Acceleration Amplification Coefficient Research Articles

Three-Dimensional Numerical Analysis of Seismic Response of Steel Frame–Core Wall Structure with Basement Considering Soil–Structure Interaction Effects

In recent years, numerous studies highlighted the crucial role of the soil–structure interaction (SSI) in the seismic performance of basement structures. However, there remains a limited understanding of how this interaction affects buildings with basement structures under varying site conditions. Based on the three-dimensional (3D) numerical analysis method, the influence of the SSI on the seismic response of high-rise steel frame–core wall (SFCW) structures situated on shallow-box foundations were investigated in this study. To further investigate the effects of the SSI and site conditions, three types of soil profiles—soft, medium, and hard—were considered, along with a fixed-foundation model. The results were compared in terms of the maximum lateral displacement, inter-story drift ratio (IDR), acceleration amplification coefficient, and tensile damage for the SFCW structure under different site conditions, with both fixed-base and shallow-box foundation configurations. The findings highlight that the site conditions significantly affected the seismic performance of the SFCW structure, particularly in the soft soil, which increased the lateral deflection and inter-story drift. Moreover, compared with non-pulse-like ground motion, pulse-like ground motion resulted in a higher acceleration amplification coefficient and greater structural response in the SFCW structure. The RC core wall–basement slab junction was a critical region of stress concentration that exhibited a high sensitivity to the site conditions. Additionally, the maximum IDRs showed a more significant variation at incidence angles between 20 and 30 degrees, with a more pronounced effect at a seismic input intensity of 0.3 g than at 0.2 g.

Study on seismic response characteristics of living stumps slope based on large-scale shaking table test

A large-scale shaking table test of a living stump slope with a geometric similarity ratio of 1:7 was designed and completed. The peak acceleration, acceleration amplification factor, and displacement response patterns of living stumps slopes under different types of seismic waves and excitation intensities were obtained. The time-frequency and energy variation characteristics were analyzed using the Hilbert-Huang Transform (HHT). The results showed that: (1) Regardless of the type of seismic wave, the peak acceleration and acceleration amplification factor of the living stumps slope surface are positively correlated with relative height and seismic excitation intensity. When the excitation intensity is ≤ 0.4 g, the acceleration amplification effect is more pronounced; when the excitation intensity is > 0.4 g, the acceleration amplification effect weakens. (2) Under the action of different seismic waves, the peak displacement of slope surface shows amplification effect along the elevation, and increases with the increase of excitation intensity. In addition, the incremental displacement gradually decreases from the toe to the top of the slope, which is expressed as D2 > D3 > D1 > D4 > D5. The peak displacement at the top of the slope is the greatest, but the incremental displacement is the smallest; the peak displacement at the toe of the slope is the smallest, but the incremental displacement is relatively large. (3) Regardless of the type of seismic wave, living stumps slope shows the characteristics of filtering the low-frequency components of the seismic waves and amplifying their high-frequency components. At the same time, the seismic Hilbert energy gradually accumulates along the elevation. PSHEA and PMSA significantly increase with elevation and excitation intensity, and they reach the maximum at the top of the slope. (4) The seismic Hilbert energy is positively correlated with the relative height and excitation intensity, and reaches the maximum at the top of the slope. With the accumulation of seismic Hilbert energy increases, the dynamic response parameters such as peak acceleration, acceleration amplification coefficient and displacement also increase synchronously, reaching the maximum at the top of the slope. The research conclusions can provide an experimental basis for the seismic design of living stumps slopes.

Dynamic responses of steep bedding slope-tunnel system under coupled rainfall-seismicity: Shaking table test

