Laminar Box Research Articles

Study of the effects of container boundary and slope on soil liquefaction by centrifuge modeling

Two centrifuge model tests were conducted as part of the Liquefaction Experiments and Analysis Project (LEAP), and three extra tests were used to compare with the LEAP tests. The two models selected from LEAP-GWU-2015 were prepared in rigid box with a slope angle of 5 degrees. One of the extra models was prepared in a laminar box with a slope angle of 5 degrees and has the same model properties as the models from LEAP-GWU-2015. The other two extra models were prepared as flat ground in rigid box and laminar box respectively and have the same model properties. The effects of the container boundary and the dip direction of the slope models on soil liquefaction were investigated by assessing the acceleration, excess pore water pressure, and ground surface deformation. From the test results for the model in the laminar box, it is concluded that the soil contained in a laminar box have different dynamic characteristics compared with a rigid box soil. For the models in a rigid box, the soil on the high side of the slope has larger excess pore water pressure value and the excess pore water pressure changes are greater than the soil on the low side of the slope during shaking. The interaction between the slope dip and the direction of input motion affects dynamic performance during a seismic event.

Limbal and Conjunctival Epithelial Cell Cultivation on Contact Lenses-Different Affixing Techniques and the Effect of Feeder Cells.

Corneal blindness due to limbal stem-cell deficiency can be treated by transplantation of cultivated limbal epithelial stem cells (LESCs). We examined LESC cultivation on a contact lens (CL) carrier. Our goal was to optimize explant affixation and assess the possible benefit of 3T3 feeder cells. Human cadaver limbal and conjunctival explants were allowed to attach to CLs under the airflow of the laminar box (dried group) or affixed on CLs using suturing (sutured group) or tissue adhesives (glued group), then cultivated with or without 3T3 feeder cells. Outgrowth efficiency was statistically analyzed. CEBPδ, p63, CK3/12, and CK13 were detected by immunofluorescence in expanded cells. Suturing and gluing provided excellent sample attachment, whereas drying was less effective. Cell expansion was better in sutured than in dried or glued samples. Presence of 3T3 feeder resulted in significantly better cell growth (P=0.048), most importantly in dried samples (P=0.008). Stepwise regression analysis indicated that cell expansion was dependent on the affixing method (P<0.001) and the presence of feeder layer (P=0.003). Expanded cells maintained their CK expression profiles and expressed putative stem-cell markers p63 and CEBPδ. The 3T3 feeder did not influence the expression of putative LESC markers or growth rate. Suturing is an effective way to fasten explants to CLs. 3T3 fibroblasts are not necessary in this system, although they may enhance cell outgrowth when samples are exposed to stress. However, once cells begin to expand, neither expression of putative stem-cell markers nor growth rate is influenced by feeder cells.

Shake Table Study on the Effect of Mainshock-Aftershock Sequences on Structures with SFSI

Observations from recent earthquakes have emphasised the need for a better understanding of the effects of structure-footing-soil interaction on the response of structures. In order to incorporate the influences of soil, a laminar box can be used to contain the soil during experiments. The laminar box simulates field boundary conditions by allowing the soil to shear during shake table tests. A holistic response of a structure and supporting soil can thus be obtained by placing a model structure on the surface of the soil in the laminar box. This work reveals the response of structure with SFSI under mainshock and aftershock earthquake sequences. A large (2 m by 2 m) laminar box, capable of simulating the behaviour of both dry and saturated soils, was constructed. A model structure was placed on dry sand in the laminar box. The setup was excited by a sequence of earthquake excitations. The first excitation was used to obtain the response of the model on sand under the mainshock of an earthquake. The second and third excitations represented the first and second aftershocks, respectively.

