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青藏直流±400 kV输变电工程中采用表面光滑的玻璃钢覆盖基础表面,以减少切向冻胀力对基础的冻拔作用。过去的研究鲜有涉及土体特别是冻土与玻璃钢基础接触面的力学特性,为指导冻土区基础设计和安全评价,采用应变直剪仪开展了多种含水率和温度条件下青藏粉土-玻璃钢接触面直剪试验研究。结果表明,青藏粉土-玻璃钢接触面屈服时相应剪切位移很小,应变硬化阶段短暂或不显著;冻结状态下接触面应力-位移性状呈脆性破坏型,存在明显峰值;融化状态时接触面的剪应力-位移性状呈塑性破坏型,其应力-位移关系曲线为弱软化型和屈服型,没有明显峰值;融化状态时接触面抗剪强度值随含水率的增加而缓慢减小,冻结状态时其强度随负温绝对值和含水率的增加而增大,且随着土体含水率的增大,温度降低导致接触面抗剪强度增强效果更加显著,土体含水率大于19%后抗剪强度趋于稳定;温度对抗剪强度的影响主要体现于黏聚力的改变,且随着含水率的增加,温度影响增强。接触面内摩擦角随负温绝对值增加而减小,随含水率的增加而减小。
Qinghai-Tibet DC ± 400 kV power transmission project using a smooth surface of glass fiber reinforced plastic covering the base surface, in order to reduce the tangential frost heaving force on the basis of the role of freezing. In the past, little research has been done on the mechanical properties of soil, especially on the basic contact surface between permafrost and FRP. In order to guide the basic design and safety evaluation of permafrost regions, Study on Direct Shear Test of FRP Contact Surface. The results show that the corresponding shear displacements at the contact surface of Qinghai-Tibet silt-FRP are small, and the stage of strain hardening is short or insignificant. The stress-displacement behavior of the interface is fragile and brittle, with obvious peak value. The contact surface The shear stress-displacement behavior is plastic failure mode, and the stress-displacement curve is weakly softening and yielding with no obvious peak. The shear strength of the interface decreases slowly with the increase of moisture content in the thawing state, When the absolute value of the negative temperature and water content increases, and with the increase of soil moisture content, the decrease of temperature leads to more significant increase of the shear strength of the contact surface. Soil moisture content is greater than 19% after the resistance The shear strength tends to be stable. The influence of temperature on shear strength is mainly reflected in the change of cohesion, and with the increase of moisture content, the temperature influence is enhanced. The friction angle of contact surface decreases with the absolute value of negative temperature and decreases with the increase of water content.