Amplitude Of Dynamic Load Research Articles

Mechanical Behavior of Geogrid Flexible Reinforced Soil Wall Subjected to Dynamic Load

The geogrid flexible reinforced soil wall is widely used in engineering practice. However, a more comprehensive understanding of the dynamic behavior of reinforced soil wall is still required for a more reasonable application. In order to explore the mechanical behavior of a geogrid flexible reinforced soil wall, the model test was carried out to investigate the dynamic deformation of geogrid reinforced soil wall subjected to a repeated load. The numerical simulation was also conducted for comparison and extension with regards to the earth pressure and the reinforcement strain. The change rules for the deformation of the wall face, the vertical earth pressure and the reinforcement strain subjected to dynamic load with four frequencies (4, 6, 8 and 10 Hz) and four amplitudes (30–60, 40–80, 50–100 and 60–120 kPa) were obtained. The factors that affect the mechanical behavior of geogrid flexible reinforced soil wall were analyzed. The results show that the dynamic deformation characteristics of reinforced soil wall are affected by the number of vibrations, the amplitude of dynamic load and the frequency of vibration. The maximum lateral displacement of the reinforced soil wall occurs on the third to the fifth layer. With an increase in dynamic load amplitude, the development of dynamic deformation gradually increases, and after a cumulative vibration of 200 × 104 times, the cumulative lateral deformation ratio and the cumulative vertical deformation ratio of the wall face is less than 1%. The vertical earth pressure of geogrid flexible reinforced soil wall increases partially along the length of the reinforcement, and the vertical earth pressure of the third layer is basically unchanged when subjected to a dynamic load. With an increase in vibration number, the change in the reinforcement strain of the third layer is more complex, and the change rules of the reinforcement strain of each layer are different. The reinforcement strain is small, with a maximum value of 0.1%.

Study on Shear Slip Characteristics of Sandstone Plane Joints under Normal Dynamic Load Disturbance

Abstract Rock joints are susceptible to slip instability due to dynamic load disturbances such as blasting, earthquakes, and fracturation. A series of direct shear tests under the dynamic load were conducted on sandstone plane joints using the RDS-200xl. The work investigated the effects of normal static loads and normal dynamic-load frequencies and amplitudes on plane joints. Besides, the following items were proposed, that is, the peak-to-valley response rate, shear velocity vibration dominant frequency, shear-stress reduction coefficient, and discrete element numerical simulation method for plane-joint direct shear tests. The results were as follows: (1) The normal dynamic load frequency played a role in attenuating the shear stress amplitude with a threshold value of 0.5 Hz. (2) The shear velocity of the plane joint was completely controlled by the high normal dynamic load frequency. Their vibrational dominant frequencies were identical. (3) The amplitude of shear stress increased, and the median stress decreased with the increased normal dynamic load amplitude. The reduction-coefficient equation for sandstone plane joints was proposed to evaluate the shear stress under the normal dynamic load disturbance. (4) The shear-stress hysteresis phenomenon existed in the plane joints under the normal dynamic load, which required excessive shear displacements to reach peak shear strength. The peak shear displacement increased with the increased normal static load. Numerical simulations and indoor tests showed that high- and low-shear-velocity regions were the main reason for shear-stress hysteresis. The findings are conducive to revealing the shear destabilization mechanism of rock joints under dynamic load disturbance.

Investigating mechanical properties of cemented gangue backfill materials subjected to static-dynamic combined loads

