A new socket roughness factor for prediction of rock socket shaft resistance

2001 ◽  
Vol 38 (1) ◽  
pp. 138-153 ◽  
Author(s):  
J P Seidel ◽  
B Collingwood
Keyword(s):  
Compressive Strength ◽  
Unconfined Compressive Strength ◽  
Resistance Coefficient ◽  
Complex Problem ◽  
Load Test ◽  
Technical Literature ◽  
Analysis And Design ◽  
Shaft Resistance ◽  
Load Tests ◽  
Pile Load Tests

Prediction of rock socket shaft resistance is a complex problem. Conventional methods for predicting the peak shaft resistance are typically empirically related to unconfined compressive strength through the results of pile load tests. It is shown by reference to international pile socket databases that the degree of confidence which can be applied to these empirical methods is relatively low. Research at Monash University has been directed at understanding and then modelling the complex mechanisms of shear transfer at the interface between the socketed piles and the surrounding rock. Important factors that affect the strength of pile sockets have been identified in laboratory and numerical studies. With a knowledge of the effect of these factors, the reasons for the large scatter around traditional empirical correlations can be deduced. A computer program called ROCKET has been developed which encompasses all aspects of the Monash University rock socket research. This program has been used to develop design charts for rock-socketed piles based on unconfined compressive strength and a nondimensional factor which has been designated the shaft resistance coefficient (SRC). Implementation of the SRC method in design requires an estimate of the likely socket roughness to be made. Very few researchers or practitioners have measured socket roughness, so there is little available guidance in selection of appropriate values. Although many socket load tests are described in the technical literature, the physical parameter which is regularly missing is the socket roughness. With a knowledge of the shaft resistance, and an estimate of all other relevant parameters, the authors have been able to back-calculate the apparent socket roughness using the SRC method. Based on the back-calculated roughness data, socket roughness guidelines for use in analysis and design of rock sockets have been proposed. Using these roughness guidelines, it is shown that the SRC method is able to predict the scatter observed in previously published international load test databases.Key words: rock socket, drilled shaft, shaft resistance, roughness, shaft resistance coefficient.

Improvement of the Geotechnical Axial Design Methodology for Colorado's Drilled Shafts Socketed in Weak Rocks

2005 ◽  
Vol 1936 (1) ◽  
pp. 100-107 ◽  
Author(s):  
Naser M. Abu-Hejleh ◽  
Michael W. O'Neill ◽  
Dennis Hanneman ◽  
William J. Attwooll
Keyword(s):  
Compressive Strength ◽  
Unconfined Compressive Strength ◽  
Design Methods ◽  
Drilled Shafts ◽  
Load Test ◽  
Empirical Methods ◽  
Weak Rocks ◽  
Rock Formations ◽  
Load Tests ◽  
Geotechnical Tests

Drilled shaft foundations embedded in weak rock formations support a large percentage of bridges in Colorado. Since the 1960s, empirical methods that entirely deviate from the AASHTO design methods have been used for the axial geotechnical design of these shafts. The margin of safety and expected shaft settlement are unknown in these empirical methods. Load tests on drilled shafts provide the most accurate design and research data for improvement of the design methods. Four Osterberg axial load tests were performed in Denver on drilled shafts embedded in soil-like claystone, very hard sandy claystone, and extremely hard clayey sandstone. An extensive program of simple geotechnical tests was performed at the load test sites, including standard penetration tests (SPT), unconfined compressive strength tests (UCT), and pressuremeter tests (PMT). Information on the construction and materials of the test shafts was documented, followed by thorough analysis of all test results. Conservative equations were suggested to predict the unconfined compressive strength and mass stiffness of weak rocks from SPT and PMT data. Colorado Department of Transportation (CDOT) and AASHTO–FHWA design methods for drilled shafts were thoroughly assessed. Design equations to predict the shaft ultimate unit base resistance ( qmax), side resistance ( fmax), and an approximate load–settlement curve as a function of the results of simple geotechnical tests were developed. The qualifications and limitations for using these design methods are presented (e.g., construction procedure, field conditions). Finally, a detailed strategic plan to identify the most appropriate design methods per LRFD for Colorado's drilled shafts was developed.

Predicting the Ultimate Bearing Capacity of Single Piles Based on CPTU

2011 ◽  
Vol 243-249 ◽  
pp. 4402-4407
Author(s):  
Yong Hong Miao ◽  
Guo Jun Cai ◽  
Song Yu Liu
Keyword(s):  
Load Test ◽  
Load Testing ◽  
Pile Capacity ◽  
Piezocone Penetration Test ◽  
Load Carrying ◽  
Load Tests ◽  
Pile Load Test ◽  
Single Piles ◽  
Pile Load Tests ◽  
Best Fit

Six methods to determine axial pile capacity directly based on piezocone penetration test (CPTU) data are presented and evaluated. Analyses and evaluation were conducted on three types piles that were failed during pile load testing. The CPT methods, as well as the CPTU methods, were used to estimate the load carrying capacities of the investigated piles (Qp ). Pile load test were used to determine the measured load carrying capacities (Qm). The pile capacities determined using the different methods were compared with the measured pile capacities obtained from the pile load tests. Two criteria were selected as bases of evaluation: the best fit line for Qp versus Qm and the arithmetic mean and standard deviation for the ratio Qp /Qm. Results of the analyses showed that the best methods for determining pile capacity are the CPTU methods.

