Dynamic Response of Laterally Loaded Pile Groups in Clay
TL;DR: In this article, the effects of pile spacing, number of piles, and configuration on displacement and bending response of pile groups in clay under dynamic lateral loading were investigated, and strong group interaction leads to significant differences in bending profiles of different row piles of the groups.
Abstract: The effects of pile spacing, number of piles, and configuration on displacement and bending response of pile groups in clay under dynamic lateral loading were investigated. The displacement response of pile group in clay is strongly nonlinear. Pile-soil-pile interaction is predominant for the groups with closer spacing and with greater number of piles. Group interaction causes reduction in the group stiffness and increase in damping of the pile group. Strong group interaction leads to significant differences in bending profiles of different row piles of the groups. Dynamic lateral loading increases the maximum bending moment and active pile length.
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TL;DR: In this paper, a series of small scale dynamic experiments have been carried out on 2 × 1 model aluminum batter pile group embedded in soft clay, and it was found that the peak lateral displacement and peak bending strain at resonance region decrease with an increase in the batter angle.
Abstract: A series of small scale dynamic experiments have been carried out on 2 × 1 model aluminum batter pile group embedded in soft clay. The batter angles vary from 0 to 20 degrees. The pile group is subjected to sinusoidal lateral loads of different magnitudes (20–90 N), constituting 20–40% of its static ultimate capacity with the frequency in the range of 1–120 Hz. The time history of pile head displacement and bending strain along the length of pile are measured. It is found that the peak lateral displacement and peak bending strain at resonance region decrease with an increase in the batter angle, particularly for higher magnitude of lateral loads.
24 citations
Cites methods from "Dynamic Response of Laterally Loade..."
...2 essentially consists of three parts: a test tank with dimensions 2.0 × 2.0 × 1.5 m, a wave absorbing Table 1 Scaling factors for dynamic laterally loaded piles Quantity 1 g (Laboratory) Prototype Prototype values Length 1/n n 16.5 Acceleration 1 1 1 Stiffness 1/nα nα 16.5 Stress 1/n n 16.5 Force 1/n3 n3 4492.125 Strain 1/n1-α n1-α 1 Displacement 1/n2-α n2-α 16.5 Pore fluid density 1 1 1 Permeability 1 1 1 Time (dynamic) 1/n1-α/2 n1-α/2 4.062 Velocity 1/n1-α/2 n1-α/2 4.062 Frequency n1-α/2 1/n1-α/2 0.246 Shear wave velocity 1/nα/2 nα/2 4.062 International Journal of Geotechnical Engineering 2016 VOL. 10 NO. 4 319 medium of saw dust (Gazetas and Stokoe 1991), and a boundary element made of mild steel basket in logarithmic spiral arc shape covered with geomembrane sheet, similar to the one reported in Boominathan and Ayothiraman (2005), and Chandrasekaran et al. (2012)....
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...…Engineering 2016 VOL. 10 NO. 4 319 medium of saw dust (Gazetas and Stokoe 1991), and a boundary element made of mild steel basket in logarithmic spiral arc shape covered with geomembrane sheet, similar to the one reported in Boominathan and Ayothiraman (2005), and Chandrasekaran et al. (2012)....
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...Boominathan and Ayothiraman (2005) showed that the response curve for the pile embedded in rigid tank is scattered and shows multiple peaks due to the reflection of long-period waves, but the same for the pile embedded in EHSS facility shows a single peak simulating half-space conditions as in the case of field....
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...The clay bed is prepared similar to Boominathan and Ayothiraman (2005, 2007)....
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TL;DR: In this article, the dynamic responses of cast in-situ reinforced concrete vertical and batter pile groups constructed in the silty sand have been investigated, and their responses were compared in terms of resonant frequency and peak displacement.
24 citations
TL;DR: In this paper, the authors evaluated the potential of earthquake-induced landslides considering seismicity of the region and the potential sources for Nilgiris are Moyar and Bhavani shears.
