Pile Penetration Research Articles

A Novel Method for Testing the Effect of Base Post-Grouting of Super-Long Piles

The base post-grouting technology is widely used in pile foundation engineering to improve its behavior. For super-long piles, due to the large compression of pile shaft, conventional static load tests cannot effectively test the effect of post-grouting at the pile base. This study introduced a novel method to test the effect of base post-grouting of three 88 m long piles. A total of three test piles were grouted at the bottom of the piles. The grouting amount of the No. 1 pile was 500 kg, the No. 2 pile was 250 kg, and the No. 3 pile was 0 kg. The transmitted wave method in the pile and dynamic penetration method were used in combination to quantitatively evaluate the effect of base post-grouting on the soil below the pile base. The influencing range of base post-grouting was firstly evaluated by the transmitted wave method in the pile, and the strength of the soil before and after grouting under the same pile base was measured by the dynamic penetration method. The test results showed that: the depth of the pile base reinforcement was 2 m for No. 1 pile, and 1 m for No. 2 pile, which was consistent with the grouting amount; the elastic modulus of the soil below the pile base after base post-grouting was about twice that of the soil before base post-grouting; the strength of the soil below pile base was largely improved after grouting; and the bearing capacity of the base soil layer increased from 35.5% to 41.7% when the grouting amount increased from 250 kg to 500 kg.

Experimental and Numerical Analysis of Pile–Rock Interaction Characteristics of Steel Pipe Piles Penetrating into Coral Reef Limestone

In order to study the characteristics of pile–rock action of steel pipe driven pile in coral reef limestone stratum, coral reef limestone at the China–Maldives Friendship Bridge site was selected to carry out indoor physical and model tests with red sandstone as the control group. The test outcomes indicate the following: (1) when substantial deformation is permitted, the coral reef limestone has a considerable strength dispersion, a low post-peak stress decrease rate, and a high residual strength, roughly 30% of the peak strength; (2) when the steel pipe pile penetrates the coral reef limestone, the pile top load shows an obvious sawtooth shape, and with the increase in penetration depth, the pile end load of the high-porosity rock sample gradually decreases, and the pile end load of the low-porosity rock sample gradually increases; (3) when the steel pipe pile is penetrated, the strain value of the red sandstone is about twice that of the coral reef limestone at the same position from the steel pipe pile. These findings indicate that the high porosity and heterogeneity cementation characteristics of the coral reef limestone make the extrusion effect during piling significantly less than that of the red sandstone. In addition, the steel pipe pile penetration process is numerically simulated using a four-dimensional discrete spring model method based on the multi-body damage criterion. The numerical simulation results further demonstrate that the pile-side rock fragmentation during steel pipe pile penetration is the primary reason for the lower bearing capacity of steel pipe piles in coral reef limestone stratums. This method provides a novel approach for studying the mechanical properties of reef limestone. The findings can serve as a guide for the design and construction of steel pipe piles in the reef limestone stratum.

Research of jacked pile penetration test based on airbag loading

In view of the problem that the model test of pile jacking cannot reproduce the soil's self-gravity and thus cannot truly reflect the pile jacking force, this paper developed an airbag loading system. The airbag is used to pressurize and simulate the overburden soil weight. The method of subsection pile jacking and coupling is ingenuously adopted to achieve long pile penetration. Because the airbag and pressure can be controlled well, it is convenient to simulate the cohesive soil foundation. The size of the model pile used in the test is larger than that of the usual centrifugal model test pile, so it belongs to large scale model test. The experimental results using this system show that the pile jacking force increases with the increase of penetration depth. The degradation of pile lateral resistance has little impact on pile jacking force. After modification based on the degradation theory of pile lateral resistance, the overall variation law of pile lateral resistance is good, and the difference value generated at the joint of pile segments is basically 0. With the increasing of pile depth, the pile lateral resistance is gradually exerted. The pile end resistance fluctuates with the depth, and accounts for a relatively high proportion of pile jacked force, which is maintained above 50%. The method of pile jacking with airbag loading in this paper provides a new idea for the study of the penetration characteristics of jacked pile.

