P. K. Robertson

A Summary Guide to the Cone Penetration Test (CPT)

A method to evaluate the susceptibility of soils to undrained strength loss that could result in flow liquefaction as well as a method to estimate the resulting liquefied undrained shear strength of predominately sand-like soils using the cone penetration test (CPT) were outlined by Robertson in 2010. Based on published data and recent case histori...

Flow liquefaction can be triggered by either cyclic or static loading and is a major issue for major geotechnical structures such as tailings dams. Flow liquefaction can occur in any saturated or near saturated contractive soil such as very loose sands and silts as well as very sensitive clays. For failure of a soil structure, such as a slope or em...

It is becoming increasingly common in the mining industry for either crushed ore or filtered mine waste to be stacked to a significant height (>100 m) in a moist state with little compaction, resulting in deposits that can be potentially loose and unsaturated. This paper presents a case history describing the characterization of stacked filtered ta...

A soil classification system is used to group soils according to shared qualities or characteristics based on simple cost-effective tests. The most common soil classification systems used in geotechnical engineering are based on physical (textural) characteristics such as grain size and plasticity. Ideally, geotechnical engineers would also like to...

Significant developments have taken place over the past 20 years to evaluate the liquefaction potential of soils using in situ tests. The cone penetration test (CPT) is now commonly used to evaluate liquefaction potential in soils. There have also been significant developments to evaluate liquefaction potential based on in situ shear wave velocity...

When sandy soils respond in a strain-softening manner to undrained loading, an estimation of the resulting undrained shear strength (Su) is required to determine the potential for flow liquefaction at a given site. One of the most commonly used methods for estimating the undrained strength of liquefied sand is an empirical standard penetration test...

Liquefaction failures of loose sand deposits can be a major concern for the stability of coastal structures. An investigation to evaluate the possible contributions of different triggering mechanisms in a major liquefaction failure that occurred in 1985 at the mouth of the Main Channel of the Fraser River has been carried out using steady-state con...

Gas can be found in many soils, but none more common than in seabed soils. Gas-charged sediments are known to be widely distributed throughout the world's oceans. Numerous research programs have studied saturated soil response to cyclic loading; however, little is known about the behavior of gassy soils subjected to cyclic loading. The response of...

A major aim of the Canadian Liquefaction Experiment (CANLEX) was to verify analysis procedures for predicting liquefaction phenomena. Towards this purpose, two loading events were carried out: a field event comprising a clay embankment built over a loose sand foundation layer, and a centrifuge test performed on a model of a sand embankment structur...

The Canadian geotechnical engineering community has completed a major collaborative 5 year research project entitled the Canadian Liquefaction Experiment (CANLEX). The main objective of the project was to study the phenomenon of soil liquefaction, which can occur in saturated sandy soils and is characterized by a large loss of strength or stiffness...

One of the primary objectives of the Canadian Liquefaction Experiment (CANLEX) project was to evaluate in situ testing techniques and existing interpretation methods as part of the overall goal to focus and coordinate Canadian geotechnical expertise on the topic of soil liquefaction. Six sites were selected by the CANLEX project in an attempt to ch...

One of the primary objectives of the Canadian Liquefaction Experiment (CANLEX) project was to develop and evaluate undisturbed sampling techniques as part of the overall goal to focus and coordinate Canadian geotechnical expertise on the topic of soil liquefaction. Six sites were selected by the CANLEX project in an attempt to characterize various...

Time domain reflectometry (TDR) can be used to determine the volumetric water content of soils. This note describes the utilization of a TDR miniprobe in triaxial testing. The TDR performance was examined with a series of tests that not only proved its reliability but also resulted in two empirical correlations. Using these correlations, the degree...

This paper attempts to evaluate the undrained shear strength of sand during flow failures, based on both laboratory testing and field observations. In the laboratory, the minimum shear resistance during monotonic loading was taken as the undrained strength, based on the criterion of stability. Triaxial compression, triaxial extension, and simple sh...

This paper presents a critical-state constitutive model for sands over a wide range of void ratios and consolidation pressures in a triaxial plane. A single set of parameters, including a unique critical-state line reached at large strain, is also used in the model, and differences in behavior in triaxial compression and extension are modeled by ac...

The behaviour of loose gassy sand was investigated with the use of a constitutive model. The constitutive model was modified from an existing model that focused on assessing the liquefaction of loose sands over a wide range of states and loading conditions. The modifications involved taking into account the compressibility and solubility of the por...

