Laminar Shear Box Research Articles

Shaking table test on the seismic performance of prefabricated utility tunnel passing through hard-soft strata under longitudinal excitation

The earthquakes have adverse effects on utility tunnels passing through hard-soft strata. This paper is the first to conduct shaking table test on the seismic performance of prefabricated utility tunnel passing through hard-soft strata under longitudinal excitation. The standard segments of utility tunnel were made by microconcrete. The prefabricated utility tunnel was assembled by standard segments of utility tunnel through bolts. The silty clay and fine sand were selected to simulate the prototype soft and hard soils. The tests were conducted using the laminar shear box. The test cases were numerically simulated, and numerical results matched experimental results well. By analyzing the seismic responses of the acceleration distribution of the soil, the utility tunnel strain, and the opening of joint, the law and mechanism of seismic response of prefabricated utility tunnel passing through hard-soft strata were revealed. The research results indicated that the relative compressive deformation between soft and hard soils fundamentally caused the axial compressive strains at the utility tunnel segments near hard-soft soils interface. The closer the segment was to hard-soft soils interface, the larger the axial compressive strain of segment. The relative tensile deformation between soft and hard soils fundamentally caused the openings of joints near hard-soft soils interface. The closer the joint was to hard-soft soils interface, the larger the opening of joint. The different mechanical characteristics of prefabricated utility tunnel joints under tension and compression were the reason for the significant difference in seismic responses between prefabricated and integral cast-in-place utility tunnels.

Influence of frozen soil site conditions on ground motion characteristics in cold regions

It is necessary to understand the site seismic response for seismic design and post-earthquake damage assessment of structures in seismically active regions. In cold regions, the presence of layered frozen soil not only affects the ground motion characteristics but also influences the seismic response of structures on these sites. This study aims to investigate the effect of frozen soil site conditions on ground motion characteristics in cold regions through shaking table tests using a laminar shear box equipped with a soil freezing system. The seismic acceleration response, displacement response, and dynamic shear stress-strain relation were analyzed for both unfrozen and frozen soil sites under various seismic waves with different intensities. The existence of the frozen soil layer has been observed to mitigate ground motion during earthquakes, resulting in a reduced peak ground acceleration compared with the unfrozen soil site. If an earthquake occurs, the high-frequency waves will be attenuated by the frozen soil layer, which possesses a dominant frequency lower than that of the unfrozen soil site. Moreover, the energy dissipation capacity of the frozen soil site is larger than that of the unfrozen soil site during earthquakes. By combining the Fourier spectral ratio curves, it can be inferred that different input ground motions have varying effects on the seismic response of both unfrozen and frozen sites. These findings serve as valuable references for seismic design of structures in cold regions.

Liquefaction-induced Soil-Pile Dynamic Interactions in Inclined Ground

Damage from earthquakes is relatively larger on inclined ground rather than on flat ground. Therefore, awareness on the importance of evaluating disaster risks on inclined ground is increasing. In particular, when piles are installed in the ground, the dynamic interaction between the ground and the pile is considerably complex, making it difficult to clearly determine the characteristics of the slope and pile. Therefore, this study numerically analyzed using centrifuge model test data with a laminar shear box and interpreted the lateral boundary of the numerical analysis section as a circulatory boundary. The excess pore water pressure, horizontal displacement of the pile, and input and response accelerations were compared and analyzed using the centrifuge model test in the numerical analysis. Consequently, the proposed numerical analysis technique could well predict the dynamic behavior of a pile installed in inclined ground.

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.

Effect of Spacing and Slenderness Ratio of Piles on the Seismic Behavior of Building Frames

The general assumption of a rigid base at the bottom of building structures during analysis and design underestimates the seismic response. Building structures resting on loose sand and soft clayey soil are vulnerable to earthquake forces. The amplification of ground motion occurs due to the presence of this loose and soft soil deposit. Moreover, the spacing and slenderness ratio of piles play a vital role in altering the behavior of the overall soil-foundation-superstructure system. This study aimed at investigating the effect of soil-pile-structure interaction using 1-g shake-table testing. Free and forced vibration tests were performed on scaled building frames with either a rigid base or a flexible base, supported on sandy soil with 50% relative density. A laminar shear box container is used for an experimental study of soil-pile-structure interaction. The design parameters, such as the spacing (S = 3D, 5D, 7D, and 9D) and slenderness ratio (L/D = 15, 30, 45, and 60) of the piles, where S, D and L are spacing, diameter and length of the piles respectively, are considered in the analysis. The results, in terms of natural frequency, damping, pile-bending moment, story lateral displacement, and inter-story drift are estimated. From the findings, it is clear that the effects due to pile spacing are more considerable than the effects due to the slenderness ratio of the piles. The bending moment in the piles spaced at 3D is increased by 102% compared to the large-spacing (S = 9D) piles. This subsequently amplifies the story lateral displacement by 180% and amplifies the inter-story drift by 167%.

