water conservancy, frozen protection technology