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universal, practlce 1n the U.S.A. We now also have the beglnnlngs of a generał awareness, due 1n part to research at the Un1versity of Florlda (SCHMERTMANN, 1971), that N-values must be cor-rected for the effects of vary1ng lateral pres-sure. The Waterways Exper1ment Statlon, Vicksburg, Mississippi, now has an act1ve program of fuli scalę research to 1nvestigate further the effects of stress and relative denslty on SPT data In sands.

Most of the publlshed SPT-design correlations have as thelr basis the accumulation of emplrlcal data. Many public soli englneering organlzations and pr1vate companies have performed in-house SPT research of an emplrlcal and local signi-flcance — the results from which are unpubllshed and often proprletory. Theoretlcal work to per-mit broadening the signlflcance of emplrical research has been almost absent.

De MELLO (1971) madę a noble attempt at a theoretlcal study of the SPT, but achieved limited success. SCHMERTMANN (1971) demonstrated a useful theoretlcal connectlon between the SPT and CPT. Any theoretlcal study of soli proper-tles and $he SPT must eva1uate the anx>unt of energy that actually reaches the sampler. The use of the wave equat1on prov1des some inslght. The Un1versity of Florlda has a research project underway to measure insi tu the energy that typ1-cally arr1ves at the sampler during routine SPT work.

The most dramatlc new SPT equipment development In recent years 1nvolves the increaslng use of continuous flight, holIow stem augers to advance the SPT hole. The operator performs the SPT Insi de the hol Iow auger stem after first re-moving the metal pług that seals the stem of the bottom flight. Such equ1pment eliminates the need for casing or drilHng mud, but may create water pressure problems.

3. OUASI-STATIC DUTCH CONE PENETRATION TEST (CPT)

3.1 Use in Practice

Anoter reason for the popularity of the SPT 1n-volves a generał łąck of an economical and ac-ceptable alternative method for s1te 1nvesti-gation and preliminarz design. Only in the past few years has the CPT become availabie in some parts of the U.S.A. to provide the engineer with a posslble suitable altemat1ve or supplement.

At present there are about 20 deep CPT sounding units operating In the U.S.A.; 5 at universities, 5 with government organlzations, and 10 with englneering consultants. Florlda represents the most active center with one 20-ton machinę and 4 10-ton raachlnes of Goudsche Machinefabriek manufacture in the State. At present approxi-mately another 20 organlzations have begun ob-tainlng CPT capability by uslng an adapter ar-rangement 1n conjunction with the hydraulic feed system on thelr SPT drill r1gs. This arrange-ment g1ves the engineer limited CPT (typlcally 2-4 tons thrust) capability in additlon to the normal r1g capability and still allows him to send out only one piece of equ1pment to do the job. The rapld expansion In U.S.A. CPT capabi-11 ty in the past two years demonstrates a rapld

and continulng growth in Interest 1n this form of penetratlon testlng.

Almost all the commercial CPT equipment in the U.S.A. uses the mechanical mantle and Begemann frlction-cone tips manufactured in Holland.

Fugro California, Inc. uses electrlcal tips.

Although used for a wlde variety of purposes, especially by the few englneers who have ex-perience with the CPT methods, the present most cormon use of the CPT In the U.S.A. 1s to ex-plore the stratigraphy, unlformlty and englneering characteristics of cohesionless soli.

3.2    Research

To datę CPT research 1n the U.S.A. has centered at the Un1versity of Florlda. However, the Universities of Kentucky, Massachusetts,

Michigan and Misslssippi are also act1ve.

Projects under study at these un1versities 1n-clude methods for evaluat1ng the s1de frlction capacity of piles, the effect of Insi tu lateral stresses on the CPT, the effect of the shape of the penetrometer tip on the CPT, uslng the fric-tion-cone to estimate shear strength parameters 1n c-0 soils, and the prediction of relative density and Hquefact1on potential 1n saturated f1ne sands from CPT data.

3.3    ASTM Standard

Currently ASTM conmlttee D18.02.06 1s in the finał stages of preparing a Standard, which will likely be published in 1-2 years. A prellminary version of this Standard has already been publlshed by SANGLERAT (1972), although the finał vers1on will be less restrictive.

4. REFERENCES

de MELLO, F. B. (1971)

The Standard Penetratlon Test Proc. 4th PanAm Conf. SMFE,

Puerto Rico, Vol. 1, pp 1-86

FLETCHER, G. F. A. (1965)

Standard penetratlon test:    its uses and abuses

Proc. A.S.C.E., Vol. 91, No. SM4, p. 67

GIBBS, H. J. & ROLTZ, W. G. (1957)

Research on determining the denslty of sand by spoon penetratlon testlng.

Proc. 4th ICSM&FE, Vol. 1, p. 35

MOHR, H. A. (1966)

Discussion of FLETCHER (1965)

Vol. 92, SM1, pp 196-199

PECK, R, HANSON W. & THORNBURN, T. (1974) Foundation Englneering, 2nd Edition John Wiley & Sons, New York

SCHMERTMANN, J. H. (1971)

Discussion of deMELLO (1971)

Vol. III, pp 90-98

SCHMERTMANN, J. H. (1972)

Discussion

Proc. A. S. C. E., Vol. 97, SM9, pp 430-3

WOODS, K., MILES, R. AND L0VELL, C. Jr. (1962) Foundation Eng., Chapt. 1, McGraw-Hill, N. Y.