A note on pile load test interpretation

1970 ◽  
Vol 7 (4) ◽  
pp. 479-481
Author(s):  
K. Peaker
Keyword(s):  
Soil Type ◽  
Test Procedure ◽  
Load Test ◽  
Building Code ◽  
Test Interpretation ◽  
Load Tests ◽  
Pile Load Test ◽  
Pile Load Tests ◽  
Pile Type

Pile load tests are normally carried out in accordance with A.S.T.M. or other building code specifications without regard to the actual pile type or soil type. The example quoted indicates that the test procedure may lead to incorrect interpretation of failure and conservative design.

scholarly journals Empirical Shaft Resistance of Driven Piles Penetrating Weak Rock

2020 ◽  
Vol 53 (12) ◽  
pp. 5531-5543
Author(s):  
John W. Barrett ◽  
Luke J. Prendergast
Keyword(s):  
Empirical Relationship ◽  
Empirical Relation ◽  
Driven Piles ◽  
Case Histories ◽  
Pile Capacity ◽  
Shaft Resistance ◽  
Fatigue Model ◽  
Load Tests ◽  
Pile Load Tests ◽  
Engineering Projects

AbstractIn this paper, an empirical relationship between the Unconfined Compressive Strength (UCS) of intact rock and the unit shaft resistance of piles penetrating rock is investigated. A growing number of civil engineering projects are utilizing steel piles driven into rock where a significant portion of the pile capacity is derived from the shaft resistance. Despite the growing number of projects utilizing the technology, little to no guidance is offered in the literature as to how the shaft resistance is to be calculated for such piles. A database has been created for driven piles that penetrate bedrock. The database consists of 42 pile load tests of which a majority are steel H-piles. The friction fatigue model is applied to seven of the pile load tests for which sufficient UCS data exists in order to develop an empirical relation. The focus of this paper is on case histories that include driven pipe piles with at least 2 m penetration into rock.

Determination of Loading Capacities for Bi-directional Pile Load Tests Based on Actual Load Test Results

2014 ◽  
Vol 43 (1) ◽  
pp. 20120325 ◽  
Author(s):  
Yongkyu Choi ◽  
Moon S. Nam ◽  
Tae-Hyung Kim
Keyword(s):  
Load Test ◽  
Test Results ◽  
Actual Load ◽  
Load Tests ◽  
Pile Load Tests

scholarly journals Large-diameter helical pile capacity – torque correlations

2017 ◽  
Vol 54 (7) ◽  
pp. 968-986 ◽  
Author(s):  
Jared Harnish ◽  
M. Hesham El Naggar
Keyword(s):  
Large Diameter ◽  
Failure Criteria ◽  
Load Test ◽  
Ultimate Capacity ◽  
Pile Capacity ◽  
Shearing Resistance ◽  
Helical Piles ◽  
Torque Capacity ◽  
Load Tests ◽  
Pile Load Tests

Large-diameter helical piles are utilized increasingly to support heavy structures. Both the magnitude of the required installation torque and the pile capacity can be directly attributed to the soil shearing resistance developed over the embedded area of the pile including the shaft and helical plates. Hence, the pile capacity can be correlated to installation torque. Such correlations are widely used in the helical pile industry as a means for quality control and quality assurance. In the current study, a total of 10 test piles were installed while monitoring the installation torque continuously with depth. The recorded installation torque profiles were demonstrated to be accurate and repeatable. Field pile load tests were conducted and their results were analyzed to determine the interpreted ultimate capacity of the test piles. The results demonstrate that the ultimate capacity of large-diameter helical piles can be interpreted from pile load test data employing the failure criteria proposed by Elkasabgy and El Naggar in 2015 and Fuller and Hoy in 1970. The measured installation torque and corresponding ultimate capacity values were employed to define torque–capacity correlation (Kt) based on embedded pile area. It was demonstrated that the proposed Kt is suitable for large-diameter helical piles.

scholarly journals Effect of lime on the mechanical response of a soil for use in unpaved forest roads

2019 ◽  
Vol 42 ◽  
pp. e44764
Author(s):  
Gissele Souza Rocha ◽  
Claudio Henrique de Carvalho Silva ◽  
Heraldo Nunes Pitanga ◽  
Ecidinéia Pinto Soares de Mendonça ◽  
Dario Cardoso de Lima ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Unconfined Compressive Strength ◽  
Mechanical Response ◽  
Soil Mass ◽  
Base Layer ◽  
Unit Weight ◽  
Engineering Practice ◽  
Technical Literature ◽  
Forest Roads ◽  
Strength Tests

