Pile Model Test Research Articles

Physical Model Tests of Piles under Freeze–Thaw Cycles Subjected to Individual and Combined Loads

Physical Model Tests of Piles under Freeze–Thaw Cycles Subjected to Individual and Combined Loads

Assessment of the bearing capacity of variable profile piles in soil using static load model tests on a testing apparatus

The paper presents the results of the study of the proposed type of variable profile piles. The proposed type of piles is reinforced concrete driven piles segmented in length. Each subsequent section has a radial displacement along the axis of symmetry relative to the previous section. The positive effect of the performance of the proposed pile is to change the nature of the lateral contact of the pile with the soil, and to increase the drag of the soil. The conducted research is aimed at solving the problem related to the relatively low bearing capacity of traditional square section piles. The research was carried out by the method of model tests of piles on a test bench (tray) at a scale of 1:10. The tests were performed for variant pile types in comparison with a standard square section prismatic pile. The adopted dimensions of the pile model allow the use of this tray without the influence of its boundary conditions on the stress-strain state of the soil. A total of 42 tests were performed, 3 tests for each type of piles compared. Evaluation of pile bearing capacity was performed by static loading of pile models with vertical indentation load until failure. According to the results of the investigations, the resistance values of the compared pile types in the soil were obtained, as well as the dependence of bearing capacity changes on the section dimensions and on the rotation angle. According to the results, the optimal pile solution was selected. The bearing capacity of the proposed optimal pile solution exceeds the bearing capacity of the standard driven pile by 22 %. The results obtained allow us to conclude about the influence of the technological solution of the proposed pile type on its serviceability in soil conditions

Effect of Expanded Body Diameter on the Soil Surrounding a Pile Based on the Half-Face Pile Model Test of Undisturbed Soil

The effect of expanded body diameter on the displacement field of soil surrounding a pile under different vertical loads was investigated using the half-face pile model test of undisturbed soil. Digital image correlation technology was used to record the displacement characteristics of soil around the pile in real time. The displacement and failure characteristics of the soil around the pile were analyzed. The results show that with an increased load, the soil below the expanded body is compressed, and the soil at both ends will slip, leading to the continuous development of cracks. In a horizontal direction, the soil surrounding the pile first moves close to the pile and then tends to stabilize or move away from the pile. The horizontal and vertical displacement of the soil decreases as the distance from the pile increases. The main area of influence on the soil is below the expanded body, in which the increased diameter of the expanded body results in a gradual increase in the area of influence. Furthermore, all of the load-settlement curves show a slow decline and the bearing capacity increases with the increased diameter of the expanded body. Therefore, the research in this paper can provide an experimental method for the study of soil displacement around drill-expanded concrete piles.

Influence of the α Angle of Flexible Concrete Expanded-Plate Piles on the Bearing Capacity under Horizontal Load

Concrete expanded-plate piles have significant advantages in the bearing capacity, settlement, and construction period. The added bearing expanded plate is the key reason for their many advantages; moreover, the slope angle (α angle: the maximum diameter of the bearing expanded plate and the angle formed on the plate) of the bearing expanded plate is the main factor to control the longitudinal symmetry. However, the concrete expanded-plate piles in practical engineering do not exist in a rigid body state, and elastic deformation will occur under variable engineering conditions. In addition, the research in this paper mainly focuses on a flexible concrete expanded-plate pile (F-CEP pile). The flexible pile mentioned in this paper refers to the bending deformation of the pile body under horizontal load, which produces large pile top displacement. This study uses the two methods of small-scale half-plane pile model test and finite element simulation analysis of ANSYS, after referring to the equipotential pile test at the actual site. In this paper, the variation law of the displacement curve and the failure law of the soil around the pile under the horizontal force when the α angle changes are analyzed, and the calculation model of the bearing capacity of F-CEP pile under the α angle change is put forward. This research aims to verify the reliability of existing research and provides strong support for the application, promotion, design, and research of F-CEP piles in construction engineering.

