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European Journal of Applied Sciences – Vol. 10, No. 3
Publication Date: June 25, 2022
DOI:10.14738/aivp.103.12416. Rawashdeh, M. A., Li, W., & Akram, W. (2022). The Normative Effect of Harmonic Loads on Pile Group Depends on the
Characteristics of Dynamic Response. European Journal of Applied Sciences, 10(3). 275-280.
Services for Science and Education – United Kingdom
The Normative Effect of Harmonic Loads on Pile Group Depends
on the Characteristics of Dynamic Response
Mohammad Al Rawashdeh
Department of Civil Engineering, Faculty of Engineering
China University of Geosciences, Wuhan 430074, China
Wu Li
Department of Civil Engineering, Faculty of Engineering
China University of Geosciences, Wuhan 430074, China
Waseem Akram
Geological Survey and Research Institute
China university of Geosciences, Wuhan 430074, China
ABSTRACT
Pile-supported machine foundations are examined in this work to identify the
dynamic features of linear and nonlinear theories. A three-pile group with a 3 m pile
length and an outer diameter of 0.114 m is given axial harmonic loading before
field-based forcing vibration testing. For four distinct eccentric moments, tests are
carried out at a static load of 12 kN. Each eccentric instant's reaction in terms of
frequency and amplitude is examined. The continuum approach technique is also
used for theoretical analysis, which employs both linear and nonlinear solutions.
All of the eccentric moments' dynamic field test findings are compared to
theoretically expected frequency-amplitude responses. In comparison to the actual
test findings, the linear solution's anticipated responses show lower resonant
amplitudes and substantially higher resonant frequencies. The dynamic response
curves predicted by the nonlinear solution fit the test findings rather well in this
situation. To achieve this degree of agreement with nonlinear analysis results,
precision in border zone parameters and soil-pile separation lengths was
necessary.
Keyword: pile group; Dynamic field test; Axial harmonic group; Dynamic response.
INTRODUCTION
To withstand uncontrollable pressures such as earthquakes, ocean waves, and wind, piles are
often utilized as foundations to support heavy machinery and other vibrating equipment.
Because of the complicated interaction between piles, soil, and piles, geotechnical engineers
often have difficulty designing pile foundations that can withstand dynamic stresses. Due to soil
nonlinearity, soil-pile separation, and slippage between the pile and soil, machine foundations
supported by piles respond nonlinearly and with large displacements. When doing pile
foundation analysis and design, it is important to incorporate machine-induced harmonic
loading. Several scientists tested soil piles in the field while researching the dynamic and
theoretical responses of soil piles to machine-induced harmonic stresses. The soil-pile system's
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European Journal of Applied Sciences (EJAS) Vol. 10, Issue 3, June-2022
Services for Science and Education – United Kingdom
stiffness and damping (also known as its impedance characteristics) have been well
investigated in theory. Pile tests have been carried out by Elkasabgy, Naggar, Biswas, and
Manna in the field [1,2]. According to continuum-based analysis, results were compared with
theoretical curves. Assuming that the aftereffects of field testing under powerful stacking are
to be accepted, the hypothetical examination gave an OK forecast of the recurrence
plentifulness reaction bends. Utilizing Novak's strategy and the limited component model
under hub symphonious pressure share a great deal practically speaking, say Khalil and
partners [3].Stacking recurrence extensively affects the actuated amplitudes, as indicated by
the aftereffects of this review. Predicting border zone characteristics and separation length
between the soil and the pile when subjected to harmonic loading is essential to effectively
forecast nonlinear responses to these loads. The experimental confirmation of many theories
was also neglected. Linear and nonlinear continuum techniques under machine-induced axial
harmonic pressure are compared in this work using a three-pile grouping.
SITE CHARACTERIZATION AND LOCATION
The Indian Institute of Technology Delhi in New Delhi, India, conducts dynamic field testing
between blocks II and III during this research project. Several in-situ and laboratory
approaches are used to investigate the subsurface soil conditions [4]. During an SPT, soil
samples from the borehole are collected from both disturbed and undisturbed areas. The soil's
characteristics are analyzed using a variety of laboratory procedures. Clayey silt is identified in
the soil layers by in-situ and laboratory testing. As can be seen in Table 1, the measured soil
parameters of the various levels were compiled.
Table 1. Soil properties at test site
AXIAL HARMONIC LOADING TEST
There are hollow steel pipes that measure 3.0 meters in length (l), 0.114 meters in outer
diameter (d), and 0.003 meters thick (t). Plies with a standard slenderness ratio (l/d = 26) were
selected for testing since they were used in the research. Using a tripod and an SPT hammer,
piles are inserted into boreholes with an augur diameter of 0.1 m to guarantee that the earth
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Rawashdeh, M. A., Li, W., & Akram, W. (2022). The Normative Effect of Harmonic Loads on Pile Group Depends on the Characteristics of Dynamic
Response. European Journal of Applied Sciences, 10(3). 275-280.
URL: http://dx.doi.org/10.14738/aivp.103.12416
and the piles are in perfect contact. To secure the pile's end bearing, a steel plate is used to seal
the pile's bottom end. Driven piles are kept at a distance of three feet apart.
A mechanical oscillator generates the harmonic force on pile foundations. Force may be
regulated by changing the rotational eccentricity () of the spinning masses. As an example, we
may write the value of the produced eccentric moment as:
m.e = (W/g).e=[0.9sin(θ/2)]/gNsec2 (1)
W represents weight and m represent the mass of eccentric rotating parts and e represents the
eccentric distance of rotating mass, and g represents the acceleration due to gravity. Along with
the oscillating mechanism and steel plates, it's put on top of the pile. Testing for axial harmonic
loading in the field using a three-pile group configuration under a static load of 12 kN each
yielded four distinct eccentric moment values (W.e = 0.868, 1.270, 1.631, and 1.944 Nm). At
different frequencies (0–50 Hz), the system's frequency-amplitude responses are measured.
Acceleration may be monitored via a vertical accelerometer attached to a central plate of dirt
pile loading. The DC motor is fitted with a frequency measuring sensor before the dynamic
testing begins. Using these curves, frequency-amplitude curves may be created. Measurement
of temporal acceleration and frequency response is done using an axial harmonic test
Experiment setup is shown in Figure 1.
Figure 1: Axial Harmonic Loading Test
THEORETICAL ANALYSIS
Using the continuum method [5], the linear and nonlinear dynamic responses of a three-pile
group are determined. Both a linear and a nonlinear soil model are being examined in the
present study (with boundary zone parameters). Forcing a boundary zone that is less elastic
and more damping than the surrounding free field, the boundary zone helps to avoid the
reflection of waves from the cylinder zone's artificial contact with its surroundings. Slope, soil- pile separation, and slippage may all be found in this border area. Uses DYNA 5, a software suite
that incorporates this theoretical technique.