The main objective of this study was to propose the application of soil-lime mixtures asa primary coating layerof unpavedforestroads based on the premise that this layer can be considered mechanically similar to a flexible pavementsub base layer, aiming to fill a gap in the current technical literature and engineering practice in this field of knowledge. In the study, a laboratory test program was carried out in a residual gneiss soil encompassing: (i) geotechnical characterization tests; (ii) compaction tests at the standard Proctor energy on soil specimens and on soil-lime mixturespecimens prepared with lime contents of 2, 4 and 6% related to the dry soil mass; (iii) unconfined compressive strength tests on soil specimens compacted at the standard Proctor optimum parameters; and (iv) unconfined compressive strength tests on specimens of soil-lime mixtures compacted at the standard Proctor optimum compaction parameters with lime contents of 2, 4 and 6%, and cured at 22.8°C in the curing periods of 3, 7, 28 and 90 days. The results showed that the addition of lime resulted in: (i) reduction in soil maximum dry unit weight (gdmax) and increase in soil optimum water content (wopt);and(ii) significant gains in soil unconfined compressive strength that evidenced the expressive occurrence of pozzolanic reactions in the mixtures.Based on the hypothesis of a similar requirement for soil-cement and soil-lime mixtures, the tested soil-lime mixtures met the minimum mechanical strength (1.2MPa) required for application as a primary coating layer of unpaved forest roads.

Field Plate Load Tests on Dredged Sediment Dump Pond with Cement Solidified Crust Above

2011 ◽  
Vol 255-260 ◽  
pp. 2751-2755
Author(s):  
Chun Lei Zhang ◽  
Qing Song Liu ◽  
Jin Bao Liu
Keyword(s):  
Compressive Strength ◽  
Bearing Capacity ◽  
Failure Mode ◽  
Double Layer ◽  
Unconfined Compressive Strength ◽  
Test Results ◽  
Dredged Sediment ◽  
Field Plate ◽  
Failure Angle ◽  
Load Tests

In order to improve the bearing capacity of dredged sediment dump pond for succeeding foundation reinforcement construction, upper layer was placed with a layer of cement solidified crust (CSC). For the special double layer foundation, field plate load tests were conducted to study the behaviors of failure mode, deformation and ultimate bearing capacity. Test results show the failure mode of the double layer foundation takes punch failure mode, the settlement around 10-15cm, the failure angle around 33-36 degree, the ultimate bearing capacities have a lineal relationship with the unconfined compressive strength and thickness of CSC, respectively.

Performance of helical piles in oil sand

2009 ◽  
Vol 46 (9) ◽  
pp. 1046-1061 ◽  
Author(s):  
Mohammed Sakr
Keyword(s):  
Full Scale ◽  
Load Test ◽  
Test Results ◽  
Lateral Loads ◽  
Oil Sand ◽  
Deep Foundation ◽  
Helical Piles ◽  
Load Tests ◽  
Pile Load Test ◽  
Pile Load Tests

The results of a comprehensive pile load-test program and observations from field monitoring of helical piles with either a single helix or double helixes installed in oil sand are presented in this paper. Eleven full-scale pile load tests were carried out including axial compression, uplift, and lateral load tests. The results of the full-scale load tests are used to develop a theoretical design model for helical piles installed in oil sand. Test results confirm that the helical pile is a viable deep foundation option for support of heavily loaded structures. The test results also demonstrated that circular-shaft helical piles can resist considerable lateral loads.

Parametric analysis of the effects of stress relief on the performance and capacity of piles in nondilative soils

2011 ◽  
Vol 48 (9) ◽  
pp. 1354-1363 ◽  
Author(s):  
Gang Zheng ◽  
Yu Diao ◽  
C.W.W. Ng
Keyword(s):  
Ground Surface ◽  
Stress Relief ◽  
Load Test ◽  
The Other ◽  
Deep Excavation ◽  
Maximum Tension ◽  
Load Tests ◽  
Pile Load Test ◽  
Effects Of Stress ◽  
Pile Load Tests

To provide support to superstructure and substructure, piles are often installed beneath a deep basement prior to its excavation. However, the effects of stress relief on the performance and capacity of piles due to deep excavation are rarely reported in the literature. In this study, two different types of pile load tests were simulated with and without considering excavation effects by conducting parametric axisymmetric finite element analyses. The first test was a pile load test on a sleeved pile from the ground surface prior to deep excavation, and the other is a load test on an unsleeved pile at the final excavated level. It is found that an excavation could reduce the pile capacity by up to 45% and pile stiffness by up to 75%. The effects of stress relief due to an excavation increase with normalized excavation depth (H/L) and excavation radius (R/H). Moreover, the maximum tension induced in a pile by excavation varies with H/L, and it has a peak value when 1 < H/L < 1.25. The value of maximum tension increases with the pile–soil modulus ratio (Ep/Esm). When Ep/Esm = 100, peak tension develops at 0.5H. On the other hand, tension reaches a peak at 0.7H when Ep/Esm = 20.

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