Seismic evaluation of frictional FRP piles in saturated sands using shaking table tests

This manuscript presents results of two shaking table tests that were used to characterize seismic performance of Fibre-Reinforced Polymers (FRP) pile groups in saturated sand. A laminar shear box with a dimension of 1.0 m × 1.0 m and a depth of 1.0 m was employed to contain the soil medium and allow the soil to respond in the same fashion as the free field. Two types of composite group piles (2 × 2) made of Carbon FRP (CFRP) and Glass FRP (GFRP) along with a series of Aluminum model piles were manufactured and embedded as frictional piles within the soil. The pile-soil models were subjected to acceleration time histories adopted from the 2010 Val-des-Bois Earthquake in Canada and the 1995 Kobe Earthquake. The foundation motions recorded along the model piles showed significantly higher levels of excitation compared to the accelerations recorded within the soil at the same level. This was attributed to strong interaction between the soil and the foundation, and higher flexural stiffness of the model piles. Pile material was also found to influence the seismic response of pile caps and its superstructure through kinematic soil-pile interaction and possible rocking motion. The aluminum pile cap experienced significantly higher acceleration response compared to the FRP piles. Among the FRP piles, GFRP piles were shown to provide slightly better performance and could be an appropriate alternative piling material for frictional traditional piles especially in liquefiable soils.

Seismic Response of a Two-Story Three-Span Subway Structural Model under High-Accelerated Geotechnical Centrifuge Shaking Table Test

The seismic response of underground structures such as subway stations is critical. However, the complex underground structure experiments under a dynamic centrifuge shaking table are significantly limited. This study conducts a shaking table test of a two-story three-span underground structure under 50 g gravitational centrifuge acceleration to investigate soil–structure interaction effects (SSI). The test is performed on a sand soil-structural model using a laminar shear box with depths of 2.5 m, and the input motion is a Parkfield wave. The experimental results indicate that the central column of the two-story three-span underground structure is the weak component during the earthquake. In addition, the numerical simulations of the soil–structure system are carried out to study the effect of buried depth and foundation soil type on the seismic response of the underground structures. The experimental and numerical results proved that the performed centrifuge test can reproduce the key seismic response characteristics of the SSI in the prototype underground structure and provided guidelines to design a similar underground structure in the future development of the urban subway systems.

Evaluation of dynamic soil-structure interaction effects in buildings with underground stories using 1 g physical experimentation in a transparent shear laminar box

This article presents a study of the Dynamic Soil-Structure Interaction (DSSI) using physical reduced–scale models of a building under different configurations of above-ground and underground stories. Each model was tested in a laminar shear box with a transparent front side. This characteristic of the device makes it possible to visualize the soil particles during the test and acquire data from the soil-structure interaction in a direct and spatially continuous way. A shaking table, an array of 3 high–speed and high–resolution cameras and a tactile dynamic pressure sensor were used. Ricker wavelets, with a wide range of frequencies and amplitudes, were used to evaluate the transfer functions in the system and the seismic response of model. Kinematic interaction effects were evaluated using the Digital Image Correlation (DIC) technique. It is verified that the experimental system allows a detailed tracking of the dynamic interaction between the building and the surrounding soil. The results show the direct relationship between the frequency content of the input wavelet and the dynamic pressure distribution acting on the underground levels, and the increase of the building’s first vibrating period. In addition, it was found that the distribution and magnitude of the lateral soil thrust is dominated by the superstructure vibration, and not the ground movement. This relationship becomes more important as the slenderness of the building increases, i.e., as the rocking mode of vibration becomes more significant. Additionally, in the case of buildings with basements, our results suggest that the combination of the increased confinement, the interaction of the foundation in terms of motion compatibility and the vibrations transferred from the superstructure to the ground produces an invariable reduction in effective base motion, suggesting that neglecting the effects of DSSI would be a conservative assumption.

