scholarly journals Compression Load Tests on Composite Foundations of Spread Footing Anchored by Helical Anchors

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Mingqiang Sheng ◽  
Zengzhen Qian ◽  
Xianlong Lu
Keyword(s):  
Composite Foundation ◽  
Embedment Depth ◽  
Load Testing ◽  
Soil Pressure ◽  
Foundation Soil ◽  
Total Load ◽  
Compression Load ◽  
Spread Footing ◽  
Interpretation Criteria ◽  
Load Tests

This study elucidates the compression behavior of a type of composite foundation of spread footing anchored by helical anchors. Three composite foundations were installed at a field site, and compression load testing was carried out on each foundation. Both the site conditions and the load tests were documented comprehensively. The compression load-settlement curves of composite foundations exhibit an initial linear-elastic segment, a curve transition, and a final linear region, and their capacities should be interpreted from the load-settlement curves. Five representative interpretation criteria (Chin, Terzaghi and Peck, slope tangent, tangent intersection, and L1–L2) were employed to determine the capacity of each foundation. Both the helical anchors and the footing share compression loadings on the composite foundation. Soil pressure cells at the center, near the edge, and at the corner of the footing represent a distribution from the lower, middle, and higher ranges of incremental soil pressures underneath the footing. Helical anchors underneath the footing approximately share 60%–80% of total load applied on the composite foundation pier, and higher compression resistance of a composite foundation can be obtained by increasing the footing embedment depth and the number of helical anchors underneath the footing.

Driven cast-in-situ pile capacity: insights from dynamic and static load testing

2021 ◽  
Author(s):  
Kevin N. Flynn ◽  
Bryan A. McCabe
Keyword(s):  
Dynamic Load ◽  
Shear Stresses ◽  
Load Testing ◽  
Pile Capacity ◽  
Compression Load ◽  
Shaft Resistance ◽  
Pile Installation ◽  
Cast Concrete ◽  
Load Tests

Driven cast-in-situ (DCIS) piles are classified as large displacement piles. However, the use of an oversized driving shoe introduces additional complexities influencing shaft resistance mobilisation, over and above those applicable to preformed displacement piles. Therefore, several design codes restrict the magnitude of shaft resistance in DCIS pile design. In this paper, a series of dynamic load tests was performed on the temporary steel driving tubes during DCIS pile installation at three UK sites. The instrumented piles were subsequently subjected to maintained compression load tests to failure. The mobilised shear stresses inferred from the dynamic tests during driving were two to five times smaller than those on the as-constructed piles during maintained load testing. This was attributed to soil loosening along the tube shaft arising from the oversized base shoe. Nevertheless, the radial stress reductions appear to be reversible by the freshly-cast concrete fluid pressures which provide lower-bound estimates of radial total stress inferred from the measured shear stresses during static loading. This recovery in shaft resistance is not recognised in some European design practices, resulting in conservative design lengths. Whilst the shaft resistance of DCIS piles was underpredicted by the dynamic load tests, reasonable estimates of base resistance were obtained.

Shaft resistance of driven cast-in-situ piles in sand

2016 ◽  
Vol 53 (1) ◽  
pp. 49-59 ◽  
Author(s):  
Kevin N. Flynn ◽  
Bryan A. McCabe
Keyword(s):  
Steel Tube ◽  
Large Displacement ◽  
Shear Stresses ◽  
Load Testing ◽  
Compression Load ◽  
Shaft Resistance ◽  
Cast Concrete ◽  
Local Shear ◽  
Load Tests

Driven cast-in-situ (DCIS) piles are classified as a large displacement pile, despite sharing certain aspects of their construction with replacement pile types. However, there are relatively few case histories of load tests on DCIS piles in the literature to verify the assumption that they behave as large displacement piles. In particular, the shaft resistance of DCIS piles in sand is uncertain due to the complex interaction between the freshly cast concrete and surrounding displaced soil after extraction of the steel installation tube. This paper describes the installation, curing, and maintained compression load testing of three temporary-cased DCIS test piles at a uniform sand site near Coventry, United Kingdom. The piles were instrumented with vibrating wire strain gauges to enable accurate measurement of the local shear stress generated on the pile shaft during maintained compression loading. The tests showed that the peak average and local shear stresses tended to mobilize at greater shaft displacements than traditional preformed displacement piles during loading. A clear reduction in normalized local shear stresses (and hence radial effective stress) at failure with distance from the pile base, i.e., friction fatigue, was evident for all piles, implying that radial stresses generated during driven installation of the steel tube are not erased upon concreting and tube withdrawal. Furthermore, the inferred normalized radial effective stresses at failure were remarkably similar to those reported for traditional preformed displacement piles in the literature.

