聚丙烯纤维土剪胀规律的试验研究及机理分析

It is observed that randomly distributed polypropylene fibers act to interlock particles and group of particles in a unitary coherent matrix thus improve the mechanical behavior of the reinforced soils. Polypropylene fiber inclusion clearly increases soil shear strength, tensile strength, and reduces the loss in strength post-peak. The effectiveness of fiber reinforcement will depend on the deformation characteristics of the host soil as well as the fiber properties and the fiber content. Stress-dilatancy relation plays an essential role in constitutive modeling for soils. A systematic series of laboratory tests will be performed to investigate the fiber reinforcement. The increase in the effective confining stress provided by the fibers can be deduced from comparing the stress-strain and strength behavior of reinforced soil and pure soil. Attention will be paid to the relationship of stress ratio and plastic strain increment ratio observed in shearing as well as their constitutive modeling. When a polypropylene fiber-soil assembly dilates in response to applied shear deformations, the work done by the driving stress will be dissipated by not only particle sliding but also the fiber deformation. Using the increase in the effective confining stress, the work dissipated by the polypropylene fiber deformation can be expressed. Based on the minimum rate of internal work assumption, the stress-dilatancy relation will be deduced from combining considerations of particle sliding and fiber deformation. The stress-dilatancy relation will help guide and form the basis for the development of a constitutive model for polypropylene fiber-reinforced soils.

随机分布的聚丙烯纤维在土体中彼此交错形成网状，可显著提高土的抗剪强度、抗拉强度，减少其峰值强度折减，增加土的塑性和韧性。聚丙烯纤维土的力学性状由土体特性、纤维特性及纤维含量等因素决定。描述土体剪胀规律的剪胀方程是建立土体本构模型的核心。对不同聚丙烯纤维含量进行一系列室内试验研究，对比聚丙烯纤维土与素土应力应变关系和强度特性，分解出聚丙烯纤维对土的约束应力。分析聚丙烯纤维土应力比和塑性应变增量比的关系，将外力克服剪胀阻力需要做的额外功分解为由土颗粒运动和纤维变形两部分所消耗的能量，揭示聚丙烯纤维土的特殊剪胀机理。利用纤维对土的约束应力表示与加筋纤维有关的耗散能，基于最小比能原理建立聚丙烯纤维土的剪胀方程。在此基础上建立纤维土的弹塑性本构模型，描述聚丙烯纤维土的特殊力学性状。

添加随机分布的聚丙烯纤维在土体中彼此交错形成网状，可显著提高砂土的抗剪强度，减少其峰值强度折减。聚丙烯纤维加筋砂土的力学性状由土体特性、纤维特性及纤维含量等因素决定。描述土体剪胀规律的剪胀方程是建立土体本构模型的核心，对比聚丙烯纤维加筋砂土与纯砂土的应力应变关系和强度特性，分解出聚丙烯纤维对砂土的约束应力。分析了聚丙烯纤维加筋砂土应力比和塑性应变增量比的关系，将外力克服剪胀阻力需要做的额外功分解为由土颗粒运动和纤维变形两部分所消耗的能量，利用纤维对土的约束应力表示与加筋纤维有关的耗散能，基于最小比能原理建立了聚丙烯纤维加筋砂土的剪胀方程，揭示了聚丙烯纤维加筋砂土的特殊剪胀机理。经过对比发现试验结果与模型结果具有良好的一致性。