Model test of static drilling and rooted energy pile considering over-consolidated behavior of soft soil

In order to study the bearing characteristics of static drilling and rooted energy piles in soft soil with different consolidation states， based on the energy pile model test， the thermal response of the model piles in normal consolidated soil and over-consolidated soil is tested. The results show that the heat diffusion in the soil around the pile decreases with the increase of the distance away from the heat exchange tube （heat source）. The over-consolidation state of the soil layer affects the generation and dissipation of pore water pressure in the soil layer. Compared with the normal consolidated soil， the dissipation rate of the pore pressure in the over-consolidated soil layer is slower. The vertical deformation of the soft soil around the pile first manifests as rebound after the temperature rises， and then becomes settlement. Compared with the normal consolidated soil， the over-consolidated soil rebounds significantly， and the subsequent settlement is smaller. The additional temperature stress of the pile body increases first and then decreases； in the case of over-consolidated soil， the maximum additional temperature stress position of the pile body is higher than that in the case of normal consolidated soil， and the negative friction caused by heating is smaller. The bearing characteristics of statically drilled rooted energy piles are closely related to the over-consolidated state of soft soil， and comprehensive consideration is required in engineering design to ensure operational safety. <fig fig-type="abstract-image" id="F1" orientation="portrait" position="float"><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="SP.J.1249-2022-39-1-93/6E4E2FEE-B986-4675-B4CC-9CA8241BD5AC-F001.jpg"/></fig>

Model tests and theoretical analysis of the vertical vibration of a single pile in saturated sandy soil

The study of vibration dynamic response of pile foundation has critical applications for seismic structure design. In this paper, firstly, the vibration characteristics of single pile with different length to diameter ratios under different vibration frequency loads were studied by the foundation pile model test method. Moreover, the amplitude-frequency curves of single pile vibration are plotted by using Fourier transform. Then the theoretical model of the pile-soil-cap system under sinusoidal periodic vibration load is established by using saturated porous medium theory, and the amplitude and frequency curves are obtained. Numerical results show that the theoretical solution can be in good agreement with the experimental results, which verifies the validation of the theoretical model. Furthermore, the resonant frequency is proven to be negatively related to the length to diameter ratio of the pile under the same pile diameter.

Experimental and theoretical investigation of transparent sand composing of fused quartz and calcium bromide solution

The thermal conductivity of soil is a fundamental physical property related to heat conduction and also one of the widely applied parameters in geotechnical engineering. Thermal needle tests were performed to measure the thermal conductivity of transparent sand. The thermal conductivity of three particle sizes of transparent sand was measured at different porosities and temperatures. The result shows that the thermal conductivity of transparent sand decreases with the increase of porosity and temperature. A modified model is proposed to calculate the thermal conductivity of the tested sand. Compared with the literature models, which are only suitable for room temperature, the modified model in this paper is applicable to a wider temperature range, ranging from 5∘C to 45∘C. It will also be beneficial to future studies on thermal reponses of granular materials, i.e., energy pile model test using transparent sand.

Lateral dynamic load tests of offshore piles based using the m-method

The static load test method is currently the standard horizontal bearing capacity test for offshore foundation piles. The static load test method requires extensive testing time, high equipment cost, and uses equipment sensitive to environmental conditions. As offshore wind power piles increase in diameter, the static load test method becomes increasingly cumbersome to use. In this contribution, a single pile model test under the action of static force and impact was carried out. Based on the m-method, the dynamic and static transformation relationship of m value in the test was explored, and a new lateral dynamic load test method for offshore piles is proposed. The new method employs the in-situ ship impact impulse test method. The m-value dynamic-static ratio (m value under dynamic force/m value under static force) exhibits a quadratic parabolic distribution relative to horizontal displacement and external load. The m value under impact can be converted into the equivalent static m value, which can be used to analyze the pile-soil interaction and evaluate the pile horizontal bearing capacity.

Construction and application of a PCC energy pile model test system

PCC energy piles represent a new type of energy pile technology. At present, research on the bearing characteristics of PCC energy piles is relatively limited. This study designs and builds a PCC energy pile model test system, including a model pile, optical fiber sensors, and heat transfer, loading, and data acquisition devises. The system is used to study the bearing characteristics of PCC energy piles under different temperatures. Results show that the temperature of the pile is transferred to the soil along the radial direction under the action of a circulating temperature and the moisture in the soil around the pile migrates along the direction of heat transfer. The migration speed increases when the temperature gradient is large. At the end of circulation, the displacement of the pile top increases by 0.6% D, the resistance at the pile end increases by 1.28 times, and the maximum strain point of the pile body is 70%L from the pile top. The PCC energy pile test system proposed in this work is feasible and applicable.

