## 1 Introduction  
In the face of a large number of geotechnical engineering problems at present, it has become the main means to carry out rock-like test research of simulated field raw rocks by selecting raw materials with wide sources, safety and environmental protection and low cost. Field testing has important theoretical guidance and engineering significance for engineering design and construction. Rock-like material is a kind of rock similar material wrapping up aggregate [1], which is formed by complex chemical reactions of cementitious material, aggregate, admixture and water. Mechanical properties of the material mainly depend on the compactness of the specimen and the internal pore microstructure. Many studies have proved that there is a strong relationship between pore structure and strength in natural and artificial porous materials, and the existence of pores has a great influence on physical properties of rocks [2; 3; 4]. Research into the effect of pore microscopic characteristics on mechanical properties can help us to improve our understanding of materials. Therefore, it is necessary to analyze and study the relationship between pore structure and mechanical properties of rock-like materials. In recent years, the research on micro-pore structure detection of porous materials has been developing rapidly. At present, the methods of micro-pore detection in rocks include mercury injection test (MICP), scanning electron microscope (SEM), nuclear magnetic resonance (NMR), etc. Among them, MICP can characterize the spatial structure of rock pores and determine the pore size distribution of different pores, and SEM is mainly used for high-resolution two-dimensional imaging of rock specimens and characterization of microscopic pore morphology. Many scholars have carried out experimental research in related directions combined with detection methods. [PERSON] [5] confirmed the existence of two main types of pores in complex carbonate reservoir rock samples by MICP, NMR and SEM. [PERSON] [6] and [PERSON] [7] quantitatively characterized the distribution of micro-pore structure in tight sandstone from multiple angles of SEM, high-pressure mercury injection and other detection methods. [PERSON] [8] studied the internal microstructure of cement mortar building materials by means of SEM, MICP and other methods of microscopic pore measurement. Nuclear magnetic resonance (NMR) testing is non-destructive testing technology which has gained rapid development in recent years, and has been widely used in the characterization of rock pore microstructure. Many scholars have taken NMR as the main research method and carried out experimental studies on the microstructure and mechanical properties of rock materials. [PERSON] [9] and [PERSON] [10] discussed the micro-pore structure evolution of sandstone under freeze-thaw cycles by NMR analysis. [PERSON] [11] and [PERSON] [12] carried out the cyclic freeze-thaw test and cyclic dynamic impact test on granite and sandstone, studying the microporosity changes of different rocks under cyclic impact by NMR. [PERSON] [13; 14; 15; 16] carried out laboratory freeze-thaw cycle tests on sandstone materials at different cycle numbers and studied the pore structure evolution and fractal characteristics of pores with different radius under freeze-thaw cycles were studied by NMR and imaging analysis. [PERSON] [17] used NMR to study the changes of porosity and pore size distribution of sandstone samples under the coupling of the freeze-thaw cycle and acidic solution. [PERSON] [18] combined NMR and electron micrography to analyze the internal relationship between the micro-pore changes and macro mechanical properties of slope rocks under rainfall conditions. With the deepening of research, many scholars have found that macroscopic mechanical properties of materials not only depend on porosity but also the pore distribution of different internal radii [19; 20; 21].