1960•Highway Research Board Special ReportRequires access
SUMMARY OF ROTARY CONE PENETROMETER INVESTIGATIONS
Willard J. Turnbull, W. G. Shockley, Robert W. Cunny
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Abstract
A ROTARY CONE PENETROMETER WAS DESIGNED TO INVESTIGATE ECONOMICALLY THE RELATIVE DENSITY OF DEEP SAND DEPOSITS ALONG RIVER BANKS. TESTS WERE CONDUCTED TO DETERMINE THE EFFECT OF SURCHARGE PRESSURE, GRADATION AND SHEAR STRENGTH OF SANDS ON THE CONE THRUST TO DEVELOP A RELIABLE RELATIONSHIP BETWEEN CONE THRUST AND RELATIVE DENSITY OF THE IN SITU FINE SAND DEPOSITS. CONE PENETRATION TESTS WERE PERFORMED ON A SATURATED FINE SAND CONFINED IN A STEEL TANK AT VARIOUS RELATIVE DENSITIES AND SUBJECTED TO VARIOUS SURCHARGE PRESSURES TO DETERMINE THE EFFECT OF SURCHARGE PRESSURE AND RELATIVE DENSITY ON CONE THRUST. UNDISTURBED SAMPLES WERE OBTAINED FROM A FINE AND A MEDIUM SAND CONTAINED IN A STEEL TANK AT VARIOUS RELATIVE DENSITIES AND SUBJECTED TO VARIOUS SURCHARGE PRESSURES TO DETERMINE CHANGE IN DENSITY CAUSED BY SAMPLING. CONE PENETRATION TESTS WERE MADE IN A DEEP DEPOSIT OF FINE SAND IN A TYPICAL SITE ALONG THE MISSISSIPPI RIVER. UNDISTURBED SAMPLES OF THE SAND WERE OBTAINED ADJACENT TO EACH CONE PENETRATION TO COMPARE THE RELATIVE DENSITY PREDICTED BY THE CONE PENETROMETER WITH THE RELATIVE DENSITY MEASURED FROM UNDISTURBED SAMPLES. ANOTHER SERIES OF CONE PENETRATION TANK TESTS IS UNDER WAY TO DETERMINE THE EFFECT OF SAND GRADATION AND SHEAR STRENGTH ON CONE THRUST. THE RELATIONSHIPS BETWEEN CONE THRUST AND NORMAL PRESSURE FOR THE DENSITIES OF SANDS TESTED ARE PRESENTED. DATA ANALYSIS INDICATE THAT THE CHANGE IN DENSITY DURING UNDISTURBED SAMPLING OF SAND IS DEPENDENT UPON OVERBURDEN PRESSURE AND LOCATION WITHIN THE SAMPLE TUBE. LOOSE MATERIAL INCREASED IN DENSITY AND DENSE MATERIAL DECREASED IN DENSITY DURING SAMPLING. CORRECTION FACTORS WERE DEVELOPED FOR BOTH OVERBURDENED PRESSURE AND LOCATION OF THE INCREMENT IN THE SAMPLE TUBE. DATA INDICATE THAT THE RELATIVE DENSITY OF FINE SAND ESTIMATED ON THE BASIS OF CONE PENETRATION RESISTANCE CAN BE VERIFIED WITHIN ABOUT 10 PERCENT BY THE COMPUTED RELATIVE DENSITY DETERMINED FROM AN UNDISTURBED SAMPLE. THE CONE IS SENSITIVE TO CHANGES OF RELATIVE DENSITY AND SHEAR RESISTANCE AND SHOULD BE CONSIDERED AN EFFECTIVE TOOL FOR ESTIMATING THE SHEAR RESISTANCE OF DEEP SAND DEPOSITS.