6585844922

ESOPT

State-of-the-art report

Penetration testing in Spain

V. Escario

1. INFLUENCE OF GEOLOGICAL CONDITIONS . ON THE USE OF PENETROMETERS.

From a geological point of view our country is traditionally divided in three main units: the "si-llceous Spain”, the "calcareous Spain” and the "clayey Spain”.

The ”siliceou8 Spain” comprises most of the Pa-leozoic levels as well as the eruptive and meta-morphic rocks of other ages. It covers a wide area of the Peninsula and obviously is constituted by materials generally speaking not interesting from the point of viewof this report, even though soft and unstable soils presenting special pro-blems may be present.

The so called "calcareous Spain” which also co -vers an extensive zonę of our country constituted by Mesozoic formations, contains mainly limes -tonelike materials which are not either interes -ting for us in this case.

The "clayey Spain” mainly formed by Cenozoic sediments is also widely spread in the country.

It covers the well known "Meseta Castellana” (plains of Castille) and the depressions of rivers Gudalquivir and Ebro. But also here, generally speaking, the soils are rather stiff and inadequa-te for penetration testing.

Spread over the above mentioned zonę a, the Qua-ternary deposits are present: river valleys, lito* rai zones, etc. These deposits cover only a smali percentage of the surface of the Peninsula but they are important from the foundations point of view, sińce our coasts are very long and our fluvial net is extensive. It is true that in many cases they are Consolidated or constituted by materials inadeąuate for penetration testing purpo-ses, like the widespread gravelly terraces of our river8, but in other places we find soft or loose deposits and even marshea, where important work9 have to be madę.

After this generał view of our country it seems reasonable to expectthat dynamie penetration tests be morę popular than static ones, sińce in soli surveys most often both soft and hard soils have to be penetrated, and the presence of coar* se particles may preclude the use of static penetration tests in many cases.

Nevertheless, as the quantitative interpretation of static tests in usually morę reliable than that of dynamie, Engineers arc getting morę interos-ted in them and they are being today rather ex -tensively used.

2. TYPES OF PENETROMETERS USED.

By cronological order the penetrometers used in Spain are the following:

a) Penetration tests (dynamie on the casing)

used by the "Servicio Geoldgico de Obras Publicas”.

b) Standard Penetration Test (SPT).

c) Dutch cone test.

d) Continuous dynamie test.

e) Other types like the Stump penetration

test, some manuał dynamie penetration test, etc.

Actually only types b, c and d may be conside-red as representative of a generalized present practice in our country and we will concentrate on them.

2.1. Standard Penetration TestJSPT). - The SPT is performed following morę or less the accepted International practice that, as it is known, is not completely standardized.

The sampler has the dimensions given in Terra-ghi-Peck's book which coincide practically with ASTM D 1586-67. Very often nevertheless, it is provided with an inner metallic liner to recover the sample, which is sent to the laboratory eon-veniently sealed, as if it were an undisturbed sample; this is very useful because, even though the sample is obviously disturbed, it keeps not only the moisture content but also the generał structure and grain size distribution of the different layers actually penetrated.

For gravelly soils a solid cone is screwed to the bottom of the sampler instead of the shoe;the angle of this cone is of 60? and the blow count,

N, is carried out in the same way as with the standard device.

The sampler is introduced with a hammer 63, 5 kg. falling 76 cm. height and the number of blows necessary to introduce it 30 cm. are re-corded as number N, after an initial penetration of 15 cm. which is not considered. Most often the hammer blows are applied by means of a ropę held by friction to a cat-head driven by a motor. The diameter of this cat-head varies from 12 to 30 cm. according to the different ans-wers we have received to our questionaire. Some companies in some cases use a free fali device, automatic or not, without applying any N correc-tion factor due to this possible source of differen-ces.

Neither the diameter of the rods used for the test nor the maximum depth to be reached without an excessive loss of energy are standardized in our country. To tackle with this problem the Spanish Rodio Company (Cimentaciones Espe-ciales,S.A.) has under experimentation a device for automatic application of the blows directly on the head of the SPT at any depth.lt is a watęr-

tight device to be used with cable type percusion machines.