Study of Physical Modelling for Piles

Physical modeling due to its simulation ability of real conditions has been developed as a proper method to study engineering issues. In this paper after the introduction of usual physical modeling systems in geotechnical engineering, we focused on a low known device of physical modeling in geotechnical practice, especially applicable in deep foundations. It is named Frustum Confining Vessel (FCV) that is one of the calibration chamber forms. It can apply high stress level by a relatively linear stress distribution. Thus, it can simulate actual states for piles in laboratory controlled conditions. The FCV test results can be used for real project by multiply scale factors. Scale factors can be explained by dimensional and similar analyses in every model and apparatus. In this study the relatively largest size of FCV among others in the world, which called FCV-AUT, was used to study physical purposes. Several various model piles (deep foundations) were made by 4 mm thick steel plate with height of 750 mm. All model piles tested in Babolsar sand as surrounding soil via FCV, and two full scale piles tested in similar conditions in the field. The experimental results and outcomes indicated the FCV can be used as a suitable device for physical modelling aims. Thus, it can be realized the FCV is more effective than simple and calibration chambers as well as laminar boxes and more economic than centrifuges.

Experimental study on the settlement of marine deposits of Anzali under cyclic loading by laminar box apparatus

ABSTRACTThe central Alborz mountain range, located in northern Iran, neighboring the Caspian Sea and where the two Persia and Eurasia plates meet, is known as a seismologically active area. In this regard, investigation of the behavior of saturated sand deposits located in this area may be of particular interest. Saturated sand deposits are subjected to instabilities owing to liquefaction or volume change due to earthquake shakings. A particular type of saturated sand deposits is Anzali sand which is abundant in Anzali port and other cities located in this area in northern Iran. This type of sand is a representative for most sands found in this area, i.e., the southern coastal line of Caspian Sea. This research is solely focused on the volume change behavior of marine deposits of Anzali area, often characterized as Anzali sand, in terms of the settlement of a model footing located on the surface of the sand by the aid of a transparent laminar shear box apparatus. Effects of a number of factors such as the frequency of the cyclic loading, the initial density of the sand, and the sample preparation method have been investigated. Observations indicated that the density index and the frequency of loading which are proportional to the energy of an earthquake have direct effects on the accumulation and amount of the final settlement of Anzali sand.

Identification of dynamic soil properties through shaking table tests on a large saturated sand specimen in a laminar shear box

Many laminar shear boxes have recently been developed into sliding-frame containers that can reproduce 1D ground-response boundary conditions. The measured responses of such large specimens can be utilized to back-calculate soil properties. This study investigates how the boundary effect in large specimens affects the identified soil properties through shaking table tests on a soil-filled large laminar box conducted at the National Center for Research on Earthquake Engineering in Taiwan. The tested soil-box system is unique because only 80% of the container is filled with soil. This system can be regarded as a two-layer system: an empty top and soil-filled bottom. The dynamic properties of this two-layer system are identified through various approaches, including theoretical solutions of wave propagation, free vibration, and nonparametric stress–strain analyzes. Therefore, the coupling effect of the box and soil can be evaluated. Results show that, compared with the two-layer system considering the influence of the box, the conventional approach with a single-layer system slightly underestimates shear wave velocity but obtains the same damping ratio of the soil layer. In addition, the identified modulus reduction and damping curves in the two-layer system are consistent with those obtained in a laboratory test on a small specimen. Furthermore, based on detailed acceleration measurements along different depths of soil, a piecewise profile of shear wave velocity is built. The identified shear wave velocity increases with depth, which is not uniform and differs from the constant velocity typically assumed for the specimen.