Centrifuge shaking table study on the hydrodynamic effects on a pile foundation bridge pier in soft soil under earthquakes

Previous investigations have shown that water-pier interaction has a considerable effect on the seismic response of bridge piers in deep water. However, most of those studies assumed that the foundation is rigid and there are few studies on the hydrodynamic effects on the piers considering soil-structure interaction under earthquakes. To investigate the hydrodynamic effects on bridge piers built on soft ground, series of centrifuge shaking table tests were conducted. In the tests, a pile foundation bridge pier was scaled down by a factor of 1:50. The height of the pier was 340 mm, and the length of the pile was 200 mm. The pile foundation pier was installed in soft soil contained in a laminar shear box. Three depths of water, i.e., no water, 150 mm and 300 mm, were considered. The dynamic responses of pier displacement, acceleration and bending moment of the pier and piles, hydrodynamic pressure on the pier, soil pressure on the pile and pore-water pressure in the soil were measured. The results show that the natural frequency of the pier decreases as the water depth increases, and the displacement of the pier with a water depth of 300mm is significantly reduced in comparison with that of no water. However, water increases the acceleration and bending moment of the pier and the pile. The results also show that as the water depth increases, the hydrodynamic pressure acting on the pier and the dynamic soil pressure exerted on the pile both increase under earthquakes.

Design of a Biaxial Laminar Shear Box for 1g Shaking Table Tests

In this paper, the design of a new laminar shear box at the Laboratory of Earthquake Engineering and Dynamic Analysis (L.E.D.A.) of the University of Enna “Kore” (Sicily, Italy), is presented. The laminar box has been developed to investigate the liquefaction phenomenon and to validate advanced numerical models and/or the numerical approaches assessed to simulate and prevent related effects. The first part of the paper describes in detail the types of soil containers that have been used in the last three decades around the world. Particular attention is paid to laminar shear box and liquefaction studies. Moreover, the most important factors that affect the performance of a laminar shear box are reported. The last part of the paper describes components, properties, and design advantages of the new laminar shear box for 1g shaking table tests at L.E.D.A. The new laminar box has a rectangular cross section and consists of 16 layers. Each layer is composed of two frames: an inner frame and an outer frame. The inner frame has an internal dimension of 2570 mm by 2310 mm, while the outer frame has an internal dimension of 2700 mm by 2770 mm. Between the layers, there is a 20 mm gap, making the total height 1600 mm.

Analysis of Multilayered Ground Amplification Characteristics by Scaled-Down Model Tests

During an earthquake, seismic waves travel through different media through the source to reach the surface. It is very necessary to study the dynamic characteristics of soil between different layers during earthquake. In order to explore the dynamic characteristics of soil under the action of ground seismic input motion, scaled-down model tests were carried out through 1 g shaking table tests based on a laminar shear box. After creating a dense lower ground with a sample of mixed silica and silty soil, and a loose upper ground with sand, the acceleration was measured by applying seismic loading through the 1 g shaking table test. Through the Peak ground acceleration, Spectral acceleration and Spectral acceleration amplification factors, the magnification variation and differences of each depth of the model and the dynamic characteristics of soil between different layers were displayed. In order to verify the reliability of the experimental data, a one-dimensional ground response analysis was carried out using DEEPSOIL software. The approximate results obtained by comparing each other can provide a basis for the accuracy of the experimental results.

Effect of excitation frequency on segmental tunnels in sand using 1 g shaking table tests

Two physical models of 1 g shaking table tests are conducted to investigate the effect of excitation frequency on dynamic responses of segmental tunnels in sand ground. Contained by a laminar shear box, the free-field model is a sand ground of 2 m in depth, while the soil-tunnel model has a miniature tunnel embedded within the ground. The tunnel is deliberately designed to imitate the structural features of typical segmental linings of shield-driven tunnels. To both physical models, ramped harmonic excitations are applied with three amplitudes at five frequencies, respectively. Interpretation of the test results is performed directly on the original model scale to avoid uncertainties brought up by scaling laws. Analysis of the free-field responses reveals that dynamic characteristics of the ground are highly dependent on the amplitudes and frequencies of the input motions due to the modulus reduction of the sand. As for the soil-tunnel model, responses of the segmental tunnel are much stronger when subjected to excitations of frequencies close to the eigenfrequency of the ground or of lower frequencies with large amplitudes. The former case could be attributed to the resonance effect. The latter one is caused by the larger shear strains induced by low-frequency excitations, as elaborated by an analytical solution. Thus, this study could offer helpful insights into the soil nonlinearity in 1 g shaking table tests and its influence on the soil-tunnel interactions.