The coupling effects of rainfall, earthquake, and complex topographic and geological conditions complicate the dynamic responses and disasters of slope-tunnel systems. For this, the large-scale shaking table tests were carried out to explore the dynamic responses of steep bedding slope-tunnel system under the coupling effect of rainfall and earthquake. Results show that the slope surface and elevation amplification effect exhibit pronounced nonlinear change caused by the tunnel and weak interlayers. When seismic wave propagates to tunnels, the weak interlayers and rock intersecting areas present complex wave field distribution characteristics. The dynamic responses of the slope are influenced by the frequency, amplitude, and direction of seismic waves. The acceleration amplification coefficient initially rises and then falls as increasing seismic frequency, peaking at 20 Hz. Additionally, the seismic damage process of slope is categorized into elastic (2-3 m/s2), elastoplastic (4-5 m/s2) and plastic damage stages (≥ 6.5m/s2). In elastic stage, ΔMPGA (ratio of acceleration amplification factor) increases with increasing seismic intensity, without obvious strain distribution change. In plastic stage, ΔMPGA begins to gradually plummet, and the strain is mainly distributed in the damaged area. The modes of seismic damage in the slope-tunnel system are mainly of tensile failure of the weak interlayer, cracking failure of tunnel lining, formation of persistent cracks on the slope crest and waist, development and outward shearing of the sliding mass, and buckling failure at the slope foot under extrusion of the upper rock body. This study can serve as a reference for predicting the failure modes of tunnel-slope system in strong seismic regions.

Centrifuge modelling on seismic failure of MSW landfills with high water level

Landfill failure threatens the safety of surrounding cities and causes soil and water pollution. High water levels can usually spur landfill failure. With the presence of earthquake, landfill instability is triggered in a greater possibility. However, the dynamic response and failure mechanism of landfills with high water level subjected to earthquakes are not yet clearly understood, and relevant experimental studies are quite scarce. This study includes a series of seismic centrifuge tests to investigate the seismic response of the landfill at different water levels. An improved method is proposed to prepare synthetic municipal solid wastes (MSWs) with similar static-dynamic properties to the actual MSWs. The failure and evolution mechanism of landfills with high water levels induced by the earthquake is revealed. Significant transitions are observed in the dynamic response of deformation, acceleration, and pore-water pressure as the water level changes. With the rise of water level, the settlement at the top of the landfill decreases first and then increases, while the horizontal displacement at the toe increases slowly, followed by a sudden drop; the acceleration amplification coefficient in the middle of the landfill increases first and then decreases; the dynamic pore-water pressure gradually decreases from positive to negative, but oscillates at the moderate water level. Three failure criteria and a hydro-earthquake coupled failure limit are proposed to demonstrate the combined effect of water level and earthquake on landfill stability. The test results provide a basis to establish seismic failure standards for landfills with different water levels and guide the seismic instability design of landfills with high water level.

Shaking table test on damage mechanism of bedrock and overburden layer slope based on the time–frequency analysis method

To systematically analyze the damage caused by bedrock and overburden layer slope under seismic action, a set of large-scale shaking table test was designed and completed. Interpolation of the acceleration amplification coefficient, Hilbert–Huang transform and transfer function was adopted. The damage mechanisms of the bedrock and overburden layer slopes under seismic action are systematically summarized in terms of slope displacement, acceleration field, vibration amplitude, energy, vibration frequency, and damage level. The results show a significant acceleration amplification effect within the slope under seismic action and a localized amplification effect at the top and trailing edges of the slope. With an increase in the input seismic intensity, the difference in the vibration amplitude between the overburden layer and bedrock increased, low-frequency energy of the overburden layer was higher than that of the bedrock, and the vibration frequency of the overburden layer was smaller than that of the bedrock. These differences cause the interface to experience cyclic loading continuously, resulting in the damage degree of the overburden layer at the interface being larger than that of the bedrock, reduction of the shear strength, and eventual formation of landslides. The displacement in the middle of the overburden is always greater than that at the top. Therefore, under the action of an earthquake and gravity, the damage mode of the bedrock and overburden layer slope is such that the leading edge of the critical part pulls and slides at the trailing edge, and multiple tensile cracks are formed on the slope surface.

