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Sweden 120

whlch wlrelessly transmits slgnals from the point to the ground surface.

Research work was 1n1tiated 1n 1973 wlthin the Committee on Penetration Testlng on the point reslstance and the frlctlon agalnst a separate s1eeve located immediately above the comcal point. In addltlon the standardlzation of the static soundlng method will be considered by the committee. Th1s research work 1s financlally supported by the Swedish Council for Buildlng Research.

Fig. 6

SGI Iskymeter. Pr1nc1p1e.

The js«kyinfcj£r (Kallstenius, 1961) is also a soundlng dev1ce with which the pull-out resls-tance of a reslstor 1s measured and continuously recorded (F1g. 6). The reslstor conslsts of foldable wlngs which first 1s driven 1nto the ground and then pulled out with a w1re ropę and a wlnch. The results can be used to determine the undralned shear strength of primarlly soft clay. The Iskymeter has been used relat1vely little the last few years. It has certaln advan-tages in comparlson with other types of pene-trometers, partlcularly 1n relat1vely thick clay deposits* sińce th1n sllt and sand layers 1n the clay can easlly be detected. Besldes the w1re ropę has a very Iow skin res1stance and pul ling requ1res no anchorlng. Due to the wlngs belng folded together when Installed 1n the ground the subsequent pul ling test can be per-formed 1n a relative1y undlsturbed soli.

Several mechanical unlts were developed around 1950. The Ą-sond (Sbkjer, 1961) 1s an example of mechanizatlórf of the Swedish welght soundlng method. The penetrometer is rotated by an electrically dr1ven motor. The number of half-turns is reglstered by a counter and the penetration depth can be read on a fixed scalę.

Heavy rock dr1111nq machines have been used sińce about 1950 for the determinatlon of the location of the rock surface. This investigation method is known as soil-roęk_sounding (Fig. 5e). Mhen casing 1s nofc~uśe3"tfiróugfi”Efie soli cover air is generałly used to remove the cuttings. The wash boring method can also be used. As a rule the borę hole is terminated when the penetration depth 1n the presumed bedrock 1$ at least 3 to 5 m. Otherwise a błock can be mistaken for bedrock. The soli-rock soundlng method has been studied by a special group withln the Committee on Penetration Testlng durlng the last two years. This group has proposed a provisional standard as well as improvements of the method which can be introduced step by step.

Light petrol driven rock drilling machines have also been used a few years for soi! penetration testing. The method is designated Hght_motor-B§Cęy§§l99-§9y™!!D9 (Fig- 5d).

Both light, medium as well as heavy penetration methods have thus been deve1oped due to the special geologlcal and topographical conditions in Sweden. The light methods (weight soundlng, pushr soundlng, light motor-percussion sounding) are especially useful in hilly and wooded terraln where 1t is difficult to transport the equ1pment. It has commonly been re-quested that one should be able to carry the equipment. The light methods are also advan-tageous in remote areas. Heavy methods (ram sounding, soil-rock soundlng) are required when the soli contains dense till, sand, gravel soils or fili.

The constructlon in Sweden is concentrated to areas covered by clay. Light equipment can thus often be used in the site investigations. The equipment is often truck-mounted and mechanized.

Economical aspects

A penetration test is usually terminated when the so called firm bottom has been reached. Firm bottom is a relative concept assoclated partly with the soundlng method belng used, partly with the actual problem. The required penetra-t1on depth will be different for polnt-bearing and for sheet plles than for stabillty calcula-tions where the deepest possible slip surface is of importance. If the penetrometer point has stopped on a stone or a boulder at moderate depths withln loose or soft soils or within a layer of dense or stlff soils which is under-lain by loose and soft soli one or morę addi-tional borę holes often will be required next to the first borę hole. Ali results should be reported, also those from the borę holes where refusal has been met re!atively close to the ground surface. The variation of the refusal