A numerical analysis is presented to model the cone penetration test (CPT) tip resistance in layered soil. Analyses are performed for two-layer soils composed of either sands with different relative densities or different materials (sand and clay). Parametric numerical modeling is used to determine the distance that a cone senses a new upcoming soi...

Rate effects on one-dimensional compressibility and undrained shear strength of a heavily overconsolidated naturally cemented clay have been studied. It is shown that in constant rate-of-strain consolidation tests the compressibility increases and the apparent preconsolidation pressure decreases with progressive decrease in rate of strain. Also a d...

A large number of steep, high cut slopes in residual soils exist in Hong Kong and many failures of such slopes have occurred, almost invariably during heavy rainfall. As a result, the long-term stability of many cut slopes is now in question.A brief review of past slope design and slope failure is presented.It has been found that the effective stre...

A multichannel electric cone penetrometer was used to perform a variety of in situ tests in saturated deltaic deposits.Factors affecting the tip bearing, friction sleeve stress, and pore-water pressures and their interpretation are studied and discussed. Pore pressure measurements were essential to evaluate the in situ test results. The effect of r...

Significant advances have been made in recent years in research, development, interpretation, and application of cone penetration testing. The addition of pore pressure measurements during cone penetration testing has added a new dimension to the interpretation of geotechnical parameters.The cone penetration test induces complex changes in stresses...

Static piezometer–friction cone tests were carried out at the tailings dam at Brenda Mines, Peachland, British Columbia to evaluate soil characteristics and seepage conditions in the dam. Several types of electric quasistatic cones were pushed to depths of 40–70 m at various locations in the dam and on the beach. The cones used included both the Fu...

An alternative approach to pressuremeter testing in sand, where the pressuremeter is pushed closed-ended, is discussed. Observations from cone penetration testing in sands are used to provide a theoretical background to the expected stress conditions around a full-displacement pressuremeter probe pushed into sand. The anticipated stress paths follo...

The status of in situ testing and its application to foundation engineering are presented and discussed. The in situ test methods are discussed within the framework of three groups: logging, specific, and combined test methods. The major logging test methods discussed are standard penetration test (SPT), cone penetration test (CPT), and the flat pl...

A study was performed in the shallow waters of the MacKenzie Delta area near Tuktoyaktuk, N.W.T., Canada, to evaluate equipment, test procedures, and techniques using a seismic cone penetrometer and operating on the landfast ice in winter. Seismic cone penetration testing was performed to determine the compressional and shear wave velocities of the...

The technique of installing prefabricated wick drains is well established in Europe and Japan, but is relatively new to North America. This paper describes the use of piezometer cone data to predict the performance of wick drains in a soft clayey silt in Burnaby, British Columbia. A description of the testing procedures and the theory to calculate...

The flat dilatometer (DMT) test was introduced by Marchetti (1980) as a new in situ penetration test for soils. The equipment and test procedures are simple, and the test provides repeatable, nearly continuous data that has been empirically correlated to soil type, undrained shear strength (su), coefficient of earth pressure at rest (K0), overconso...

Cone penetration testing (CPT) in Canada is usually performed using locally available drilling rigs. The limited pushing capacity of most drilling rigs coupled with the risk of damage to expensive cone penetrometers has tended to restrict the CPT to generally loose or soft soils. Therefore, in regions dominated by stiff glacial soils the more rugge...

Data have been reviewed from sites in Europe and North and South America as well as published data from South Africa. The review has concentrated on dissipation data from piezocone tests (CPTU) to compare predicted coefficient of consolidation and permeability values using published interpretation techniques with available reference values. The res...

According to the International Reference Test procedure for the standard penetration test (SPT), in situations where comparisons of SPT results are important, calibrations should be made to evaluate the efficiency of the equipment in terms of energy transfer. However, equipment to measure the energy transfer of the hammer anvil system is not common...

A modified version of the spectral analysis of surface waves (SASW) equipment and analysis procedure has been developed to determine in situ shear-wave velocity variation with depth from the ground surface. A microcomputer has been programmed to acquire waveform data and perform the relevant spectral analyses that were previously done by signal ana...

An interpretation method has been developed to incorporate nonlinear soil behavior to interpret undrained pressuremeter test results. The method makes use of both the loading and unloading portions of the pressuremeter test. The proposed interpretation method accepts that some level of soil disturbance may exist during the early loading portion of...

