Becker Penetration Test Research Articles

Gravel liquefaction assessment using dynamic cone penetration and shear wave velocity tests based on field performance from the 1964 Alaska earthquake

Evaluating the liquefaction potential of gravelly soils using in-situ testing remains a challenge in geotechnical engineering practice. The Chinese Dynamic Cone Penetration (DPT) test provides an alternative for in-situ testing in gravelly soils to Becker Penetration Test (BPT) and the Standard Penetration test (SPT). The Chinese DPT was recently correlated with liquefaction resistance based on field performance data from the Mw 7.9 Wenchuan earthquake. In this study, liquefaction resistance was evaluated using the DPT and shear wave velocity measurements at eight sites in Seward and Old Valdez, Alaska, where gravel liquefaction took place and two sites in Valdez, where no liquefaction occurred in the 1964 Alaska earthquake. The DPT-based liquefaction triggering curve predicted liquefaction potential at all test sites with moderate accuracy. N′120 blow counts from SPT hammers were generally consistent with those from the DPT hammer after energy correction. Back-calculated energy correction factors were typically within 10% of the theoretical energy correction factor. These results suggest that the DPT can provide liquefaction hazard evaluations accurately and economically for many gravelly soils. Liquefaction evaluations using currently available Vs-based triggering curves developed for sands often indicated no liquefaction at sites where liquefaction occurred at the Alaska sites. In contrast, a Vs-based triggering curve developed from a data set of gravelly soil sites correctly predicted liquefaction at all sites.

Prediction, Performance, and Uncertainty in Dynamic Pile Load Testing as Informed by Direct Measurements from an Instrumented Becker Penetration Test

AbstractDynamic load testing and signal matching is commonplace for pile capacity verification but can be subject to nonuniqueness and uncertainty. Whether this uncertainty may be reduced with addi...

Evaluation of Becker penetration test interpretation methods for liquefaction assessment in gravelly soils

The Becker penetration test (BPT) is the only tool available for characterizing gravelly soils with a probe diameter that is meaningfully larger than that of the standard penetration test (SPT) and the cone penetration test (CPT). Measurements on the BPT system during operation provide information on how penetration is controlled by the driving energy and frictional resistance along the shaft. This has led to development of the instrumented Becker penetration test (iBPT), which uses measurements of force and acceleration obtained directly behind the drill string tip to compute the residual energy and displacement induced by each hammer blow. These measurements are used to produce a continuous profile of normalized blow counts that are repeatable, unaffected by varying driving energy or accumulated shaft resistance, and can be used to directly estimate equivalent SPT N60 blow count values as per DeJong et al. and Ghafghazi et al. in their 2017 studies. The measurements obtained also enabled evaluation of previously developed methods by Harder and Seed in 1986 and Sy and Campanella in 1994. This evaluation revealed that the hammer energy normalization approaches employed by Sy and Campanella and especially Harder and Seed are not robust across the broad range of conditions observed. The predicted equivalent SPT N60 values by Harder and Seed and Sy and Campanella methods are influenced by the shaft resistance magnitude as both methods are based on above-ground field measurements. Estimated N60 values produced by the two methods can be inconsistent with each other, with N60 values produced by the iBPT, and with measured N60 values obtained directly from SPT (where values are obtained in the absence of gravel).

Instrumented Becker Penetration Test. II: iBPT-SPT Correlation for Characterization and Liquefaction Assessment of Gravelly Soils

AbstractThe Becker penetration test (BPT) is a widely used tool for the characterization of gravelly soils, especially for liquefaction assessment. An instrumented Becker penetration test (iBPT) wa...

Instrumented Becker Penetration Test. I: Equipment, Operation, and Performance

AbstractThe Becker penetration test (BPT) is a widely used tool for characterizing gravelly soils, especially for liquefaction assessment. Interpretation of BPT data is complicated by the variable ...