Shaking Table Tests of Chuandou-Type Timber Structure Building for Seismic Fortification High-Intensity Area

ABSTRACT This study investigated the seismic performance of Chuandou-type timber structure buildings intended for seismic fortification in a high-intensity zone. An earthquake simulation shaking-table test was conducted on a two-layer Chuandou-type structure constructed in Yunnan, China. The El Centro, Kobe, and artificial waves were used as input excitations. The natural frequency, stiffness, acceleration response, and displacement response to the earthquake events were determined. The experimental results indicate that as the acceleration intensity of the earthquake increases, the natural frequency and stiffness of the model structure decrease. The acceleration amplification coefficient of each layer varied from 0.47 to 1.95. The energy dissipation of column foot slip, mortise-tenon joint friction and extrusion were visible, and the dynamic amplification coefficient of the first layer was less than one except for Kobe wave excitation. When the input peak acceleration is 0.63 or 0.95 g, the model shocks violently and exhibits a spectacular whiplash effect, with the model’s maximum inter-story drifts being 1/23 and 1/26, respectively. However, the model did not tilt or collapse, which displays that the Chuandou-type structure had an overall good deformation and self-centering ability. Additionally, it satisfies the standards of the Chinese Code for Seismic Design of Buildings (GB2011–2010).

Seismic Performance Evaluation and Retrofit Strategy of Overhead Gas-Insulated Transmission Lines

The overhead gas-insulated transmission line (GIL) in ultra-high-voltage converter stations, distinct from traditional buried pipelines, demands a thorough investigation into its seismic behavior due to limitations in existing codes. A refined finite element model is established, considering internal structure, slip between various parts, and the relative displacement at the internal conductor joint. Seismic analysis reveals the vulnerability of the GIL at the corner of the pipeline height change, with two failure modes: housing strength failure and internal conductor displacement exceeding the limit. Furthermore, the acceleration amplification coefficient of the support generally exceeds 2.0. Two retrofit methods, namely increasing the fundamental frequency of all supports and fixing the connections between all supports and the housing, have been proposed. The results indicate the effectiveness of both methods in reducing the relative displacement. Fixing all the supports effectively reduces the stress, whereas the other one yields the opposite effect. The seismic performance of a GIL is determined not by the dynamic amplification of supports, but by the control of relative displacement between critical sections, specifically influenced by the angular deformation of the pipeline’s first-order translational vibration mode along the line direction. Seismic vulnerability analysis reveals a reduction of over 50% in the failure probability of the GIL after the retrofit compared to before the retrofit, with the PGA exceeding 0.4 g.

Dynamic response and progressive damage modes of fault-crossing tunnels simulated using similar materials

Tunnels are widely constructed because they can effectively withstand seismic loads and avoid tunnel collapse in high-intensity seismic zones. However, in the case of fault-crossing tunnel, the fault crossing tunnel will be seriously damaged in seismic activities because the tunnel lining follows the deformation of surrounding rock. Therefore, the researches of the dynamic response and failure modes of fault-crossing tunnel are highly significant. In this study, quartz sand, cement and detergent were used to simulate similar materials of surrounding rock. A gypsum-based materials have been selected as similar materials for tunnels. The shaking table model tests were conducted on fault-crossing tunnel and conventional tunnel based on the Xianglushan Tunnel. The dynamic response characteristics of the fault-crossing tunnel were analyzed, and draw the conclusions: The acceleration amplification coefficients of the two sets of tests exceeded 1. The acceleration dynamic response of the fault-crossing tunnel was greater than the conventional tunnel, and the acceleration dynamic response at the fault was greater than the monitoring surface on both sides, rendering the acceleration dynamic response at the fault abrupt. Compared to other cross sections, tunnel lining structures at faults had the strongest dynamic response. The maximum peak strain value of the fault-crossing tunnel was magnified 4.4 times, and the bending moment value was magnified 2.3 times, relative to those of the conventional tunnel. The fault markedly increased the strain peak and bending moment values, causing cracks and damage even at a small peak acceleration value, weakening the seismic capacity of the tunnel. The lining at the fault was dominated by longitudinal cracks, and dislocation occurred. The degree of destruction and development of tunnel at faults was greater than that of other cross sections. The research results and conclusions could provide a reference to prevent the destruction of fault-crossing tunnel in an earthquake.

