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State-of-the-art report

Penetration testing in Israel

A. Komornik

The most common type of penetration testing used in Israel is the SPT method as standardized by ASTM Designation D-1586-67, Studies have shown need of ensuring free hammer fali of the proper height, with minimum friction. A special trigger roechanism was developed for this purpose. The SPT method is ordinarily used only in sandy materials. Occasionally the Dutch Cone Penetrometer is employed for special cases in softer strata. The SPT results in sands are interpreted, with allowance for overburden pressure, to estimate re-lative density. Correlations with fric-tion angle, raodulus of subgrade reaction, and qgasi-modulus of elasticity have been used for design. The SPT is sometimes used for construction control.

GEOLOGICAL CONDITIONS

The Land of Israel contains a large number of regions and subregions. The country has a Mediterranean climate, characterized by a sharp seasonal division between a rainy winter and a totally dry summer, hilly topography, rock foundations, in which limestones and ch41ks predorainate. Three lengthwise strips, running north-south may be considered, consisting of the Coastal Plain, the Hill Regions, and the Rift. In the north, the Galilean Coastal Plain is covered by alluvial soil.

A swelling clay, high in montmorillonite, predominates in the Iow areas away from the seashore. In some narrow ridges pa-rallel to the seashore, the uppermost se-diraents are sands and calcareous shelly sandstones, known by the local narae "Kur-kar". Sand dunes, Kurkars, and alluvial clays are found along the Coastal Plain throughout the center of the country and further south through the Camel, Sharon and Plesha (Philistea) plains. The Hill Regions in the north are characterized by marinę carbonate sediments:    limestone,

dolomites, chalks and marls, with a soil cover of highly plastic clay developed from the parent rocks. In the south the Hill regions of the Negev differ from the Galilee in their climate and desert topo-graphy. The deepest exposed strata con-sist of marinę marls, shales and lime-stones, overlain by Nubian sandstonę, hard dolomite and limestones, chalks, flints, phosphates, and shales. Locally these are overlain by Pleistocene loess. The loess ranges from sandier deposits in the south, particularly in wadi areas, to clayey loess materials closer to the center of the country. Along the eastern border of Israel is found the Jordan - Dead Sea -Arava depression, which is part of the great African Rift Valley system. Faul-ting in this zonę was followed by volca-nism in the northern portion, producing basaltic flows. Decomposition of the ex-posed basalt produced highly plastic clays at the surface.

Wind transported materials, including sand, silt and clay, were drifted generally from the south to the north. As a result, the larger sizes were deposited in the Sinai area and the Negev while the finer sizes were carried morę to the north. Winds and shore currents accumulated sandy materials along the coastal plain, where sand dunes are predorainant, often covering clay sediments. In the mountainous regions, erosion exposed the hard calcareous rocks and produced accumulations of clayey soils in the vallyes.

Along the coast, and in mountainous or desert regions, the deposits of granular materials are often naturally found in a dense condition . Occasionally upper lay-ers of loose dure sand may be encoun-tered. However, strata of soft clays, peats and silts are found in locations of river outlets, and along the Rift Valley where the remains of previous lakes are found.

Typical locations where the soil is soft enough to be suitable for static penetrometer testing include Haifa Bay, The Hula Basin, Lakę Tiberias, and the Dead Sea.

PENETROMETERS USED

The Standard Penetration Test (SPT) as deseribed by Terzaghi and Peck (1974) is used extensively in site investigations wherever sandy layers are encountered.

It allows evaluation of the relative density of the layer tested and provides a means of sampling sandy materials. It has been found to be a useful tool in su-pervision of earth fili compaction, es-pecially under water. In some areas, the SPT has been helpful in evaluating the strengfch. In some cases the test has re-sulted in discovery of open voids or loose thin sand layers between sandstone plates, which otherwise could not have been de-tected. The SPT equipment has been de-veloped in generał accordance with A.S.T.M. Designation D-1586-67. A split spoon sampler is used, having an internal diameter of 1 3/8 in )3.5 cm) and an outer diameter of 2 in (5 cm). The length of the split part of the spoon is 24 in (64 cm) and has a Steel driven shoe on one end and threaded connections to the wash or drilling rods on its other end. A spring retainer is always used in the driving shoe to insure that samples are always obtained. A Steel bali is seated at the top of the sampler in order to prevent water pressure from pushing the samples out of the tubę when retrie-ving samples from below water table.

The driving weight of 140 lbs (63.5 kg) is arranged as a hollow cylinder sliding freely on a guide pipę and haramering on a driving head connected to the drilling rods. Until four years ago, the height of fali of 30 in (76 cm) was marked on the guiding rods and the weight was lif-ted by means of a manila ropę wrapped about two turns around a winch head and a ropę passing over a well lubricated sheave, supported on a tripod. This