This study aims to investigate the mechanical properties and failure mechanisms for the cemented gangue backfill materials (CGBM) of the roadside filling structures along the gob-side entry with no coal pillars under static-dynamic combined loading. Cuboid cemented gangue backfill samples (CGBS) with dimensions of 50 × 50 × 100 mm were first prepared, with the fractal dimension D = 2.6 characterizing the particle size distribution of aggregates, and then conducted static-dynamic combined loading tests in terms of various pre-static loads (5–11 MPa), amplitudes (2–5 MPa), frequencies (1–16 Hz) and dynamic loading cycles (20–320 cycles). The test results indicate significant differences in the mechanical properties, acoustic emission (AE) responses, maximum principal strain fields, and ultimate failure modes of CGBS under different static-dynamic combined loading paths. With an increasing pre-static load, dynamic loading amplitude and number of cycles, the peak stress decreases by 21.28 %, 12.48 % and 11.84 % respectively, while the peak stress first decreases and then increases with the dynamic loading frequency and reaches the minimum value at the “characteristic frequency” of 4 Hz. The irreversible strain generally experiences an “acceleration - constant speed” variation during the dynamic loading as a result of the gradually stable damage effects. The dynamic elastic modulus increases by 45.84% in the pre-static load range of 5–11 MPa, while decreases with the dynamic loading amplitude. The dissipated energy increases by a factor of 6.5 with the dynamic loading amplitude, and by 27.52% with the pre-static loads. The significantly stimulated cracking activities at the beginning of dynamic loading result in extremely violent AE responses, and then the AE signals weaken due to the dominate role of opening and closure of existing cracks. The RA and AF calculation results illustrate that shear cracks become active at the initial dynamic loading and macroscopic failure stages. As the degradation effects of dynamic loading intensify, three various failure modes of inclined shear failure, “Y” shaped shear failure and conjugate shear failure for the CGBS are respectively classified, especially the conjugate shear failure characterized by two cone-shaped blocks. The findings will contribute to a better understanding of the mechanical responses and failure mechanisms of the roadside filling body during the dynamic mining.

Simulation of the Damage and Failure Characteristics of Coal under True Triaxial Static–Dynamic Loads

The damage evolution rules for coal under true triaxial combined static–dynamic loads are important to understand and reveal the mechanism of rockburst in coal mines. The numerical simulation was carried out using FLAC3D to explore the coupling effect of static and dynamic stress, especially the influence of dynamic load parameters. The results show that the increase in dynamic load amplitude not only makes the plastic zone grow exponentially and shortens the damage development time, but also decreases the residual strength of the coal sample, which leads to a much more violent dynamic failure. The stress wave propagation can be more stable in the coal sample with the increase in dynamic load frequency and the development time of the plastic zone also shows synchronous fluctuating features, and when the frequency is like the intrinsic frequency of the coal sample, the dynamic load has a significant stimulation effect. The static and dynamic loads have different damage effects on the coal sample under the true triaxial stress path, the weight decreases in descending order, namely the minimum principal stress, the maximum principal, the amplitude of the dynamic load and, lastly, the dynamic stress frequency, according to the entropy weight method analysis.

Mathematical Analysis of the Vibratory Pile Driving Rate

Vibratory piling technology does not require analytical tools to predict displacement rates and arising forces. The authors consider the problem of vibratory driving of a pile into a homogeneous unsaturated sandy massif under the action of static and dynamic loads. The purpose of this study is to develop a new analytical solution to the problem of the vibratory pile driving rate in a homogeneous sand base taking vibration creep into account. The solution is provided for the quasi-dynamic problem statement (inertial terms in equations of motion are neglected): the sand medium develops viscous properties due to vibration under the action of the dynamic component of the load, and a pile is driven into the viscous sand base due to the static component of the vertical load. The obtained mathematical model converges with the results of laboratory flume and field experiments performed by other researchers earlier, where the pile vibratory embedding rate increased along with an increase in static loading, the amplitude of dynamic load, and vibration frequency. It can be used to predict the pile or sheet pile driving rate into the unsaturated sand base under the action of vibration, and also to evaluate the necessary parameters of pile driving to obtain the required value of the pile embedding rate.

Frequency- and intensity-dependent impedance functions of laterally loaded pile groups in cohesionless soil

The frequency-dependent horizontal impedance functions of a model floating 2 × 2 pile group, embedded in cohesionless sand under a 1g condition, were investigated experimentally. The tests were conducted using large amplitude loads inducing soil yielding. The soil-pile system was housed in a laminar shear box fastened to the top of a unidirectional shaking table. Quasi-static and dynamic loads were applied in a lateral direction under the fixed pile-head condition to evaluate the force–displacement relationship and the horizontal impedance functions, respectively. The results of the quasi-static loading exhibited rate-dependent behavior for the lateral load-bearing capacity of the piles. Notably, the analysis of the soil surface near the piles, using a stereo-PIV calibration, demonstrated a consistent failure pattern despite the significant variation in velocity. Furthermore, an important observation was the convergence of the horizontal dynamic impedance functions towards the secant static stiffness as the amplitude of dynamic loading increased.