Seismic response of reduced-scale modular block and rigid faced reinforced walls through shaking table tests

This paper focuses on understanding the seismic response of geosynthetic reinforced retaining walls through shaking table tests on models of modular block and rigid faced reinforced retaining walls. Reduced-scale models of retaining walls reinforced with geogrid layers were constructed in a laminar box mounted on a uniaxial shaking table and subjected to various levels of sinusoidal base shaking. Models were instrumented with ultrasonic displacement sensors, earth pressure sensors and accelerometers. Effects of backfill density, number of reinforcement layers and reinforcement type on the performance of rigid faced and modular block walls were studied through different series of model tests. Performances of the walls were assessed in terms of face deformations, crest settlement and acceleration amplification at different elevations and compared. Modular block walls performed better than the rigid faced walls for the same level of base shaking because of the additional support derived by stacking the blocks with an offset. Type and quantity of reinforcement has significant effect on the seismic performance of both the types of walls. Displacements are more sensitive to relative density of the backfill and decrease with increasing relative density, the effect being more pronounced in case of unreinforced walls compared to the reinforced ones. Acceleration amplifications are not affected by the wall facing and inclusion of reinforcement.

Evaluation of Soft Clay Field Consolidation Using MEMS-Based In-Place Inclinometer–Accelerometer Array

Abstract The objectives of this study are: (1) to compare data recorded with a recently developed in-place inclinometer–accelerometer system to data measured with other established instrumentation through full-scale laminar box tests and field test sites, and (2) to evaluate possible causes for discrepancies between the measured and theoretical soil settlement at a bridge replacement site on soft clay. The performance of the three-dimensional (3D) micro-electro-mechanical systems (MEMS)-based in-place inclinometer–accelerometer array is evaluated for monitoring the settlement and lateral spreading of a very soft, 30-m-deep clay deposit at a New York State Department of Transportation (NYSDOT) bridge realignment site. Brief design details are given of the developed instrumentation system, which utilizes MEMS devices to measure angles relative to gravity, in addition to signals proportional to acceleration. The estimated theoretical accuracy of the system-displacement measurement is assessed empirically using thousands of datasets from several long-term field installations. This new instrumentation system was also included in a full-scale laminar box test of a sloping saturated fine sand deposit. This full-scale test provides a means of evaluating measured acceleration data. In all cases, data recorded with the developed in-place inclinometer–accelerometer system is compared to data measured with state-of-the-practice instrumentation. These comparisons were extremely favorable and justified the future use of this instrumentation for many geotechnical applications. This study also includes an evaluation of commercially available geotechnical software settlement predictions as compared to measured data at the NYSDOT bridge realignment site. The results of this study indicate that the effectiveness of the prefabricated vertical drains (PVDs) is not constant throughout the monitoring period and that the changes in effectiveness cannot be captured in commercial software using a constant ch.

Impact and cyclic shaking on loose sand properties in laminar box using gap sensors

This paper focuses on using high-frequency GAP-SENSORs (GSs), accelerometers, and load cells in a laminar shear box (LSB) filled with loose Toyoura sand to understand the effects of impact loads and cyclic shaking at 1-G on soil properties. The shear wave velocity at small strain (Vs) was calculated directly from first arrival reference using displacement time-history of two GSs under impact loading. Moreover, from first peak using the reduced deformation amplitude technique, damping ratio was calculated. In addition, shaking table tests were performed under harmonic loading with amplitude of acceleration inside the model ground varying from 0.02g to 1g. The frequencies of excitation varied from 1Hz to 10Hz. GSs and inside accelerometers were used to directly measure the outside lateral deformation and shear stress at different elevations of LSB, respectively. Results show that the shear modulus (G) and the damping ratio (D) behavior of model sand are generally consistent with the behavior presented by similar tests using only accelerometers. In addition, damping ratio increases as frequency loading increases. Characteristic changes in two shear stress components in shaking loading conditions were also investigated using high precision inside load cells.

