Piezo-friction-cone penetrometer testing in soft clays

1987 ◽  
Vol 24 (4) ◽  
pp. 645-652 ◽  
Author(s):  
J.-M. Konrad
Keyword(s):  
Pore Pressure ◽  
Water Pressure ◽  
Testing Procedure ◽  
Soil Conditions ◽  
Cone Penetrometer ◽  
In Situ Testing ◽  
Soft Clays ◽  
Tip Resistance ◽  
Full Design

A comprehensive in situ testing program using a 50-kN electric piezo-friction-cone penetrometer was carried out at three different sites in soft marine clays. In these soils, the measured penetration resistance and friction are less than 4% of the full design capacity of the load cells. Although the strain gauges are temperature compensated, the importance of temperature effects in these soil conditions is demonstrated. The paper outlines a testing procedure to minimize the errors associated with zero shift in cone testing and to obtain meaningful data in weak soils with 50-kN penetrometers.Pore-water pressure measurements along the shaft are essential to evaluate the in situ test results in soft soils. Pore pressure distribution along the shaft is dependent on soil type, and measurements should be made at both ends of the friction sleeve for complete soil characterization.Friction along the shaft is not uniform and is negligible over an initial length of about 2 cone diameters in soft clays. Key words: soft clays, pore pressure, friction, tip resistance, in situ testing.

Calibration of a Miniature Cone Penetrometer for Highway Applications

1998 ◽  
Vol 1614 (1) ◽  
pp. 8-14 ◽  
Author(s):  
Pradeep U. Kurup ◽  
Mehmet T. Tumay
Keyword(s):  
Ground Improvement ◽  
Cone Penetration Test ◽  
Test System ◽  
Soil Parameters ◽  
Cone Penetrometer ◽  
Penetration Test ◽  
Cone Penetration ◽  
Tip Resistance ◽  
In Situ Investigation

The electronic cone penetrometer is an important in situ investigation tool of choice for site characterization. Application of this proven concept of the cone penetration test (CPT) to highway design and construction control by miniaturization is described. A miniature cone penetrometer with a projected cone area of 2 cm2 has been developed and implemented in a continuous intrusion miniature cone penetration test system (CIMCPT). This device may be used for rapid, accurate, and economical characterization of sites and to determine engineering soil parameters needed in the design of pavements, embankments, and earth structures. The miniature cone penetration test (MCPT) gives finer details than the standard 10-cm2 cross-sectional area reference cone penetrometer. This makes the MCPT attractive for subgrade characterization, quality-control assessment, compaction control of embankments, and assessment of ground improvement effectiveness for transportation infrastructure. In situ calibration of the CIMCPT system was conducted at a highway embankment site in Baton Rouge, Louisiana. MCPT penetration profiles were compared with those obtained by using the standard cone penetrometer at the same site. The tip resistance of the MCPT was 10 percent higher than that of the reference CPT. The sleeve friction and friction ratio of the reference CPT were higher than that of the MCPT by 12 and 23 percent, respectively. Calibration was also performed to determine empirical cone factors required for estimating undrained shear strength from MCPT data.

Friction Correction Equation for the Dynamic Cone Penetrometer in Subsoil Strength Testing

2000 ◽  
Vol 1714 (1) ◽  
pp. 89-97 ◽  
Author(s):  
Moshe Livneh
Keyword(s):  
Skin Friction ◽  
Testing Procedure ◽  
Strength Testing ◽  
Cone Penetrometer ◽  
Extensive Experience ◽  
Testing Apparatus ◽  
Dynamic Cone Penetrometer ◽  
Torque Moment ◽  
Penetration Depths

Extensive experience gained with the dynamic cone penetrometer (DCP) in Israel has led to some modifications in both the testing apparatus and the testing procedure. One such modification is introduction of a theoretical corrective equation when the penetration is not performed vertically in order to isolate the skin friction that develops along the penetrating rod, which significantly affects DCP values. For this purpose, the torque moment is measured at various penetration depths by the same technique applied for the well-known Vane test. This corrective equation is then modified in light of the results obtained for validating in situ DCP tests.