Multibody dynamics modelling of a 6-axle truck to quantify the effects of pavement and vehicle parameters on dynamic loads

ABSTRACT The actual service life of the pavement is related to dynamic tire loads. To accurately calculate dynamic loads, a multibody dynamics model of a 6-axle heavy truck was developed. The difference between simulated and experimental RMS values of wheel centre force and acceleration was within 15%. Based on the validated dynamics model, the effects of ride quality index (RQI), vehicle speed, load capacity, and suspension damping coefficient on dynamic impact factor (DI) and dynamic load amplitude (DLA) were explored. When the vehicle was fully loaded, both DI and DLA increased with decreasing RQI, increasing vehicle speed, and increasing suspension damping coefficient. Among them, the effect of RQI and vehicle speed on DLA and DI was much greater than that of suspension damping factor. In addition, the dispersion of DI values for each axle increased as the vehicle mass decreased. Therefore, it is necessary to consider the combined effects of RQI, vehicle speed and load capacity when applying dynamic tire loads in pavement design or life estimation. The procedure in this paper facilitates the accurate calculation of dynamic loads for different pavement and vehicle parameters and is recommended to be used in vehicle-pavement coupled analysis.

Method and apparatus for dynamic testing of structural joints

The dynamic testing technique is used during the design phase of structures and series production. This test evaluates the structural capacity, especially of the assemblies, to withstand different forces and rates of impact encountered under realistic operational conditions. This study proposes a magnetic pulse exciter for high-speed impact loading in dynamic tests because of its capability to provide single and repeatable pulse loading over a wide range of force up to 20 kN and pulse durations from 10 up to 1000 ms. The method transforms accumulated electrical energy in a capacitor bank into mechanical energy. For experimental investigations, flat and cylindrical coil devices were used for a capacitor-type pulse current generator. The proposed method has been experimentally validated on timber beams in a specified volume of force loading. The technique demonstrated a potential for controlling force and energy parameters. The effects of operating voltage on coil and ‘metal plate - coil’ distance on the amplitude of dynamic loading have been investigated. Aluminium and steel plates fastened to the object at the point of impact were used to improve excitation efficiency. The developed technique can be used in experimental studies on model joints and real objects.

Fracture Mechanism of Crack-Containing Strata under Combined Static and Harmonic Dynamic Loads Based on Extended Finite Elements

Based on the existing research results, a theoretical fracture model of strata under the compound impact of static and harmonic dynamic load is improved, and the fracture characteristic parameters (stress intensity factor, T-stress, and fracture initiation angle) under the two far-field stress are determined according to the crack dip angle. Additionally, the effects of harmonic dynamic load on the distribution of the stress field and the fracture characteristic (the crack initiation angle, the fracture degree, the number of fracture units, and the fracture area) are further calculated and discussed by theoretical model solution, extended finite element simulation, and the secondary development of the simulation module, respectively. The research results show that the far-field stress, stress intensity factor, and T-stress vary in harmonic form with time under the compound impact of static and harmonic dynamic loads. The frequency of dynamic load affects the number of reciprocal fluctuations of stress intensity factor and T-stress as well as the crack initiation time, but has less influence on the crack initiation angle and fracture degree. While the amplitude of dynamic load affects the stress intensity factor, the extreme value of T-stress and fracture characteristics of the crack. This study has theoretical guiding significance for parameters’ optimization and realization of resonance impact drilling technology.

Mechanical and Acoustic Emission Characteristics of Coal-like Rock Specimens under Static Direct Shear and Dynamic Normal Load.

In underground engineering, shear failure is a common failure type in coal-rock mass under medium and low strain-rate disturbance loads. Analyzing the shear failure mechanical properties of coal-rock mass under dynamic normal load is significant. In order to reveal the influence of disturbance load on the shear mechanical properties of coal rock, a dynamic and static load coupling electro-hydraulic servo testing machine was used to conduct the shear tests of coal-like rock materials under dynamic and constant normal load. The amplitude of dynamic load is 10 kN and the frequency is 5 Hz. The damage process of the specimens was detected by the acoustic emission (AE) detection system. The results imply that the shear failure process of coal-like rock materials under constant normal load can be divided into four stages. The normal disturbance decreased the shear strength of the specimens and increased the shear modulus of the specimens. With the increase in normal load, the influence of disturbance on the shear strength of the specimen decreased. By analyzing the AE parameters, it was found that the dynamic load made the internal damage of the specimen more severe during the shear failure process. The damage variable was calculated by AE cumulative energy, and the damage evolution was divided into three stages. The shear failure mechanism of the specimen was judged by RA (rise time/amplitude) and AF (average frequency). It was found that from the elastic deformation stage to the unstable development fracture stage, the proportion of shear fracture increased. When the dynamic normal load was 10 kN and 30 kN, the fracture was mainly shear fracture; When the dynamic normal load was 50 kN, the fracture was mainly tensile or mixed fracture. The dynamic normal load affects the shear strength and failure mechanism. Therefore, the influence of disturbance load on coal-rock mass strength cannot be ignored in underground engineering.

