Subsurface Exploration Using the Standard Penetration Test and the Cone Penetrometer Test

Rogers, J. David

doi:10.2113/12.2.161

Cited by 93 publications

(29 citation statements)

References 20 publications

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“…In CPT the penetrometer is inserted slowly at a constant rate of about 2 cm s −1 to avoid dynamic effects such as the generation of excessive pore pressure (Rogers, 2006). With our deployment technique, there may be dynamic effects somewhat similar to experienced in the Standard Penetration Test (SPT).…”

Section: Experimental Impact Penetrometer (X-pen)mentioning

confidence: 99%

Using the inertia of spacecraft during landing to penetrate regoliths of the Solar System

Paton

Green

Ball

et al. 2015

Advances in Space Research

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The high inertia, i.e. high mass and low speed, of a landing spacecraft has the potential to drive a penetrometer into the subsurface without the need for a dedicated deployment mechanism, e.g., during Huygens landing on Titan. Such a method could complement focused subsurface exploration missions, particularly in the low gravity environments of comets and asteroids, as it is conducive to conducting surveys and to the deployment of sensor networks. We make full-scale laboratory simulations of a landing spacecraft with a penetrometer attached to its base plate. The tip design is based on that used in terrestrial Cone Penetration Testing (CPT) with a large enough shaft diameter to house instruments for analysing pristine subsurface material. Penetrometer measurements are made in a variety of regolith analogue materials and target compaction states. For comparison a copy of the ACC-E penetrometer used on the Huygens mission is used. A test rig at the Open * Corresponding author University is used and is operated over a range of speeds from 0.9 to 3 m sand under two gravitational accelerations. The penetrometer was found to be sensitive to the target's compaction state with a high degree of repeatability. The penetrometer measurements also produced unique pressure profile shapes for each material. Measurements in limestone powder produced an exponential increase in pressure with depth possibly due to increasing compaction with depth. Measurements in sand produced an almost linear increase in pressure with depth. Iron powder produced significantly higher pressures than sand presumably due to the rough surface of the grains increasing the grain-grain friction. Impacts into foamglas produced with both ACC-E and the large penetrometer produced an initial increase in pressure followed by a leveling off as expected in a consolidated material. Measurements in sand suggest that the pressure on the tip is not significantly dependent on speed over the range tested, which suggests bearing strength equations could be applied to impact penetrometry in sand-like regoliths.In terms of performance we find the inertia of a landing spacecraft, with a mass of 100 kg, is adequate to penetrate regoliths expected on the surface of Solar System bodies. Limestone powder, an analogue for a dusty surface, offered very little resistance allowing full penetration of the target container. Both iron powder, representing a stronger coarse grained regolith, and foamglas, representing a consolidated comet crust, could be penetrated to similar depths of around two to three tip diameters, probably more if impacting with a slightly higher speed.

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Section: Experimental Impact Penetrometer (X-pen)mentioning

confidence: 99%

Using the inertia of spacecraft during landing to penetrate regoliths of the Solar System

Paton

Green

Ball

et al. 2015

Advances in Space Research

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“…Over the past few decades, the CPT has become increasingly popular because of its reliability, repeatability, and stream of continuous data [1]. SPT blow count (N) correlations are useful for coarse-grained soils, primarily sands, but there is considerable uncertainty in making accurate correlations of fine-grained soils comprised of silts and clays [11].…”

Section: Cyclic Resistance Ratiomentioning

confidence: 99%

“…The CPT is often used in the first phase of a site investigation, followed by test borings to confirm the CPT data. It is also less prone to error due to the differences in equipment and technique, and is generally more reliable than the SPT [11,13] Difficulties with oversize clasts and poor repeatability are often associated with the SPT; therefore, correlations have been proposed to estimate the CRR for clean sands and silty sands using the corrected penetration resistance measured by the CPT.…”

Section: Cone Penetrometer Testmentioning

confidence: 99%

Review on Liquefaction Potential of Silts from CPT Data

Ahmed¹,

Rogers²,

Cravens³

2014

JGRE

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Soil liquefaction occurs when pore water pressure of low cohesion materials equals or exceeds the effective confining pressure. Sudden increases in pore water pressure may occur in response to dynamic loads, such as earthquake shaking, or shear strain engendered by sudden movement (static liquefaction). This study focused on the evaluation of the liquefaction potential of silty soils using CPT (cone penetration test) data. There is much less CPT data on the behavior of silts under dynamic loading, as compared to sandy soil mixtures. Robertson and Wride proposed a method of evaluating liquefaction evaluation for silt-sand mixtures using CPT data, when the soils contain less than 35% fines. Until more research is conducted, soils comprised of more than 35% fines cannot be reliably evaluated using CPT data alone. This is true for isolated silts or silt mixtures, which require laboratory testing to evaluate their liquefaction potential. Experience has shown that soils with > 35% silt can liquefy if drainage is retarded or severely restricted by bounding low permeability horizons, such as silty clays or clayey silts, which prevent dissipation of dynamically induced pore water pressures.

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“…where (N 1 ) 60 5 the SPT blow count normalized to an overburden pressure of approximately 100 kPa and a hammer energy ratio of 60 percent, N 5 the raw SPT blow counts, C E 5 the correction for rod energy, C B 5 the correction for borehole diameter, C R 5 the correction for rod length, C S 5 the correction for samplers, and C N 5 the correction for effective overburden stress, which is based on the following equation (Liao and Whitman, 1986;Rogers, 2006): where P a 5 a reference pressure of 100 kPa and s 0 V 5 the vertical effective stress. For some SPT profiles that lacked borehole equipment information, some of the correction factors, such as C B , C S , and C E , were taken as 1.0 (65-115 mm), 1.0 (standard sampler), and 0.6 or 0.85 (safety hammer).…”

Section: Correcting Spt N-valuesmentioning

confidence: 99%