Bedding slope damage accumulation induced by multiple earthquakes

The 2017 catastrophic Xinmocun landslide was triggered on a bedding slope in the Songpinggou Gully, Maoxian County, China. Previous research primarily focused on the dynamic slope response and deformation characteristics of a single earthquake, and focus on the effect of damage accumulation on slope stability is lacking. The shaking table tests were conducted in this study to understand historical earthquake-induced damage accumulation in bedding slopes. The acceleration amplification coefficient (BPGA) and plastic effect coefficient (PEC) were used to reflect the damage accumulation of bedding slope under the influence of multiple earthquakes. The results revealed that the bedding surface-induced seismic motion amplification contributes to damage constrained on the slope sliding surface. The damage accumulation during multiple earthquakes contributed to slope peak ground acceleration (PGA) amplification increasing and model's natural frequency decreasing in non-linearly form. The shortening of the gap between the driving force frequency and the model's natural frequency had a great impact on the slope damage accumulation. These findings suggest that the accumulation of damage caused by historical earthquake amplification contributes significantly to post-earthquake instability. Future evaluations of slope stability should consider the accumulation and reduced frequency of slope deformation associated with multiple earthquakes.

Dynamic Response Law and Failure Mechanism of Slope with Weak Interlayer under Combined Action of Reservoir Water and Seismic Force

The southwestern region of China is close to the Eurasian earthquake zone. Many engineering areas in southwestern China are affected by earthquakes and are close to the epicenter of earthquakes that occur in this region. During earthquakes, slopes with weak interlayers are more likely to cause large-scale landslides. In response to the low stability of slopes with weak interlayers in reservoir dam areas, the dynamic response law and failure mechanism of weak interlayered slopes under the combined action of reservoir water and seismic forces were studied through shaking table model tests and finite element numerical simulation software. The height of the water level and the size of the seismic waves were changed during these tests. The research results indicate that seismic waves are influenced by weak interlayers and are repeatedly superimposed between the weak interlayers and the slope surface, resulting in an acceleration amplification effect that increases by approximately 1.8 times compared to homogeneous slopes. Vertical earthquakes have a significant impact on the dynamic response of slopes, and their peak acceleration amplification coefficient can reach 0.83 times the horizontal peak acceleration. The stability of weak interlayers during earthquakes is the worst within the range of the direct action of reservoir water. The failure mode of a slope is as follows: earthquake action causes cracking in the upper part of the slope, and as the earthquake increases in intensity, and the infiltration of reservoir water intensifies, the cracks expand. The soft and muddy interlayer in the front section of the slope forms a sliding surface, and ultimately, the sliding failure forms an accumulation body at the foot of the slope. In reservoir dam areas, the stability of a slope is closely related to the engineering safety of the reservoir dam. Therefore, when a strong earthquake and the water level in a reservoir jointly affect a weak-interlayer slope, the slope is in the stage of plastic deformation and instability. The stability of the slope may be overestimated, and the slope is likely vulnerable to sliding instability, which needs to be monitored and treated.

Shaking table test on dynamic response of a deposit slope with a weak interlayer reinforced by the pile-anchor structure

Owing to its low shear strength, the presence of a weak interlayer frequently plays an adverse role on slope stability. Through a shaking table test, this study investigated the dynamic response of the deposit slope with weak interlayer at the exit of the Zheduo Mountain Tunnel reinforced by pile-anchor structures. The acceleration field of the slope, peak value of the dynamic earth pressure of the pile, deformation of the pile, anchor cable tension and load-sharing ratio were considered. The findings demonstrate that as an earthquake intensifies, the slope soil behind a pile gradually becomes compressed; subsequently, tension cracks emerge at the back edge of the slope and expand significantly, eventually forming a penetrating sliding surface. Under various earthquake intensity levels, the acceleration amplification coefficient of the slope increases with the elevation. A weak interlayer can amplify the amplitude of the Fourier spectra, which results in a difference in the vibration between the deposit and bedrock and damage to the slope. When the acceleration exceeds 0.3g, the soil behind pile begins to squeeze it, and the peak value of the dynamic earth pressure first increases and then decreases along the elevation of the pile, reaching its maximum near the sliding surface. The load-sharing ratio of the pile-anchor structure steadily decreases as the peak acceleration of the seismic wave, tension of the anchor cable, and limiting effect of the anchor cable on the pile displacement increase. We suggest that the amplification effect of seismic acceleration should be considered in the seismic design of pile-anchor structures, with local reinforcement near the sliding surface of the pile, and the load-sharing ratio of the structure should be flexible.

