Metakaolin (MK), which has a fine particle size and higher activity in high alkaline environments, has been widely used in the fields of soil treatment engineering to stabilize soils. MK is used to replace part of ordinary Portland cement (OPC) with 0 : 15, 2 :13, 4 : 11 and 6 : 9 mass ratios of MK to OPC in this study. The mechanical property (e.g. stress‐strain relationship, strength, and deformation performance) and microstructure characteristics of MK‐based geopolymer cemented silty clay are investigated using unconfined compressive strength (UCS), nuclear magnetic resonance (NMR), and scanning electronic microscopy (SEM) tests. In addition, strength increase coefficient (ζ_s) and elasticity modulus increase coefficient (ζ_e) are defined to evaluate the effects of curing time on the mechanical property of MK‐based geopolymer cemented silty clay. Moreover, the relationships among porosity, UCS, and E₅₀ of MK‐cemented silty clay are studied. By incorporating 2% MK, the UCS and E₅₀ of MK‐cemented silty clay at 28 d are 1.32 and 1.30 times compared with MK0 group, respectively. The increase rate of UCS and E₅₀ from 1 d to 7 d is faster compared with that from 7 d to 28 d. Furthermore, the microstructure of the sample modified by 2% MK is most homogeneous and dense. Finally, the optimistic mass ratio between MK and cement is 2 : 13 for silty clay in this test condition.

Defects, such as holes and flaws, greatly affect the mechanical behavior, failure mechanism, and stress wave propagation of frozen soil. To completely characterize the relationship between the dynamic strength and deformation of frozen silty soil containing prefabricated cracks, frozen silty soil specimens with different numbers of prefabricated cracks (zero, one, two, and three cracks) were developed, and dynamic uniaxial compression experiments were performed using the split Hopkinson pressure bar (SHPB) system. The effects of the strain rate and prefabricated crack number on dynamic stress–strain curve characteristics were analyzed. The compound damage variable, which can consider comprehensively the coupling effects of macro- and mesodefects, was calculated based on Lemaitre equivalent strain theory. Two dynamic damage constitutive models were developed and verified based on the conventional Taylor–Chen–Kuszmaul (TCK) and Zhu–Wang–Tang (ZWT) models, and their applicability, advantages, and disadvantages were compared. Strain rate enhancement and prefabricated crack weakening effects were detected for the dynamic compressive strengths of frozen silty soil. It was observed that the two constitutive models essentially could predict the dynamic curves trend under different strain rates and prefabricated crack numbers through a comparison of the theoretical and experimental results. The ZWT model could well reflect the increasing stage compared with the TCK model.

Dynamic compressive tests are performed in three frozen soil types under different stress states at freezing temperatures of −5°C and −15°C with impact loading pressures from 0.3 MPa to 0.6 MPa. The effects of frozen soil type, freezing temperature, impact loading pressures, and stress states on incident energy and energy absorption characteristics, such as absorbed energy and energy absorbency rate, are investigated. The experimental results show that most of the incident energy is reflected back to the incident bar, and incident energy linearly increases with the increase of impact loading pressures. Both absorbed energy and energy absorbency rate are found to be negatively correlated with freezing temperature, and there values under confining pressure state are larger than that under uniaxial condition. The effects of confining pressure on absorbed energy are quite different at different freezing temperatures. In addition, frozen soil type also affects absorbed energy and energy absorbency rate. Meanwhile, impact loading pressure shows an increased effect on the absorbed energy, but it has little effect on energy absorbency rate in the research.

The dynamic stress‐strain relationship of artificial frozen silty clay under one‐dimensional coupled static and dynamic loads is obtained using modified split Hopkinson pressure bar (SHPB) equipment. The variation in dynamic compressive strength, dynamic deformation modulus, energy dissipation, and failure mode of artificial frozen silty clay with axial precompressive stress ratio are studied in this research. Experimental results indicate that the dynamic stress‐strain curves under uniaxial state and one‐dimensional coupled static and dynamic loads can be divided into four stages, i.e., compaction stage, elastic stage, plastic stage, and failure stage. The dynamic compressive strength, first‐stage deformation modulus, second‐stage deformation modulus, and absorbed energy density of artificial frozen silty clay present a trend of first increase and then decrease with the increase of axial compressive stress ratio, and the axial compressive stress ratio corresponding to the peak value is 0.7 in this test. In addition, there is a very similar effect of axial precompressive stress ratio on dynamic compressive strength and second‐stage deformation modulus of artificial frozen silty clay. At 0.4 axial compressive stress ratio, spall phenomenon appears at circumferential direction and center position of the frozen soil specimen has no obvious failure. Shear failure appears at 0.7 to 0.9 axial compressive stress ratio, and the larger the axial compressive stress ratio applies, the more obvious the shearing surface appears; moreover, comminution failure mode appears at 1.0 axial compressive stress ratio.