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Spain

The boring is usually madę by percussion or rota-ry drilling. If casing is necessary, no spccial restrictions are taken concerning the diameters and they are selected according to the generał boring needs, such as depth to be rcached and the -refore number o£ telescoping changes, typc and diameter of the undisturbed samples to be recove-red. etc., without taking into account the fact that SPT tests will be performed. Neverthcss the usual rangę of diameters falls within the limits given by ASTM D 1586 (57, 2 and 152 mm ).

When the boring is performed in submcrgcd non-cohesive soils, in order to avoid piping at the bot-tom, a permanent watcr head is mantaincd insi -de the casing. Only in special cases a bentonite slurry is used. The operations for extracting the boring tools are performed as slowly as possible, specially when cleaning up at the depth whcre the SPT is to be run, and the bailers uscd are often specified to have a smali diameter as compared to the one of the hole, in order to avoid any suc-tion effect to the sand.

Sometimes instead of using the typical rotary drilling, helical augers with a hollow core are used and the SPT is performed at given dcpths aftcr extracting the bottom pług.

2.2. Dutch cone test. - The static or Dutch conc test is carried out in Spain in a similar way as abroad . The cone has a 609 angle and 10 cm^{1 2} ba-se area. Either the simple cone or the Begcman type with a friction mantle usually 13 cm. long are used.

The cone is pushed down at a speed of 2 cm/sec. At each given depth, the point resistancc for a penetration of 4 cm is first measured; then the friction mantle plus cone resistancc for a further 4 cm. penetration; afterwards the total lateral resistance of the rods is taken; finally, the cone plus total lateral resistance is measured. The last two operations are carried out for lengths of penetration which vary for different jobs or uscrs and in certain cases some of them may be missed

Some Consultants like running a few Dutch cone tests close to borings where undisturbed sampling or SPT are performed, to get some correlation for the particular site being investigated; in that way a morę realistic interpretation can be obtai-ned for other points where only cone tests or borings are madę.

The eąuipment available in Spain is of the usual type where the cone is moved by a rod located in-side another hollow one. Both rods are pushed down hydraulically and the forces applied measured by means of manometers. Later in this Report we will comment some of the drawbacks of this system.

The machines are usually of 10 to 12 Tn. capaci-ty. There are several types. Some of them have

to be transported by truck or other means and the reaction provided by anchors screwed to the ground or by providing some kind of deadweight. As the time and cost of this operation is an im-portant part of the overall test, it is getting morę common having truck or trailer mounted machines. In fig. 1 one of the latest models madę in Spain is shown. As it is seen the back of the truck is raised by fixed hydrauiic jacks, the screws for the anchorage are forced down in the ground mechanically by the same motor provided to the machinę. With that motor, besides the cone test, rotary drilling may be performed at a distancc of 30 cm. from the loeus of the cone. Al80 hollow helical auger holes can be madę. Undisturbed samples and SPT may be obtained fran the borings with the eąuipment provided in the truck.

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Fig. 1. - Truck mounted eąuipment for running static cone and SPT tests and boring and sampling operations.

1

With portablc machines of this type a very fast survey can be madę, sińce they are easily instal-led and operated and practically all types of samples can be recovered and in situ tests performed.

2

3. Continuous dynamie penetration test. - This test is the Borro's type penetration test. It is run with a light derrick to hammer down a rod with a special point in the ground. The energy is supplied by an engine 5 to 7 H. P. The Steel point of 4 x 4 cm2 cross section, is 20 cm long and is finished with a pyramid of 909 apex angle.