Behaviour of a sensitive clay during pile driving

1981 ◽  
Vol 18 (1) ◽  
pp. 67-85 ◽  
Author(s):  
M. Roy ◽  
R. Blanchet ◽  
F. Tavenas ◽  
P. La Rochelle
Keyword(s):  
Scale Effects ◽  
Test Site ◽  
Penetration Resistance ◽  
Pile Driving ◽  
A Value ◽  
Pore Pressures ◽  
Tip Resistance ◽  
Average Unit ◽  
Sensitive Clay ◽  
Static Zone

A full scale investigation with six instrumented test piles has been carried out on the Saint-Alban test site in order to study the behaviour of friction piles in soft sensitive soils. The first part of this investigation, reported in this paper, deals essentially with the effects of pile driving on the induced pore pressures and their dissipation and on the disturbance of the clay around the pile.It is shown that the induced pore pressures at the pile tip ΔuT, and at the pile surface Δus, correspond to 1.6σvo and 0.8σvo respectively. If the failure pattern developed during driving is interpreted by means of the theories of expansion of cavities, it is shown that the induced pore pressures calculated at the pile–soil contact agree well with the measured values; these pore pressures are fully dissipated after 600 h.Immediately after driving, a decrease in the undrained shear strength varying between 0 and 30% was observed in a zone of 3 diameters around the pile. The strength in that zone was nearly fully recovered after the pore pressures had dissipated.The tip resistance measured during driving was quite in excess of the static zone penetration resistance qc, indicating possible scale effects. The average unit skin friction was observed to decrease from a value in the order of cu to about 0.10σvo′ and to be directly related to the pore pressures, i.e., to the effective stresses in the clay around the pile.

scholarly journals Undrained shear strength from piezocone tests

1987 ◽  
Vol 24 (3) ◽  
pp. 392-405 ◽  
Author(s):  
J.-M. Konrad ◽  
K. T. Law
Keyword(s):  
Shear Strength ◽  
Undrained Shear Strength ◽  
Cavity Expansion ◽  
Pore Pressures ◽  
Clayey Silt ◽  
Tip Resistance ◽  
Sensitive Clay ◽  
Rigidity Index ◽  
New Interpretation ◽  
Undrained Shear

With the advent of piezocones — penetrometers measuring both the mechanical resistance and induced pore pressures near the tip during penetration into the soil — a new interpretation of penetrometer test data is possible. This paper presents a review of available interpretation methods for obtaining the undrained shear strength of soft soils, and introduces a new interpretation taking into account measured pore pressures. The undrained shear strength is considered to be solely related to the ultimate cavity expansion pressure, which is one of the components of the tip resistance. The other component is calculated assuming that effective friction is developed at the cone–soil interface.Parametric studies on the parameters required for strength determination based on the proposed method are also presented. Special self-boring pressuremeter tests to obtain relevant values of soil rigidity index, which is a key parameter for cavity expansion modelling, are described. Tests were conducted at three sites having the characteristics of soft sensitive clay, stiff sensitive clay, and clayey silt. The operational undrained strength mobilized during the cone insertion derived from the proposed model is equal to or lower than the CK0U triaxial strength, which depends on soil brittleness. The proposed approach yields results consistent with known soil behaviour at all three sites. Key words: piezocone penetrometer, pressuremeter, excess pore-water pressure, undrained shear strength, rigidity index, in situ tests, laboratory test.

Testing of drivability of concrete piles and disturbance to sensitive clay

1976 ◽  
Vol 13 (2) ◽  
pp. 139-160 ◽  
Author(s):  
Bengt H. Fellenius ◽  
Laval Samson
Keyword(s):  
Shear Strength ◽  
Pile Group ◽  
Undrained Shear Strength ◽  
Strength Reduction ◽  
Glacial Till ◽  
Pile Driving ◽  
Shaft Resistance ◽  
Concrete Piles ◽  
Pore Pressures ◽  
Sensitive Clay

