OPTIMIZATION OF GROUTING METHOD AND AXIAL PERFORMANCE OF PRESSURE GROUTED HELICAL PILES

2021 ◽  
Author(s):  
Mohamed A. Mansour ◽  
M. Hesham El Naggar
Keyword(s):  
Earth Pressure ◽  
Friction Angle ◽  
Grout Injection ◽  
Pile Capacity ◽  
Shaft Resistance ◽  
The Third ◽  
Lateral Earth Pressure ◽  
Helical Piles ◽  
Supporting Soil ◽  
Soil Interface

Pressure grouted helical pile (PGHP) is an innovative piling system that allows a significant increase in helical pile capacity with relatively low additional cost. The pile is constructed by applying pressurized grout during the installation of conventional helical piles. The grout is injected into the ground through two nozzles welded to the hollow pile shaft. This paper presents a comprehensive laboratory study to investigate the effect of three different nozzles configurations on the shape and axial performance of PGHP. The results reveal a significant increase in the PGHP shaft resistance over that of the un-grouted helical pile due to the formation of a continuous grout column with a larger diameter, higher friction angle at the pile/soil interface, and higher lateral earth pressure around the pile. The shape and diameter of the created grout column depend on the nozzles configuration used for grout injection. An increase in the end-bearing resistance is observed due to grout dissipation into the supporting soil voids. The study also shows that PGHPs installed with the third nozzles configuration have the fastest installation rate and the highest compression and pullout resistances. Thus, the third nozzles configuration is recommended for PGHP construction.

Active earth pressure in cohesive soils with an inclined ground surface

2000 ◽  
Vol 37 (1) ◽  
pp. 171-177 ◽  
Author(s):  
Nirmala Gnanapragasam
Keyword(s):  
Analytical Solution ◽  
Ground Surface ◽  
Earth Pressure ◽  
Failure Surface ◽  
Friction Angle ◽  
Active Earth Pressure ◽  
Overburden Pressure ◽  
Retaining Structure ◽  
Lateral Earth Pressure ◽  
Fixed Orientation

An analytical solution is developed to determine the active lateral earth pressure distribution on a retaining structure when it consists of a cohesive backfill (internal friction angle ϕ > 0, cohesion c > 0) with an inclined ground surface. The solution derived encompasses both Bell's equation (for cohesive or cohesionless backfill with a horizontal ground surface) and Rankine's solution (for cohesionless backfill with an inclined ground surface). The orientation of the failure surface is also determined. Results indicate that, unlike the soil-wall scenarios of Bell and Rankine where the failure planes are parallel with a fixed orientation independent of the overburden pressure, for sloping cohesive backfill (ϕ > 0, c > 0) the slope of the failure surface is a function of the overburden pressure and becomes shallower with depth, thus forming a curvilinear failure surface. The solution developed can also be used to check the sustainability of a slope. The analytical solution can be programmed conveniently in a computer.Key words: retaining structure, active earth pressure, cohesive backfill.

scholarly journals Study on the earth pressure of a foundation pit adjacent to a composite foundation with rigid-flexible and long-short piles

PLoS ONE ◽  
2021 ◽  
Vol 16 (5) ◽  
pp. e0251985
Author(s):  
Yuancheng Guo ◽  
Shaochuang Gu ◽  
Junwei Jin ◽  
Mingyu Li
Keyword(s):  
Three Dimensional ◽  
Earth Pressure ◽  
Friction Angle ◽  
Element Model ◽  
Composite Foundation ◽  
Deep Soil ◽  
Foundation Pit ◽  
Testing Procedures ◽  
Retaining Structure ◽  
Lateral Earth Pressure

Model tests were performed to investigate the lateral earth pressure acting on the retaining structure adjacent to both natural ground (NG) and composite foundation (CFRLP), which were supported with rigid-flexible and long-short piles. Two testing procedures, namely, applying a load to the foundation and rotating the retaining structure along its toe, were considered. The results indicate that the additional lateral earth pressure acting on the retaining structure adjacent to the CFRLP is less than that of the NG in the depth of the reinforcement area strengthened by flexible piles. Compared with NG, the CFRLP yielded a smaller normalized height of application of the lateral earth pressure, suggesting that the CFRLP blocked the horizontal diffusion of the load and had a strong ability to transfer the surcharge load to the deep soil. When rotating the retaining structure, the lateral earth pressure acting on the upper part of the retaining structure experienced limited reduction once the displacement at the top of the retaining structure was greater than 8 mm, whereas the pressure acting on the lower part of the retaining structure continued to decrease with increasing displacement. In addition, a three-dimensional finite element model (FEM) was used to investigate the influence of the pile parameter and the wall-soil friction angle on the additional lateral earth pressure.

