Skin Friction Of Piles Research Articles

Analysis of effect of different construction methods of piles on the end effect on skin friction of piles

Based on the comparative analysis of end effect on skin friction of displacement-pile (driven pile), the end effect on skin friction of bored pile is studied. The end effect on skin friction between driven pile and bored pile is different and the end effect on skin friction of bored pile is reduce of skin friction in the soil layer adjacent to the pile end. The degradation degree of skin friction is deduced with the increase of the distance from pile end. The concept of additional mud cake formed by the effect of cushion at the bottom of borehole during pouring concrete is introduced to explain the mechanism of end effect on skin friction of the bored pile. The test results of post-grouting piles indicate that the post-grouting technique is an effective way to improve the end effect on skin friction of bored pile.

Skin Friction of Non-Displacement Piles Related to Simple Shear Mode with Large Strain State Friction Angle

A rational method for evaluating the skin friction of non-displacement piles in sandy soils is presented by reconsidering the model which has already been proposed by the authors. The revision of the model is mainly made by assuming the soil-pile interaction mechanism as a simple direct shear mode in relation to the large strain state of soils. The model is characterized by a coefficient of effective horizontal stress averaged through the whole length of the pile derived as a function of a large strain state friction angle. The characteristics and ability of the model are shown by the parametric studies and the applicability of the model is verified through a database of full scale pile load tests.

Influence of a permanent liner on the skin friction of large-diameter bored piles in Hong Kong granitic saprolites

The skin friction of large-diameter bored piles in Hong Kong granitic saprolite manifested high variability. The influence of one construction detail, a full-length permanent liner, is studied by examining full-scale load test results and by numerical simulation of this construction detail. It is concluded that the use of a full-length liner will give very low skin friction because the local method of constructing a large-diameter bored pile with a full-length permanent liner leads to a significant reduction in radial stress acting on the pile–soil interface.Key words: construction, pile, stress, skin friction, numerical simulation.

Behavior of Large Diameter Floating Bored Piles in Saprolitic Soils

ABSTRACT In Hong Kong large diameter long bored piles and barrettes are often used to support tall buildings to resist both vertical and horizontal loads. These piles penetrate through and may be founded in saprolitic soils or rocks. Generally, the design for side shear resistance (often called skin friction) of large diameter bored piles (drilled caissons or shafts) in saprolites involves considerable uncertainty and design parameters must usually be verified by field tests. In this paper, 28 full-scale load tests on large diameter machine bored piles constructed in various saprolitic soils were reviewed in detail, in particular the degree of mobilization of side shear resistance using a mobilization rating factor. The diameter of these floating piles ranges from 1.0 m to 1.5 m and the depth from 22 m to 75 m. The authors were heavily involved in the recent construction and testing of 12 of these piles. For bored piles constructed under water, 90% ultimate side shear resistance was mobilized at an average local pile displacement of 1.9% of the pile diameter with a 95% confidence range of 0.9% to 3.0%. For piles constructed under bentonite, ultimate side shear resistance was achieved at a local pile displacement of 1% of the pile diameter. For non-grouted bored piles constructed under water, the mobilized side shear resistance lies between 0.5 N ¯ and 2.0 N ¯ (kPa) and β ¯ values fall within 0.1 and 0.5, with average values of 1.2 N ¯ (kPa) and 0.3 respectively. Post-grouting improves the capacity of side shear resistance by a factor of about 2 as compared with the non-grouted piles constructed under water. On the contrary, piles constructed under bentonite show a reduction of capacity of side shear resistance between 50% and 70% depending on the method of analysis.