Abstract: The Nilgiris district in the Tamilnadu state of India is frequented by many landslides in the recent past. Though many of these landslides are rainfall-induced, there is a need to evaluate the potential of earthquake-induced landslides considering seismicity of the region. In this paper, deterministic seismic hazard of Nilgiris is carried out by considering a study area of 350 km radius around Nilgiris. Seismotectonic map of the Nilgiris, showing the details of faults and past earthquakes, is prepared. The peak ground acceleration (PGA) at bed rock level and response spectrum are evaluated. The potential sources for Nilgiris are Moyar and Bhavani shears. The PGA at bed rock level is 0.156 g corresponding to maximum considered earthquake 6.8. Ground response analysis for seven sites, in the Nilgiris, is carried out by one-dimensional equivalent linear method using SHAKE 2000 program after considering the effect of topography. PGA of surface motion got amplified to 0.64 g in Coonoor site and 0.44 g in Ooty site compared to 0.39 g of the input motion. The bracketed duration of time history of surface acceleration has increased to 20 s in Coonoor site and 18 s in Ooty site compared to that of 8 s of input motion. Results from seismic displacement analysis using Newmark’s method revealed that out of seven sites investigated, five sites have moderate seismic landslide hazard and two sites (Coonoor and Ooty) have high hazard.
13 citations
Cites background from "Dynamic Response of Laterally Loade..."
...Most of the landslides in Nilgiris occurred during monsoon seasons and are predominantly rainfall-induced (NDMG 2009; Jaiswal et al. 2011; Chandrasekaran et al. 2013b; Ganapathy and Rajawat 2015)....
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...Several researchers emphasized the importance of evaluation of proper seismic input in the analysis of shallow (e.g., Gazetas and Mylonakis 2005) and pile foundations (e.g., Finn et al. 1997; Chandrasekaran et al. 2013a)....
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...Nilgiris district, located in the state of Tamilnadu, in PI is affected by numerous landslides historically (Bhandari 2006; NDMG 2009; Chandrasekaran et al. 2013b)....
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TL;DR: In this article, the authors proposed an innovative ground improvement technique, which involves partial cementation of granular columns resulting in Pervious Concrete Piles, which can transfer the load below failure surface without compromising on permeability criteria, thereby improving stability.
Abstract: Ground improvement is the process by which soil behaviour is altered mainly by physical means Typical examples range from inclusion of structural elements such as piles or soil nails, to use of any compaction technique in which the bearing capacity of soil is enhanced The use of stone columns in conjunction with soft or weak soils represents a very cost-effective way of improving bearing capacity In addition, stone columns being highly permeable provide natural drainage, thereby accelerating consolidation However, the physical behaviour of stone columns is affected by nature of the soil in which they are embedded In particular, they offer little resistance to lateral loading generated by soil movement This paper advocates the use of an innovative ground improvement technique, which involves partial cementation of granular columns resulting in Pervious Concrete Piles This study includes formulation of mix design (1:1:4) for pervious concrete and detailed analysis of pile behaviour under axial and lateral loading It was found that under same axial loading conditions, the load-carrying capacity of pervious concrete model pile exceeded four times that of a granular column with same dimensions A series of lateral loading tests were conducted on 5-cm-diameter pervious concrete model piles with length/diameter ratios of 6, 10 and 14 The bending moment profile shows that pervious concrete pile behaves in the same way as flexible piles subjected to lateral loading This type of behaviour has potential to transfer the load below failure surface without compromising on permeability criteria, thereby improving stability
10 citations
TL;DR: In this paper, a numerical study of the comparison of the static and seismic responses of LSDW and pile group under similar material quantity in soft soil was conducted. And it was found that the horizontal bearing capacity of LSDw is considerably larger than that of pile group, while pile group clearly shows a local bending deformation pattern during the static loading process.
Abstract: Lattice-shaped diaphragm wall (hereafter referring to LSDW) is a new type of bridge foundation, and the relevant investigation on its horizontal behaviors is scant. This paper is devoted to the numerical study of the comparison on the static and seismic responses of LSDW and pile group under similar material quantity in soft soil. It can be found that the horizontal bearing capacity of LSDW is considerably larger than that of pile group, and the deformation pattern of LSDW basically appears to be an overall toppling while pile group clearly shows a local bending deformation pattern during the static loading process. The acceleration response and the acceleration amplification effects of LSDW are slightly greater than that of pile group due to the existing of soil core and the difference on the ability of energy dissipation. The horizontal displacement response of pile group is close to that of LSDW at first and becomes stronger than that of LSDW due to the generation of plastic soil deformation near the pile-soil interface at last. The pile body may be broken in larger potential than LSDW especially when its horizontal displacement is notable. Compared with pile group, LSDW can be a good option for being served as a lateral bearing or an earthquake-proof foundation in soft soil.