Analysis of the Effect of Stopping Dewatering on Group Piles Foundation

2011 ◽  
Vol 250-253 ◽  
pp. 1348-1355
Author(s):  
Jun Fa Zhang ◽  
Lei Tao ◽  
Jian Jun Wen ◽  
Wen Xiang Liu
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Groundwater Table ◽  
Shaanxi Province ◽  
Analysis Program ◽  
In Situ Testing ◽  
Building Foundation ◽  
Abnormal Phenomenon ◽  
Group Piles

After the construction of building foundation with high groundwater table was finished, stopping dewatering of pit could create some effect on the force of foundation. In this paper, equivalent temperature-changed method was brought forward to simulate the influence of stopping dewatering which could conveniently use current structural analysis program to simulate the change of pore water pressure in soil. And based on ANSYS program, this method was applied in the project of Telecom Network Management Center in Shaanxi Province. Numerical results indicate that the effect of stopping dewatering on pile-raft system is significant, and some ‘abnormal phenomenon’ in In-Situ Testing is reasonably explained.

Monotonic and dilatory pore-pressure decay during piezocone tests in clay

1998 ◽  
Vol 35 (6) ◽  
pp. 1063-1073 ◽  
Author(s):  
S E Burns ◽  
P W Mayne
Keyword(s):  
Pore Pressure ◽  
Pore Water Pressure ◽  
Soil Mechanics ◽  
Water Pressure ◽  
Cavity Expansion ◽  
Coefficient Of Consolidation ◽  
Soft Clays ◽  
Fine Grained ◽  
Cavity Expansion Theory ◽  
Pore Pressure Response

During a pause in cone penetration in fine-grained soils, pore-water pressure dissipation tests are performed to evaluate the coefficient of consolidation. For standard piezocones with shoulder filter elements, soft clays and silts show a monotonically decreasing response with time; however, dissipation tests performed in heavily overconsolidated silts and clays show dilatory behavior, with the pore-pressure behavior increasing from the initial measured value to a maximum, and then decreasing to hydrostatic values. This paper presents a theoretical framework which combines cavity-expansion theory and critical-state soil mechanics with an analytical solution to the radial consolidation equation. The method is able to describe the pore-pressure response curve for dissipation tests performed in soils which demonstrate either monotonically decreasing or dilatory pore-pressure behavior.Key words: cavity expansion, consolidation, piezocone, pore pressure.

scholarly journals Instrumented Impact Cone Penetrometer

1973 ◽  
Vol 10 (3) ◽  
pp. 397-409 ◽  
Author(s):  
Umesh Dayal ◽  
John H. Allen
Keyword(s):  
Field Tests ◽  
Strength Properties ◽  
Experimental Program ◽  
Cone Penetrometer ◽  
Test Results ◽  
In Situ Testing ◽  
Penetration Mechanism ◽  
Side Friction ◽  
Local Side

The present paper describes the development of an instrumented impact cone penetrometer for a direct measurement of in situ strength properties of a soil target. The developed penetrometer, in addition to providing acceleration signatures (as obtained by previous investigators), is capable of recording cone thrust and local side friction simultaneously and continuously. The procedures have been outlined for estimating in situ strength properties and soil type of the target materials throughout the penetrated depth from the output records of these sensors. Typical test results generated from an on-going experimental program aimed at providing the data for (1) understanding the penetration mechanism, (2) development of penetration theory, and (3) designing the penetrometer for field tests, i.e. in situ testing of ocean floor soils, are also presented.

scholarly journals In situ equilibrium pore-water pressures derived from partial piezoprobe dissipation tests in marine sediments

2013 ◽  
Vol 50 (12) ◽  
pp. 1294-1305 ◽  
Author(s):  
Nabil Sultan ◽  
Sara Lafuerza
Keyword(s):  
Slope Stability ◽  
Pore Pressure ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Design Parameters ◽  
Short Term ◽  
Pore Water Pressures ◽  
Time Required

