Research Papers for PANDA® DCP

Density vs PANDA Cone Resistance (Qd), Friction Angle (degrees), SPT (N), and CPT (Qc)

Consistency of cohesive (silts & clays) and intermediate soils – PANDA Cone Resistance (Qd), Strength (kPa), SPT (N), and CPT (Qc)

This paper proposes a methodology that consists of testing Lateritic soils in-situ and in the laboratory, studying cone resistance according to compaction parameters in order to estimate the boundary effects and to propose a model to take them into account when predicting in-situ dry unit weight.

Historical background on the PANDA Instrumented DCP and the development of the Compaction Control database relating density to cone resistance Qd and standard NF P 94-105.

Research behind the PANDA and the PANDOSCOPE by the product inventor, Dr Roland Gourves.

The compaction control consists in measuring the dry density and compares it with the standard Proctor density. The cone resistance in a known granular medium is directly linked to the dry density. It is the comparison between the in-situ penetrogram and a reference curve which permits the compaction. This reference curve corresponds, for a given soil and a required compaction level to the core resistance (for a passed compaction). A calibration process is necessary to establishes the reference curves. This paper sets out the compaction control method and the calibration process.

Dr. Roland Gourves, principle lecturer in soil mechanics at CUST, Blaise Pascal University, Clermont-Ferrand, France has designed and developed the Panda (a lightweight hand held dynamic cone penetrometer for testing soils and materials) since 1991. It has become widely used and accepted across France, parts of central Europe and in small numbers around the world. Sinced it’s initial development the Panda has been continuously developed to be used to test the compaction of fill in earth works through software analysis as well as in site investigation. Trials have been carried out at nine sites across the UK (both working sites as well as Building Research Establishment test bed sites) to clarify the usefulness and reliability of the software analysis and correlations for use in the UK.

The Building Research Establishment (BRE) has carried out a programme of research to evaluate the potential of dynamic probing as an economical, repeatable and operator insensitive test for profiling and assessing soil properties. This paper describes the dynamic probing test procedure, equipment specifications and the treatment of results. Dynamic probing was carried out at 10 clay soil test bed sites, 6 in the UK and 4 in Norway, to cover a reasonably wide range of undrained shear strengths and plasticities. Correlations between dynamic probing data and undrained shear strength as well as the results from Standard Penetration Test and static cone penetrometer tests have been obtained and, potentially, will allow wider application of dynamic probing to ground investigation.

The company Geotecnia Ambiental together with the Geotechnical Group of the Pontificia Universidad Católica de Valparaíso, with financing from INNOVA-CORFO of Chile, approached the challenge of adapting innovative, efficient, environmentally sustainable and precise technologies as alternatives in the process control of soil compaction of Chilean road infrastructure and backfill projects, through an investigation from 2012 and 2014. During the investigation more than twenty state of the art control technologies that exist on a world level were reviewed. Based on the background information dynamic lightweight penetrometer PANDA and the dynamic load plate LFG Pro were selected, of French and German engineering respectively, for use in Chile. Advantages and disadvantages for each system, as well as fields of application, output parameters and proposed methodology were all considered for use in future compaction control projects.

A Soil Compaction Control Technology Assessment and Demonstration

This project involved compaction control tests with three techniques generally used in the New York metropolitan area, including: The Gamma Densitometer, The Dynamic Cone Penetrometer, and the more recently developed Soil Compaction Meter. The project also included the assessment of the PANDA – a French developed soil compaction control technology. The tests were conducted in six different trenches with typical sandy backfill material compacted under different pre-selected site conditions.

Analysis of the test results demonstrated the reliability, efficiency, as well as the main advantages and limitations of each testing procedure. In particular, it was demonstrated that the PANDA provides a highly reliable tool for post-construction compaction quality control, which, due to its user-friendly software, is practically operator independent. This report briefly presents the main field test data along with site observations and summary of the main features, technical performance and cost details related to each testing procedure.