A possible physical meaning of Case damping in pile dynamics

This paper presents some possible interpretations of the physical meaning of the lumped, toe, and skin Case damping factors, jcL, jct, and jcs, respectively, which are extensively utilized in the dynamic analysis of pile driveability and capacity. A single degree of freedom model is employed to relate the Case damping to the hysteretic damping ratios of soil and pile materials. This relation and the damping ratios of soils and piles show that the Case damping factors for piles in sandy and clayey soils may overlap at all strain magnitudes. Coupling of pile toe and skin resistance is analyzed, and the jcLfactor is found to be a function of the skin and toe resistance ratio of the pile. Consequently, the jcLfactor is an important indicator with which the skin friction and toe resistance of piles can be separated. A database of 133 cases of dynamic pile tests in Florida has been used to substantiate the analyses and interpretations. The effects of the assumptions made in this paper are also discussed.Key words: pile dynamics, wave equation, Case damping, hysteretic damping, bearing capacity, skin friction.

Influence of Pile Plugging on Skin Friction in Overconsolidated Clay

Field tests were conducted to investigate the influence of the method of installation and degree of soil plugging on the skin friction developed along displacement piles subjected to static axial loading in overconsolidated clay. The study was conducted at the National Geotechnical Experimentation Site at the University of Massachusetts in Amherst and included the installation and testing of 44 pipe piles with diameters ranging from 60 to 168 mm and embedment lengths ranging from 1.5 to 10.7 m. The methods of pile installation included both driving and jacking. Some piles were installed with 60° apex cone tips while others were installed open ended. Results of the test program indicated that the method of installation had a significant influence on the amount of soil plugging in open-ended piles. In addition, it was found that the pile installation method and degree of plugging significantly affected the resulting axial compressive skin friction. It is suggested that the plugging effect on skin friction results from differences in lateral stresses that develop along pile shafts, while the effect of the installation method is related to installation disturbance. An effective stress method of analysis is proposed for estimating ultimate pile skin friction taking into consideration the influence of installation method and plugging on pile capacity.

Pile Skin Friction in Sands from Constant Normal Stiffness Tests

Abstract Many interface and sand-to-sand direct shear tests have been performed with a constant normal stiffness to investigate the effects of interface roughness, normal stiffness, soil relative density, initial normal stress, and cyclic displacement amplitude on the soilinterface response. It is demonstrated that the patterns of behavior in these tests are similar to those observed in model pile tests and that the constant normal stiffness (CNS) condition is required to account for the effects of the volume changes that occur as soil adjacent to a pile is sheared. In dense sands that tend to expand in volume when sheared, the shear and normal stresses developed are significantly higher than for constant normal load (CNL) conditions and increase with higher values of normal stiffness. For loose sands that compress when sheared, the stresses are lower than in CNL tests and decrease for higher values of normal stiffness. The CNS tests replicate the reduction in shear stress during displacement-controlled cycling and the subsequent loss of capacity reported for model and full-scale piles. The reduction of skin friction during cycling and the subsequent loss of pile frictional capacity is found to be greatest for loose sands, high normal stiffness, large displacement amplitudes, and rough interfaces.

Influence of soil density on pile skin friction in calcareous sediments : Poulos, H G; Al-Douri, R H Proc 6th Australia-New Zealand Conference on Geomechanics, Christchurch, 3–7 February 1992P375–380. Publ New Zealand: New Zealand Geomechanics Society, 1992

Influence of soil density on pile skin friction in calcareous sediments : Poulos, H G; Al-Douri, R H Proc 6th Australia-New Zealand Conference on Geomechanics, Christchurch, 3–7 February 1992P375–380. Publ New Zealand: New Zealand Geomechanics Society, 1992

膨潤性塗料を用いた負の摩擦力低減対策杭の研究 : その1 材料特性

This is report on the results of an indoor test conducted on a swelling paint that was developed to reduce the negative skin friction of piles used in the bored precast pile method. The swelling paint consists of synthetic resin elastomer, a high water-absorbing polymer, a filler, and a solvent. The paint forms a hard dry coat when the solvent evaporates. Once dry, the paint swells when submerged in water. The result that the shear strength of swelling layer is represented by the shear strain rate, temperature and the swelling rate of the dry coat was obtained empirically.