Geotechnical behaviour of layered paste tailings in shaking table testing

ABSTRACT Interest in the use of paste tailings technology and understanding of the cyclic behaviour of paste tailings has significantly increased in the past years. However, no studies on geotechnical response of paste tailings to cyclic loading by shaking table testing technique has been performed. Thus, a one-dimensional shaking table testing program was performed to assess the behaviour and liquefaction susceptibility of the layered paste tailings under cyclic loading conditions. The paste tailings were deposited subsequently in three thin layers in a flexible laminar shear box mounted on top of the shaking table, and the response of accelerations, displacements and pore water pressures to seismic loading was measured at the middle depth of each layer of the tailings. Results showed that the acceleration for the bottom and middle layers were similar to that of the base of the shaking table; however, this was not the case for the top layer. The studied paste tailings were resistant to liquefaction during the cyclic loadings, but liquefied after the end of the shaking phase. All layers of paste tailings were subjected to contraction and dilation during the shaking.

Effect of Seismic Loading on Variation of Pore Water Pressure During Pile Pull-Out Tests in Sandy Soils

Experimental model was done for pile model of L / D = 25 installed into a laminar shear box contains different saturation soil densities (loose and dense sand) to evaluate the variation of pore water pressure before and after apply seismic loading. Two pore water pressure transducers placed at position near the middle and bottom of pile model to evaluate the pore water pressure during pullout tests. Seismic loading applied by uniaxial shaking table device, while the pullout tests were conducted through pullout device. The results of changing pore water pressure showed that the variation of pore water pressure near the bottom of pile is more than variation near the middle of pile in all tests. The variation of pore water pressure after apply seismic loading is more than the variation before apply seismic loading near the middle of pile and near the bottom of pile and in loose and dense sand. Variation of pore water pressure after apply seismic loading and uplift force is less than the variation after apply seismic loading in loose sand at middle and bottom of pile.

Dynamic response of thickened tailings in shaking table testing

In this study, an instrumented thickened tailings deposit model was designed, built and employed to evaluate the behaviour of layered thickened tailings to dynamic loading by using a shaking table equipment. The thickened tailings were deposited subsequently in three thin layers in a flexible laminar shear box mounted on top of the shaking table. Cyclic loading with a peak horizontal acceleration of 0.13 g and a frequency of 1 Hz was applied to the layered tailings deposit. Different types of sensors were placed to monitor the accelerations, displacements, volumetric water content and pore water pressures at the intermediate depth of each layer. Results indicated that the acceleration for the bottom and middle layers were similar to that of the base of the shaking table; but, this was not the case for the top layer. The measurements of vertical displacements indicated that all layers of thickened tailings experienced initially contraction and subsequently dilation during the shaking. The excess pore water pressure ratios were found to exceed unity through all layers of thickened tailings when the shaking ended. In other words, the results showed that the layered thickened tailings are susceptible to liquefaction under the considered testing conditions. It is also found that upward pore water migration to the top layer and downward pore water flow to the bottom layer occurred in the thickened tailings deposit. This water migration generated additional pore water pressure and also impacted the vertical displacement and liquefaction susceptibility of the thickened tailings material. The results of this study give a better understanding of the dynamic behaviour of thickened tailings, which is crucial for the safety of thickened tailings systems as well as sustainable mining.

Temperature induced changes in the behaviour of cementing fine-grained soils under dynamic loadings

ABSTRACT Cemented paste backfill (CPB) has been extensively used in the mine industry to backfill underground mine cavities for ground support and/or tailings management. Once placed in mine underground cavities, the geotechnical and liquefaction response of the CPB under dynamic (cyclic) loadings is a key design concern in mine backfilling. Moreover, fresh CPB might be exposed to several sources of heat that might affect its cyclic behaviour and liquefaction potential. This manuscript presents findings of assessing the effect of backfill temperature on its geotechnical and liquefaction response to cyclic loading by using shaking table. CPB mixtures were prepared under different temperatures, poured into a flexible laminar shear box, cured (under the same mixing temperature) for 2.5 hours, and then exposed to cyclic loading using 1-D Shaking table. Obtained results illustrate that CPB prepared and cured under the temperature of 20°C can be prone to liquefaction under the studied loading conditions. However, CPB prepared and cured below a temperature of 35°C is resistant to liquefaction. These results provide better comprehension of the effect of backfill temperature on the cyclic behaviour of CPB, and thus assist in designing more efficient CPB structures.

