城市固体废弃物应变硬化机制与强度参数确定方法

 通过对常规三轴仪进行改装，开展最大竖向应变达50%的城市固体废弃物(MSW)三轴剪切试验。试验表明：大应变条件下MSW试样发生破坏且其破坏应变随填埋深度增大而减小。通过组分分离得到MSW的基本相和加筋相，并对其分别进行三轴固结排水剪切(CD)试验，发现其应力–应变曲线均呈应变硬化型。在此基础上，对基本相进行筛分，并结合不同粒径粒组的微观结构阐述基本相中有机纤维体的存在形式及其加筋作用机制。进一步对各粒组进行CD试验，发现除粒径小于0.075 mm的粒组外其余粒组的应力–应变关系均表现为应变硬化。通过基本相灼烧前后的CD试验比较，发现有机纤维体在应变达到一定程度后才开始发挥加筋作用，且剪切过程中伴随着纤维体断裂以及纤维体与颗粒间滑移。最后，基于MSW的三轴剪切试验结果，分别对三轴固结不排水剪切(CU)试验和CD试验抗剪强度参数的确定方法进行探讨。

STRAIN-HARDENING MECHANISMS AND METHODS FOR DETERMINING STRENGTH PARAMETERS OF MUNICIPAL SOLID WASTE

A series of triaxial shear tests on municipal solid waste(MSW) with the maximum vertical strain of approximately 50% were carried out by a modified triaxial apparatus. The test results show that MSW samples failed under large-strain condition and the failure strain decreases with the increasing of the landfill depth. The basic and reinforced phases of MSW were separated and triaxial consolidated drained(CD) shear tests were carried out on each phase. The results show that the stress-strain curves of both basic and reinforced phases have the strain-hardening characteristics. The structural formation and reinforcement effect of the organic fibers in basic phase were described through sieving and microscopic observation on granule groups. Then CD tests of several granule groups were carried out and the results demonstrate that every group has a strain-hardening stress-strain curve except the group with particle diameter smaller than 0.075 mm. The stress-strain curves of the basic phase before and after burned were compared，showing that the organic fibers will not play the reinforcement effect until a certain value of strain is reached. Fiber fracture and slipping along the interface seem to exist during shearing. Finally，based on the results of triaxial shear tests，methods for determining the shear strength parameters of triaxial consolidated undrained shear(CU) and CD tests were discussed respectively.