scholarly journals A Parametric Study of Effect On Single Pile Integrity Due to An Adjacent Excavation Induced Stress Release in Soft Clay

2018 ◽  
Vol 8 (4) ◽  
pp. 3189-3193 ◽  
Author(s):  
D. A. Mangnejo ◽  
M. A. Soomro ◽  
N. Mangi ◽  
I. A. Halepoto ◽  
I. A. Dahri
Keyword(s):  
Soft Clay ◽  
Bending Moment ◽  
Small Strain ◽  
Single Pile ◽  
Stress Release ◽  
Pile Shaft ◽  
Induced Stress ◽  
Parametric Studies ◽  
Pile Settlement ◽  
Pile Integrity

To gain new insights into single pile responses to adjacent excavations in soft ground, numerical parametric studies are carried out. An advanced hypoplastic (clay) constitutive model which takes account of small-strain stiffness is adopted. The effects of excavation depths (i.e. formation level) relative to pile were investigated by simulating the excavation near the pile shaft (i.e., He/Lp=0.67), next to (He/Lp=1.00) and below the pile toe (He/Lp=1.33). Among the three cases, the excavation in case of He/Lp=1.33 resulted in the largest pile settlement (i.e. 7.6%dp). On the other hand, the largest pile bending moment was induced in case of He/Lp=0.67.

scholarly journals Single Pile Settlement and Load Transfer Mechanism due to Excavation in Silty Clay

2018 ◽  
Vol 8 (1) ◽  
pp. 2485-2492 ◽  
Author(s):  
M. A. Soomro ◽  
K. F. Memon ◽  
M. A. Soomro ◽  
A. Memon ◽  
M. A. Keerio
Keyword(s):  
Load Transfer ◽  
Bending Moment ◽  
Small Strain ◽  
Transfer Mechanism ◽  
Ground Movement ◽  
Major Influence ◽  
Silty Clay ◽  
Single Pile ◽  
Load Transfer Mechanism ◽  
Pile Settlement

In densely built areas, development of underground transportation system often involves excavations for basement construction and cut-and-cover tunnels which are sometimes inevitable to be constructed adjacent to existing piled foundations. In order to gain new insights into single pile responses (i.e. settlement and load transfer mechanism) to an adjacent excavation in saturated silty clay, a three-dimensional coupled- consolidation numerical analysis is conducted in this study. An advanced hypoplasticity (clay) constitutive model with small-strain stiffness was adopted. A linear increase in pile settlement was observed due to excavation-induced stress release. This is because part of the pile is placed within the boundaries of a major influence zone due to excavation-induced ground movement. Based on a settlement criterion, apparent loss of pile‘s capacity is 14%. A maximum bending moment of about 350 kNm is induced in the pile with the maximum deflection of 28 mm. In addition, mobilisation of shear strength at the pile-soil interface was found to be a key factor governing pile-soil-excavation interaction. During excavation, a downward load-transfer mechanism in the piles can be identified.

scholarly journals 3D Numerical Modeling of Pile Group Responses to Excavation-Induced Stress Release in Silty Clay

2018 ◽  
Vol 8 (1) ◽  
pp. 2577-2584
Author(s):  
M. A. Soomro ◽  
A. S. Brohi ◽  
M. A. Soomro ◽  
D. K. Bangwar ◽  
S. A. Bhatti
Keyword(s):  
Load Transfer ◽  
Pile Group ◽  
Small Strain ◽  
Transportation Systems ◽  
Silty Clay ◽  
Pile Groups ◽  
Stress Release ◽  
3D Numerical Modeling ◽  
Hypoplastic Model ◽  
Induced Stress

Development of underground transportation systems consists of tunnels, basement construction excavations and cut and cover tunnels which may encounter existing pile groups during their construction. Since many previous studies mainly focus on the effects of excavations on single piles, settlement and load transfer mechanism of a pile group subjected to excavation-induced stress release are not well investigated and understood. To address these two issues, three-dimensional coupled-consolidation numerical analysis is conducted by using a hypoplastic model which takes small-strain stiffness into account. A non-linear pile group settlement was induced. This may be attributed to reduction of shaft resistance due to excavation induced stress release, the pile had to settle substantially to further mobilise end-bearing. Compared to the Sp of the pile group, induced settlement of the single pile is larger with similar settlement characteristics. Due to the additional settlement of the pile group, factor of safety for the pile group can be regarded as decreasing from 3.0 to 1.4, based on a displacement-based failure load criterion. Owing to non-uniform stress release, pile group tilted towards the excavation with value of 0.14%. Due to excavation-induced stress release and dragload, head load of rear piles was reduced and transferred to rear piles. This load transfer can increase the axial force in front piles by 94%.

