【作者】 梁宁慧；

【导师】 刘新荣；

【作者基本信息】 重庆大学 ， 土木工程， 2014， 博士

【摘要】 多尺度聚丙烯纤维混凝土(Multi-scale polypropylene fiber concrete，简称MPFC)是指同种品质，几何形态不同的两种或两种以上的聚丙烯纤维混掺在混凝土中的新型复合建筑材料。聚丙烯细纤维对混凝土的早期塑性开裂有抑制作用，对后期硬化混凝土抗裂性改善较小。以往采用聚丙烯纤维与钢纤维混掺的方法阻止硬化混凝土的开裂，提高韧性。但钢纤维存在易锈蚀，价格高等缺点，而聚丙烯粗纤维是一种新型增强增韧材料，具有耐腐蚀性能好，价格低等优点。在环境较为恶劣的工程中可代替钢纤维使用。鉴于此，本研究采用室内试验、理论分析和数值模拟相结合的方法，对MPFC试件进行较为深入的力学性能研究，主要研究内容和成果如下：①对MPFC进行抗裂性试验研究，结果表明聚丙烯细纤维在塑性态混凝土中的阻裂效应优于粗纤维，聚丙烯粗纤维在混凝土硬化阶段的抗裂效果优于细纤维；多尺度聚丙烯纤维在塑性态混凝土中的阻裂存在着正、负两种效应，在硬化阶段的抗裂效果与粗纤维相当。②通过单轴拉伸试验研究MPFC的抗拉性能，结果显示MPFC的抗拉峰值荷载较素混凝土有较小提高；MPFC在单向拉伸荷载作用下，应力-应变曲线下降段出现了低应力-应变硬化现象，MPFC抗拉韧性的改善幅度优于单掺聚丙烯纤维混凝土。③对MPFC进行单轴抗压试验研究，结果显示MPFC抗压峰值荷载有小幅提高；MPFC的抗压应力-应变曲线下降段比素混凝土平缓。MPFC峰值后的应力随应变的增加降低缓慢，应力一应变曲线下包面积较大，其峰值后的抗压韧性性能得到较好改善。④对MPFC进行四点弯曲试验研究，结果表明MPFC的抗弯强度有小幅提高；MPFC在弯曲荷载作用下，荷载-挠度曲线下降段出现非常明显的低荷载-变形硬化特性，曲线所包面积较大，峰值荷载后抗弯韧性的改善幅度远大于聚丙烯细纤维混凝土，同时也大于聚丙烯粗纤维混凝土。通过对比拉、弯性能指标建立MPFC拉弯对应关系，MPFC弯拉强度比值在2.15～2.80之间，抗弯韧性指数大于抗拉韧性指数，但数据整体变化趋势相同，表明四点弯曲试验可以代替单轴拉伸试验，成为评价MPFC独特力学性能的简单实用试验方法。⑤根据试验结果，建立适合于描述MPFC抗拉、抗压特性的损伤本构模型，得到聚丙烯纤维混凝土损伤因子的曲线形状参数，为此类MPFC在工程中的应用提供理论基础。⑥基于有限差分理论，推导多尺度聚丙烯纤维混凝土拉压损伤本构模型的有限差分表达形式；结合FLAC3D软件良好的开发平台，利用VC++程序实现多尺度聚丙烯纤维混凝土损伤模型的二次开发，获得该模型的动态链接计算程序，并通过试验模拟和算例分析验证二次开发模型程序的正确性和合理性。⑦利用多尺度聚丙烯纤维混凝土损伤模型的二次开发计算程序，对多尺度聚丙烯纤维隧道衬砌进行数值分析。结果表明多尺度聚丙烯纤维改善了混凝土的抗变形能力，提高了混凝土的刚度。更多还原

【Abstract】 Multi-scale polypropylene fiber concrete (MPFC) refers to the new type ofcomposite building materials that the same quality with different geometry of two ormore than two kinds of polypropylene fiber mix in concrete. Polypropylene fine fibercan prevent the early plastic cracking of concrete, but in the hardened process ofconcrete, toughness and crack resistance is improved very small. Steel fiber can reducethe crack number, shorten the crack length and improving toughness for hardening ofthe concrete, but steel fiber is easy to rust and the price is higher. Polypropylene crudefiber is a new kind of enhanced toughening materials, has a good performance atcorrosion resistant and the price is lower, so steel fiber can be substituted by thepolypropylene crude fiber in the engineering of the relatively bad environment. In viewof the above background, researches carried out in this paper would use a combinationmethods including testing research, theoretical analysis and numerical simulation, themain research contents and conclusions can be drawn as follows:①The crack resistance tests of MPFC show that the polypropylene fine fiber isbetter than crude fiber in the plastic state concrete for crack resistance effect, however,the polypropylene crude fiber is better than fine fiber in the hardening stage; Thecracking resistance of multi-scale polypropylene fiber has both positive and negativeeffects in the plastic state concrete and it is the almost same for anti-cracking effect tocrude fiber in the hardening phase.②The uniaxial tension tests of MPFC show that the peak tensile loads of MPFCwere increased; The decline period of the stress-strain curve of uniaxial tensile load forMPFC appears strain hardening characteristics for low stress, and the tensile toughnessof MPFC is better than that of only mixing polypropylene fiber concrete.③The compressive tests of MPFC show that the compressive peak load of MPFCis increased; The MPFC compressive stress-strain curve of the decline is flat than theplain concrete. The stress decrease slowly with increasing strain after peak for MPFC,stress-strain curve area is larger, the compressive resilience performance is improved.④Four-point bending tests of MPFC show that the bending strength of MPFCincrease slightly; The decline period of the load-deflection curve of bending load forMPFC appears strain hardening characteristics in low load and low load curve area islarger, the flexural toughness of MPFC is greater than that of the polypropylene finefiber concrete and is better than that of the polypropylene crude fiber concrete. The relationships between tensile and flexural properties are established by the comparisonof basic mechanical indexes under tensile and bending load. MPFC flexural-tensilestrength ratio is between2.15to2.80, flexural toughness index is greater than thetensile toughness index, but the same change in the overall trend of the data.Thecomparison results show that the four-point bending test method is a simple andpractical method to estimate the special mechanical performance of MPFC substitutingfor the uniaxial tensile test method.⑤According to the results of tensile and compressive test, established the MPFCdamage constitutive model of tensile, compression characteristic, getting the curveshape parameter of polypropylene fiber concrete damage factor. It provides a theoreticalbasis for widely application in engineering with MPFC.⑥On the basis of the finite difference theory，finite difference expression oftension and compression damage constitutive models for multiple-scales polypropylenefiber concrete were derived; Combined with the good redevelopment platform ofFLAC3Dsoftware and using VC++program to achieve the secondary development ofdamage model for multi-scale polypropylene fiber concrete, the dynamic linkcalculation procedure of the models were obtained. And through the simulation andtest numerical example to verify the correctness and rationality of the secondarydevelopment program model.⑦The secondary development calculation program for the damage model ofmulti-scale polypropylene fiber concrete was applied to numerical analysis ofmulti-scale polypropylene fiber tunnel lining. The results show that the multi-scalepolypropylene fibers improved the deformation resistance and the rigidity of theconcrete.更多还原