Traditionally pressuremeter tests results are interpreted using only the loading pressure–expansion data. An interpretation method has been developed that makes use of both the loading and unloading portions of a pressuremeter test and incorporates nonlinear, undrained soil behaviour. This method has been modified to handle large trains. The propos...

Effective techniques are currently available to obtain undisturbed samples of cohesive soils. However, little advance has been made in the procurement of undisturbed samples of cohesionless soils such as sands, silty sands, and clayey sands. In the area of earthquake design and liquefaction, researchers and practitioners are becoming increasingly a...

A state-boundary surface defines a boundary in stress – void-ratio space above which no stress state can exist. The applicability of the state-boundary surface for sand has not gained widespread attention primarily because sand is not generally considered to be a difficult soil from a design point of view apart from liquefaction. Liquefaction is a...

A study has been carried out to investigate the influence of fines and gradation on the skeletal collapse behaviour of loosely prepared sand samples. Loose sand samples, formed by moist tamping and consolidated to the same effective stress level, were prepared with varying percentages of both plastic and non-plastic fines (< 74 μm) and non-plastic...

In situ ground freezing to obtain undisturbed samples of a loose sand beneath the Duncan Dam in British Columbia is described. This was the first known use of ground freezing to assist in obtaining samples at depth greater than 10 m in Canada. Once frozen, the sand was cored and brought to the surface using a Cold Regions Research and Engineering L...

Loose cohesionless saturated materials have proved responsible for a number of serious or catastrophic flow slides. Liquefaction failures with no obvious triggering mechanism have also been recorded. This phenomenon of sudden liquefaction without a presence of cyclic shear stresses is often referred to as spontaneous or static liquefaction. Results...

Shear wave velocity (Vs) measurements were carried out in a triaxial testing program on three different cohesionless soils. The Vs was measured using bender elements during consolidation and at ultimate steady state. After consolidation the soil samples were loaded in shear under constant strain rate triaxial compression either drained or undrained...

A framework for estimating the ultimate undrained steady state shear strength of sand (Su) from in situ tests, which combines the theory of critical state soil mechanics with shear wave velocity measurements, is presented. For a particular direction of undrained loading, samples of a given sand at a constant void ratio will reach the same Su, despi...

Spontaneous flow liquefaction is a recurrent process in the progradation of the Fraser River delta. A portion of the Fraser River delta was investigated by seismic and resistivity cone penetration testing, by the spectral analysis of surface waves method and by soil and vapour sampling in an effort to determine site stratigraphy, in situ state, and...

Liquefaction flow slides are recurrent phenomena in the Fraser River delta near Sand Heads. The reasons for these failures are unexplained and remained speculative. An investigation of a liquefaction flow slide that occurred in 1985 in the Fraser River near Sand Heads has been undertaken using steady state concepts. For liquefaction flow slides to...

Water-pluviated samples of Ottawa sand were tested in monotonic, undrained triaxial extension tests. The specimens exhibited similar "limited strain softening" behavior, and they all experienced phase transformation from contraction to dilation at small axial strains. The tests were stopped at different stages and the samples were frozen to obtain...

Methane gas, found in loose deltaic deposits, can contribute to the triggering of flow liquefaction of submarine slopes. The behavior of loose gassy sand is studied in the laboratory using monotonic consolidated undrained triaxial compression tests. Samples consisted of reconstituted Ottawa sand prepared to degrees of saturation ranging from 80 to...

Soil liquefaction is a major concern for structures constructed with or on sandy soils. This paper describes the phenomena of soil liquefaction, reviews suitable definitions, and provides an update on methods to evaluate cyclic liquefaction using the cone penetration test (CPT). A method is described to estimate grain characteristics directly from...

The detection of shear zones along which a mass of soil is moving is essential for understanding the state of stability of natural slopes. Weaker zones in clay soils can be identified from low values of cone penetration test (CPT) tip resistance measured during penetration. This paper presents a case history illustrating the identification of softe...

Flow liquefaction is a major design issue for large soil structures such as mine tailings impoundments and earth dams. If a soil is strain softening in undrained shear and, hence, susceptible to flow liquefaction, an estimate of the resulting liquefied shear strength is required for stability analyses. Many procedures have been published for estima...

