交通荷载下纤维加筋土非共轴特性及本构模型研究

With the rapid development of traffic, high-intensity traffic load pressure leads to subgrade disease stability problems more and more frequently. Fiber- reinforced technology can effectively upgrade the deformation properties of soil and improve the strength of soil. This technology has a widely application prospect in many embankment engineering and slope engineering. Traffic load will cause the principal stress axis rotates continuously and make the soil show non-coaxial characteristics. Further clarifying the reinforcement mechanism and non-coaxial characteristics of fiber-reinforced soil under traffic load is a key scientific problem to be solved for extending the application of this soil-reinforced technology. In this subject, a variety of laboratory tests, theoretical study, numerical simulation and engineering application will be carried out to explore the non-coaxial characteristics of fiber soil under traffic load. By laboratory HCA experiments, the non-coaxial deformation rules will be studied with different fiber content and fiber length. Then the best mixture ratio of fiber will be determined for embankment soil admixture. Based on the thought of non-coaxial constitutive models，the non-coaxial constitutive model of fiber reinforced soil is established by adding non-coaxial items in the Drucker-Prager model. With the help of ABAQUS platform, the numerical simulation of the laboratory HCA experiments will be carried out. By checking codes, the parameters of new non-coaxial constitutive model will be determined. The deformation and stability calculation of the reinforced embankment under traffic load will be carried out to verify the validity of the new constitutive model.This subject will make great scientific significance to improving the engineering design and theoretical analysis of the fiber-reinforced soil subgrade.

随着交通迅猛发展，高强度交通荷载导致路基病害频发。纤维加筋能有效改善土体变形性质，提高土体强度，在国内诸多路堤及边坡工程中有广泛应用前景。交通荷载会引起土体主应力轴连续旋转，使土体呈现非共轴特性。研究交通荷载下纤维加筋的补强机制和非共轴特性是这一土体补强措施推广运用亟待解决的关键科学问题。本项目从室内试验、规律分析、数学建模和工程应用四个方面，探索纤维加筋机理和非共轴力学性状。通过HCA实验研究不同纤维掺量、纤维长度时土的强度和变形规律，获得纤维作为路基土掺料的最优配合比。基于土体非共轴本构理论，在Drucker-Prager模型上新增非共轴项，建立纤维土的非共轴本构。在ABAQUS平台上进行HCA实验的数值仿真，校核程序并率定参数取值。对纤维加筋路基工程进行有限元计算，与实测数据对比以验证新建本构的有效性和合理性。本项目对提高纤维加筋土路基工程设计和理论分析水平具有重要科学意义。

纤维加筋土技术作为一种新型的土体补强技术有广泛的应用前景和环保价值，要拓展其在交通工程中的发展潜能，必须弄清开展复杂应力路径下纤维加筋土的力学特性试验研究进一步分析纤维加筋土在主应力轴连续旋转条件下强度和变形的演变规律，探索在交通荷载条件下纤维加筋土的补强机制及力学性状。本课题对素土、纤维加筋土进行一系列直接剪切试验、无侧抗压强度试验，微观电镜扫描试验，土样试验状态影像分析试验等，从宏观、细观、微观等多角度研究了纤维加筋机理，从力学强度改良的角度比较分析获得纤维加筋改良土的最优施工参数。基于SEM电镜扫描试验对土样性状进行微观分析，研究复杂应力状态及不同实验条件对土样中纤维的“弯曲”形态及“交织”形态的影响，弄清了复杂应力条件下纤维-土骨架的相互作用机理。对纤维加筋土进行包括①定向剪切条件；②主应力轴连续旋转条件；③主应力轴连续旋转及幅值耦合条件三组工况下力学特性试验，纤维加筋土均表现出明显的非共轴特性。随着主应力方向角的增大，纤维加筋土的非共轴角甚至会超过主应力方向角的大小。在主应力偏转的非比例加载过程中纤维加筋土的非共轴角也随着着主应力方向角周期性波动。交通荷载条件下，纤维加筋改良路基土的变形稳定计算时，非共轴特性不可忽略。本课题通过在传统弹塑性本构模型基础上添加非共轴项，建立了纤维加筋土的非共轴塑性本构模型，并基于数值软件ABAQUS的二次开发端口，将已建立的纤维加筋土非共轴本构模型嵌入数值分析软件中对室内实验进行数值仿真，理论计算结果和实验结果的一致性验证了新建模型的有效性和合理性。