Fluid–Structure Interaction Analysis and Verification Test for Soil Penetration to Determine the Burial Depth of Subsea HVDC Cable

Recently, there have been frequent reports of subsea cable breakage accidents caused by the drop of an anchor pile for aquaculture works involving subsea cables for high-voltage direct current (HVDC) transmission embedded in the southwest sea of Korea. To determine the burial depth that can ensure the safety of subsea HVDC cables embedded under the seabed from the drop of anchor files, the soil penetration characteristics of anchor piles should be reasonably estimated. In the present study, the penetration characteristics of anchor piles into the soil under which subsea HVDC cables are embedded were evaluated using numerical simulations and field verification tests. The numerical simulation for the soil penetration phenomena of anchor piles was carried out using the fluid–structure interaction analysis method using the general purpose nonlinear finite element analysis code based on explicit time integration. Regarding the soil into which anchor piles penetrate, three types of soil—a clay layer, a sand layer, and a clay–sand mixed layer—were considered, which are the representative soil types in the southwest sea of Korea, where many subsea HVDC cables have been embedded. The result of fluid–structure interaction analysis showed that the maximum penetration into the clay layer was higher than that into the sand layer and the clay–sand mixed layer by 86.3% and 36.4% or more, respectively. The error rates of the field verification test and the fluid–structure interaction analysis were found to be 9.8%, 2.4%, and 2.4% in the clay layer, the sand layer, and the clay–sand mixed layer, respectively, which were found to be reasonable levels when considering that it was the numerical simulation for the soil penetration of an anchor pile resulting from drop impacts. The penetration depths of anchor piles were found to be the deepest in the clay layer, showing values of 3.9 to 4.1 m, and those in the sand layer were the shallowest, showing values of 1.9 to 2.1 m.

Torpedo pile penetration by combined water jet and mechanical vibrations in cohesive sedimentary beds

The penetration efficiency and safety of piles on the seabed affect the cost of offshore structures and the reliability of relevant equipment, which entails to the success or failure of the development and utilization of ocean resources. However, the traditional methods of pile penetration, including pressing method, impact driving method and vibro-driving method, are difficult to adapt to the complex marine environment. In this study, the torpedo pile penetration in cohesive sedimentary bed was investigated by applying downwardly directed vertical water jet and mechanical vibrations. The experimental work was developed in the laboratory through a series of pile penetration tests in different types of cohesive sediments. During the penetration processes of the torpedo pile, the relevant influencing factors such as water content of cohesive sediment, vibration intensity and water jet velocity were considered. The experimental results show that the penetration depth of the torpedo pile increases with the increase of water jet velocity, vibration intensity and water content of cohesive sediment. Based on the dimensionless analysis and data regression, a formula for the critical penetration depth of the torpedo pile in cohesive sediment is proposed, which is correlated with the water jet velocity and vibration intensity, as well as the torpedo pile and soil properties. In addition, the formula is verified by the experimental data of other study, which presents good consistency.

A case study of bearing capacity of piles partially embedded in rock

In the design of piles partially embedded in rock, the main factors that influence the strength and deformability of the rock and the transmission of loads from pile to rock are of utmost relevance to pile behavior. Most empirical methods were developed based on data from specific regions. Differences in geological conditions, drilling methods and other features are not considered in most procedures. The article deals with a case of piles partially embedded in rock located in the town of São Lourenço da Mata, Pernambuco, Brazil. The rock mass consists of ancient deposits, formed mainly by granites of different compositions, gneiss and schists. The deposits have been deformed by several tectonic processes. Results from 99 dynamic loading tests enabled comparison between the mobilized lateral and pile toe resistance, with the estimated capacity obtained from the design methods known in the literature. In the prediction, the lateral shear resistance due to pile penetration in residual soil was also considered. Because failure was not reached in the dynamic tests, the estimated capacity was higher than the mobilized resistance. The resistances mobilized by the pile shaft friction in soil, by the pile shaft friction in rock and by the mobilized toe resistance in rock in the dynamic loading tests are compared to design methods known in the literature. Five static loading tests indicated failure loads greater than the mobilized resistance in the dynamic methods. The comparisons allow recommendations of the most consistent design methods to use in similar cases in practice.

Micromechanical analysis of the particle corner breakage effect on pile penetration resistance and formation of breakage zones in coral sand

Although particle corner breakage has proven to be the major breakage mode of irregular grains, most pile–soil interaction analysis has focused on particle fracture breakage, thus the microscopic mechanism of sharp settlement/stress change for piles in coral sand remains unclear. This particle corner breakage–based study features laboratory pile penetration tests as well as DEM simulations. In the laboratory tests, in-situ sand samples that avoid slipping loss of corner debris are obtained and adopted. During DEM simulations, the cluster method is adopted with the linear parallel bond model. Unlike with classical friction resistance of piles, the particular shrinkage of friction resistance of piles in coral sand can be seen as resulting from a dual effect of corners. An additional increase in confining pressure was not efficient at improving the ultimate friction-bearing capacity of piles in crushable angular grains. As indicated by a diagram describing relationships between corner breakage and effective contacts, the force transmission in soil is newly generated, allowing interpretation of the sharp decrease of pile friction-bearing capacity. Findings indicate that higher grain angularity increases particle breakage within a narrower shear zone in soil samples. Finally, a particular relationship between particle breakage mode and the breakage zone around the pile tip is derived. This study sheds light on the microscopic mechanism of pile penetration in crushable granular soils, offering guidance for evaluating the ground-bearing capacity of angular granular soils.