PANDA Dynamic Cone Penetrometer (DCP) correlations with Cone Penetration Test (CPT)

PANDA Dynamic Cone Penetrometer (DCP) vs Cone Penetration Testing (CPT), Shear Vane and traditional DCP / Scala in New Zealand

Dynamic Lightweight Penetrometers (DLP) are an attractive technology when prospecting tailings storage facilities due to their low cost, ease of transportation and use. One of the shortcomings of LPs is that their sounding depth is usually limited to less than 10 m. Thus, DLPs are not intended to fully replace conventional penetrometers when deep characterization of soils is required. However, they are an attractive tool for routinary control of dams. Lightweight penetrometers have been used in Chile in recent decades as a tool for monitoring the compaction degree of retaining walls in tailings dams. In addition to this, DLPs have been used in thickened tailings deposits to characterize stiffness and strength of materials. For instance, a series of correlations between DLP’s cone resistance (qd) and friction angle (𝜙) and undrained shear strength (Su) of thickened tailings have been proposed. There have also been a series of efforts to correlate qd with the tip resistance of other well documented techniques, e.g. CPT, SPT, DSPT. Nevertheless, there still exist a series of uncertainties related to the effects of tailings state parameters, e.g. water content (w %), confining pressure (𝜎′𝑣) and void ratio (e), on the resulting qd. This is experimentally explored in the present study using a pressure chamber under controlled conditions. The outcomes of this study will contribute for the rational interpretation of DLP’s results when used for the monitoring of tailings dams.

An analysis of the dynamic variability cone resistance parameter (qd) is shown, which is obtained from the variable energy dynamic lightweight penetrometer test (Panda 2 ®). The assessment variability was estimated using classic statistical tools.

Estimations were performed for the qualitative characteristics as a function of the relative density (RD %), this parameter was obtained using a correlation with qdN1 (normalized dynamic cone resistance parameter). Then, the level of compaction, mechanical behavior and risk of liquefaction is determined showing weak zones. The data processing and geospatial modeling were made using the software Rockworks v.14 ®.

This work enabled a validation of the hypothesis regarding reconstruction of the internal structure of a tailings deposit, through the compaction test parameters whether quantitative (dynamic cone resistance parameter, qd) or qualitative (compaction, mechanical behavior). Weak zones and corroborating the quality of the compaction test process was performed. Furthermore post compaction control recommendations were completed.

Tailings storage facilities (TSFs) in Chile are now built using the downstream method of construction, an approach that was triggered by the failure of a number of upstream constructed facilities during or immediately after large seismic events. In Australia, the upstream method continues to be used, because of the significantly lower cost and the perceived lack of a credible seismic risk. The design of TSFs in Australia is moving towards the adoption of maximum credible earthquake (MCE) considerations, particularly for closure, where the design life is increasingly expected to be ‘in perpetuity’.

Recent research in Chile has shown the viability of using a lightweight penetrometer, the PANDA penetrometer, as a tool for rapid, inexpensive and regular in-situ determination of the state of deposited tailings. The PANDA has been calibrated against density measurements and is frequently used to estimate the relative density, which is a useful indication of liquefaction susceptibility.

This paper describes an approach for managing upstream TSFs in Australia using the PANDA penetrometer for regular in-situ testing which, when coupled with the results of laboratory compressibility measurements, can be used to predict the future state of tailings once buried to a significant depth.

Transportation agencies commonly use large size aggregates, often referred to as rock cap or aggregate subgrade, e.g., by Illinois Department of Transportation (IDOT), for stabilizing weak subgrades at wet of optimum moisture states. Adequate characterization of these large rocks is not possible in the laboratory with the use of standard tests. Accordingly, a cone penetration based strength index is the best field assessment tool since shear strength profile is closely linked to unbound aggregate or aggregate subgrade layer performance. To this end, an innovative variable energy dynamic cone penetration (DCP) device, popularly known as PANDA in France, was utilized in a recent Illinois Center for Transportation (ICT) research study involving the performance assessment of large size aggregates over soft subgrades. Twelve full scale working platform sections were constructed with six different types of virgin and recycled large size aggregate materials. Accelerated pavement testing (APT) was carried out on these sections to monitor the rutting progression with number of passes of a certain wheel load assembly. To evaluate layer properties and adequately relate them to rutting performance, PANDA tests were conducted along with traditional DCP soundings on the loading applied pavement test section centerlines.

A Geo-endoscopic probe was also used in the holes opened by the PANDA tests to identify layer interfaces and visually document subsurface moisture conditions. The PANDA and Geo-endoscopy testing has proven very beneficial in the performance assessment of the large size aggregate subgrade materials under simulated traffic loading.