Effect of Freeze-Thaw Cycles on Dynamic Characteristics of Undisturbed Silty Clay

We conducted dynamic triaxial tests of undisturbed soil samples under different control parameters using the Global Digital Systems (GDS) dynamic triaxial instrument. We investigated the dynamic and engineering characteristics of undisturbed soil under a freeze-thaw cycle. When the dynamic load amplitude and the number of freeze-thaw cycles were adjusted, we explored the cumulative plastic strain, dynamic elastic modulus, and dynamic strength of undisturbed soil, and we then proposed appropriate fitting formulae to compute the cumulative plastic strain, dynamic elastic modulus, and dynamic strength. The findings revealed that as the number of freeze-thaw cycles increased, the cumulative plastic strain grew, the dynamic strength progressively fell, and the dynamic elastic modulus dropped first, but then increased. The critical physical and dynamic features of soil changed dramatically during one to six freeze-thaw cycles. This study's suggested formula for the average growth ratio can directly reflect the cumulative plastic strain fluctuation of soil throughout freeze-thaw cycles. The formula has a good fitting effect on undisturbed soil, according to the test findings, and the accumulative plastic strain, dynamic elastic modulus, and dynamic strength may be computed within a specified range. The findings of this study contribute to a better understanding of the effect of the freeze-thaw cycle on the dynamic characteristics of undisturbed silty clay, as well as a theoretical foundation for the design and construction of silty clay highway subgrade in seasonally frozen regions as well as the dynamic analysis of vehicle simulation in seasonally frozen regions.

Evaluating the response of piles subjected to static and multiple dynamic axial loads

Piles often move horizontally during earthquakes. In case of superstructure interactions, accurate prediction of pile response becomes more challenging due to vertical propagation of shear wave during the earthquake that sways the superstructure causing vertical axial movement. To effectively design the pile foundation, a series of large-scale 1-g model pile tests were performed in sand and clay. Multiple axial load tests (Dynamic Load Test (DLT) and Static Load Test (SLT)) were conducted on the fully instrumented piles to assess their stiffness and capacity. Mainly, the characteristics of loading rate effect, loading test sequence effect, and cyclic effect were experimentally evaluated. The axial force, skin friction distribution, and velocity response along the pile, and pile's response in cohesive and non-cohesive soils under multiple dynamic loads with similar load amplitude were examined. It was found that the dynamic capacity of the pile exceeded the static capacity (by 30–40% for sand, and 60–80% for clay). In sands, the dynamic capacity of the pile obtained from the first DLT is 45% smaller than that of the second DLT, whereas in the latter case, it is 20% larger than the second DLT. It is also notable in SLT that, the secant stiffness of the pile plummeted comparatively more in clay. In general, the stiffness and capacity of the pile-soil system are largely governed by the loading rate and sequence of loading tests, depending on the soil properties. Also, the results show that the axial force along the pile shaft decreased nonlinearly with depth in both sand and clay; however, it lessened rapidly in the clay. The skin friction of the pile body increased gradually with hammer blows in sand, while a different trend is observed in the case of clay. The velocity response of different locations on the pile is almost identical. Furthermore, in sand, under a similar dynamic load amplitude, the normalized velocity (vn) of the pile slowly lowers at higher number of blows, whereas in clay, the vn of each blow is almost similar.

Damage and Failure Characteristics of Surrounding Rock in Deep Circular Cavern under Cyclic Dynamic Load: A True Triaxial Experiment Investigation

For ensuring safety and efficiency during the construction of deep engineering, it is essential to explore the failure mode of the surrounding rock mass under dynamic disturbance and high geo-stress. We conducted true triaxial load tests for rock-like material with a preexisting circular hole, and monitored the acoustic emission (AE) signal during the whole test. The result demonstrates the evolution characteristics of damage and failure mode with different cyclic dynamic load amplitudes and intermediate principal stress. With the increase in cyclic dynamic load amplitude or the decrease in intermediate principal stress, the failure source mainly occurs at the two horizontal side walls of the surrounding rock where the failure patterns change from the slabbing to wall caving and, finally, to rockburst. The former failure mode can actually serve as an important precursor for the latter. Based on such mechanisms, the precursor can be indirectly detected in forms of AE signal released by microcracking. The research can provide a reliable guidance for the rock stability control and faithfully forecasting the larger-scale failure during the excavation of deep circular cavern.