The results reported are of an investigation of a group of thirteen 12 in. (30 cm) diameter precast concrete piles driven through 60 ft (18 m) of sensitive marine clay followed by 10 ft (3 m) of silt and sand and 13 ft (4 m) of very dense silt to end bearing in glacial till. The purpose of the test is to study the drivability of the piles through very dense soil and to measure the disturbance caused to the sensitive clay by the driving of displacement piles. Following a literature review, the paper presents the soil conditions at the site and the testing program. The test results are discussed and experience gained from the follow-up of the driving of 520 piles at the site is presented.Visual observations during pile driving, and analysis of driving records, show that a high pile quality is necessary at the site. The large driving resistance encountered in the very dense silt (150 to 300 blows/ft) would prevent low quality piles from reaching the competent glacial till and developing the needed bearing capacity.Pile loading tests showed the piles to have an ultimate bearing capacity exceeding 450 tons (4.0 MN). It was established that the shaft resistance in the clay during test loading was between 100 and 125% of the undrained shear strength of the clay as measured by field vane testing. In comparison, an uplift test to failure showed that the uplift shaft resistance along the pile in the clay was only 60% of the undrained shear strength of the clay.The pile driving developed large pore pressures in the clay which exceeded the effective overburden stresses. The excess pore pressures dissipated over a period of slightly more than 3 months. Vane testing within the pile group immediately after driving showed that a shear strength reduction of about 15% was caused by the piles. At a distance of 2 ft (0.6 m) outside the pile group, no strength reduction was found. The reduction within the group was gradually regained during the dissipation of the induced pore pressures. Laboratory testing on clay samples obtained within the pile group 75 days after pile driving showed a smaller value of the preconsolidation pressure of the clay, but no change in the compression indices.

Study on Pile-Soil Interaction during Pile Sinking and Drivability of Pile in Offshore Platform

2012 ◽  
Vol 164 ◽  
pp. 137-141
Author(s):  
Yu Peng Song ◽  
Yong Fu Sun ◽  
Cheng Lin Cao ◽  
Shu Ling Li
Keyword(s):  
Bohai Sea ◽  
Influence Factors ◽  
Penetration Resistance ◽  
Offshore Platform ◽  
Pile Driving ◽  
Main Mode ◽  
Jacket Platform ◽  
Soil Plug ◽  
Steel Piles

The main mode of pile-soil interaction and the influence factors of pile sinking in offshore platform construction were analyzed and discusses the reasons that penetration resistance increases after stop driving and then continue. To study the drivability of piles of specified driving hammer, taking a jacket platform of Bohai Sea for instance, the results showed that continuous driving will make the open-end steel piles be driven to the designed depth, and driven-on will cause soil plug and pile driving refusal. Based on the results, the paper gives some suggestions about pile driving.

Comparison of Measured and Back Estimated Cone Penetration Resistance of Sand

2008 ◽  
Author(s):  
Meen-Wah Gui ◽  
Dong-Sheng Jeng
Keyword(s):  
Penetration Resistance ◽  
Cavity Expansion ◽  
Cone Penetration ◽  
Cone Penetration Tests ◽  
Cone Tip Resistance ◽  
Tip Resistance ◽  
Cone Penetration Resistance ◽  
Expansion Theory ◽  
Cavity Expansion Theory ◽  
Penetration Tests

The application of cavity expansion theory in the back estimation of cone penetration tests conducted in calibration chambers has been carried out by many researchers. However, the theory is seldom employed by centrifuge modelers. Based on the work of spherical cavity expansion of previous researchers, this study proposed an analytical solution that incorporates the effects of cone geometry and surface roughness and the effect of compressibility to estimate the cone tip resistance. The calculated results are compared with the measured cone penetration resistance of four cone penetration tests performed in the centrifuge. The cone penetration tests were conducted in granular soil specimens having relative densities ranging between 54% and 89%. The comparison demonstrates the capacity of the cavity expansion theory in the prediction of the centrifuge cone penetration resistance.