scholarly journals The Responses of an End-Bearing Pile to Adjacent Multipropped Excavation: 3D Numerical Modelling

2019 ◽  
Vol 5 (3) ◽  
pp. 552 ◽  
Author(s):  
Dildar Ali Mangnejo ◽  
Naeem Mangi
Keyword(s):  
Soft Clay ◽  
High Stress ◽  
Three Dimensional ◽  
Bending Moment ◽  
Small Strain ◽  
Ground Movement ◽  
Stress Regime ◽  
Moment Capacity ◽  
Negative Skin Friction ◽  
End Bearing Pile

It is well recognised that superstructure load is transferred to surrounding soil through piled foundation. Consequently, the high stress regime (stress bulb) is generated surrounding of the pile. On the other hand, the excavation in the ground inevitably results in the ground movement due to induced-stress release. These excavations are sometimes inevitable to be constructed adjacent to existing piled foundations. This condition leads to a big challenge for engineers to assess and protect the integrity of piled foundation. This research presents three-dimensional coupled consolidation analyses (using clay hypoplastic constitutive model which takes account of small-strain stiffness) to investigate the responses of an end-bearing pile due to adjacent excavation at different depths in soft clay. The effects of excavation depths (i.e., formation level) relative to pile were investigated by simulating the excavation near the pile shaft (i.e., case S) and next to (case T). It was revealed that the maximum induced bending moment in the pile after completion of excavation in all the cases is much less than the pile bending moment capacity (i.e. 800 kNm). Comparing the induced deflection of the end-bearing pile in the case T, the pile deflection in case S is higher. Moreover the piles in cases of S and T were subjected to significant dragload due to negative skin friction.

Numerical Analysis of the Bearing Behavior of Single Pile under Horizontal Load

2014 ◽  
Vol 580-583 ◽  
pp. 287-290
Author(s):  
De Fu Ma ◽  
Guang Jun Guo ◽  
Xia Yang ◽  
Zhi Dong Zhou
Keyword(s):  
Mechanical Characteristics ◽  
Bending Moment ◽  
Displacement Curve ◽  
Single Pile ◽  
Horizontal Load ◽  
Soil Resistance ◽  
Distribution Law ◽  
Foundation Design ◽  
Pile Shaft ◽  
Bearing Behavior

Understanding the pile behavior and predicting the capacity of piles under horizontal load are important topics in foundation design. In this paper, the mechanical characteristics of single pile under horizontal load is analyzed based on FLAC3D finite difference software, and the load-displacement curve, the bending moment, shear force, soil resistance under all levels of load and the distribution law of p-y curve along the pile shaft are obtained. accordingly the following conclusions can be made: the bending moment of the upper part of pile body is big, the maximum bending moment is at the height of 2~3 meters and it is almost zero below the depth of 9 meters. The bending moment increases with the increase of load, the point of maximum bending moment moves down along the pile body with the increasing of horizontal load. and the location of the point of maximum bending moment moves from 2 meters below the ground to 3 meters below it. The distribution of soil resistance along the pile shaft is a reverse "S", the maximum of pile lateral soil resistance is at the height of about 2~3 meters below the ground.

Effect of Earthquake on a Single Pile Located in Sloping Ground

2016 ◽  
Vol 7 (1) ◽  
pp. 57-72 ◽  
Author(s):  
R. Deendayal ◽  
T. G. Sitharam ◽  
K. Muthukkumaran
Keyword(s):  
Lateral Displacement ◽  
Soft Clay ◽  
Ground Surface ◽  
Bending Moment ◽  
Single Pile ◽  
Earthquake Loading ◽  
Element Analysis ◽  
Sloping Ground ◽  
Sea Bed ◽  
D 20

Piles are often constructed on natural slope such as sea bed slope in off-shore structures. When piles are constructed on sloping ground, the behaviour of piles under earthquake loading is different from the piles on horizontal ground surface. The dynamic response of a pile subjected to external excitation is a complex phenomenon resulting from the interactions between the pile and the surrounding soil. In the present study, a finite element analysis of a single field pile located on sloping ground was carried out. A single pile of length 30m with embedment length to diameter ratios (L/D) 20, 25 and 30 was located on a crest of soft clay of slopes 1V:1H and 1V:5H, and subjected to dynamic earthquake loading (California Earthquake,1990). From the study, the behaviour of acceleration with time, lateral displacement and bending moment behavior along the pile shaft was studied.

scholarly journals Numerical Study of Laterally Loaded Piles in Soft Clay Overlying Dense Sand

