6585844959

Penetration testing in Australia esopt

J.C. Holden State-of-the-art report

The report brlefly examlnes the Influence of geological condltions on the possible use of penetration testing In Australia and then analyses the actual effort currentty expended on penetration testing. The penetration tests performed In Australia -comprislng mainly S.P.T.'s, quasl-statlc cone penetration tests, and various other dynamie tests - are dlscussed In detali. Finally, some views are expressed on the trends and needs in the futurę development of penetration testing.

Bridge construction, which forms a signiflcant part of construction activity (see Appendlx ), Is mostly assoclated with streams and hence their alluvłal sediments. Except in a few cases where layers of large gravel are found, the quasi-static C.P.T. is Ideałly suited for these sltuatlons, especlally In the soft estuarlne deposlts that are formed by numerous rivers in th8 Coastal areas.

3. EFFORT EXPENDED ON PENETRATION TESTING

1. INTRODUCTION

To provide the factual data for this report, a survey was conducted among all organlsations In Australia that may have been performing foundation lnvestlgatlons. The questionnaire and a detalled analysis of the results from the que$tionnaire are presented in an expanded version of this report entltled “Current Status of Penetration Testing In Australia”(HOLDEN. 1974). The detalled report examlnes separately the practices of different groups of organisations-viz., boring contractor, commercial site investigator (i.e, foundation englneering consultant), government or semi-government, unlverslty or technlcal college, and other organlsations.

The questions related to only deep penetration tests. sińce shallow tests - I.e. less than about 1 m below ground surface, such as pocket penetrometer tests, Proctor Needle tests and surface probes • were considered to be beyond the scope of this symposlum. A penetration test is defined as a test In whlch a device - e.g. rod, penetrometer, sampler - is caused to penetrate the soli by any means - e.g. steady thrust, hammaring, screwing. vibration • and the resistance to penetration measured.

The terminology pertaining to the quasi-static cone penetration test (C.P.T.) used in thp questionnaire and in this report Is defined in the list of Deflnltlons from the proposed A.S.T.M. Tentatlve Standard Method for the Deep, Ouasl-Static. Cone Penetration Test (ref: SANGLERAT, 1972, Appendlx A).

2. GEOLOGICAL CONDITIONS

Penetration tests, especlally quasi-static tests, are severely llmlted in certain soils: detrital solls contalning large gravel or boulders. residua! soils contalning zones of parent rock In varying States of decompositlon, and highly-cemented solls. With the exception of gravels, whlch are extremely difficult todrill and test, these soils should be lnvestlgated, in the case of heavily-loaded structures, using diamond coring preferably In con)unctlon with pressuremeter tests. However, the Standard Penetration Test (S.P.T.) is often used In Australia In an attempt to gain an indicatlon of the properties of these soils • with dubious success.

A study of the Austraiian erwironment, outlined In the Appendix, glves a better appreclation of the geologlcal factors affecting the possible use of penetration tests in foundation lnvestłgations. The use of penetration tests In the major urban construction areas is somewhat restricted by the large proportion of sound rock at shallow depths underlying the three largest citfes -Sydney, Melbourne and Brisbane. However, the other two large clties are aimost entirely located on penetr-able soils: Adelaide on Ouaternary alluvium and colluvium; Perth on Ouaternary sands.

The most dominant soils in the three largest cities are the mostly-saturated, stiff residuaI solls, whlch require a large capacity thrust machinę for the quasi-static C.P.T.

3.1 Proportions ot Dłtferent tnvestlgatlon Methods

For typical subsurface foundation investlgations, the varlous methods are used In the following proportlons:-

(a) SamplIng and coring (direct methods) 65%

(b) In-situ testing (indirect methods) 28%

The proportion of indirect methods used In Australia (35%), although much smaller than the proportion of direct methods (65%), Is significantly hlgher than the proportion (24%) found in an International survey (AITCHISON, DOVER. and LANG, 1971).

Consultants use in-situ tests (38%) much morę than other major groups (c.f. Boring Contractors 15%: Govemment 25%; Academic 15%). Out of the 76 organlsations that conduct foundation lnvestlgatlons, only 6 (8%) do not use in-situ tests.

3.2 Proportion ot Penetration Testing

With one exception, all organisations that perform in-situ tests use penetration tests. A high proportion (71%) of in-situ testing effort is spent on penetration tests. The three major groups - boring contractors, consultants, and government - all have about the same divislon of effort. It is interesting to notę that one-fifth of all effort spent on foundation łnvestigations In Australia Is spent on penetration testing.

3.3 Proportions ot Different Penetration Tests

The great popularIty of the S.P.T. in Australia is evldenced by the fact that aimost every organisation (93%) that performs in-situ tests uses the S.P.T. By contrast, out of the 31 organisations (44% of in-situ testers) that use the quasl-static C.P.T., only hall (16) of them possess C.P.T. equlpment that is In use (see later).

Moreover, only 3% of foundation lnvestigatlon effort In Australia Is spent on the C.P.T. This appears very Iow when compared with Holland, where the proportion is be!ieved to exceed 90%. Obviously the different geologlcal condltions cannot entirely account for this vast difference. An explanatlon may be gleaned from the reasons given for the test's unsuitability, which are summarlsed as follows:-(I) highcosts,

(ii) lack of available equipment,

(III) other methods (e.g. the S.P.T.) are considered satisfactory,

(iv) limlted application due to geologlcal condltions,

(v) samples are required, and

(vi) lack of experlence.