SURVEYING OF SOILS AND/OR WEATHERED LEVELS ABOVE THE ROCK LINE

ERKUNDUNG VON LOCKERBOEDEN BZW. VERWITTERUNGSHORIZONTEN UEBER DER FELSLINIE

AS THE DIFFERENCE IN THE COST OF ROAD PROJECTS, WHICH DEPENDS ON WHETHER ROCKY OR RESIDUAL SOILS ARE INVOLVED, GREATLY AFFECTS THE ACCOUNTS, IT IS DESIRABLE TO MAKE AN ACCURATE ASSESSMENT OF THE ROCK LINE BELOW SOIL OR RESIDUAL LEVELS. BORED SAMPLES OFTEN DO NOT PROVIDE THE INFORMATION REQUIRED. SEISMIC TECHNIQUES CAN BE SUCCESSFULLY APPLIED IF THE ROCK LINE FORMS THE BOUNDARY BETWEEN STONES HAVING A NOTICEABLE DIFFERENCE IN SOUND VELOCITIES. LAYERS OF RESIDUAL SOIL HOWEVER GRADUALLY CHANGE INTO ROCK, AND THE SOUND VELOCITY INCREASES CORRESPONDINGLY. TRAVEL TIME CURVES ARE OBTAINED INSTEAD OF TRAVEL TIME STRAIGHTS. FROM COMPARISONS OF NUMEROUS MEASUREMENTS MADE BEFORE THE START OF CONSTRUCTION, BOTH ON CUTTINGS AND ON CUT-AND-FILL, AND FROM EVALUATIONS OF THE POSITION OF THE ROCK LINE DURING CONSTRUCTION IN A TRADITIONAL MANNER, THE DEPTH OF THE ROCK LINES MAY BE DETERMINED EMPIRICALLY FROM THE TRAVEL TIME CURVES OBTAINED DURING THE SEISMIC MEASUREMENTS. DURING THE EXECUTION OF THE SEISMIC MEASUREMENTS, EMPHASIS SHOULD BE PLACED NOT ONLY ON THE SEEKING OF THE ROCK LINE, BUT ALSO ON THE STUDY OF THE CONDITION OF THE WEATHERING CRUST ITSELF WITH RESPECT TO CLASSIFICATION INTO SOIL CLASSES, PROPORTION OF STONES, POSITION OF THE SLOPE, ETC. EFFORTS ARE ALSO BEING MADE TO REDUCE THE COSTS OF THE STUDY AND ACCELERATE THE WORK IN ORDER TO BRING ABOUT AN IMPROVEMENT OVER CONVENTIONAL METHODS OF EXAMINATION.