Experimental Study on Influence of Disc Number on Soil Failure State of Concrete Expanded-Plate Pile under Horizontal Force in Oceanographic Engineering

Qian, Y.; He, M., and Wang, R., 2020. Experimental study on influence of disc number on soil failure state of concrete expanded-plate pile under horizontal force in oceanographic engineering. In: Gong, D.; Zhang, M., and Liu, R. (eds.), Advances in Coastal Research: Engineering, Industry, Economy, and Sustainable Development. Journal of Coastal Research, Special Issue No. 106, pp. 660–663. Coconut Creek (Florida), ISSN 0749-0208.As a new type of variable section pile, concrete expansion piles have the advantages of high bearing capacity, strong overturning resistance, and flexible design position. However, the effects of disc parameters on failure state and bearing capacity need further study. In this study, taking disc number as the main parameter, an innovative semisection pile model test method of undisturbed soil is proposed to study the influence of disc number on horizontal bearing capacity and soil failure state of concrete expanded piles under horizontal force. The research results of this study have further improved the test method, test device, and theoretical research conclusion of the undisturbed soil half-section model, which promotes popularization and application of concrete expansion piles.

Study on Visualization and Failure Mode of Model Test of Rock-Socketed Pile in Soft Rock

Computed tomography (CT) technology is a kind of nondestructive image reconstruction technology. CT visualization technology is introduced into the physical model test of a single pile, which can visualize a rock-socketed pile in soft rock under different pile top loads. In this article, the visualization process of a model test of a rock-socketed pile in soft rock is carried out by medical CT. The implementation procedure, the composition of the device, and the technical requirements of the test equipment, as well as the CT scanning operation of nondestructive visualization technique of the single pile model test, are introduced in detail. The influence of a marked layer setting, side wall effect, size of the model cylinder, and model pile on the visualization effect of a single pile model test is discussed. The feasibility and reliability of the model test visualization technology of a rock-socketed pile in soft rock are demonstrated by examples, and the failure mode of rock-socketed pile in soft rock is intuitively revealed to be the spherical cavity expansion mode of the pile end.

A Simplified Nonlinear Method for a Laterally Loaded Pile in Sloping Ground

A simplified nonlinear method was proposed to evaluate lateral behavior of a pile located in or nearby a slope, based on the traditionalp-ymethod. This method was validated with field test results of a steel pipe pile in clay and model tests of piles in sand slopes. The comparison indicated that the calculated horizontal displacement and bending moment of piles agree well with experimental results. Then, parametric studies were performed, and it shows that horizontal displacement, rotation, bending moment, and shear force increase along with increasing slope angles; the depth of maximum moment locates at about 1.6 Dbelow ground surface for horizontal ground, while this value turns to be about 3.6 Dand 5.6 Dfor sloping ground of 30° and 60°, respectively. The study clearly shows that slope angle has a significant effect on the deflection and lateral capacity of piles.

Simplification of Vertical Live Loading for In-Service Bridge Pile Foundation and Application in Single Pile Model Test

In order to calculate the static load model and the live load of the bridge pile foundation on the validation of the simplified, with a single pile in clay under vertical cyclic loads on the pile top settlement and axial force of pile model test, the effect of vertical cyclic loading condition, bearing capacity and settlement of single pile. The influence of cycle times on the settlement of pile head and the axial force of pile body is put forward, which provides the data support for the evaluation of the bearing capacity of the later bridge pile foundation.