Optimised screw pile design for offshore jacket foundations in medium–dense sand

Screw piles are well-suited foundations for offshore jacket structures, as they can be installed without significant underwater noise and have a large axial capacity. However, installation requirements for such large piles must be reduced to enable their installation in the field. This study combines geometry and installation optimisation to lower force and torque installation requirements. An original pile geometry, composed of a large diameter upper section connected to a smaller diameter lower section by a transition piece, was tested in a geotechnical beam centrifuge. The advancement ratio (AR), describing the relative vertical movement per pile rotation, was varied below the threshold usually recommended. The results show that a low AR reduces the pile penetration resistance and even generates some pull-in, while the torque remains almost unaffected. The torque is mainly associated with the upper section of the pile, which has a greater diameter to resist lateral loading in service. The pile capacity in tension generally increases as AR is reduced and reaches a maximum for AR = 0·5, while the compressive capacity reduces. It was shown that a simplified method can be used to estimate pile capacity, providing that some AR-dependent reduction factors can be calculated or assumed.

Experimental Study of Compaction and Expansion Effects Caused by Penetration of Core Pile During Construction of SDCM Pile

Experimental Study of Compaction and Expansion Effects Caused by Penetration of Core Pile During Construction of SDCM Pile

Breakage effect of calcareous sand on pile tip resistance and the surrounding soil stress

Due to the irregular shape, high porosity and fragility of calcareous sand particles, the construction of reef engineering is seriously affected, and the application of pile foundation engineering technology in calcareous sand stratum is also faced with great challenges. Based on the discrete element method (DEM), the pile installation process in the fractured calcareous sand stratum and non-fractured silica sand stratum are simulated, respectively, and the influence of particle breakage of calcareous sand on soil stress around the pile and pile tip resistance are discussed. The results show that the particle contact has no obvious dominant direction, and the particle breakage has little contribution on the variation of the particle contact normal directions while has great influence on the number of contact normals and the magnitude of contact normal force which is more uniform after particle breakage. The vertical and horizontal stresses in calcareous sand stratum are obviously lower than that in siliceous sand stratum. With the increase of the pile penetration depth, the number of crushing particles increases gradually. The particle breakage only can be found within the range of 3 times of pile diameter at the bottom of the pile and also within the range of 1 time of pile diameter around the pile. The effect of particle breakage on pile tip resistance is mainly reflected in the later stage of pile sinking. In calcareous sand, when the pile tip resistance increases to a certain extent, particle breakage occurs and the stresses in the soil cannot continually increase. Therefore, the pile tip resistance fluctuates around a stable value (∼0.3MPa). This is the reason that the pile tip resistance in calcareous sand is far less than that in siliceous sand, which is prone to pile foundation failure.

Numerical study on the installation effect of a jacked pile in sands on the pile vertical bearing capacities

The installation effect of a jacked pile in silica sand is investigated numerically. A simplified state-dependent dilatancy model is used to model the sand behavior and the sand grain crushing effect is considered by modifying the critical state line at large confining pressures. The Arbitrary Lagrangian-Eulerian (ALE) technique is adopted to model the pile penetration and the load-displacement behavior at the operational loading stage is simulated using standard finite element method with the initial states being the equilibrium of the pile-jacking-disturbed soil stress and void ratio fields and a free pile head. The numerical procedure has been verified against some calibration chamber tests and centrifuge tests. Simulations of wished-in-place piles are performed for the quantitative study of the installation effect. The results show that the capacity ratios between the jacked and wished-in-place piles become higher for long piles in dense sand. Linear fittings have been applied to obtain the capacity ratios as functions of the relative density and the penetration length-to-diameter ratio, which can be used for a quick estimation of the bearing capacity difference between jacked and wished-in-place piles.