Characterization of gravelly alluvium

Characterizing project sites where gravelly alluvium is present poses particular challenges. Conventional field and laboratory techniques are significantly limited when large gravel particles either prevent their operation or adversely influence their measurements. The deposition of gravelly alluvium often involves complex, energy and sediment load dependent processes that can result in highly spatially variable deposits comprised of gravel to clay sized particles. This pervasive variability warrants an integrated site characterization approach anchored in an understanding of the geological formation processes and the expected controlling deformation/failure mechanisms, confirmed by the site investigation, simplified as part of site idealization, and verified during construction and long term monitoring. Systematic incorporation and handling of the site variability during the site idealization process is particularly important. Recent work at several gravelly alluvial sites has allowed the development of new approaches and techniques for improved site characterization. In particular, the benefit of continuous sonic sampling is demonstrated and a systematic method for evaluating gravel influence on SPT N values is outlined. Finally, an overview of the instrumented Becker Penetration Test (iBPT), a closed-ended, large diameter penetrometer with new direct energy measurement at the drill string tip is presented.

Recent Advances in Gravelly Soils Liquefaction Evaluation

Many gravelly soils liquefied cases history especially in the 2008 Wenchuan earthquake warn that loose to moderate density of gravels have much potential to liquefy under a given earthquake shaking. The large diameter triaxial apparatus is a relative feasible means to explore the liquefaction mechanism of gravelly soils to some extent. Becker penetration test (BPT) could be droved hrough gravelly soils layer, but BPT was not directly correlated with field behavior. Because of a wider range of grain sizes than those reported from previous earthquakes, gravels characteristics liquefied in the Wenchuan earthquake are representative and universal. The gravels liquefaction evaluation method developed from the Wenchuan earthquake should be feasible for worldwide use. The recent and ongoing developments in gravels liquefaction was highlighted

Liquefaction Resistance of Soils: Summary Report from the 1996 NCEER and 1998 NCEER/NSF Workshops on Evaluation of Liquefaction Resistance of Soils

Following disastrous earthquakes in Alaska and in Niigata, Japan in 1964, Professors H. B. Seed and I. M. Idriss developed and published a methodology termed the ''simplified procedure'' for evaluating liquefaction resistance of soils. This procedure has become a standard of practice throughout North America and much of the world. The methodology which is largely empirical, has evolved over years, primarily through summary papers by H. B. Seed and his colleagues. No general review or update of the procedure has occurred, however, since 1985, the time of the last major paper by Professor Seed and a report from a National Research Council workshop on liquefaction of soils. In 1996 a workshop sponsored by the National Center for Earthquake Engineering Research (NCEER) was convened by Professors T. L. Youd and I. M. Idriss with 20 experts to review developments over the previous 10 years. The purpose was to gain consensus on updates and augmen- tations to the simplified procedure. The following topics were reviewed and recommendations developed: (1) criteria based on standard penetration tests; (2) criteria based on cone penetration tests; (3) criteria based on shear-wave velocity measurements; (4) use of the Becker penetration test for gravelly soil; (4) magnitude scaling factors; (5) correction factors for overburden pressures and sloping ground; and (6) input values for earthquake magnitude and peak acceleration. Probabilistic and seismic energy analyses were reviewed but no recommen- dations were formulated.

Twentieth Canadian Geotechnical Colloquium: Recent developments in the Becker penetration test: 1986-1996

The Becker penetration test (BPT) has proven to be a versatile and practical tool for characterizing coarse-grained soils. The most important factors affecting BPT interpretation are performance of the diesel hammer used in the Becker drill system and soil friction acting on the casing during the penetration test. Major developments in BPT from 1986 to 1996 are described in this paper. Extensive recent field measurements of hammer performance and casing friction are presented. The field data show that transferred energies in the BPTs are variable and depend on the drill rig hammer system, driving system, and combustion and ground conditions. The data also indicate that HAV180-type rigs give higher transferred energies than AP1000-type rigs. Casing friction measurements show that shaft resistances are variable and erratic, but that friction values in gravelly soils are generally less than those in sandy soils for the same embedment. A recently developed pull-up test using a tension load cell to directly measure casing friction shows considerable promise. Finally, a case study of a vibro-replacement project in coarse gravelly soils in which BPT was used for compaction specification and control is presented. The field measurements show, for the first time, that BPT casing friction in densified ground is significantly higher than that in undensified ground. This emphasizes the importance of considering casing friction in BPT interpretation for quality control of densification projects.

Correlations of mud-injection Becker and standard penetration tests

Recent studies have shown that a major uncertainty in the correlation between the Becker penetration test (BPT) and the standard penetration test (SPT) is soil friction acting on the Becker casing. An innovative mud-injection technique of conducting the BPT, known as the Foundex Becker penetration test (FBPT), was developed to reduce casing friction. Test data from side-by-side conventional BPT and mud-injection FBPT conducted at a sand site and a gravel site are presented in this paper. The test data show the significant effect of casing friction in both sandy and gravelly soils. Energy-based direct FBPTnSPT correlations derived from the sand site are applied to FBPT data at the gravel site. The equivalent SPT N60 values at the gravel site are compared with those estimated using rigorous BPTnSPT correlations that explicitly consider casing friction, and the results are encouraging.