A Safety Concept for Penetration Analysis of Suction Caissons and Anchors in Clay and Layered Soils

2018 ◽  
Author(s):  
Hendrik Sturm ◽  
Julia Roberts
Keyword(s):  
Penetration Resistance ◽  
Offshore Structures ◽  
Wall Friction ◽  
Layered Soils ◽  
Safety Concept ◽  
Safety Factors ◽  
Tip Resistance ◽  
Standards And Guidelines ◽  
Partial Safety Factors ◽  
Suction Caissons

Suction caissons and anchors are widely used for the foundation of both bottom-fixed and floating offshore structures. They are installed by means of self-weight and underpressure applied to the inside of the skirt compartment. The penetration resistance during installation is the sum of the tip resistance and wall friction of the skirt, both of which are functions of the foundation geometry, soil properties, soil-state and boundary conditions. Several authors have proposed methods to predict the penetration resistance during installation. In general, high estimates of soil strength parameters are used to predict the installation resistance for design purposes. In addition, safety factors may be applied when predicting the achievable penetration depth and the corresponding loads acting on the structural components. However, current standards and guidelines lack a consistent approach for evaluating these loads and safety factors. In order to apply a consistent safety concept in the structural caisson design, two methods for assessing the penetration resistance and hence required suction pressure are investigated; a simplified CPT-based method and a more advanced bearing-capacity-based method. For that purpose, a probability-based analysis has been performed, assuming statistical distributions of the corresponding input parameters, and a representative target failure probability. The performance of the two methods methods is investigated using the example of a generic sand and a generic clay profile. Based on these analysis, partial safety factors for the use in a deterministic design are proposed.

Development of pore pressures in quasi-static penetration tests in sensitive clay

1982 ◽  
Vol 19 (2) ◽  
pp. 124-138 ◽  
Author(s):  
Marius Roy ◽  
Michel Tremblay ◽  
François Tavenas ◽  
Pierre La Rochelle
Keyword(s):  
Penetration Test ◽  
Sensing Element ◽  
Cone Penetration ◽  
Pore Pressures ◽  
Soil Deposits ◽  
Sensitive Clay ◽  
Rate Of Dissipation ◽  
Excess Pore Pressures ◽  
Penetration Tests ◽  
Static Cone Penetration Test

The static cone penetration test is a valuable tool for the investigation of soil deposits but its potential may be further improved in the future if the pore pressures generated around the cone tip during the penetration are measured.A new sounding instrument called a piezocone was built at Université Laval to investigate the magnitude, effects of rates of penetration, and rate of dissipation of the excess pore pressures according to the location of the porous stone on the apparatus.The magnitude of the pore pressures induced during driving is a maximum at the cone tip and then decreases along the shaft as measured by porous stones located behind the cone tip. Induced pore pressures at the tip are independent of the rate of penetration, but a very small rate effect may influence the pore pressures measured behind the cone tip. The results show that the use of the ratio u/qc for soil characterisation may be considered only after adoption of standards regarding the location of the sensing element and the rate of penetration.The new sounding tool models the penetration of a single pile relatively well and its use is suggested for the study of pore pressures during the penetration of piles and their dissipation with time.

Continuous-interval shear wave velocity profiling by auto-source and seismic piezocone tests

2013 ◽  
Vol 50 (4) ◽  
pp. 382-390 ◽  
Author(s):  
Taeseo Ku ◽  
Paul W. Mayne ◽  
Ethan Cargill
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Test Site ◽  
Cone Penetration ◽  
Cone Penetration Testing ◽  
Large Numbers ◽  
Tip Resistance ◽  
A Site ◽  
Exploratory Procedure

A new exploratory procedure for collecting continuous shear wave velocity measurements via cone penetration testing using a special autoseis source is presented whereby wavelets can be generated and recorded every 1 to 10 s. The continuous-interval seismic piezocone test (CiSCPTu) offers a fast, productive, and reliable means to expedite the collection of downhole shear wave velocity profiles, as well as additional readings on cone tip resistance, sleeve friction, and penetration porewater pressures with depth. A site in Windsor, Virginia, is utilized for illustrating the collection of data, calibration, and post-processing issues arising from large numbers of wavelets that require filtering, windowing, and selection in both time and frequency domain analyses. At the test site, the geology consists of shallow Holocene deposits of clays and sands to 8 m that are underlain by much stiffer calcareous sandy marine clay soils of Miocene age, which extend beyond the termination depths of the soundings at 30 m.

Sign in / Sign up

Export Citation Format

Share Document