不同纤维掺量风积沙水泥基材料三轴试验研究

Triaxial test study on aeolian sand cement-based materials with different fiber content

风积沙储量丰富,分布广泛,取材方便,在沙漠地区已将其作为建筑材料应用于铁路路基及沙害防治工程建设之中。通过添加纤维能够实现提升风积沙水泥基材料的物理力学性能以满足工程服役要求。为了揭示纤维增强风积沙水泥基材料在环境应力及工程服役荷载作用下的应力应变性能,评价纤维对风积沙水泥基材料的加筋效果,开展聚丙烯纤维增强风积沙水泥基材料三轴试验,通过改变纤维的掺量以及侧向围压的大小,分析应力应变曲线特征值的变化规律,探究材料的变形及破坏规律。研究结果表明:试件破坏时的裂缝发展方向与轴向的夹角随围压增大由0°到90°逐渐过渡。与无围压作用下试件的应力应变曲线存在明显峰值点这一特点相比,三向应力共同作用时曲线的下降段变得舒缓,当围压超过15 MPa时,曲线会一直上升至试验结束。随纤维掺量的提升,试件的峰值应力先升后降,掺量0.5%时为最大值,与不掺纤维的对照组相比其峰值应力提升了17.3%~27.4%;在以上试验数据的基础上,推演出聚丙烯纤维增强风积沙水泥基材料的应力应变本构方程。研究成果对纤维增强风积沙水泥基材料在沙漠铁路建设中的工程应用具有借鉴和参考价值。

Aeolian sands, which are abundantly available, widely distributed, and easy to acquire, have been used as construction materials in railway subgrade and sand hazard control projects in desert regions. The physical and mechanical properties of aeolian sand cement-based materials can be improved by adding fibers to satisfy the requirements of engineering services. In order to reveal the stress-strain performance of fiber reinforced aeolian sand cement-based materials under environmental stress and engineering service loads, and evaluate the reinforcement effect of fibers on the aeolian sand cement-based materials, the triaxial tests of polypropylene fiber reinforced aeolian sand cement-based materials were carried out. By changing the amount of fiber and the lateral confining pressure level, the variation law of the characteristic values of the stress-strain curve was analyzed, and the deformation and failure law of the material was explored. The results show that, the angle between the crack development direction and the axial direction during the failure of the specimen gradually transits from 0° to 90°as the confining pressure increases. Compared with the obvious peak point of the stress-strain curve under no confining pressure, the descending section of the stress-strain curve under the combined action of threedimensional stress states becomes slower. When the confining pressure exceeds 15 MPa, the curve rises until the end of the test. With the increase of fiber content, the peak stress of the specimens first increased and then decreased. It reached the maximum when the fiber content was 0.5% and increased by 17.3%~27.4% as compared to the control group without fiber. Based on the above test data, the stress-strain constitutive equation of polypropylene fiber reinforced aeolian sand cement-based material was deduced. The research results in this paper have reference value for the engineering applications of fiber reinforced aeolian sand cement-based materials in desert railway construction.