Excess pore-water pressure has a significant effect on submarine slope stability and sediment deformation, and therefore its in situ equilibrium measurement is crucial in carrying out accurate slope stability assessments and accurately deriving geotechnical design parameters. In situ equilibrium pore-water pressure is usually obtained from pore pressure decay during piezocone tests. However, submarine shelves and slopes are often characterized by the existence of low-permeability (fine-grained) sediments involving long dissipation tests that are an important issue for offshore operational costs. Consequently, short-term and (or) partial dissipation tests are usually performed and in situ equilibrium pore-water pressures are predicted from partial measurements. Using a modified cavity expansion approach, this paper aims to predict for four different sites the in situ equilibrium pore-water pressures. Comparisons between predicted and observed in situ equilibrium pore-water pressures allowed the development of a guide to evaluate the minimum time required to perform short-term dissipation tests for a given marine sediment. The main finding of this Note is that the second derivative of the pore pressure, u, versus the logarithm of time, t, ∂2u/∂ln(t)2 must be positive to calculate accurately the in situ equilibrium pore-water pressures from partial measurements.

Evolution of the factor of safety following excavation in clay

2009 ◽  
Vol 46 (5) ◽  
pp. 487-493 ◽  
Author(s):  
J. S. L’Heureux ◽  
S. Leroueil ◽  
J. F. Laflamme
Keyword(s):  
Pore Pressure ◽  
Factor Of Safety ◽  
Clayey Soil ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soil Mass ◽  
Eastern Canada ◽  
Soft Clays ◽  
Clay Deposits ◽  
The Difference

Numerical analyses have been performed to study the evolution of the factor of safety following the excavation of a cut in clay. The analyses consider variable thickness of the clayey soil deposit under the excavation. The results show that, for a given clayey soil, there is a relation between the time for full dissipation of excess pore-water pressure from the soil mass following the excavation and the geometry of the cut (Htot/Hexc). The analytical results agree reasonably well with pore pressure measurements made in excavations in clay deposits from eastern Canada. This suggests that time to reach full pore pressure equilibration following the excavation of a cut in homogenous clayey soil deposits can be predicted when knowledge of the coefficient of swelling–consolidation is available. Lastly, results obtained in the present study show that 50% of the difference between the short- and long-term factors of safety may be lost at values as low as about 8% of the time to reach equilibration of pore pressures. This means that the time during which one can rely on the short-term strength of the clayey soil following the excavation may be relatively short, especially for soft clays.

scholarly journals In situ strength characterisation of peat and organic soil using full-flow penetrometers

2011 ◽  
Vol 48 (7) ◽  
pp. 1085-1099 ◽  
Author(s):  
N. Boylan ◽  
M. Long ◽  
F.A.J.M. Mathijssen
Keyword(s):  
Organic Soil ◽  
Cone Penetrometer ◽  
Uniform Measure ◽  
In Situ Testing ◽  
Strength Parameters ◽  
Resistance Factors ◽  
Fibrous Peat ◽  
Penetration Tests ◽  
Range Of Values

Full-flow penetrometers have been shown to overcome problems experienced with the cone penetrometer when measuring resistance in very soft peat and organic soil, and give a much more uniform measure of resistance than the cone in fibrous peat. However, at present there is no guidance on the interpretation of strength parameters in these soils using the T-bar and ball. This paper examines the results of tests using these devices at two research sites in the Netherlands in conjunction with high-quality Sherbrooke sampling for laboratory testing. In fibrous peat, the T-bar and ball provided a more uniform measure of resistance with a lower degree of scatter than the cone. The in situ testing results have been compared with the laboratory tests to assess the range of resistance factors relating penetration resistance to the undrained shear strength (su) and have been shown to occupy a lower range of values than the cone penetrometer. However, penetration tests in these soils are likely to be influenced by partial drainage effects and this should be considered during testing and the subsequent interpretation of results. Recommendations are made for the use of full-flow penetrometers to obtain strength parameters in these soils.

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