Behaviour of flexible piles under inclined loads

1990 ◽  
Vol 27 (1) ◽  
pp. 19-28 ◽  
Author(s):  
V. V. R. N. Sastry ◽  
G. G. Meyerhof
Keyword(s):  
Soft Clay ◽  
Ground Surface ◽  
Embedment Depth ◽  
Loose Sand ◽  
Bending Moments ◽  
Soil Pressure ◽  
Inclined Loads ◽  
Load Tests ◽  
Test Pile ◽  
Flexible Model

The lateral soil pressures, bending moments, pile displacements at ground surface, and bearing capacity of instrumented vertical single flexible model piles in homogeneous loose sand and soft clay under central inclined loads have been investigated. The results of these load tests are compared with theoretical estimates based on the concept of an effective embedment depth of equivalent rigid piles. Reasonable agreement has been found between the observed and predicted behaviour of flexible piles. The analyses are also compared with the results of some field case records. Key words: bending moments, clay, displacements, inclined loads, instrumentation, lateral soil pressure, model test, pile, sand.

Investigation of Grouted Coupler Connection Details for Accelerated Bridge Construction

2021 ◽  
pp. 036119812199939
Author(s):  
Brent Phares ◽  
Yoon-Si Lee ◽  
Travis K. Hosteng ◽  
Jim Nelson
Keyword(s):  
Crack Width ◽  
High Performance ◽  
Static Load ◽  
High Performance Concrete ◽  
Precast Concrete ◽  
Chloride Penetration ◽  
Load Testing ◽  
Test And Evaluation ◽  
Load Tests ◽  
Precast Elements

This paper presents a laboratory investigation on the performance of grouted rebar couplers with the connection details similar to those utilized on the precast concrete elements of the Keg Creek Bridge on US 6 in Iowa. The testing program consisted of a series of static load tests, a fatigue test, and evaluation of the chloride penetration resistance of laboratory specimens. The goal of this testing was to evaluate the ability of the grouted rebar couplers to develop flexural capacity at the joint between the precast elements as well as the durability of the connection. For structural load testing, seven full-scale specimens, each with #14 epoxy-coated rebars spliced by epoxy-coated grouted couplers, were fabricated and tested in three different loading cases: four-point bending, axial tension plus bending, and a cyclic test of the system in bending. The static load testing demonstrated that the applied axial load had a minimal effect on the formation of cracks and overall performance of the connection. When ultra-high performance concrete was used as a bedding grout, the initiation of crack was slightly delayed but no considerable improvement was observed in the magnitude of the crack width during loading or the crack closure on unloading. The results of the seventh specimen, tested in fatigue to 1 million cycles, showed little global displacement and crack width throughout the test, neither of which expanded measurably. No evidence of moisture or chloride penetration was detected at the grouted joint during the 6-month monitoring.

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.

scholarly journals Bi-Directional Static Load Tests of Pile Models

2020 ◽  
Vol 10 (16) ◽  
pp. 5492
Author(s):  
Michał Baca ◽  
Włodzimierz Brząkała ◽  
Jarosław Rybak
Keyword(s):  
Bearing Capacity ◽  
Static Load ◽  
Load Testing ◽  
Pile Capacity ◽  
Pile Shaft ◽  
Load Tests ◽  
S Curve ◽  
Definition Of ◽  
Standard Tests ◽  
Static Load Testing

This work examined a new method of bi-directional static load testing for piles, referencing the Osterberg test. Measurements were taken, on a laboratory scale, using six models of piles driven into a box filled with sand. This method allowed for separate measurements of pile base and pile shaft bearing capacities. Based on the results, the total pile bearing capacity and equivalent Q–s diagrams were estimated. The results obtained show that the structure of the equivalent curve according to Osterberg is a good approximation of the standard Q–s curve obtained from load tests, except for loads close to the limit of bearing capacity (those estimates are also complicated by the inapplicability and ambiguity of a definition of the notion of limit bearing capacity); the equivalent pile capacity in the Osterberg method represents, on average, about 80% of the capacity from standard tests.