Exploring the Evolution of Lateral Earth Pressure using the Distinct Element Method

2013 ◽  
Vol 30 (1) ◽  
pp. 77-86 ◽  
Author(s):  
M.-C. Weng ◽  
C.-C. Cheng ◽  
J.-S. Chiou
Keyword(s):  
Distinct Element ◽  
Earth Pressure ◽  
Friction Angle ◽  
Distinct Element Method ◽  
Analysis Model ◽  
Particle Assembly ◽  
Failure Patterns ◽  
Lateral Earth Pressure ◽  
Reference Parameters ◽  
Element Method

ABSTRACTThis study adopted the distinct element method (DEM) to explore the key influencing factors on the variations of lateral earth pressure, including packing type, interior friction angle, particle stiffness and particle size. The reference parameters for the DEM model were retrieved from direct shear tests of a rod assembly. Based on the reference parameters, the evolution of lateral earth pressure is further simulated, and a parametric study was conducted. The results showed that: (1) the analysis model could effectively capture the variation of lateral earth pressure under both active and passive conditions, and the simulated failure patterns were consistent with those from the sandbox tests; (2) the greater interior friction angle ϕinterior decreased the active coefficient Ka and increased the passive coefficient Kp; (3) increasing particle stiffness decreased the active coefficient Ka and increased the passive coefficient Kp; (4) larger particle sizes led to a larger active coefficient Ka and a smaller passive coefficient Kp; and (5) when the particle assembly was arranged in order, its lateral pressure was much larger than that of the randomly packed assembly.

Axial compressive capacity of driven piles in sand: a method including post-driving residual stresses

2001 ◽  
Vol 38 (2) ◽  
pp. 364-377
Author(s):  
Ahmed Shlash Alawneh ◽  
Osama Nusier ◽  
Abdullah I Husein Malkawi ◽  
Mustafa Al-Kateeb
Keyword(s):  
Residual Stresses ◽  
Bearing Capacity ◽  
Relative Density ◽  
Friction Angle ◽  
Accurate Estimate ◽  
Driven Piles ◽  
Pile Capacity ◽  
Shaft Resistance ◽  
Load Tests ◽  
Pile Load Tests

In this paper, empirical formulae were developed between the well-known pile bearing capacity factors (Nq and β) and parameters which include friction angle of sand, relative density, average effective vertical stress, and deformability of the soil below the pile toe. The developed empirical formulae were totally based on a database comprised of 28 well-documented compressive pile load tests collected exclusively from geotechnical literature. The actual measurements of shaft and end-bearing resistances of each pile in the database were adjusted to account for post-driving residual loads. Calculation of pile bearing capacity factors (Nq and β) was based on the adjusted shaft and end-bearing resistances rather than the actual unadjusted measured resistances for residual loads. Comparison of predicted and measured compressive capacity of an independent database comprised of 18 pile load tests showed that the developed formulae yield a reasonably accurate estimate of compressive pile capacity in cohesionless soils.Key words: driven piles, residual load, toe resistance, shaft resistance.

Effect of particle fabric on the coefficient of lateral earth pressure observed during one-dimensional compression of sand

2013 ◽  
Vol 50 (5) ◽  
pp. 457-466 ◽  
Author(s):  
Sheri Northcutt ◽  
Dharma Wijewickreme
Keyword(s):  
Relative Density ◽  
Stress Measurement ◽  
Earth Pressure ◽  
Friction Angle ◽  
Fraser River ◽  
Initial Particle ◽  
River Sand ◽  
One Dimensional ◽  
Lateral Earth Pressure ◽  
The One

The effect of initial particle fabric on the one-dimensional compression response of Fraser River sand was investigated. One-dimensional compression with lateral stress measurement was carried out on reconstituted Fraser River sand specimens using an instrumented oedometer. Laboratory specimens were reconstituted by air pluviation, tamping, and vibration and were prepared with an initial relative density ranging from medium loose to very dense. For Fraser River sand in one-dimensional compression, air-pluviated specimens yielded the highest values for the coefficient of lateral earth pressure at rest (Ko), tamped specimens produced the lowest Ko values, and vibrated specimens produced intermediate Ko values. The results from the present study demonstrate that specimens resulting from different laboratory reconstitution methods (i.e., different initial particle fabrics) exhibit different one-dimensional compression responses and produce different Ko values. A “fabric factor” was introduced to account for the effect of the initial particle fabric on the measured coefficient of lateral earth pressure at rest. Using the fabric factor, the constant volume friction angle, and the specimen relative density, a new empirical equation defining the coefficient of lateral earth pressure at rest during normally consolidated loading is proposed.