Shaking Table Test on Dynamic Damage Characteristics of Bedrock and Overburden Layer Slopes

Abstract This article performs groups of shaking table tests to study the dynamic damage characteristics of the slope that is composed with inclined bedrock, upper overburden soil layer, and weak soil interlayer. The prototype is of the entrance slope of the Mount Zheduo tunnel, which is located in the mountains of the western Sichuan Plateau in China. The test model is designed based on the similarity theory. The peak ground acceleration (PGA) amplification coefficient, Fourier transform, and transfer function theory are employed to analyze the test results. The results before slope failure indicate that the PGA amplification coefficient of both the overburden layer and the weak interlayer increases as the excitation intensity increases. At the same time, the dynamic response of weak interlayer is amplified on low-frequency wave excitation while that is impaired when high-frequency seismic waves dominate. When the slope is damaged, the slope undergoes large shear deformation: the whole overburden layer slides along the weak interlayer, and the PGA amplification coefficient of the weak interlayer sharply decreases. The frequency response function indicates that the vibration relationship between the upper part of the weak interlayer and the slope surface is very close, and the slope surface vibration may be mainly affected by the vibration in the upper part of the weak interlayer, which reflects the early predictability in the failure symptoms of the slope.

Shaking table tests of large cross-sectional multi-crack tunnel linings

To study the dynamic response law of large-section cracked lining structures under seismic waves, comparative tests of large-scale shaker tunnel models of non-destructive lining structure (model 1), a crack in the vault of the lining structure (model 2), and two parallel cracks in the vault of the lining structure (model 3) were carried out by applying 0.1-1.0 g progressively increasing the peak acceleration of the input waves. This paper visually showed the distribution of cracks in three groups of the lining structures. In addition, the acceleration response of the lining and surrounding rock, dynamic soil pressure, the dynamic strain on the inner and outer surfaces of the lining, and dynamic internal force variation were obtained, and the seismic performance of three groups of lining structures was discussed. The results showed that the seismic weak positions of model 1 were the arch shoulder and the arch foot, the seismic weak positions of model 2 were the arch shoulder, the arch foot, the initial damage area, and the inverted arch, and the seismic weak positions of model 3 were the positions of the arch foot, the cracks of the vault, the inverted arch, and the arch wall. The soil pressure values at the vault of three groups of models were model 2 > model 1 > model 3 in turn. The surrounding rock amplified the input seismic waves. With the gradual increase of the peak acceleration, the seismic energy was gradually consumed due to plastic damage to the lining structure or the loosening and destruction of the overlying soil, resulting in the acceleration amplification coefficient value of the surrounding rock in the upper part of the lining structure showing a changing trend of first increasing and then decreasing. When the peak acceleration was 0.2 g, the crack propagation phenomenon occurs in the initial crack position of model 2 and model 3. When the peak acceleration was 0.4 g, the cracking phenomenon occurs at the right arch foot of model 1. The above phenomenon confirmed the conclusion that cracks can weaken the seismic performance of the structure. When the peak acceleration was 0.8 g, the peak values of the amplification coefficient of the lining at the inverted arch and near the filled soil surface were about 1.2 and 1.6 respectively. The research results can provide a reference for the seismic performance evaluation of cracked tunnels.

Shake table test and numerical analysis of the seismic response of buried long-distance pipeline under longitudinal non-uniform excitation

To investigate the seismic response characteristics of buried pipelines under longitudinal non-uniform seismic excitation, a three-dimensional finite element overall analysis model is established on finite element analysis software based on the shaking table test of buried oil and gas pipelines under longitudinal non-uniform excitation. The calculated results are compared with the experimental analysis results to evaluate the correctness and reliability of the established model. The acceleration response, strain response, and displacement response of buried oil and gas pipelines and surrounding soil under longitudinal traveling wave excitation at different seismic intensities are compared and analyzed using finite element models to supplement the test conditions. The test and analysis results show that the longitudinal displacements at each measurement point under longitudinal non-uniform excitation follow the same pattern except for differences in displacement magnitude and the vibration pattern of the tube and soil when the peak input acceleration reaches 1.00 g. As shown by both experimental and numerical simulation results, the soil acceleration amplification coefficients along the soil height fluctuate between 0.5 and 1.5. The pipe acceleration time curves and Fourier spectrum exhibit the same simulated and experimental pipe acceleration waveforms, and they both show significant amplification in the low to medium frequency band of 5–20 Hz. The testing and numerical simulated pipeline axial strain peak curves are similar and in good agreement, indicating the high reliability of the experimental results.