Repeated load testing of a model plane strain footing

1978 ◽  
Vol 15 (2) ◽  
pp. 190-201 ◽  
Author(s):  
Gerald P. Raymond ◽  
Fadel El Komos
Keyword(s):  
Plane Strain ◽  
Cyclic Load ◽  
Load Test ◽  
Repeated Loading ◽  
Load Testing ◽  
Wheel Load ◽  
Foundation Soil ◽  
Static Tests ◽  
Static Test ◽  
In Series

A study is reported of experiments on model plane strain footings subject to repeated loading. The load was returned to zero at the end of each cycle. This is characteristic of a train wheel load passing over a railroad tie.Four series of tests were conducted. Series A consisted of static tests, which provided a comparison with series B. Series B consists of applying a cyclic load on the footing between zero load and a constant upper value. The upper value was varied from test to test and ranged from 13.5 to 90% of the static failure load. Series C was acyclic test that was a continuation of series B after a considerable deformation had occurred. The berms caused by the cyclic load test of series B were removed and a second cyclic test was conducted on the same foundation soil as the original test. Series D was a static test that was done as a continuation of series B. After removing the berms, as in series C, a static test was conducted in a manner similar to that for series A.The results have been quantified by the use of a hyperbolic fit and show that wider footings should perform better than narrower ones. This has been substantiated by examination of experimental railroad tests conducted by the Association of American Railroads.

Design Research and Technical Application of the Multi-Type-Pile Composite Foundation

2012 ◽  
Vol 170-173 ◽  
pp. 110-114
Author(s):  
Yan Gao ◽  
Hui Min Li ◽  
Ji Ling Yao
Keyword(s):  
Bearing Capacity ◽  
Design Research ◽  
Composite Foundation ◽  
Social Benefits ◽  
Drilling Machine ◽  
Construction Technology ◽  
Practical Application ◽  
Technical Application ◽  
Foundation Soil ◽  
High Rise

Through project example, analysis of the multi-type-pile composite foundation (lime pile plus CFG pile) in the practical application of liquefied foundation of high-rise building, especially using the ZFZ construction technology which forwards formed a hole and reverses packed into a compaction pile by a long spiral drilling machine to eliminate liquefaction of foundation soil and improve the bearing capacity of foundation is very notable, in addition, it also produces good economic and social benefits, so it has great value of promotion and use.

scholarly journals Intermittent cyclic load testing of polymer railway sleepers

2021 ◽  
pp. 095440972110454
Author(s):  
Aran van Belkom ◽  
Matthias Pittrich ◽  
Vit Lojda
Keyword(s):  
Laboratory Tests ◽  
Cyclic Load ◽  
Strain Curve ◽  
Elastic Behaviour ◽  
Test Time ◽  
Loading Frequency ◽  
Load Testing ◽  
Heat Accumulation ◽  
Strength Assessment ◽  
Load Tests

Before a new type of railway sleeper can be used in track, standardised laboratory tests must be carried out to determine its suitability. In addition to static load tests, assessments usually include cyclic load tests consisting of millions of load cycles, representing passing trains during the sleeper’s service life. In these laboratory tests, the loading cycles are applied continuously without resting periods to condense the test time. Traditional sleeper materials (timber, concrete) possess elastic properties for which such testing is appropriate. However, polymer sleepers exhibit viscoelastic properties, such as creep, a loading rate-dependent stiffness and heating due to non-linearity of the stress-strain curve. Subjecting polymer sleepers to continuous cyclic load tests with a load frequency reflecting permissible track speed can cause the sleeper to heat up. Intermittent testing with pauses between numbers of load cycles is proposed in this paper as a possible solution. The aim is to propose a laboratory loading procedure that adopts a traffic-resembling load of a railway line, considering an effective compromise between polymer visco-elastic behaviour and time consumption of the laboratory tests. The loading frequency is kept at the desired strain rate for track evaluation, giving a representative sleeper stiffness and strength assessment. Exemplary tests with varying test arrangements and loading procedures were performed to quantify the effects of intermittent loading in comparison with continuous loading. The proposed method eliminated most of the test-induced creep and heat accumulation, resulting in a more representative stiffness and strength assessment, which justifies the proposed intermittent testing for polymer sleepers. The proposed intermittent procedure is an optional test regime in ISO 12856-2 for polymer sleeper testing.

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