A semi‐analytical solution for displacement‐controlled elliptical cavity expansion in undrained MCC soil

AbstractConventional cavity expansion theory is a one‐dimensional problem and is not applicable for the two‐dimensional cavity expansion issue, which is also required for geotechnical problems. This paper proposes a novel semi‐analytical solution for displacement‐controlled elliptical cavity expansion (DC‐ECE) in undrained soil. The displacement and strain fields for DC‐ECE are obtained from the strain path method (SPM) with the aid of conformal mapping theory. The effective stress can be subsequently obtained by the incremental stress‐strain calculation using a suitable constitutive model such as the MCC model. Then, the computed effective stress results are substituted into the stress equilibrium equation to give the pore pressure solution. The new semi‐analytical solution reveals the non‐axisymmetric characteristics of DC‐ECE and allows the elastic‐plastic (EP) boundary, excess pore pressure, stress, and displacement to be calculated. The proposed method provides a solution to non‐axisymmetric cavity expansion issues and it can be applied to geotechnical engineering problems, including vertical drain installation, flat dilatometer tests and noncylindrical pile penetration in clay.

Counter-toppling force on the composite pile with injected grout for a precast spur dike

In this study, a new design of a precast spur dike is described, and a composite pile with injected grout was introduced to enhance the toppling stability of the spur dike. To investigate the toppling process and counter-toppling force of the pile with injected grout, toppling tests of the composite pile with injected grout in sedimentary beds were conducted in the laboratory. The results indicated that the grouting agent reacted with the soil and formed a bulbous wedge, which significantly improved the counter-toppling force of the pile. Four different stages (incipient stage, slow toppling stage, plastic stage, and pull out stage) in the deformation process of the composite pile were observed and described herein. The horizontal counter-toppling force was found mainly influenced by the pile geometry, penetration depth, soil properties, grout volume, and grout injection rate of the grouting agent. Empirical equations for the shape of the wedge and the horizontal forces at the incipient and critical instants of the pile toppling were developed.

Numerical modelling of large deformation problems in geotechnical engineering: A state-of-the-art review

Many problems in geotechnical engineering involve large movements or rotations, examples include natural processes such as landslides, and man-made processes such as earthmoving and pile penetration. While the use of numerical modelling, primarily the finite element method (FEM), is now routine in geotechnical design and analysis, the limitations of conventional FEMs soon become apparent when attempting to model large deformation problems. For this reason, the search for alternatives remains a key goal of many geotechnical researchers, both to find accurate methods but also to develop efficient ones. In this review paper, prompted by Technical Committee 103 of the International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE), we survey the current state-of-the-art in numerical modelling techniques aimed at large deformation problems in geotechnics. The review covers continuum and discontinuum methods and provides a clear picture of what is and is not currently possible, which will be of use to both practitioners seeking suitable methods and researchers developing existing or new methods.

Development of numerical models for the long-term behaviour of monopile foundations under cyclic loading considering the installation effects

In most geotechnical simulations, the initial condition of the soil is assumed to be homogenous in terms of the void ratio and stress distribution. Thus, the influences of the installation process are not considered. In the study presented in this paper, the effects of the installation process by vibratory and impact driving means on the cyclic deformation behaviour of monopile foundations are investigated. The development and validation of different numerical models for the simulation of cyclic horizontal loading are presented. In the first model, the installation effects are taken into account in the form of the initial conditions of soil, which are based on a separate simulation for pile penetration. In the second model, a simplified approach uses some simple modifications of the initial value of soil in a certain zone around the pile shaft. With the results of small-scale model tests, the numerical approaches are validated. It is observed that the piles with impact and vibratory driving have significantly different deformation behaviours under cyclic loading.

DEM study of particle scale and penetration rate on the installation mechanisms of screw piles in sand

Screw piles are efficient anchors to sustain large uplift loads and can be installed with low noise or vibration. Screw piles dimensions are currently increasing, renewing research interest to reduce the installation requirements (torque and crowd or vertical force). The Discrete Element Method (DEM) is an ideal technique to investigate the complex soil behaviour during screw pile installation. Different techniques such as particle upscaling or increase of pile penetration rate have been used to reduce the CPU time to more acceptable durations (e.g. few days or weeks). This paper investigates how such techniques can affect the accuracy of the results and change the installation mechanisms. Results show that maintaining a low particle scaling factor is essential to reproduce the correct mechanism at low pile advancement ratio (AR, defined as the vertical displacement per rotation divided by the helix pitch). The pile overflighting (AR ≤ 1) creates an upwards movement of particles, which in turn creates some tension in the pile. Smaller advancement ratios require smaller particles to accurately capture this effect. Results also show that the pile penetration rate must be maintained relatively low to avoid spurious inertial effects.

