再生细骨料地基动力特性试验研究

Experimental study on dynamic response of ground with recycled fine aggregates

建筑固废的处理再利用是使得建筑垃圾资源化的重要措施。为了进一步推进建筑固废动力特性的研究和工程应用,以建筑固废破碎筛分后的再生细骨料为材料,制备成地基土试样。利用三轴动力测试,分析了排水条件下,不同级配(级配良好、级配较差)、相对密度Dr(45%、70%)、围压σc(25、50、100、200 kPa和400 kPa)和含水率(0%、5%、15%、25%和30%)对再生细骨料地基动力特性的影响,并与标准砂地基的动力特性进行对比分析。试验结果表明:再生细骨料的比重为1.912,小于标准砂的(2.65),使得再生细骨料试样动剪切模量小于标准砂的;阻尼比在剪应变γ较小(γ<0.03%)时与标准砂的差别不大,而剪应变较大(γ>0.03%)时小于标准砂的;在四个影响因素中,围压的变化对动剪切模量的影响最大,围压增大时,动剪切模量明显增大,其次影响较大的是相对密度以及含水率,级配的影响相对最小。通过对可破碎性的分析发现,再生细骨料在小围压(σc<200 kPa)条件下基本未发生破碎,即使在围压为400 kPa、等效循环应力比rcs为0.3的条件下也只发生了少量破碎,此破碎量符合国家标准。

The treatment and reuse of construction solid waste is an important measure to make construction waste into resources.In order to further promote the research on the dynamic characteristics of building solid waste and its engineering application,the recycled fine aggregate(RFA)after crushing and sieving of building solid waste was used as the material to prepare foundation soil samples.The dynamic response of ground with recycled fine aggregates was investigated through cyclic triaxial testing system in the drained condition.In this study,the effects of factors including gradation(well graded and poor graded),relative density(45%,70%),effective confining pressure(25,50,100,200 kPa and 400 kPa)and moisture content(0%,5%,15%,25%and 30%)were examined by comparing with the response of standard sand.The results show that the specific gravity of RFA is 1.912,which is smaller than that of standard sand(2.65),and making the dynamic shear modulus of RFA smaller than that of standard sand.The damping ratios of RFA are almost the same with the standard sand when the shear strain is below 0.03%and lower than the standard sand when the shear strain is above 0.03%.It is also showed that the confining pressure is the most obvious factors on the dynamic response of RFA specimens.The dynamic shear modulus increases obviously when the confining pressure increases.The relative density and water content are the secondary important factors,and the gradation has the least effect.Through crushing analysis,in the small confining pressure(within 200 kPa),the particles are hardly crushed,even in the confining pressure of 400 kPa and equivalent cyclic stress ratio of 0.3,the amount of particle crushed is small,which is conformed to the national standard code.