Arkansas Bridge Foundations. Field Investigation: Fid-Bau Portal

Arkansas Bridge Foundations. Field Investigation

S. I. Thornton / R. C. Welch

A bridge site investigation includes a preliminary investigation and a detailed site investigation. The preliminary investigation begins with an office review of aerial photographs, soil and geologic maps, and existing boring logs and includes a visual examination and/or geophysical survey of the site. The detailed investigation includes boring and sampling, field testing, or a combination of the two. Shelby tube samples may be obtained in clays of medium to stiff consistency, and fixed piston samplers may be used in clays from soft to very stiff consistency. Very soft, sensitive clays may be tested in-situ with the field vane shear apparatus. The Denison core barrel and Pitcher sampler are used to sample hard clays, cemented sands, and soil-gravel mixtures. Samples may be obtained from auger and rotary drilled holes. Auger borings may be used in clays of medium to stiff consistency and sand deposits above the water table. Rotary drilling methods may be used in all soils and rock except deposits of coarse gravel, boulders and cobbles, or permeable fractured rock. Hard to sample deposits of sand may be tested in-situ with the Dutch cone and Standard Penetration sounding methods. Intermixed soil and rock deposits may be tested in-situ with the Menard Pressuremeter. Rock layers are cored, usually by diamond drilling methods, to determine the soundness of the rock and whether the rock is thick enough to support the bridge foundation.