Effects of confining pressure and water content on failure strain energy density of frozen silty sand are investigated in a comprehensive experimental program of triaxial compressive test under the condition of various confining pressures and a wide range of water content. The results show that when the water content is about 30.6%

the frozen soil is prone to plastic failure

while brittle failure occurs at other water contents. The influence of confining pressure on failure strain energy density can be divided into low confining pressures phase

medium confining pressures phase and high confining phase. And water content has an important effect on the boundary confining pressure. Two types of the effect of water content on failure strain energy density are observed. When confining pressure is low（50 k Pa）

failure strain energy density begins to increase with increasing the water content

and reaches a maximum（600 k Pa） at water content of 30.6%. Then

as the water content continues to increase

the damage energy density decreases. When the water content reaches 60 k Pa

the further increase of the water content no longer affects the damage energy density

i.e.

the damage energy density of the frozen soil is close to that of the ice. When the confining pressure is high（≥ 500 k Pa）

there is no initial increase in the failure strain energy density compared to the low confining pressure stage.