Factors affecting stress distribution of a 3×3 pile group in dry sand based on three-dimensional large shaking table tests

To investigate the factors influencing stress distributions of piles during earthquakes, a physical model test was conducted using the large shaking table at E-defense. The tests were run on a 3×3 pile group supporting a foundation with and without a superstructure set in a dry sand deposit prepared in a cylindrical laminar box. Experimental variables included the natural period of a superstructure and the presence of foundation embedment. Based on the test results and discussions, the following conclusions are made: (1) When the natural period of a superstructure was shorter than or close to that of the ground, the inertial force of the superstructure mainly controlled pile stresses, in which both shear force and bending moment tended to be the largest in the leading pile. When the overturning moment is small in this case, sway motion dominates in which bending moment has maxima at both pile head and a certain depth in the ground. When the overturning moment becomes large enough to induce a rotation of foundation, by contrast, rocking motion dominates in which pile bending moment is small at the pile head, increasing with depth with a peak at some depth; (2) When the natural period of superstructure was much longer than that of the ground, the inertial force from the superstructure gets small and ground displacement may control the pile stresses in such a way that the shear forces at the pile heads were almost the same within a pile group. In this case, pile stress distributions with depth were mainly controlled by the sway motion due to the ground displacement, in which bending moment becomes a maximum only at the pile head and decreases with depth; and (3) The combination of the effects of the sway and rocking motions on pile stress varied depending on such factors as the presence of foundation embedment, natural periods of superstructures, aspect ratios of structures (height/width) and ground displacement.

Shaking table studies on geosynthetic reinforced soil slopes

This paper describes shaking table model studies conducted on unreinforced and reinforced soil slopes. A computer controlled hydraulically driven single degree of freedom shake table was used in these tests. Model soil slopes were constructed using clayey sand (SC) in a laminar box. Two different slope angles were used in tests. Two different types of reinforcement, namely, a woven geotextile and a biaxial geogrid were used in the tests. The models were instrumented with ultrasonic displacement transducers and accelerometers at different locations. The slopes were subjected to horizontal base shaking of known acceleration and frequency and the displacement and acceleration were monitored for time increments. Comparison of displacement and acceleration of tests with different slope angles and with reinforcing layers of different stiffness values resulted in some important observations regarding the response of these soil slopes under seismic shaking conditions. Tensile stiffness of the reinforcement plays an important role in controlling the seismic deformations and the beneficial effects of reinforcement are more pronounced in flatter slopes. Acceleration amplifications did not alter with the inclusion of reinforcing layers in the model studies reported in this paper because of the dimensional limitations. Numerical modeling of the geosynthetic reinforced soil slopes subjected to base shaking is also presented and the models are verified with the experimental results.

Simulation of seismic liquefaction: 1-g model testing system and shaking table tests

In this paper, we focus on the development and performance of the 1-g model testing system to monitor the liquefaction occurrence of saturated soils, under subsequent one-dimensional shake table tests. The system is composed of one-dimensional laminar box, cone penetration system, soil model, system for hydraulic soil pumping to achieve loose soil deposit, instrumentation and associated testing hardware. In order to simulate the free-field conditions in the laboratory, the laminates slide on each other using rollers placed between each laminate. The static calibration test results demonstrate that the friction effects between the laminates and the rollers are satisfactorily low. The loosest and the most liquefiable sand deposit is prepared inside the laminar box by hydraulic filling process and subjected to four subsequent shaking tests at different intensities. First, the laminar box and shake table performance is verified by using time-histories of acceleration and displacement test results. Then, the measured data inside the soil and on the laminates are compared with the numerical model. The previously calibrated numerical model UBCSAND which shows the seismic loading conditions in the free field is used in the simulations. Those shake table test results and the numerical simulations of the box and the soil indicate that the usefulness of the laminar box system for shaking table tests is satisfactory for dynamic model tests in 1-g gravity.