Analysis of Seismic Damage Modes of Landslides Containing Tunnels under Horizontal Earthquake Action

With the vigorous development of railway and highway construction, tunnel construction often follows the mountains and rivers, crossing high-intensity landslide areas, and potential earthquakes triggering damage in areas including tunnel landslides have become a hot issue today. Based on this, this paper performs a shaker test on the tunnel-containing landslide body, inputs horizontal seismic waves, and tests the acceleration response data of different bits in the landslide body. By analyzing the temporal and frequency domain transformations of the acceleration response at different positions in the slope body combined with the deformation characteristics of the slope, and then analyzing the seismic response of the slope under the action of the front and back seismic sequences, the results show that (1) the existence of the tunnel has the effect of energy dissipation and vibration reduction, making the energy input at T8, and the measuring point on the upper part of the tunnel at the lowest. (2) When the seismic wave is transmitted, it will cause reflection around the tunnel, forming complex seismic wave field, resulting in the irregular distribution of acceleration amplification coefficient. (3) There is a high correlation between seismic responses of different levels. When the acceleration response of the preseismic response to the landslide-containing tunnel is not considered, the acceleration response of the postseismic response to the slope and the structure will be lower than the real value. (4) The sequence of failure at different locations of landslide mass containing tunnel is found through marginal spectrum analysis. It is concluded that the failure mode of landslide mass with tunnel is extrusion and sliding out of the middle slope. The research results can provide some reference for the reinforcement design of landslide with tunnel in high-intensity area.

Seismic response analysis of buried oil and gas pipeline under bidirectional multi-point excitation

Aiming at the seismic response of buried oil and gas pipeline under bidirectional multi-point excitation, the shaking table test of buried oil and gas pipeline under bidirectional multi-point seismic excitation was carried out by using a new layered shear continuum model of soil box and pipeline model. The seismic response law of acceleration and strain of buried oil and gas pipeline under bidirectional multi-point excitation, as well as the response law of soil acceleration and displacement around the pipeline, are clarified through experiments. The results show that: compared with the bidirectional consistent excitation, the curve of soil acceleration amplification coefficient under bidirectional multi-point excitation has a wider fluctuation range, and the soil displacement changes more significantly. The peak acceleration of the pipeline increases with the increase of loading grade and presents a decreasing amplitude and multi-peak phenomenon. The variation law of pipeline strain under bidirectional consistent excitation and bidirectional multi-point excitation is basically the same, showing a trend of large strain in the middle of the pipeline and small strain on both sides, but the strain response of the pipeline under bidirectional multi-point excitation is more prominent. Therefore, the influence of bidirectional multipoint excitation should be considered in seismic response analysis of buried oil and gas pipelines.

Analysis of the Working Response Mechanism of Wrapped Face Reinforced Soil Retaining Wall under Strong Vibration

A series of shaking table tests were carried out to explore the dynamic characteristics and working mechanisms of wrapped-face reinforced soil-retaining walls under strong vibration. Under the 0.1–1.0 g horizontal peak ground acceleration (HPGA), the damping ratio of sand shows a downward trend as a whole, so the acceleration amplification coefficient decreases with the increase of HPGA. However, when HPGA reaches 1.0 g, the acceleration amplification coefficient increases; the range of acceleration amplification coefficient at the top of the wall is 1.69–1.36. When HPGA is 1.0 g, the maximum cumulative residual displacement of the panel is 2.96% H, and the maximum uneven settlement of the sand is 3.57% H, both of which have exceeded the limit of the specification. With the increase of HPGA, the ratio of the dynamic earth force increment to the total dynamic earth force gradually approaches 50%. Since the reinforcement effect of geogrid is not considered, the predicted value of traditional earth pressure theory is different from the measured value. According to the Washington State Department of Transportation displacement index, the deformation range of wrapped-face reinforced soil-retaining walls is divided into three stages: the quasi-elastic stage, the plastic stage, and the failure stage.