The electric cone penetration test (CPT) has been in use for over 40years and is growing in popularity in North America. This paper provides some recent updates on the interpretation of some key geotechnical parameters in an effort to develop a more unified approach. Extensive use is made of the normalized soil behaviour type (SBTn) chart based on...

Although the cone penetration test (CPT) and flat-plat dilatometer test (DMT) have been used for over 30 years, relatively little has been published regarding comprehensive correlations between the two in situ tests. This paper presents preliminary correlations between the main parameters of the CPT and DMT. The key to the proposed correlations is...

Application of the Cone Penetration Test (CPT) for the evaluation of seismic performance is reviewed and updates presented. The role of the CPT in geotechnical earthquake engineering is presented. The use of the CPT to identify soil behavior type and the normalization of CPT parameters is also reviewed and updates presented. The case-history based...

A research program was undertaken to study the load-transfer behavior of full-scale multi-helix screw anchors installed in natural soils. Four triple-helix screw anchors were instrumented with strain gauges at incremental distances along the inside of each anchor shaft. The test anchors were installed in glacio-lacustrine clay and aeolian sand depo...

A numerical modeling procedure was used to quantify calibration chamber size and boundary eeects for cone penetration testing in sand. In the numerical analyses, chamber diameter and boundary conditions were varied to investigate the eeects of chamber size and boundary conditions on cone tip resistance. These analyses show that, for loose sand, a c...

A semiempirical approach to estimate liquefaction-induced lateral displacements using standard penetration test ~SPT! or cone penetration test ~CPT! data is presented. The approach combines available SPT- and CPT-based methods to evaluate liquefaction potential with laboratory test results for clean sands to estimate the potential maximum cyclic sh...

Soil liquefaction is a major concern for many structures constructed with or on sand or sandy soils. This paper provides an overview of soil liquefaction, describes a method to evaluate the potential for cyclic liquefaction using the Cone Penetration Test (CPT) and methods to estimate post-earthquake ground deformations. A discussion is also provid...

A numerical modeling procedure for penetration mechanism is introduced to quantify chamber size effect and boundary conditions. Analyses are carried out for normally consolidated sand with K0 equal to 0.5, and for loose, medium dense, and dense sand. In the numerical analysis, calibration chamber diameter and the boundary conditions are varied to i...

Almost all natural soils are highly variable and rarely homogeneous. In this study, the seismic response of the Wildlife Site, Imperial Valley, California, U.S.A., has been analysed to assess the effect of ground heterogeneity on liquefaction assessment in a probabilistic analysis framework. Cone penetration test (CPT) data recorded at the site hav...

Engineering judgment and reliance on factors of safety have been the conventional tools for dealing with soil heterogeneity in geotechnical practice. This paper presents a review of recent advances in treating soil variability. It presents the implications of geostatistical techniques and up-scaling methods used for quantifying the heterogeneous pe...

An integrated approach to estimate liquefaction-induced ground settlements using CPT data for sites with level ground is presented. The approach combines an existing CPT-based method to estimate liquefaction resistance with laboratory test results on clean sand to evaluate the liquefaction-induced volumetric strains for sandy and silty soils. The p...

The relationship between the shapes of the yield surface and the undrained effective stress path (UESP) of loose sand is investigated for triaxial loading conditions. It is shown that the UESP can be used in the construction of capped yield surfaces for sands. The stress ratio Mp, measured at a point where the UESP of loose sand reaches a peak, has...

In very loose sand, the ratio M p of shear stress to mean normal stress at the peak point of the undrained effective stress path (UESP) is very close to the stress ratio M at the peak point of the capped yield surface. Stress ratios M p can therefore be used in constructing yield surfaces of sands. These stress ratios have also been used in the pas...

An opportunity to re-examine the liquefaction potential of hydraulically placed tailings sand has been provided by the Canadian Liquefaction Experiment (CANLEX). As part of this experiment, undisturbed samples of tailings sand were recovered after freezing the tailings in situ. Examination of undisturbed cores of frozen tailings sand clearly showed...

In situ ground freezing with liquid nitrogen can be an excellent technique for obtaining high quality undisturbed samples from a wide range of loose sand deposits, with their in situ conditions preserved. This paper describes the techniques used during the CANLEX project to carry out in situ ground freezing and undisturbed sampling of the loose san...

The Canadian geotechnical engineering community has completed a major collaborative 5 year research project entitled the Canadian Liquefaction Experiment (CANLEX). The main objective of the project was to study the phenomenon of soil liquefaction, which can occur in saturated sandy soils and is characterized by a large loss of strength or stiffness...