Twentieth Canadian Geotechnical Colloquium: Recent developments in the Becker penetration test: 1986-1996

Twentieth Canadian Geotechnical Colloquium: Recent developments in the Becker penetration test: 1986-1996

Becker and standard penetration tests (BPT–SPT) correlations with consideration of casing friction

The Becker penetration test (BPT), through correlations with the standard penetration test (SPT), is widely used for foundation design and liquefaction assessment in gravelly soils. Most of the existing correlations, however, do not adequately account for the variable energy output of the diesel hammer used in the Becker system, and shaft friction on the Becker casing is ignored. An alternative and more rational approach to BPT–SPT correlations is presented, based on experimental and numerical studies conducted at the University of British Columbia. The research involves performing SPT, BPT, and other in situ tests at several sites in British Columbia and includes dynamic measurements of energy transfer in the SPT and BPT. Stress-wave measurements and wave-equation analyses are used to evaluate the effect of friction on the BPT blow count. New BPT–SPT correlations are proposed that consider the energy transfer in both tests and explicitly consider casing friction in the BPT. A recommended procedure for estimating equivalent SPT N60 from BPT blow count is presented. Key words : Becker penetration test, standard penetration test, dynamic measurement, pile driving, stress-wave propagation.

Standard penetration test energy measurements using a system based on the personal computer: Discussion

where c is the longitudinal wave speed in the rods; E is Young's modulus of the rods; A is the cross-sectional area of the rods; K , and K2 are theoretical correction factors to account for the load cell position in the rods and the finite length of the drill rods, respectively; Kc is a wave speed correction factor, and F(t) is the measured force-time history. The integration is carried out over the duration of the impact compression pulse, At, which is approximately 2Lrlc, where L' is the total length of the drill rods and sampler below the transducer location. This force integration method was proposed by Schmertmann and Palacios (1979) and has been adopted in the ASTM Standard D4633-86 (ASTM 1986) and in the International Reference Test procedure for SPT energy measurement (International Society of Soil Mechanics and Foundation Engineering (ISSMFE) 1988). The main feature of the proposed SPT energy measurement system is the use of bonded strain gauges, which has several practical advantages. Strain gauges are relatively cheap compared with the piezoelectric load cell, and they do not introduce a change in cross-sectional area of the rod. The PC-based system also displays the force-time history in real time, which allows the operator to view the force wave trace for every blow. The authors show applications of the new system to three projects involving the SPT and one project involving the Becker hammer test (BHT; more commonly known as the Becker penetration test, BPT). The energy results presented in the paper are interesting, but several conclusions drawn by the authors are not supported by considerations of wave mechanics principles. In addition, the application of the force integration method to the BHT is not appropriate. The authors' SPT and BHT energy data are explored in more detail in this discussion.

Dynamic performance of the Becker hammer drill and penetration test

The Becker penetration test (BPT) blow counts are commonly correlated to the standard penetration test (SPT) N-values for foundation design and liquefaction potential assessment in coarse-grained soils. Most of the existing correlations, however, do not adequately account for the variable energy output of the ICE 180 diesel hammer used in the Becker system, and the shaft resistance acting on the Becker pipe is often ignored. To obtain reliable BPT–SPT correlations, an extensive study of the BPT has been conducted at several sites in British Columbia. Dynamic measurements of Becker drill rigs and penetration tests were conducted that included hammer combustion and bounce chamber pressures, as well as force and acceleration near the top of the drill pipe. The dynamic field data are presented, including the maximum energy transferred to the top of the Becker pipe (ENTHRU). An energy approach for correcting Becker blow counts to a reference ENTHRU level of 30% of the hammer-rated energy is proposed. Different combustion conditions, drill rigs, and pipe sizes are investigated in the study. The test results show that ENTHRU is a fundamental and useful parameter for normalizing the BPT blow counts to account for the variable energy transfer from the diesel hammer. Key words : penetration test, dynamic measurement, energy, pile driving, diesel hammer, stress-wave propagation.