Shaking Table Test Study on Dynamic Response of Bedding Rock Slope with Weak Rock

A shaking table model test was conducted to study the dynamic response and failure mechanism of a bedding rock slope with weak rock layer based on the “Xiaguiwa” landslide in the Jinsha River basin of Sichuan-Tibet. The influence of schist-like weak rock layer on bedding rock slope is considered. The test results show that the Peak Ground Acceleration (PGA) amplification coefficient varies rhythmically from the inside to the surface of the slope, and 0.3 g and 0.6 g are the slope appears cracking and instability. schist-like weak rock layer makes the seismic wave enhance obviously, but in the slope flexure position, the seismic wave near the weak rock layer is slightly weakened instead, and the maximum displacement often occurs above the weak rock layer. the “bucking” occurs at 1/4 of the slope height, and the fracture degree at the middle and lower part of the slope is greater than that at the middle and upper part, and the slope damage surface appears to be “concave at the top and convex at the bottom”. The damage process of the model slope is divided into four stages. The model test results reflect the influence of the weak rock layer on the seismic dynamic response and damage process of the bedding rock slope.

Study on dynamic safety distance of multi-storey buildings on the top of loess slope

In view of the frequent occurrence of strong earthquakes and the actual characteristics of buildings built on the top of slopes in the loess region of Western China, the dynamic response and stability law of loess slope under the building load on the top of the slope are discussed by using the three-dimensional finite element numerical calculation method. Taking the slope safety factor, acceleration amplification coefficient, building permanent displacement and slope sliding range as evaluation indexes, the dynamic safety of buildings on the top of the slope under earthquake is analyzed, and the recommended value of dynamic safety distance between top building and slope shoulder is put forward. The results show that: firstly, affected by the amplification effect of slope elevation, the dynamic response of buildings on the top of slope is stronger than that of buildings under slope. At the same time, affected by the amplification effect of the free surface of the slope, the dynamic response amplitude of the building is negatively correlated with the distance from the slope shoulder. Secondly, the horizontal acceleration ratio between the top building and the under building is the largest at the height of 3–6 m, indicating that the multi-storey building with pile raft foundation is most prone to damage at this height. Thirdly, the dynamic safety distance of multi-storey buildings with pile raft foundation located on the top of loess slope with slope height H ≤ 30 m and slope gradient 25° ≤ α ≤ 70° can be 24 m.

Shaking table test and numerical simulation of shallow foundation structures in seasonal frozen soil regions

Frozen soil layers can induce the formation of double or multilayers on the ground. Such formations change the dynamic characteristics and dominant period of soil, directly influencing the stability and safety of upper buildings. In this paper, the frozen soil-structure interaction system in cold region was taken as the research object. The frozen soil model was made artificially, and two kinds of structure models with different natural frequencies were designed. Through a series of shaking table tests and finite element numerical analysis, the influence of structural natural frequency, soil frozen depth and seismic load on the seismic response of structure were studied. The test results indicate that ground freezing could weaken the soil–structure interaction effect and the nonlinear development of the soil structure. The effect of peak acceleration amplification of the ground is significant close to the surface. The acceleration amplification coefficient of the ground surface decreased as the freezing depth increased, which indicates that the freezing of the ground suppressed the acceleration response of the ground surface. If the peak frequency of a seismic wave is close to the natural frequency of the structure, it can significantly amplify the seismic response of the structure. Owing to the interaction between the soil and the structure, the degree of liquefaction of the ground varied with different structures. Subsequently, a nonlinear finite element program was used to establish the dynamic calculation model of frozen soil-structure interaction system considering the gradient change of stiffness of frozen soil and the dependence of frozen soil on temperature. On the basis of validating the numerical model rationality, the seismic response of frozen soil-structure interaction system under horizontal seismic excitation was further explored. The analysis results show that the seismic response of the structure increased significantly with amplitude excitation; the greater was the freezing depth, the greater was the seismic response of the structure, The influence of the frozen ground on the seismic response of structures in the design of structures in frozen soil areas should be considered. In summary, the dominant period of the ground, the dynamic characteristics of a structure, the type of seismic wave, and the degree of liquefaction of the ground have a significant influence on the seismic response of the structure. Therefore, considerable attention should be paid to the influence of frozen soil on the dynamic characteristics of a structure in frozen soil regions.