6 citations
References
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TL;DR: In this paper, both static and dynamic lateral load tests were carried out on model aluminium single piles embedded in soft clay to study its bending behaviour, and the results showed that the load transferred to the pile, pile head displacement and the strain variation along the pile length were measured using a Data Acquisition System.
Abstract: Static and dynamic lateral load tests were carried out on model aluminium single piles embedded in soft clay to study its bending behaviour Model aluminium piles with length to diameter ratios of 10, 20, 30 and 40 were used Static lateral load tests were conducted on piles by rope and pulley arrangement upto failure and load–deflection curves were obtained Dynamic lateral load tests were carried out for different magnitudes of load ranging from 7 to 30 N at wide range of frequencies from 2 to 50 Hz The load transferred to the pile, pile head displacement and the strain variation along the pile length were measured using a Data Acquisition System Safe static lateral load capacity for all piles is interpreted from load–deflection curves Dynamic characteristics of the soil–pile system were arrived from the acquired experimental data The soil–pile system behaves predominantly in nonlinear fashion even at low frequency under dynamic load The displacement amplitude under dynamic load is magnified by 45–65 times the static deflection for all piles embedded in soft clay But, the peak magnification factor reduces with an increase in the magnitude of lateral load mainly because of increase of hysteretic damping at very soft consistency The maximum BM occurs at the fundamental frequency of the soil–pile system Even the lower part of the pile affects the pile head response to the inertial load applied at the pile head The maximum dynamic BM is magnified by about 15 times the maximum static BM for model piles in tested consistency of clay The maximum dynamic BM occurs at a depth of about 15 times the depth of maximum static BM for model piles, which indicates an increase of active pile length under dynamic load
44 citations
"Dynamic Response of Laterally Loade..." refers background or result in this paper
...These regions are characterized predominantly by soft marine clays with a thickness varying from 5–20 m, hence pile foundations are commonly employed to support these structures [Boominathan and Ayothiraman, 2007]....
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...The efficacy of the EHSS was verified to dampen stress waves significantly and frequency responses are not interfered by the reflected stress waves which was a common problem in the studies conducted in rigid tanks [Boominathan and Ayothiraman, 2007]....
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Journal Article•
TL;DR: In this article, the authors used the SKEW CROSS-HOLE METHOD and test results are shown to be consistent with the results shown in Fig. 1 and shown in Figure 1.
Abstract: ALTHOUGH THE CROSS-HOLE METHOD (DESCRIBED IN THE PAPER) USING ONLY TWO BOREHOLES APPEARS TO BE SIMPLE AND CONVENIENT FOR SOME APPLICATIONS, PRACTICAL EXPERIENCE PROMPTS SEVERAL QUESTIONS. THE WAVES GENERATED IN THIS METHOD ARE PREDOMINANTLY COMPRESSIONAL. ALSO, LARGE AMPLITUDE CHARACTERISTICS VIBRATIONS AND CHATTERING ARE BROUGHT INTO PLAY, ALL FACTORS WHICH MAKE IDENTIFICATION OF SHEAR WAVE ARRIVALS DIFFICULT. THE TRIGGERING TRANSDUCER, ATTACHED TO A METAL PLATE AT THE TOP OF THE EXCITER ROD, PROBABLY HAS BUILD-UP CHARACTERISTICS DIFFERENT FROM THOSE OF THE TRANSDUCER ON THE SOIL. SINCE THIS IS AN IMPORTANT FACTOR IN OBTAINING THE INTERVAL TIME, INFORMATION ON THE TRIGGERING PULSE STATE WOULD BE USEFUL. CORRECTIVE MEASURES ARE SUGGESTED. EXPERIMENTS HAVE BEEN PERFORMED WITH THE SKEW CROSS- HOLE METHOD AND TEST RESULTS ARE GRAPHICALLY ILLUSTRATED. THE IDENTIFICATION OF SH-WAVES OR THE DETERMINATION OF THE TIME OF ARRIVAL IS EASY. IDENTIFICATION OF SV-WAVES IS NOT AS EASY AS REVERSAL OF THE DIRECTION OF THE EXCITING IMPULSE IS DIFFICULT. THE ABILITY TO EXCITE AND IDENTIFY BOTH SH AND SV ARRIVALS PERMITS THE DEGREE OF ANISOTROPY OF THE SOIL TO BE DETERMINED.
