干湿循环下纤维改性滨海水泥土力学特性研究

Study on mechanical properties of coastal cement soil modified by fiber under dry-wet cycle

为了探究聚丙烯纤维对滨海水泥土力学特性的影响,考虑7 d和28 d两个龄期,以及0,1,3,5,7,9共6个干湿循环,开展了干湿循环下聚丙烯纤维改性滨海水泥土(PFCC)的无侧限抗压试验,并建立了可同时考虑峰值前应力增长速率和峰值后强度跌落速率的PFCC脆性指数新模型,用以评价纤维滨海水泥土的脆性破坏。试验结果表明:PFCC试样的抗压强度随着干湿循环次数的增加逐渐增大;试样的脆性指数也随干湿循环次数的增加逐渐增大,且7 d养护龄期下的试样在干湿循环5次后,其脆性指数大于同龄期下正常养护的试样,而28 d养护龄期下的试样干湿循环后其脆性指数一直大于同龄期下正常养护的试样;随着干湿循环次数的增加,纤维改性滨海水泥土的脆性指数逐渐增大,纤维对水泥土试样的加筋作用逐渐减弱。

In order to study the effect of polypropylene fiber on the mechanical properties of coastal cement-soil,the unconfined compression test for coastal cement-soil modified by polypropylene fiber(PFCC)under dry-wet cycles was carried out,considering two curing ages of 7d and 28d and six dry-wet cycles of 0,1,3,5,7 and 9.Moreover,a new PFCC brittleness index model which can consider both the pre-peak stress growth rate and the post-peak strength drop rate was established to evaluate the brittle failure characteristics of PFCC.The test results showed that the compressive strength of PFCC specimens increased with the increasing of dry-wet cycles.The brittleness index of PFCC samples also increased with the increasing of dry-wet cycles,and the brittleness index of the samples under 7d curing age after 5 times of dry-wet cycles was greater than that of the samples under normal curing at the same age,while the brittleness index of the samples under 28d curing age in dry-wet cycles was always greater than that of the samples under normal curing at the same age.With the increase of dry-wet cycles,the brittleness index of PFCC increased gradually,and the reinforcement effect of fiber on cement soil samples decreased gradually.