AgdaPkt 2018-05-21 Joint SA PFA - Laserfiche WebLink

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353 Main Street Apartments Redwood City, California May 1, 2018 (Original Report Dated November L8,20L6) disturbed samples of granular soils were transferred to polythene bags to preserve their moisture. Bulk soil samples, were obtained from the auger cuttings. Selected soil samples were tested in our laboratory to measure moisture content and dry unit weight as they provide good indications of the other engineering properties of the soil. Atterberg Limits tests were performed to aid in the soil classification and as an indicator of the expansion potential of soils. The results of laboratory tests performed on soil samples collected from our borings are shown on the boring logs corresponding to the sampling depths. Undisturbed samples of softer and more sensitive clayey soils were taken using a 3.O-inch outside diameter thin walled (Shelby Tube) sampler. The Shelby Tube sampler was hydraulically pushed into the soil at specified locations. The samples were sealed and labeled as soon as they were collected and transported to the laboratory in an upright position with minimal disturbance. At the completion of drilling activities, the borings were backfilled with cement grout. Cone Penetration Test On August 30, 20L6, Middle Earth Geo Testing, lnc. (MEGT) performed a total of four CPT soundings throughout the site. The CPT soundings were performed with MEGT's 25 ton truck mounted CPT rig. The soundings were conducted in accordance with ASTM specifications and pushed to depths of 60 and 70 feet below the ground surface. A CPT involves pushing a standardized size instrument of a conical shape into the ground at a specified constant rate. The cone used for this project had a t¡p area of L0 cm2 and a friction sleeve area of 150 cm2. The cone was pushed into ground at a constant rate of 20-mm per second using the 25-ton truck as reaction weight. The cone was fitted with load cells, which recorded the total force acting on the cone (Qc), sleeve friction (F'), and pore pressure (u) readings at 5 cm depth intervals. The data collected from the CPT was used to interpret site stratigraphy, soil consistency, and strength using published relationships. Generally, cohesive soils (clays) have high friction ratios (sleeve friction divided by cone bearing - Rr), low cone bearing, and generate large excess pore water pressures. Cohesionless soils (sands) have lower friction ratios, high cone bearing, and generate little in the way of excess pore water pressures. The CPT data collected from the site is presented in Appendix A. Subsurface Profile The soil borings revealed the presence of approximately 6.5 feet of fill material overlying Bay Mud. The fill material consisted of a random mixture of lean and fat clays, with variable amounts of sand and gravel. The fill was generally stiff with moisture content ranging from L3 to 24 percent. Below the fill material, bluish gray, soft Bay Mud was encountered to depths ranging 4301842-001 1610-038.SER.REV2 7.B. - Page 62