The Canadian geotechnical engineering community has completed a major collaborative 5 year research project entitled the Canadian Liquefaction Experiment (CANLEX). The main objective of the project was to study the phenomenon of soil liquefaction, which can occur in saturated sandy soils and is characterized by a large loss of strength or stiffness...

Dissipation of excess pore pressures during piezocone testing in firm to stiff overconsolidated fine-grained soils provides data curves that cannot be interpreted using published theoretical solutions. Available solutions are based on either cavity-expansion or strain-path methods, which have been developed for soft, normally consolidated soils and...

This paper attempts to evaluate the undrained shear strength of sand during flow failures, based on both laboratory testing and field observations. In the laboratory, the minimum shear resistance during monotonic loading was taken as the undrained strength, based on the criterion of stability. Triaxial compression, triaxial extension, and simple sh...

Dissipation of excess pore pressures during piezocone testing in firm to stiff overconsolidated fine-grained soils provides data curves that cannot be interpreted using published theoretical solutions. Available solutions are based on either cavity-expansion or strain-path methods, which have been developed for soft, normally consolidated soils and...

Horizontal Directional Drilling enables the drilling of horizontal boreholes 50 mm (2 inches) to 1200 mm (48 inches) in diameter beneath surface/subsurface obstacles, over extended horizontal distances. Recently, this technology has expanded its application beyond the oil, gas, and utilities industries to include the sampling and logging of soils i...

Helical Anchors, also known as Screw Anchors, have been used in many engineering applications. They provide structural stability against axial compression, uplift, overturning, and lateral forces. Predicting the loading capacity of helical anchors installed in Alberta is difficult because of the complexity of the sediments found in Alberta due to t...

This paper presents the test results obtained from a field experimental study conducted by the University of Alberta on screw anchor piles used in Alberta. A total of 18 pile load tests including compression, tension and lateral pile tests were performed on two sites underlain by soils typically found in Alberta. The axial and lateral loading behav...

Soil liquefaction is a major concern for strctures constrcted with or on sandy soils. This paper describes the phenomena of soil liquefaction, reviews suitable definitions, and provides an update on methods to evaluate cyclic liquefaction using the cone penetrtion test (CPT). A method is described t.o estimate grain characteristics directly ûom the...

Preface. Acknowledgements. Symbol List. Conversion Factors. Glossary. 1. Introduction. 2. Equipment and procedures. 3. Checks, corrections and presentation of data. 4. Standards and specifications. 5. Interpretation of CPT/Piezocone data. 6. Direct application of CPT/CPTU results. 7. Additional sensors that can be incorporated. 8. Geo-Environmental...

Pipelines are often subjected to transverse and longitudinal movements due to displacements in the ground caused by landslides. As landslide movements develop, pipelines can undergo transverse and longitudinal displacements and the resistance offered by the surrounding soil steadily increases depending on the soil characteristics. This resistance r...

The initial state of a sand, defined by the void ratio and effective mean normal stress, can be used to predict its large-strain response. Laboratory studies have shown that the shear-wave velocity of a sand is controlled primarily by the effective confining stresses and void ratio. Since shear-wave velocity can be measured both in the field and in...

Postearthquake deformations of the Wildlife site, Imperial Valley, Calif., following the 1987 Superstition Hills earthquake, have been interpreted by finite-element deformation analyses. The analyses consider the stress redistribution and reconsolidation caused by the development of liquefaction. The stress redistribution analysis was conducted und...

An SPT energy calibration system is described that has been developed based on a microcomputer. The load cell to measure the compressive stress wave beneath the SPT anvil consists of a 0.5-m length of strain-gauged AW rod. Specialized software has been developed to record the force-time record for each hammer blow on a portable microcomputer. Examp...

Loose cohesionless materials can collapse during either static or dynamic loading, resulting in a rapid buildup of pore pressure and associated reduction in shear resistance. As the cohesionless material collapses, it rapidly loses resistance until the acting shear stress decreases to the available residual or steady-state strength. Specially desig...

Postearthquake deformation analyses of the lower San Fernando dam were conducted using an incremental finite-element method. In the analyses, an undrained elastoplastic model was used to simulate the collapse of liquefied materials. The model is developed based on the critical-state boundary-surface theory, the concept of steady-state strength, and...