高聚物胶凝堆石料静力特性试验研究

Experimental research on mechanical properties of PFA-reinforced rockfill materials

采取加固措施可提高土体抗剪强度、减小变形等。采用聚氨酯高聚物胶凝堆石料加固土石坝以改良堆石料强度、变形特性。开展了聚氨酯胶凝堆石料三轴剪切试验研究,结果表明:聚氨酯胶凝堆石料偏应力-轴向应变曲线具有明显的非线性,抗剪强度提高;采用抛物线拟合偏应力-轴向应变曲线,可反映其应变软化和应变硬化,并得到初始弹性模量随聚氨酯含量的提高而提高;聚氨酯泡沫填充堆石颗粒间孔隙并将堆石颗粒黏结在一起,减少颗粒破碎、颗粒重排列,使堆石料剪缩特征减弱,当聚氨酯含量高时表现出剪胀;聚氨酯增加了堆石料准黏聚力,对内摩擦角无明显影响。通过有限元方法对堆石坝变形和稳定性进行分析,结果表明,聚氨酯加固堆石坝可减少边坡浅层滑动,增大滑弧深度,提高坝坡稳定安全系数。

The reinforcement could increase the shear strength of soil and reduce the deformation of soil. Polyurethane foam adhesive（PFA） is adopted to reinforce rockfill materials. A series of triaxial shear tests on the PFA-reinforced rockfill materials is conducted. The test results show that the PFA-reinforced rockfill materials exhibit a nonlinear deviatoric stress-axial strain behavior. The shear strength increases with increasing the PFA ratio. A parabola formula is used to fit the deviatoric stress-axial strain curve and reflect the strain softening and hardening behaviors of the PFA-reinforced rockfill materials. The initial elastic modulus of the PFA-reinforced rockfill materials increases with increasing the PFA ratio. The mechanical effect of the PFA is to fill the voids among particles and then to bond the particles. As a result, the particle breakage and rearrangement reduce and the feature of volumetric shrinkage decreases. The dilatancy behavior increases with increasing the PFA ratio. Adding PFA into rockfill materials can enhance the cohesion, but it has no obvious effect on the frictional angle. The deformation and stability of a dam are analyzed using the finite element method. It is shown that the PFA-reinforced method can largely reduce the shallow slide of slope, enlarge the depth of the slip circle and increase the stability of rockfill dam.