This paper presents current detailed technical knowledge on the PANDA and Geo-endoscopy test equipment and highlights field results associated with the recent ICT project soundings conducted in the pavement working platform test sections.

This study compared results of field tests and laboratory tests on chemically stabilized soil at different curing times to assess whether a relationship exists between field and laboratory measurements. The goal was to determine if a field testing method could be used to assess whether the strength and stiffness in the field are consistent with laboratory measurements used for design.

Field testing included three devices that are portable, quick, and easy to use. These devices include: the Dynamic Cone Penetrometer (DCP), the PANDA penetrometer, and the Portable Falling Weight Deflectometer (PFWD). Laboratory testing was conducted to determine the unconfined compressive strength (UCS) and resilient modulus (MR) of laboratory specimens prepared using additive contents that were similar to samples taken from field test locations.

Correlations were examined and involved basic soil measurements (mineralogical, electrical, chemical and index properties) and mechanical properties (UCS and MR), and field test results (DCP, PANDA, and PFWD). The strongest trend was observed for the PFWD – MR comparison. The trend showed that both the PFWD modulus and MR increase with increasing curing time, as expected. These observations show that development of correlations between field and laboratory test results holds promise. However, development of such correlations will require that field and laboratory tests be performed on nearly identical soils and under identical curing conditions.

Results of compressive strength and resilient modulus measured in situ using a Variable Energy Dynamic Penetrometer (VEDP) – PANDA DCP, Light Weight Deflectometer – Portable Impulse (LWD-PI), and Plate Load Test (PLT) and laboratory Unconfined Compressive Strength (UCS) during a full-scale trial on the Australian Rail Track Corporation (ARTC) Inland Rail project. These alternative tests reduce the level of laboratory testing effort while the near real time display of results aids in construction time frames which is of particular benefit to projects in remote locations. The methods can be combined with traditional field testing methods to develop site-specific correlations and validate geotechnical parameters assumed in the design.

A comparison of two methods of determining the stiffness of track-bed materials (dynamic penetration and dynamic plate load) comparing the PANDA / PANDOSCOPE and the Light Weight Deflectometer.

By means of a detailed parametric study of the settlement of ballast material per- formed on a full-scale track model, a predicting model for ballast settlement under cyclic loading has been developed. The model is based on track parameters: axle load, train speed and the initial mechanical state of ballast. A light dynamic penetrometer allows the characterization of the latter. Several loading tests, were performed, together with a characterization of the initial state of ballast close to the sleepers. The results show a settlement evolution in three stages (short, medium and long term settlement) depending on the initial conditions of the material and the intensity of the vibration.

The proposed model describes the three stages in the settlement evolution. With this model, we obtain a prediction of settlement evolution with an error less than 10% for almost all experimental data.

As a conclusion a method is proposed which has been tested on a track and which allows one to estimate the settlement of the sleepers by considering train traffic and cone penetration resistance in order to obtain an average settlement curve and a probability to reach a threshold value. This is a first step towards a general framework for the evaluation of the geometric potential degradation of railway tracks, which is a major issue for the cost reduction of maintenance operations on railway tracks.

Ballast is a major railway component whose behaviour is still not sufficiently controlled. The identification of mechanisms leading to track ageing is difficult to achieve as the process occurs over several years at particle scale.

Models have been proposed to take into account ballast characteristics and provide a description of geometrical and structural modifications of ballast particles through time. To be relevant, these models must be supplied with reliable and realistic input data such as on-site density and stiffness modulus.

This article presents results that could provide these parameters, starting with on-site tests that link them with cone penetration energy.

Coastal structures are often submitted to intense wave forcing. In some cases, structures may have stability disorders due to the constant weakening of their foundations and to momentary liquefaction of the sea bed. Studies have shown that if classical geotechnical characterization is a necessity, air content in the soil is also a key parameter for liquefaction evaluation. That is why on site air content measurement and its time variation during a tide period may provide information and help to determine a better understanding of this problem. Unfortunately, this parameter is difficult to measure during investigations.

This article presents a technique based on the use of geoendoscopy and automatic image analysis, which makes it possible to characterize coastal soils and to estimate their air content. After a description of the technique, the results obtained on laboratory tests and on a real site are presented.

