预裂型水泥稳定碎石强度与温缩特性机理仿真

针对水泥稳定碎石材料易产生裂缝，从而降低路面使用寿命这一问题，基于粗集料预处治技术提出了一种预裂型水泥稳定碎石材料改良思路；通过对水泥稳定碎石中一定比例的粗集料进行预处治，使其表面裹附一层新的物质，从而形成新的界面，分散了收缩过程中降低开裂对材料整体均一性的影响，继而仿真分析了这种新型材料的强度特征和温度收缩裂缝发展的内部机理；基于离散单元法建立了预裂型水泥稳定碎石仿真模型，并分别开展了虚拟无侧限压缩试验和有限制梁温度收缩开裂试验。研究结果表明：在假设预处治粗集料仅影响粗集料界面强度的前提下，试件的无侧限抗压强度与界面强度比和预处治粗集料替换比这2个关键参数之间呈现出良好的线性相关性，可通过回归公式进行计算与预测；当界面强度比大于40%时，预处治粗集料替换比的增加仅会降低材料的强度而不能避免局部贯穿裂缝的产生；当界面强度比小于40%时，随着预处治粗集料占比的增加，试件在收缩过程中产生的裂缝由局部贯穿宽裂缝转变为均匀分布的微裂缝，从而保证了材料在收缩开裂后的整体均一性；当界面强度衰减至未处治材料的30%以下，且预处治粗集料替换比大于30%时，可有效减少试件内部贯穿裂缝的产生，从而缓解了水泥稳定碎石的温缩开裂。

Simulation on strength and thermal shrinkage property mechanisms of pre-cracked cement stabilized crushed stone

For the problem that the cement stabilized crushed stone tends to develop cracks, thus reducing the service life of pavements, an idea based on the coarse aggregate pretreatment technology was proposed to improve the pre-cracked cement stabilized crushed stone material. Some coarse aggregates of the cement stabilized crushed stone were pretreated to make their surfaces coated with a layer of new material, and thus a new interface was formed, to alleviate the influence of reducing cracks on the overall uniformity of the material during the shrinkage process. Then, the strength properties and the internal mechanism of crack development under the thermal shrinkage of new material were analyzed through simulations. A simulation model of the pre-cracked cement stabilized crushed stone was built based on the discrete element method. The virtual unconfined compression tests and restrained thermal shrinkage and cracking beam tests were conducted, respectively. Research results show that under the premise that the pretreatment of coarse aggregates only affects the interface strength of coarse aggregates, there is a good linear correlation between the unconfined compressive strength of the specimen and the two key parameters including the interface strength ratio, as well as the pretreated coarse aggregate replacement ratio. The unconfined compressive strength can be calculated and predicted through the regression formulas. When the interface strength ratio is higher than 40%, the increase in the pretreated coarse aggregate replacement ratio will only reduce the material's strength and cannot avoid the locally transverse cracks. When the interface strength ratio is lower than 40%, the cracks appearing during the shrinkage process of the specimen will change from the locally transverse cracks to the evenly distributed micro-cracks as the pretreated coarse aggregate percentage increases, thus ensuring the overall uniformity of the material after the shrinkage cracking. When the interface strength is less than 30% of that of the untreated material, and the coarse aggregate replacement ratio is higher than 30%, the internally transverse cracks of the specimen will be effectively reduced, and the thermal shrinkage cracking of the cement stabilized crushed stone can be alleviated.