透水性级配碎石基层填料永久变形特性及预估模型

Permanent Deformation Behavior and Prediction Models of Unbound Permeable Aggregate Base Materials

透水性级配碎石基层填料因其大而连通的孔隙可有效增强道路系统的排水和生态功能,对“海绵城市”建设意义重大,但其在交通荷载重复作用下的变形稳定性仍有待深入研究。针对由颗粒堆积理论提出的石砂比(G/S)指标所设计的5种不同的透水性级配碎石填料试样,开展了室内动-静三轴试验,研究了级配和应力状态对填料抗剪强度和累积塑性(永久)应变特性的影响,相应地提出了基于级配和剪应力比的力学-经验法预估模型,验证了模型的准确性。研究结果表明:相同G/S值的填料试样在同一围压水平下的轴向累积塑性应变随剪应力比的增大而增大,在同一剪应力比水平下的轴向累积塑性应变随围压的增大而增大;G/S=1.6~1.8的级配碎石填料抗剪强度和抗永久变形性能均最佳,预估模型对于不同G/S值、剪应力比和围压水平下透水性级配碎石填料轴向累积塑性应变的预测具有较高的准确性。

Unbound permeable aggregate base(UPAB)materials,with large connected air voids,can effectively improve the drainage and ecological function of road systems,thereby promoting the construction of sponge cities.However,it is necessary to study the deformation stability of such materials under the application of repeated traffic loads.Five different samples were created with different UPAB gradations,using the gravel-to-sand ratio(G/S)concept,derived from the particle packing theory.To study the effects of gradation and stress states on permanent deformation characteristics,a series of monotonic and repeated load triaxial compression tests on specimens with different G/S values were conducted.A mechanistic-empirical permanent deformation model was developed based on the laboratory test results,and the accuracy of the model was verified.The accumulated plastic axial strain of specimens with the same G/S value increases with increasing shear stress ratio(SSR)at the same level of confining pressure as well as with increasing confining pressure at the same SSR level.An optimum G/S ratio,approximately 1.6,which would yield the best permanent deformation behavior,is identified.The developed model shows high accuracy at different combinations of G/S,SSR,and confining pressure levels.