Numerical investigation of dual-row batter pile wall in deep excavation

To evaluate the performance of dual-row batter pile wall (DRBPW) in deep excavations, a three-dimensional numerical model was established. The plastic hardening (PH) constitutive model in FLAC3D was adopted, considering the hardening property of the soil. A series of parametric study was conducted to investigate the effect of different factors. By analyzing the maximum lateral displacement, the pile shaft deflection and bending moment of both the leading and trailing row, the effect of inclination angle, pile diameter, penetration depth, and row spacing on the behavior of DRBPW was determined. The following conclusions could be drawn: (1) The bearing capacity of DRBPW is quite larger than that of the dual-row vertical pile wall (DRVPW). With the increase of inclination angle, a substantial reduction of lateral displacement could be observed. However, the beneficial role of batter pile is almost negligible when the inclination angle is not larger than 5°. The recommended inclination degree of the batter pile is 10° to 15°. (2) The maximum displacement of the leading and trailing rows lies at a distance below the pile cap, while the maximum bending moment is located at a small distance below the dredging line. The maximum bending moment of the leading pile is approximately twice that of the trailing one, thereby indicating that the leading pile bear more lateral earth pressure than the trailing pile. (3) The pile diameter, penetration depth and row spacing should be maintained in a suitable range; otherwise, the DRBPW may fail earlier than expected. The slender ratios is recommend to be set not larger than 30. The penetration ratio should not be less than 0.22. The optimal row spacing for the DRBPW is four times the diameter.

A New Spatial Deformation Measurement Method Using 3D Reconstruction Technology during Pile Penetration

Non-intrusive observation of the spatial deformation field of the soil has been a difficult problem for model test measurements. Based on the advantage that the visualization test method of transparent soil can observe the two-dimensional (2D) deformation inside the soil, this study proposes a new automatic tomographic scanning measuring device to observe the three-dimensional (3D) spatial soil deformation inside the transparent soil model. A series of 2D laser speckle images of different vertical cross sections before and after deformation were obtained, and an improved 3D reconstruction algorithm was used to reconstruct the 3D displacement field of soil after deformation. Different types of jacked-pile penetration model tests were carried out to investigate the spatial disturbance of the soil around the pile caused by the squeezing effect of the jacked-pile. The test results showed that the developed novel automatic tomographic scanning measuring device with the modified 3D reconstruction procedure could be an innovative tool in geotechnical physical model experiments. The model test results visually revealed the mechanism of the soil squeezing effect of jacked-piles with different pile head forms. Moreover, the spatial disturbance effect caused by different penetration stages was also discussed herein.

Analysis of the existing pile response induced by adjacent pile driving in undrained clay

An analytical method for quantitatively predicting the existing pile behavior induced by adjacent pile driving is of great engineering significance to evaluate the potential influence of adjacent pile penetration on existing piled buildings. In this paper, a simplified two-stage approach is employed to derive the vertical and lateral responses of the existing pile during adjacent pile installation. First, the free-field soil movement due to pile penetration is estimated by an improved source-sink imaging technique considering the existence of the top free surface. The validity and accuracy of this calculation approach are subsequently examined via comparison with published studies. Second, the shear-displacement method and improved Pasternak foundation model incorporating the impact of lateral soil displacement are introduced to investigate the pile-soil interaction. Moreover, based on the Randolph-Worth logarithmic attenuation function and Mindlin’s solution, the pile group response considering the shielding effect of piles is analyzed. Finally, the present solution for a single pile response is validated with the existing theoretical solution and the simulation solution, and extensive parameter studies are conducted to systematically discuss the variation of the behavior of the existing single pile and pile group.

Investigation of three sophisticated constitutive soil models: From numerical formulations to element tests and the analysis of vibratory pile driving tests

The performance of three advanced constitutive models has been evaluated based on element tests and on a comparative study on the simulation of vibratory pile driving tests in saturated sand. The inspected constitutive models are the Sanisand model and Hypoplasticity with Intergranular Strain (Hypo+IGS) as well as with Intergranular Strain Anisotropy (Hypo+ISA) extension. The performance of the constitutive models is first evaluated by the simulation of element tests used for the parameter calibration of the sand used in the model tests. The constitutive models are then applied for the simulation of a vibratory pile driving test. The pile penetration, the driving force, the pore water pressure development and the incremental displacement in the vicinity of the pile tip are compared to the measurements in the model tests. The strengths and weaknesses of the different constitutive models are assessed. Generally, the model predictions showed good agreement with the experimental results. Despite different constitutive formulations (hypoplastic vs. elasto-plastic), all three models were able to reproduce the main mechanisms of the driving process properly. It may be concluded that all three models allow a proper prediction of vibratory pile driving as long as a proper calibration of the material parameters is secured.