Estimation of Pile Friction Degradation from Shearbox Tests

Abstract An uncemented carbonate sand has been subjected to cyclic loading in a modified shearbox apparatus under constant normal load and constant normal stiffness conditions. The behaviour in the tests using a constant normal stiffness shows many similarities with the variation of skin friction on piles under cyclic loading. It is demonstrated that the response in the shearbox tests with a constant normal stiffness may be predicted from the response observed in conventional shearbox tests, and that conventional shearbox tests can thus provide valuable information on the degradation of skin friction of piles under cyclic loading.

杭基礎の弾塑性沈下解析 : 建築物の即時沈下予測方法(その2)

The analytic method for pile foundations by means of elasto-plastic finite element method based on vertical loading test was proposed. The ground element including around pile top is taken as an elasto-plastic material which rigidity is changed with the increment of strain, and the pile skin friction model is supposed as elasto-plastic model. In the pile vertical loading tests this method is effective on the pile quantitative and qualitative analysis that are about characteristics both settlement and transmission of the axial force. That is possible to precisely recreate actual settlement characteristics by this method.

Development of skin friction and base resistance of instrumented large bored piles under working load conditions : Kruizinga, J Proc 1st International Geotechnical Seminar on Deep Foundations on Bored and Auger Piles, Ghent, 7–10 June 1988P435–442. Publ Rotterdam: A A Balkema, 1988

Development of skin friction and base resistance of instrumented large bored piles under working load conditions : Kruizinga, J Proc 1st International Geotechnical Seminar on Deep Foundations on Bored and Auger Piles, Ghent, 7–10 June 1988P435–442. Publ Rotterdam: A A Balkema, 1988

Skin friction of pile evaluated from friction meter test : Hanzawa, H; Fukaya, T; Kishida, T Proc eighth asian regional conference on soil mechanics and foundation engineering, Kyoto, 20–24 July 1987V1, P369–372. Publ Japan: Japanese Society for Soil Mechanics and Foundation Engineering, 1987

Skin friction of pile evaluated from friction meter test : Hanzawa, H; Fukaya, T; Kishida, T Proc eighth asian regional conference on soil mechanics and foundation engineering, Kyoto, 20–24 July 1987V1, P369–372. Publ Japan: Japanese Society for Soil Mechanics and Foundation Engineering, 1987

Effect of loading rate on pile skin friction in sands : Mao Yuan; Poulos, H G University of Sydney School of Civil and Mining Engineering research reportR519, March 1986, 19P

This paper describes simple model pile tests to investigate the effect of loading rate on pile skin friction in reconstituted silica and carbonate sands. The tests show that the ultimate skin friction of the pile increases as the loading rate increases in carbonate sands, but that there is no effect in silica sands (a).

Scale Effects of Ultimate Pile Capacity

Methods of estimating the ultimate bearing capacity of piles in sand from the results of static cone and standard penetration tests are compared with the results of load tests on driven and bored piles of different sizes and embedment ratios in the sand bearing stratum. An empirical reduction factor of the ultimate unit point resistance in sand is established, which decreases with greater pile base diameter and with greater average static cone or standard penetration resistance near the pile point. Similarly, for piles in stiff fissured clay an empirical reduction factor of the undrained shear strength is established, which decreases with greater pile base diameter and is greater for driven than for bored piles. The ultimate unit skin friction of piles in a given sand or clay is practically independent of the pile diameter.