Failure analysis and fatigue life prediction of high-speed rail clips based on DIC technique

With the development of rail transportation, the fatigue failure of rail clips has become an issue, which affects the operational safety of trains. In this study, reasons for the fatigue failure of rail clips were investigated to improve their service life. A digital image correlation (DIC) technique was conducted to obtain strain fields, vibration modes, and natural frequencies of a rail clip. The strain and displacement of a rail clip under dynamic cyclic loading were also obtained. A fastener system refinement model was developed to analyze the static, dynamic, and modal responses of the clip. The experimental tests and modal simulation results were mutually verified. The fatigue life was analyzed based on the verified FE model. The results revealed that the maximum strain and minimum fatigue life occur at the heel of the clip, in good agreement with the actual fracture position. As the amplitude and frequency of dynamic cyclic load increased, the fatigue life of the clip decreased sharply. Moreover, the normal wheel–rail force accompanied by high-frequency rail corrugations accelerated crack initiation and reduced the fatigue life. The findings of this study provide guidance for improving the service life of rail clips.

Controls on Post‐Seismic Landslide Behavior in Brittle Rocks

AbstractEarthquakes trigger widespread landsliding in tectonically active landscapes. The effects of strong ground shaking on hillslope stability persist into the post‐seismic stage; rates of landsliding remain elevated in the years following an earthquake. The mechanisms that control the spatial pattern and rate of ongoing landsliding are poorly constrained, hindering our ability to reliably forecast how landscapes and landslide hazard evolve. To address this, we undertook a detailed geotechnical investigation in which we subjected representative rock samples to dynamic loading, simulating the effects of earthquake ground shaking on hillslopes of different configuration. Our results indicate that post‐seismic hillslope strength is not an intrinsic rock property; rather, it responds to the amplitude of imposed dynamic loads and the degree of pre‐existing shear surface formation within the rock. This path‐dependent behavior results from differences in the character of fractures generated by dynamic loads of different amplitude, and the ways in which apertures are mobilized or degraded in subsequent (post‐seismic) shearing. Sensitivity to dynamic loading amplitude is greater in shallow landslides in which shear surfaces are yet to fully form; such hillslopes can be strengthened or weakened by earthquake events, depending on their characteristics. In contrast, deeper landslides on steeper hillslopes in which shear surfaces have largely developed are less likely to display differences in behavior in response to dynamic loading because strain accumulation along pre‐existing fractures is dominant. Our results demonstrate the need to consider path‐dependent hillslope stability in numerical models used to forecast how landscapes respond to earthquakes and how post‐seismic hazard evolves.

Simulation on compound percussive drilling: Estimation based on multidimensional impact cutting with a single cutter

In the present study, a 3D FEM of compound percussive system considering a loading–unloading cycle was employed to simulate the dynamic single-cutter-rock interaction. By conducting the sensitivity analysis, the effects of the impact velocity of cutter, the dynamic load amplitude, the ratio μ of torsional impact to axial impact frequency on the cutting force and penetration depth were investigated. Moreover, a range of simulations were conducted on the stratum lithology (Granite, Marble and Sandstone). As revealed from the results, the cutting forces increase first and then decrease rapidly with the increase in the torsional impact velocity. Besides, the amplitude of the cutting force in the simulation of duration time was improved. The larger the dynamic load, the faster the cutting forces will reach the peak. The penetration depth curve exhibits the step characteristics and increases with the dynamic load amplitude and impact velocity amplitudes. With the ratio μ increasing continuously (μ<2), the amplitude of cutting force and penetration depth tends to be improved. However, the relationship between the torsional and axial impact frequencies might have an optimal value. The stronger rock achieved a higher penetration depth. The penetration depth and the penetration rate could be obtained regardless of rock types when μ=1.5. The penetration rate will demonstrate an improvement of 49.02% under the axial impact and 35.92% under the torsional impact. Finally, the field applications of compound percussive drilling is conducted. The numerical simulation results agree well with field experiment results, with an average accuracy of 91.2% of well Guo X-8 and 96.7% of well Pu X-32, respectively. The study on the mechanism of the compound percussion drilling technology for rock breaking theoretically supported the subsequent development and optimization of the tools.