Centrifuge modelling of heating effects on energy pile performance in saturated sand

2015 ◽  
Vol 52 (8) ◽  
pp. 1045-1057 ◽  
Author(s):  
C.W.W. Ng ◽  
C. Shi ◽  
A. Gunawan ◽  
L. Laloui ◽  
H.L. Liu
Keyword(s):  
Earth Pressure ◽  
Continuous Heating ◽  
Saturated Sand ◽  
Pile Capacity ◽  
Shaft Resistance ◽  
Heating Effects ◽  
Energy Piles ◽  
Different Temperatures ◽  
Load Tests ◽  
Pile Load Tests

The operation of energy piles in summer can expel excess heat of the buildings into the ground by the use of a heat pump. Despite having been implemented for decades, the design of energy piles still relies heavily on empiricism, as there is limited understanding about heating effects on pile capacity. A series of centrifuge model tests on aluminum energy piles in medium dense saturated sand is reported in this study to investigate heating effects on the settlement patterns as well as capacities of single piles. In total, four in-flight pile load tests under three different temperatures, namely 22, 37, and 52 °C, and different loading sequences were carried out. Variations of pile capacity were interpreted with the help of a nonlinear elastic analysis. The test results show that after heating at zero applied axial load, toe resistance of the pile was mobilized as a result of constrained downward thermal expansion of the pile. Heating to a higher temperature caused the neutral plane to shift towards the pile toe due to a larger degree of mobilization of end-bearing resistance. It is also found that for a pile under a maintained working load, the pile head heaved initially by 1.4%D (D, pile diameter) when the temperature increased by 30 °C, but it gradually settled to 0.8%D after 4 months of continuous heating at the constant temperature. The post-pile settlement is believed to be caused by thermal contraction of sand. Subsequent pile load tests show that pile capacities increased by 13% and 30% with incremental temperatures of 15 and 30 °C, respectively. With an increasing temperature, shaft resistance increased but at a reducing rate. At a higher elevated temperature, toe resistance increased more rapidly than shaft resistance due to a larger downward expansion of the pile. For simplicity, earth pressure coefficients with values of 1.1K0 and 1.3K0 were found to be suitable for estimating the capacities of aluminum model piles with temperature increments of 15 and 30 °C, respectively.

Lateral Earth Pressure Coefficient of Soils Subjected to Freeze–Thaw

2017 ◽  
Vol 140 (2) ◽  
Author(s):  
Xiaodong Zhao ◽  
Guoqing Zhou ◽  
Bo Wang ◽  
Wei Jiao ◽  
Jing Yu
Keyword(s):  
Pressure Coefficient ◽  
Earth Pressure ◽  
Retaining Walls ◽  
Saturated Soil ◽  
Frozen Soils ◽  
Freeze Thaw ◽  
Lateral Earth Pressure ◽  
Soil Deposits ◽  
Earth Pressure Coefficient ◽  
Water Saturated

Artificial frozen soils (AFS) have been used widely as temporary retaining walls in strata with soft and water-saturated soil deposits. After excavations, frozen soils thaw, and the lateral earth pressure penetrates through the soils subjected to freeze–thaw, and acts on man-made facilities. Therefore, it is important to investigate the lateral pressure (coefficient) responses of soils subjected to freeze–thaw to perform structure calculations and stability assessments of man-made facilities. A cubical testing apparatus was developed, and tests were performed on susceptible soils under conditions of freezing to a stable thermal gradient and then thawing with a uniform temperature (Fnonuni–Tuni). The experimental results indicated a lack of notable anisotropy for the maximum lateral preconsolidated pressures induced by the specimen’s compaction and freeze–thaw. However, the freeze–thaw led to a decrement of lateral earth pressure coefficient  K0, and  K0 decrement under the horizontal Fnonuni–Tuni was greater than that under the vertical Fnonuni–Tuni. The measured  K0 for normally consolidated and over-consolidated soil specimens exhibited anisotropic characteristics under the vertical Fnonuni–Tuni and horizontal Fnonuni–Tuni treatments. The anisotropies of  K0 under the horizontal Fnonuni–Tuni were greater than that under the vertical Fnonuni–Tuni, and the anisotropies were more noticeable in the unloading path than that in the loading path. These observations have potential significances to the economical and practical design of permanent retaining walls in soft and water-saturated soil deposits.

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