2021 ◽  
Vol 7 (4) ◽  
pp. 730-746
Author(s):  
Amanpreet Kaur ◽  
Harvinder Singh ◽  
J. N. Jha
Keyword(s):  
Layer Thickness ◽  
Soft Clay ◽  
Bending Moment ◽  
Layered Soil ◽  
Clay Layer ◽  
Pile Groups ◽  
Dense Sand ◽  
Lateral Capacity ◽  
Laterally Loaded ◽  
Pile Length

This paper presents the results of three dimensional finite element analysis of laterally loaded pile groups of configuration 1×1, 2×1 and 3×1, embedded in two-layered soil consisting of soft clay at liquid limit overlying dense sand using Plaxis 3D. Effects of variation in pile length (L) and clay layer thickness (h) on lateral capacity and bending moment profile of pile foundations were evaluated by employing different values of pile length to diameter ratio (L/D) and ratio of clay layer thickness to pile length (h/L) in the analysis. Obtained results indicated that the lateral capacity reduces non-linearly with increase in clay layer thickness. Larger decrease was observed in group piles. A non-dimensional parameter Fx ratio was defined to compare lateral capacity in layered soil to that in dense sand, for which a generalized expression was derived in terms of h/L ratio and number of piles in a group. Group effect on lateral resistance and maximum bending moment was observed to become insignificant for clay layer thickness exceeding 40% of pile length. For a fixed value of clay layer thickness, lateral capacity and bending moment in a single pile increased significantly with increase in pile length only up to an optimum embedment depth in sand layer which was found to be equal to three times pile diameter and 0.21 times pile length for pile with L/D 15. Scale effect on lateral capacity has also been studied and discussed. Doi: 10.28991/cej-2021-03091686 Full Text: PDF

scholarly journals Design Charts for Axially Loaded Single Pile Action

2019 ◽  
Vol 5 (4) ◽  
pp. 922-939 ◽  
Author(s):  
Anis Abdul Khuder Mohamad Ali ◽  
Jaffar Ahemd Kadim ◽  
Ali Hashim Mohamad
Keyword(s):  
Clay Soil ◽  
Skin Resistance ◽  
Soft Clay ◽  
Single Layer ◽  
Load Test ◽  
Engineering Properties ◽  
Single Pile ◽  
Dense Sand ◽  
Design Charts ◽  
Pile Length

The objective of this article is to generating the design charts deals with the axially ultimate capacity of single pile action by relating the soil and pile engineering properties with the pile capacity components. The soil and are connected together by the interface finite element along pile side an on its remote end.  The analysis was carried out using ABAQUS software to find the nonlinear solution of the problem. Both pile and soil were modeled with three-dimensional brick elements. The software program is verified against field load-test measurements to verify its efficiency accuracy. The concrete bored piles are used with different lengths and pile diameter is taken equals to 0.6 m. The piles were installed into a single layer of sand soil with angles of internal friction (20° t0 40°) and into a single layer of clay soil with Cohesion (24 to 96) kPa.  The getting results showed that for all cases study the total compression resistance is increased as pile length increased for the same property of soil, also illustrious that the total resistance of same pile length and diameter increased as the soil strength increasing. In addition, the same results were obtained for the end bearing resistance, skin resistance and tension capacity. Design charts were constructed between different types of soil resistance ratio and the pile length/diameter ratio (L/D) for all cases of study. One of improvement found from these curves that it is cheaply using piles of larger diameter than increasing their lengths for dense sand and to increasing piles lengths for loose sand. Moreover, it is inexpensively using piles of larger length in soft clay soil than increasing their diameter and piles of larger diameter in firm and stiff clay soils than increasing their length.

On wave-induced stress in a ship executing symmetric motions

1973 ◽  
Vol 275 (1247) ◽  
pp. 1-32 ◽  
Keyword(s):  
Natural Vibration ◽  
Bending Moment ◽  
Natural Vibration Frequency ◽  
Frequency Range ◽  
Induced Stress ◽  
Head Waves ◽  
Rational Explanation ◽  
Different Response ◽  
Wave Matching ◽  
Wave Induced

The equation of motion of a simple beam in head waves is solved in terms of modal responses. Examination of the resulting expression for wave-induced bending moment indicates that at lower wave frequencies large fluctuating stresses are generally associated with 'ship-wave matching', a phenomenon governed by the relative geometry of ship and wave; whereas large stresses in the higher frequency range are the result of 'resonant encounter' during which the encounter frequency of ship with wave corresponds to a natural vibration frequency of the ship as a beam. The contrasting characteristics of these different response mechanisms are shown to provide a rational explanation of the fluctuating stresses induced in large or flexible ships in confused seas.

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