40 citations
TL;DR: In this paper, a linear elastic theoretical analysis was developed to predict the dynamic response of the groups and the analysis produced good estimates of the experimental results for a constant value of Young's modulus for each site.
Abstract: Lateral dynamic experiments were performed on small-scale pile groups at two different sites, one with stiff soil and the other with soft soil. The pile diameters and spacings were varied to create spacing to diameter (\Is/d\N) ratios of between 2.25 and 15.0. The results showed the group interaction effects to be negligible at \is/\id ratios greater than 12 for the stiff site, and greater than 16 for the soft site. The experiments are the first to alter both the pile diameter and the pile spacing and confirm that the spacing-to-diameter ratio is an important parameter when calculating group interaction effects. The dynamic testing was found to cause a permanent nonlinear response in the groups. A simple linear elastic theoretical analysis was then developed to predict the dynamic response of the groups. The analysis produced good estimates of the experimental results for a constant value of Young’s modulus for each site. The values of Young’s modulus used in the modeling were found to be typical of those for lateral loads on pile foundations.
38 citations
"Dynamic Response of Laterally Loade..." refers background in this paper
...Plotting of measured responses of pile group with steady state frequency is common for sinusoidal loading and reported in literature (e.g., Hassini and Woods 1989; El-Marsafawi et al.,1992; Han and Vaziri, 1992; Burr et al., 1997)....
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...Scale effects are generally considered greater for non cohesive soils rather than cohesive soils used in the present study [Burr et al., 1997]....
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01 Oct 2005
TL;DR: In this article, the effect of the magnitude of the applied force and the pile length on the lateral stiffness of the soil-pile system has been investigated and it is found that rigid piles behave linearly even at higher magnitudes of applied force, but that flexible piles behave non-linearly as the magnitude increases.
Abstract: Dynamic experiments in lateral mode were carried out on model aluminium single piles in a simulated elastic half-space filled with clay soil to determine dynamic constants of the soil–pile system and to study the bending behaviour of piles. Model piles with various lengths were subjected to steady-state harmonic vibrations with different magnitudes of force of 7–30 N applied over a wide range of frequencies from 2 Hz to 50 Hz. The load transferred to the pile, pile head displacement and strain gauge readings at different locations on the pile were measured. It is observed consistently that the magnitude of the applied force and the pile length significantly affect the natural frequency of the soil–pile system. It is found that rigid piles behave linearly even at the higher magnitudes of applied force, but that flexible piles behave non-linearly as the magnitude of the applied force increases, which leads to a substantial reduction of the lateral stiffness of the soil–pile system. Damping of the soil–pile ...
30 citations
"Dynamic Response of Laterally Loade..." refers background in this paper
...The response curve for the pile embedded in the rigid tank is scattered and show multiple peaks due to the reflection of long-period waves [Boominathan and Ayothiraman, 2005]....
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TL;DR: In this article, the authors discuss why physical modeling is still needed, and the manner in which it may be used in conjunction with numerical analysis to develop the simple conceptual models that are used for the major part of design.
Abstract: Physical modelling in geotechnical engineering is used extensively, in spite of the high investment costs for experimental facilities and the contrasting decline in computing costs. The paper discusses why physical modelling is still needed, and the manner in which it may be used in conjunction with numerical analysis to develop the simple conceptual models that are used for the major part of design. Two example problems are discussed, one in relation to scale effects when dealing with interface shearing involving dilation, and one in the area of penetration testing. In both cases, physical modelling is shown to reveal limitations in analytical models. An approach for in situ determination of the consolidation coefficient, by means of variable rate penetration testing, is described.
27 citations
"Dynamic Response of Laterally Loade..." refers background in this paper
...It is generally accepted that minimum dimension of embedded structure (diameter of pile in the present study 25 mm) of 20–30 times more than the mean particle size of soil (less than 75 micron in the present study) is sufficient to avoid scaling effects [Ovesen, 1979; Randolph and House, 2001]....
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