为研究碾压混凝土劈裂过程中层面裂缝演化规律，对不同砂浆处理的碾压混凝土开展劈裂抗拉试验，分析试件破坏形态和不同龄期的劈裂抗拉强度，结合数字图像相关（digital image correlation，DIC）技术观测碾压混凝土劈裂过程中层面裂缝发展规律，获取裂缝相关参数，包括裂缝宽度、裂缝扩展速率，并测定层面附近的显微硬度，分析裂缝扩展速率与显微硬度的关系。结果表明：砂浆处理可以有效提高层面结合效果和劈裂抗拉强度，降低裂缝扩展速率；层面裂缝发展过程分为初始、萌生、扩展、贯通4个阶段，扩展速率在贯通阶段呈陡增趋势，未处理试件的裂缝宽度最大；层面显微硬度明显低于上下层，砂浆处理能增强层面显微硬度，层面显微硬度与裂缝扩展速率、劈裂抗拉强度的决定系数R2均在0.9以上，相关性较高。

Roller compacted concrete has the characteristics of low hydration heat, zero slump, high application speed, and low cost, making it suitable for constructing large concrete structures. The roller compacted concrete dam is constructed layer by layer using the roller compacted construction method with dry and hard concrete. However, layered construction often forms many layers, and the interlayer joints of rolled concrete are the weak link in engineering. Under continuous loads, cracks, holes and other defects will inevitably appear, endangering the anti-skid stability of the layer and posing a threat to the safety and durability of the dam. Layer cracks are a significant sign of structural failure. Therefore, it is necessary to conduct research on the crack propagation law of roller compacted concrete under load. Three different types of mortars (cement mortar, nano SiO2 mortar, and expansion agent mortar) were designed to treat the layer of roller compacted concrete specimens, and a universal testing machine was used to apply splitting load for splitting tensile test. The splitting tensile strength and surface morphology of different specimens were recorded. During the splitting tensile test, the DIC analysis system was used to collect the strain of the specimen during the splitting process, in order to obtain a strain cloud map of the entire process of crack formation and propagation in the roller compacted concrete layer. The variation patterns of crack width and propagation rate were calculated and analyzed through system software. The cutting machine was used to extract the layer of roller compacted concrete, and the microhardness of different mortar treatments was tested using a microhardness tester. The microhardness has a high linear relationship with crack propagation rate and splitting tensile strength. The experimental results indicated that: (1) The mortar treatment could better embed aggregates and provide mechanical interlocking force for layer bonding. Therefore, the splitting tensile strength of the compacted concrete layer was improved after mortar treatment. Nano SiO2 and expansion agents could promote cement hydration and fill pores, and the improvement effect of the three types of mortar was based on the following: nano SiO2 cement mortar. (2) Under the action of splitting load, strain concentration zones gradually appeared on the layer of roller compacted concrete. Based on the change of strain color gradient, the crack development process was divided into initial stage, initiation stage, expansion stage, and penetration stage. Mortar treatment could improve the stability of the layer structure and delay the development of layer cracks. The load displacement curve shown that the peak loads of the specimen layer treated with cement mortar, nano SiO2 mortar, and expansion agent mortar were 44.43 kN, 52.90 kN, 62.48 kN, and 59.81 kN, respectively. (3) The width and propagation rate of cracks were basically 0 in the initial stage, and then began to rise, with a sharp increase in the expansion stage. The crack propagation rate of the layer treated with nano SiO2 mortar were the smallest. (4) The microhardness of layer was lower than that of the upper and lower layers of rolled compacted concrete, and the determination coefficients between microhardness, crack propagation rate, and splitting tensile strength are 0.941 and 0.960, respectively. When carrying out roller compacted concrete construction, the layer as a weak structure, the occurrence of cracking needs to be considered. The expansion law of cracks on the layer of roller compacted concrete was studied through DIC technology, which could provide reference value for improving the bonding quality of roller compacted concrete dam layer and reducing the occurrence of cracks.