Simplification of Vertical Live Loading for In-Service Bridge Pile Foundation

In order to determine the distribution of live load on the in-service bridge pile, the live load were statistically analyzed that the distribution at the end of the beam at the fulcrum of the beam and the T beam in the middle and small span of the highway bridge, the proportion of live load is obtained in the counter force at the end of the beam. According to the statistical results, the corresponding relationship between the ratio of cyclic loading and the span of highway bridge is established, and according to the traffic volume and the effective number of trips calculated by different types of vehicles, the relation between the number of cyclic loads and the operation time of the bridge pile foundation is analyzed. The above results were combined with the time cycle of the vehicle on the bridge, a simplified calculation model of static load and live load on bridge pile foundation is established, which the obtained results can be directly applied to the test and loading of in-service bridge pile foundation and to guide the single pile model test in the laboratory, and has a strong application value.

Study on Active Earth Pressure of Sheet Pile Model Test on Foundation Pit Engineering

In recent years, building density in the city is increasing as the promoting of urban modernization. Deep foundation pit excavation and bracing is a topic in geotechnical engineering, including strength and stabilization of soil mechanics, and transmutation and sedimentation of deep foundation, and common effect between soil and shoring structure. The paper based on the design and fabrication of indoor model test device. This paper respectively explored the destroy mechanism of cantilever and anchored sheet pile support structure on the soil pressure under the different loads, and comprehensively carried through cantilever and anchored sheet pile support test under four-grades excavation depth and four-grades load combination, and specially researched the transformation of soil pressure. At the same time, the piles spacing changed among 3cm, 4cm and 5cm. Theoretical results showed that the active earth pressure increased with the increase of load and excavation depth. Model test results showed that the earth pressure behind the piles increased with the increase of excavation depth and the load. The biggest earth pressure was 19.38kPa when loading 40kPa. The changing curves of soil pressure were similar when piles spacing was 3cm and 4cm. Earth pressure after the piles was negative when piles spacing exceeded 4cm, which illustrated that active earth pressure had changed into passive soil pressure.

Research on Negative Skin Friction on Pile by a Simple Model Experiment

Accompanied by the substantive construction of domestic ports, the negative skin friction on pile becomes a common problem. In order to provide references for the related experiment research in the future, the designs of model experiments reported in the literatures were emphatically analyzed and compared. Compared to conventional pile model test, the model test on negative skin friction on pile needs to apply load on soil surface and it is difficult to simulate large surcharge by conventional test methods. An experimental scheme which could produce large surcharge load by conventional test conditions is given in this paper. Pile stress, displacement of pile top and layered settlement of soil was tested under different surcharge level. The depth of neutral point and the group effect of NSF are discussed.

Study on Earth Pressure of Foundation Pit Excavation by Model Test

As there are more and more high-rise buildings in the big cities, some new foundation pits are usually near old high-rise construction. In this case, foundation pit excavation is an engineering problem which needs to be solved urgently. This paper aims at the problem where the new foundation pit is closing to a high-rise building with a cement fly-ash grave (CFG) composite foundation, though cantilever retaining pile model test, simulate the excavate process, and make a testing system to measure datum in order to research on the characteristics of the earth pressure.

Stress-level effects in model tests on piles

Results are presented from several series of centrifuge model tests of piles installed in beds of uniform dry sand. Using identical model geometries, but varying acceleration factors, the tests demonstrate quite clearly the nature and extent of stress-level variations on the performance of piles. The results are interpreted initially in terms of bearing capacity coefficients Nt and lateral earth pressure coefficients Ks, and subsequently in terms of angle of friction [Formula: see text], determined using available relationships. Controlled laboratory experiments with varying levels of overburden pressure around the piles indicated consistent reductions in Nt, and to a lesser extent in Ks. Quantitative interpretations in terms of angle of friction variations depend on selection from a range of empirical correlations available and have been made for two of those commonly used. Comparison of shaft loads in compression and extension confirms the widespread belief that there is a difference, which is found to vary quantitatively depending on the relative density. Key words : model tests, piles, sand, centrifuge, stress level.

Model tests of piles in calcareous sands : Nauroy, J F; Le Tirant, P Proc Conference on Geotechnical Practice in Offshore Engineering, Austin, Texas, 27–29 AprilP356–369. Publ New York: ASCE, 1983

Model tests of piles in calcareous sands : Nauroy, J F; Le Tirant, P Proc Conference on Geotechnical Practice in Offshore Engineering, Austin, Texas, 27–29 AprilP356–369. Publ New York: ASCE, 1983