Experimental study on seismic vibration control of an offshore wind turbine with TMD considering soil liquefaction effect

Wind energy is clean and sustainable. Taiwan is establishing offshore wind farms using wind turbines in the Taiwan Strait. However, these are located in an earthquake-prone area with sandy seabed conditions. To ensure their safety and reliability, the turbines’ support structure must be protected against wind, waves, and seismic loads. Tuned mass dampers (TMDs) are commonly employed to reduce structural vibrations. A TMD is more simply incorporated into turbine structures than are other energy dissipation devices. In this study, a 1:25-scale test model with a TMD was constructed and subjected to shaking table tests to experimentally simulate the dynamic behavior of a typical 5-MW wind turbine with a jacket-type support structure and pile foundation. The scaled-down wind turbine model has a nacelle without rotating blades; therefore, the aerodynamic and rotational effects due to the rotating blades were ignored in this study. A large laminar shear box filled with saturated sandy ground was used to simulate the typical seabed conditions of Taiwanese offshore wind farms. The TMD system was designed to be tuned the first-mode frequency of the test model. Two ground accelerations, selected by considering wind farm site condition and near-fault characteristics, were used for excitation in the test. The responses of the test model with and without the TMD system were compared, and the influence of soil liquefaction on the effectiveness of TMD vibration control was addressed.

Seismic Response of Flat Ground and Slope Models through 1 g Shaking Table Tests and Numerical Analysis

In order to verify the reliability of numerical analysis, a series of 1 g shaking table tests for flat ground and slope were conducted using a laminar shear box subjected to different seismic waves. Firstly, numerical analyses, using the DEEPSOIL and ABAQUS software, were done to compare the results of flat ground experiments. After that, finite element analyses with ABAQUS were conducted to compare the results of slope experiments. For numerical analyses, considering the influence of the boundary, the concept of adjusted elastic modulus was proposed to improve the simulation results. Based on the analyses, it is found that in terms of acceleration-time history and spectral acceleration, the numerical analysis results are in good agreement with the experiment results. This implies that numerical analysis can capture the dynamic behavior of soil under 1 g shaking table test conditions.

Evaluation of the Hydrodynamic Pressure Effect of Cylindrical Liquid Storage Tank on The Granular Soil Behavior Under Seismic Excitation

Many liquid storage tanks around the world have been affected by earthquakes, and the seismic analysis of such tanks is much more complicated due to the Fluid-Structure Interaction. Besides, when the soil properties are taken into the consideration, the analysis with the Fluid-Soil-Structure Interaction becomes very complicated. In this paper, a series of shaking table tests are conducted on a model of the cylindrical water tank rested on dry granular soil and the equivalent load is considered to study the effect of hydrodynamic pressure generated in the storage water tank on the soil behavior. An experimental investigation of (1:100) scale model has been carried out on a shake table that was manufactured with specific mechanical parts and flexible laminar shear box. The preparation of the test included three cases in different relative densities (medium, dense, medium-dense). Three earthquake histories (Kobe, El-Centro and Ali Al-Gharbi) were implemented to study a wide range of the acceleration. The results showed that the acceleration at the bottom-depth of the soil column is slightly higher than at the mid-depth, while at the top portion of the soil column, the acceleration comparatively becomes less than that at the mid-depth. The settlement due to hydrodynamic pressure in the storage base tank is significantly reduced compared with results of nonhydrodynamic pressure in all cases of the acceleration history. In addition, the lateral stress at the surface gives higher than the stress at a depth equal to the diameter of the base tank.

Effect of Hydrodynamic Pressure on Saturated Sand Supporting Liquid Storage Tank During the Earthquake

This paper aims to illuminate the influence of hydrodynamic pressure generated in a water storage tank on the behavior of saturated sand that its support. Experimental tests were performed on two cylindrical water tank models using a fabricated shaking table which consists of a flexible laminar shear box. The first model is a water storage tank partially full of water, and the second one is a tank model with an equivalent load of water pressure to simulate the water storage tank without hydrodynamic pressure. Three earthquake histories (Kobe, El-Centro, and Ali Al Gharbi) were implemented on models to study a varied range of acceleration. It was found that the settlement and lateral displacement directions in the water storage tank were significantly increased compared to the equivalent load resulted in the second model in all cases of the acceleration histories. Also, it was monitored the pore water pressure during the testing period, and it was noticed that the excess pore pressures were affected by the hydrodynamic pressure and increased compared to the results recorded at the condition of no hydrodynamic pressure.