基于DIC技术的固废粒料包裹格栅加筋试验研究

Experimental Study on Reinforced Geogrid of Construction and Demolition Wastes Based on DIC Technology

为了控制高速公路改扩建新老路基拼接后的差异沉降,该文针对老路台阶松散、含水率过高,提出一种层状处置结构,即在老路台阶面设置一层固废层包裹格栅,对比了其与砂包裹、掺入消解石灰等措施的处置效果,并采用数字散斑相关技术(DIC)观测加筋影响带,进而确定路基不同层位固废包裹层厚度。进一步分析颗粒旋转与位移情况,验证DIC观测所确定加筋影响带的可靠性与准确性。试验结果表明:①在提高老路台阶筋土界面强度的措施中,效果由优至劣依次为:固废C(粒径为10~20 mm)>固废B(粒径为5~10 mm)>砂>固废A(粒径为1~5 mm)>掺灰6%>掺灰4%,增强效果随包裹固废粒径的增大而提升;②DIC试验结果表明:加筋影响带随法向应力的增大而减小,且格栅上方厚度大于格栅下方,发生旋转的颗粒主要集中在格栅下方3 cm内,格栅上方5 cm内;③基于加筋影响带厚度确定固废包裹层最佳厚度建议值:对于路基中部约为20 cm,路基底部铺设厚度约为15 cm,路基上部铺设层厚度应不小于25 cm。

In order to control differential settlement caused by new and old subgrade connections after expressway reconstruction and expansion,this paper proposed a layered treatment structure for the loose steps of the old road with high water content.A layer of construction and demolition waste was laid on the step surface of the old road to wrap the geogrid.The treatment effect was compared with that of sand wrapping and lime mixing,and the digital speckle correlation(DIC)was used to observe the reinforced influence zone,so as to determine the thickness of different layers of the subgrade wrapped by construction and demolition wastes.The particle rotation and displacement were further analyzed,and the reliability and accuracy of the reinforced influence zone determined by DIC observation were verified.The test results show that:①Among the measures to improve the interface strength of reinforced soil in the old road steps,the effect from good to bad is construction and demolition wastes C(particle size of 10‒20 mm)>construction and demolition wastes B(particle size of 5‒10 mm)>sand>construction and demolition wastes A(particle size of 1‒5 mm)>mixed ash of 6%>mixed ash of 4%,and the reinforcement effect increases with the increase in the particle size of the construction and demolition wastes;②The DIC test results show that the area of the reinforced influence zone decreases with the increase in normal stress,and its thickness above the geogrid is greater than that below the geogrid.The particles that rotate are mainly concentrated within 3 cm below the geogrid and 5 cm above the geogrid;③The recommended thickness of the layer wrapped by construction and demolition wastes is determined based on the thickness of the reinforced influence zone:about 20 cm in the middle of the subgrade,about 15 cm in the bottom of the subgrade,and not less than 25 cm in the upper part of the subgrade.