Pile response in submerged lateral spreads: Common pitfalls of numerical and physical modeling techniques

A three dimensional dynamic numerical methodology is developed and used to back-analyze experimental data on the seismic response of single piles in laterally spreading slopes. The aim of the paper is not to seek successful a-priori (Type A) predictions, but to explore the potential of currently available numerical techniques, and also to get feedback on modeling issues and assumptions which are not yet resolved in the international literature. It is illustrated that accurate simulation of the physical pile–soil interaction mechanisms is not a routine task, as it requires the incorporation of advanced numerical features, such as an effective stress constitutive soil model that can capture cyclic response and shear-induced dilation, interface elements to simulate the flow of liquefied ground around the pile and proper calibration of soil permeability to model excess pore pressure dissipation during shaking. In addition, the “conventional tied node” formulation, commonly used to simulate lateral boundary conditions during shaking, has to be modified in order to take into account the effects of the hydrostatic pore pressure surplus that is created at the down slope free field boundary of submerged slopes. A comparative analysis with the two different lateral boundary formulations reveals that “conventional tied nodes”, which also reflect the kinematic conditions imposed by laminar box containers in centrifuge and shaking table experiments, may underestimate seismic demands along the upper part of the pile foundation.

Mitigation of liquefaction of saturated sand using biogas

Some recent studies have indicated that the liquefaction potential of saturated sand can be greatly reduced if the sand can be made slightly unsaturated. One way to reduce the degree of saturation of sand is to inject gas into sand. This approach offers a cost-effective solution for mitigating liquefaction hazard over a large area. However, it is not easy to inject gas into sand in a uniform manner. A biogas method was developed in this study to overcome this difficulty. In this method, denitrifying bacteria are used to generate tiny, inert nitrogen gas bubbles in sand. Shaking table tests using a fully instrumented laminar box are conducted on both saturated sand and sand containing microbially generated nitrogen gas bubbles. Comparisons of the results of these tests indicate that the pore water pressure generated in the partially saturated sand was much smaller than that in saturated sand. Thus the proposed method is effective in reducing the liquefaction potential of sand.

Shaking table test of utility tunnel under non-uniform earthquake wave excitation

A series of shaking table tests were conducted on scaled utility tunnel models with and without construction joints under non-uniform input earthquake wave excitation. Details of experimental setup are first presented with particular focuses on: design and fabrication of double-axis laminar shear box with a rectangular hole opened on its side walls; design of two devices for measuring the slippage between the interface of test soil and the structure, and the relative deformation and rotation between joints of the structure model; and procedure for construction of input earthquake wave. The experiments were conducted in three phases. Phase 1 is free-field test. A 2-norm index is suggested to quantify the boundary effect and it is found that the designed laminar box does not impose significant boundary effect. Phases 2 and 3 are model tests in longitudinal and transversal directions, respectively. Test results are discussed in items of shear force–slip relationship at the soil–model structure interaction surface, movement and rotation of the construction joint, and effect of non-uniform earthquake input. The comparison shows that structural response under non-uniform earthquake excitation is larger than that under uniform excitation. The effect of spatial distribution of earthquake excitation should be considered in the seismic design of utility tunnel.

Mechanics of Lateral Spreading Observed in a Full-Scale Shake Test

This paper examines in detail the mechanics of lateral spreading observed in a full-scale test of a sloping saturated fine sand deposit, representative of liquefiable, young alluvial and hydraulic fill sands in the field. The test was conducted using a 6-m tall inclined laminar box shaken at the base. At the end of shaking, nearly the whole deposit was liquefied, and the ground surface displacement had reached 32 cm. The presented analysis of lateral spreading mechanics utilizes a unique set of lateral displacement results, DH, from three independent techniques. One of these techniques—motion tracking analysis of the experiment video recording—is especially useful as it produced DH time histories for all laminar box rings and a complete picture of the lateral spreading initiation with an unprecedented degree of resolution in time and space. A systematic study of the data identifies the progressive stages of initiation and accumulation of lateral spreading, lateral spread contribution of various depth ranges and sliding zones, their relation to the simultaneous pore pressure buildup, and the soil shear strength response during sliding. DOI: 10.1061/ASCEGT.1943-5606.0000409 CE Database subject headings: Soil liquefaction; Residual strength; Hydraulic fill; Full-scale tests; Lateral displacement. Author keywords: Liquefaction; Residual strength; Hydraulic fill; Full-scale tests; Lateral displacement.