Theoretical and Experimental Studies of Impact Energy and Rock-Drilling Efficiency in Vibro-Impact Drilling

Abstract Vibro-impact drilling has been proven to be a viable technique for enhancing the rate of penetration (ROP) in deep and ultra-deep well drilling. It is essential to study the effects of impact parameters on impact energy and rock-drilling efficiency for impact tool design and operating parameter optimization. In this paper, the influences of impact parameters including impact frequency, dynamic loading amplitude, and loading on impact energy were analyzed by a theoretical method. Then, a full-scale drilling experiment was conducted to study the rock-drilling efficiency. The results are as follows: the optimal frequency is higher than the resonance frequency of the rock. The impact energy increases with the dynamic loading amplitude. The penetration rate at dynamic loading amplitude of 4 kN (0.13137 mm/s) is 38.7% higher than that of 2 kN (0.09473 mm/s). When the impact frequency is lower than 150 Hz, the rock-drilling efficiency increases with the impact frequency and dynamic loading amplitude. The penetration rate is 0.1051 mm/s at impact frequency of 150 Hz, which is 29.8% higher than that of 10 Hz. The impact energy and penetration rate at square loading waveform are the largest. The impact energy per second at loading waveform of square, sine, and triangle is 19.6 J, 12 J, and 7.91 J, respectively, when the impact frequency is set to optimal frequency of impact energy. This study provides a theoretical guidance for the optimization design of vibro-impact drilling technology.

Experimental Research on the Rheology Slip Damage Mechanical Properties of Sandstone under the Dynamic Loading

The soft sandstone is taken as samples, and the RLW-2000M triaxial rheological testing machine is used as the main equipment to test the axial stress-strain, the axial rheological deformation in this paper. The axial strain is selected as damage variables, the damage degree expression is derived, and the effect of each factor on damage degree is studied. Research results show that axial deformation increases with the passage of time, and the hysteresis curve change from sparse to dense under the action of the dynamic loading. The axial deformation increase with the increase of the dynamic loading amplitude, and it increases with the decrease of frequency. The damage degree of specimen tends to be stable after mutation and increases with the increase of the dynamic loading amplitude. The research results will provide the scientific basis for us to disclose the rule of rheology-damage evolution of sandstone under the action of dynamic loading.

Numerical Simulation of Composite Beam Subjected to Harmonic Force Vibration

Simply supported steel and concrete composite beams connected by a number of headed stud shear connectors were adopted considering the existence of interface slip under the effect of forced vibration. ANSYS software is used to carry out the finite element simulation. Static load was applied first then different load cases of harmonic loadings were applied. The comparison between available experimental data and the obtained results from the numerical analysis proves the reliability of the developed model. The analysis results confirm that the shear connection degrees are a significant index related to the longitudinal shear ability and the overall flexure stiffness of the composite beam. The increase of average slip and mid-span deflection are mostly affected by the static load and with a little significant under dynamic load, whereas, the slip amplitude is mostly affected by the dynamic loading amplitude. The magnitudes of deflection rely on the frequency range and amplitude of loads and the value of frequency reflects the magnitude of applied load that make the deflection vary with the applied loads.

Liquid water–vapour migration tracing and characteristics of coarse-grained soil under high-speed railway train loading in cold regions

Although high-speed railway (HSR) subgrades in cold regions are filled with coarse-grained soil (CGS), they still undergo frost-heaving displacement. The liquid water–vapour migration mechanism can explain the frost-heaving process; therefore, the characteristics of liquid water–vapour migration in CGS are investigated in this study. The results show that in CGS, vapour migration is dominant under unidirectional freezing and dynamic loading. The water redistribution in the frozen zone and freezing front is primarily caused by vapour migration, whereas that in the unfrozen zone is primarily caused by liquid water migration. The final migration height of liquid water and the amount of vapour migration are positively correlated with the amplitude and frequency of dynamic loading. Continuous pore-structure changes and soil-particle movement provide favourable conditions for vapour migration, which are amplified by increasing the dynamic loading amplitude or frequency. A pumping action produced by dynamic loading exists inside CGS. In the design and maintenance of HSR subgrades in cold regions, vapour migration merits careful consideration because it induces more than 50% of the frost-heaving displacement.