The aim of the thesis was to answer historical questions about cities by assessing the informative potential of data available to archaeologists. It involved looking at the characteristics of the urban soil to understand how human activities have shaped the urban space and socio-spatial elements. More specifically, the analysis focused on assessing the thickness of the urban soil and its division into distinct functional layers in the city of Tours and sites of comparison.

Bringing together the perspectives of archaeologists and geotechnicians made it possible to develop stratification production models (maps charting the thickness of the archaeological deposit) and methods to model the heterogeneity of the deposit. Results reveal that a theoretical 100m2 grid is sufficient to understand variations in the thickness of the deposit. Vertically, the scale of analysis needed to distinguish the so-called “homogeneous” zones is roughly 10–25cm.

At the site level, an archaeological-mechanical referential frame was established for sites in Tours and Lyons. The study shows that the PANDA penetrometer can improve the characterization of the archaeological deposit. In the medium term, these advances can be furthered by developing a common referential frame for a group of sites.

Apports du pénétrométre à la connaissance d’un site préhistorique. Le cas de l’abri de Diepkloof, province du Cap, Afrique du Sud – Arnaud Lenoble, Michel Martinaud (2003) French

Diepkloof is a large sandstone shelter containing Late and Middle Stone Age deposits with a good preservation of the organic remains. Since these sediments are extremely loose, this site provides a simple case for estimating of penetrometric techniques in an archaeological context.

Mainly used in civil engineering, a dynamic penetrometer is a heavy instrument which allows the measurements of the variations of a cone resistance (in MPa) as a fonction of the depth along a vertical line. These measurements yield about the material compaction. The PANDA which has been used in this shelter is a light-weight (20 kg) dynamic cone penetrometer for soil investigation. It uses variable energy (the blow from a hammer) and can be operated by one person.

Measurements have been recorded along two profiles. Two kinds of data are investigated. Firstly, the depth of the is documented which allows the estimation of the volume of the deposits in this cave : between 400 and 500 m3. Secondly, the variability in the sediment compaction is used to characterize the infilling of the shelter. Roof fall blocks are abundant in the entrance whereas rock fragments are scarce in the backfill. It is found that the top of the deposits between the surface and a depth of 1 .5 m contains numerous hard lenses recognized as saltcrusts. In comparison, the bottom of the infilling is extremely loose and, in fact, is not yet reached by the excavations. Finally, this study provides arguments to discuss the site formation processes and makes easy the best choice for future excavations.

The available sand for the soil replacement underneath a breakwater is mixed with shells, with variable shell contents ranging up to 50%. Based on experience, the substituted sand in the foundation has to be compacted by vibrocompaction. Data from literature is not representative for the existing specific sand mixture. Therefore, in order to understand the behaviour of the sand shell mixture of the project site compacted by vibrocompaction, a series of tests in large calibration chambers combined with laboratory tests are designed and executed. The aim is to evaluate the sand shell mixture behaviour and to find practical correlations among the strength (from in-situ tests), relative density (from laboratory tests) and (in-situ) settlement due to vibrocompaction.

The strength of sand shell mixture is tested with the Panda 2 dynamic cone penetrometer. The sand is tested for different degrees of compaction and for different vibration conditions. The results show that the settlements due to vibrocompaction and the increase in resistance are not perfectly correlated. Based on the observation, it is understood that the settlements cannot be used as the only acceptance criterion for the required strength during the vibrocompaction campaign and achieved strength should also be monitored.

The Panda 2®, developed by Roland Gourvès in 1991, is a lightweight dynamic cone penetrometer. It provides the dynamic cone resistance (qd) and depth in real time with a high sampling frequency. Nevertheless it cannot take soil samples so the penetration test is called ‘blind’.

The aim of this paper is to propose an automatic methodology to predict the soil grading from the cone resistance using artificial neural networks. We have built a database based on the Panda® laboratory tests on soil samples and insitu tests next to boreholes during various geotechnical studies performed in France. Then the neural networks was used to classify the cone resistance logs according to grain size distribution of the tested soils by means of feature extraction using different signal analysis. The results show that we are able to separate 4 soil classes with 98% accuracy.

Part of Application of Statistical Techniques – Prof Mark Jaksa – University of Adelaide – 5th International Conference of Geotechnical and Geophysical Site Characterisation ISC5 Australia 2016