CPT-Based Evaluation of Liquefaction and Lateral Spreading in Centrifuge

Two series of centrifuge model tests were conducted using Nevada sand. Four saturated models placed in a mildly inclined laminar box and simulating a 6-m-thick deposit were shaken inducing liquefaction effects and lateral spreading. The sand was deposited at a relative density, Dr =45 or 75%; two of the 45% models were subjected to overconsolidation or preshaking. The second series involved in-flight measurements of static cone tip penetration resistance, qc , simulating the standard cone penetration test (CPT) 36-mm cone. Values of qc increased with Dr , overconsolidation, and preshaking. A normalized resistance, qc1N , was assigned to each of the four liquefaction/lateral spreading models. Increases in Dr , overconsolidation, and preshaking decreased liquefaction and ground deformation, but relative density alone captured these effects rather poorly. Conversely, qc1N predicted extremely well the liquefaction and lateral spreading response of the four models, confirming Seed’s hypothesis to explain the s...

Seismic behaviour of rigid-faced reinforced soil retaining wall models: reinforcement effect

ABSTRACT: This paper presents the results of shaking table tests on models of rigid-faced reinforced soil retaining walls in which reinforcement materials of different tensile strength were used. The construction of the model retaining walls in a laminar box mounted on a shaking table, the instrumentation and the results from the shaking table tests are described in detail and the effects of the reinforcement parameters on the acceleration response at different elevations of the retaining wall, horizontal soil pressures and face deformations are presented. It was observed from these tests that the horizontal face displacement response of the rigid-faced retaining walls was significantly affected by the inclusion of reinforcement and even low-strength polymer reinforcement was found to be efficient in significantly reducing the deformation of the face. The acceleration amplifications were, however, observed to be less influenced by the reinforcement parameters. The results obtained from this study are helpful in understanding the relative performance of reinforced soil retaining walls under the different test conditions used in the experiments.

Laminar Box System for 1-g Physical Modeling of Liquefaction and Lateral Spreading

AbstractDetails of a large scale modular 1-g laminar box system capable of simulating seismic induced liquefaction and lateral spreading response of level or gently sloping loose deposits of up to 6 m depth are presented. The internal dimensions of the largest module are 5 m in length and 2.75 m in width. The system includes a two dimensional laminar box made of 24 laminates stacked on top of each other supported by ball bearings, a base shaker resting on a strong floor, two computer controlled high speed actuators mounted on a strong wall, a dense array advanced instrumentation, and a novel system for laboratory hydraulic placement of loose sand deposit, which mimics underwater deposition in a narrow density range. The stacks of laminates slide on each other using a low-friction high-load capacity ball bearing system placed between each laminate. It could also be reconfigured into two smaller modules that are 2.5 m wide, 2.75 m long, and up to 3 m high. The maximum shear strain achievable in this system is 15 %. A limited set of instrumentation data is presented to highlight the capabilities of this equipment system. The reliability of the dense array sensor data is illustrated using cross comparison of accelerations and displacements measured by different types of sensors.

Effect of Soil Permeability on Centrifuge Modeling of Pile Response to Lateral Spreading

This paper presents experimental results and analysis of six model centrifuge experiments conducted on the 150 g-ton Rensselaer Polytechnic Institute centrifuge to investigate the effect of soil permeability on the response of end-bearing single piles and pile groups subjected to lateral spreading. The models were tested in a laminar box and simulate a mild infinite slope with a liquefiable sand layer on top of a nonliquefiable layer. Three fine sand models consisting of a single pile, a 3×1 pile group, and a 2×2 pile group were tested, first using water as pore fluid, and then repeated using a viscous pore fluid, hence simulating two sands of different permeability in the field. The results were dramatically different, with the three tests simulating a low permeability soil developing 3–6 times larger pile head displacements and bending moments at the end of shaking. Deformation observations of colored sand strips, as well as measurements of sustained negative excess pore pressures near the foundations i...