不同建筑固废再生骨料取代率下粗粒土填料永久变形试验及预估模型

Permanent Deformation Prediction Model of Coarse-grained Fill Materials Incorporating Different Proportions of Aggregates Recycled from Building Demolition Wastes

为探究城市建筑拆除固废再生骨料部分或全部取代天然骨料用于粗粒土路基填料的可行性,开展了一系列不同再生骨料取代率、含水率、围压和剪应力比等组合下的室内大型动三轴试验,定量研究了土性参数和应力状态对试样累积塑性应变特性的影响规律;基于不同试样轴向塑性应变累积的多阶段特征,提出了相应的预估模型,并开展了预估模型参数与各试验变量之间的统计相关性分析,据此进一步优化了预估模型。研究结果表明:含水率、剪应力比和围压的增大均会促进试样累积塑性应变的增长,取代率为85%的再生骨料路基填料具有较优的抗永久变形能力;剪应力比为0.7是再生骨料路基填料安定行为划分区间的重要参考量,位于塑性蠕变区间试样的后压实阶段和次循环压缩阶段的分界点,可初步定为2000次。所建立的预估模型很好地反映了试样的安定行为特性和累积塑性应变发展的多阶段特征,可为相似路基填料的长期路用性能评定提供理论依据。

To explore the feasibility of partially or completely replacing natural aggregates with recycled aggregates from construction and demolition waste for coarse-grained soil subgrade filling,a series of laboratory monotonic/repeated load triaxial tests were conducted under different combinations of recycled aggregate replacement proportion,moisture content,confining pressure,and shear stress ratio.The effects of aggregate properties and stress states on the shear strength and accumulative plastic strain characteristics of the specimens were investigated.Based on the multistage characteristics of the accumulated plastic axial strain of the different specimens,a new plastic strain prediction model was established.The model parameters were statistically correlated with the test variables of stress states and physical properties,and the prediction model was optimized accordingly.The results show that the increases in moisture content,shear stress ratio,and confining pressure promote an increase in the accumulative plastic strain of the specimens,and that the recycled aggregate subgrade filling with a replacement proportion of 85%exhibits better resistance to permanent deformation.The shear stress ratio of 0.7 is an important threshold for the shakedown behavior of recycled aggregate subgrade filling,and the post-compaction stage and the secondary cyclic compression stage of the specimens in the plastic creep category can be preliminarily separated upon 2000 load applications.The prediction model established in this study reflects the shakedown behavior of the specimens and the multistage characteristics of accumulated plastic axial strain development,which can provide a theoretical basis for the long-term road performance evaluation of similar subgrade fillings.