Experimental investigation of the distribution of stresses in large bored situ-cast piles

1. Diagrams were obtained of the distribution of specific skin friction of bored situ-cast piles with a diameter of about 1 m and length of 18 m and of their transformation as a result of flooding the soils and successive loading of the pile with gradual involvement of shearing resistance forces in a downward direction. 2. Before the long bored situ-cast piles broke loose, the specific skin friction in homogeneous soil is practically constant over the length of the pile, which confirms the correctness of the concept used in [3]. 3. On flooding soils at the base of the piles, when the external load is equal to zero and there is still no slumping of the soil layers under their own weight, substantial normal stresses occur in the cross sections of long bored situ-cast piles, as a result of which they are additionally loaded by the soil hanging on them. 4. The foot of long bored situ-cast piles penetrating loose layers of loam soils and supported on a layer of loam with e=0.662 carried no more than 10% of the total load applied to the pile prior to breaking loose. Thus it behaves as a friction pile before breaking loose. 5. After the pile breaks loose, the normal contact stresses on its foot increase in direct proportion to settlement. It follows from this that to increase the point resistance before breaking loose it is necessary to preliminarily compact the bottom of the hole of the bored situ-cast pile.

Skin friction of bored piles formed in clay under bentonite : Fearenside, G R; Cooke, R W Construction Industry Research and Information Association report N77, May 1978, 31P

The effect of bentonite on the skin friction of bored cast in place concrete piles was investigated by maintained load and constant rate of penetration tests. Of the seven test piles constructed in london clay, three were concreted under bentonite and four under dry conditions. Soft toes were installed to eliminate end bearing. Although the ultimate test loads varied widely, there was no evidence that the use of bentonite adversely affected the skin friction. Some load variation may be attributable to the different shaft surface characteristics produced by augers and drilling buckets (a).

Experimental study of negative skin friction of piles in the case of slumping of soils from their own weight

1. Investigations were carried out to determine for the first time by direct measurement the magnitude of the loading (negative) friction forces of piles in the case of slumping of soils under their own weight. The maximum magnitude of these forces in the given experiment was 282 kN.

Penetration Tests and Bearing Capacity of Cohesionless Soils

From comparison between standard (dynamic) and static penetration resistances on number of sites, simple approximate correlation has been obtained to estimate relative density and angle of internal friction; proposed relationships applied to determine ultimate bearing capacity of footings and point resistance and skin friction of piles; results compared with field loading tests on plates and piles.

An investigation of the Bearing Capacity of Some Bored and Driven Piles in London Clay

Synopsis The article describes a soil investigation and loading tests which were made on bored and driven concrete piles in London clay to study their bearing capacity and settlement. It was found that the shearing strength of the fissured clay decreased rapidly with time after sampling, due to opening of the fissures which could not be closed sufficiently by large triaxial pressures. Water from concrete of bored piles installed in an unlined auger borehole softens the clay and this softening could not be avoided except by an unworkable dry mix. Whilst the point resistance can be based on the natural shearing strength, the skin friction of these bored piles is closely given by the fully softened strength. On the other hand, the skin friction of concrete piles driven into stiff to hard clay seems to have an upper limit of 2,000 lb. per square foot. At a factor of safety of 3 against shearing failure, the settlement of widely spaced bored and driven piles in London clay is unlikely to be greater than 1 inch. L'article déit un examen du sol et des essais de charge faits sur des pieux de béton, forés et enfoncés, dans l'argile de Londres, afin d'en examiner la charge limite et le tassement. On a trouvé que la résistance au cisaillement de l'argile fissurée après le prélèvement d'échantillons diminue rapidement en fonction du temps, par suite de l'ouverture de fissures qu'on n'a pu suffisamment refermer moyennant une grande pression triaxiale. L'eau provenant du béton des pieux foré dans un sondage non-cuvelé ramollit l'argile, et l'on n'a pu éviter ce ramollissement qu'en employant un mélange trop sec pour en permettre l'utilisation. Alors que la résistance à un point donné peut être basée sur la résistance spécifique au cisaillement, le frottement superficiel de ces pieux forés est donné avec une bonne approximation par la résistance dans l'état ramolli. Par contre, le frottement superflciel de pieux de béton enfoncés dans une argile tenace ou dure semble avoir une limite supéieure de 2,000 livres par pied caré. Avec un facteur de sécurité de 3 centre une rupture par cisaillement, l'affaissement de pieux largement éartés, forés ou enfoncés dans l'argile de Londres, ne dépassera probablement pas un pouce.