Laserfiche WebLink
NI <br /> y fMW <br /> '" . <br /> 1, <br /> f <br /> 3 <br /> i <br /> 1 <br /> f I <br /> Ij <br /> 7f � <br /> The above measurements are made continuously,while the probe is being pushed into the € 1 <br /> soil at a constarr penetration rate of 2 cm/sec (0.8 In/sec). The pushing is interrupted j <br /> at 1-m (3.3-fi) intervals to enable new sections of pipe to be attached to the top of the <br /> string. <br /> As shown in Figure 2, two built-in load cells with bonded strain gauges are used ;o <br /> measure tha cone tip and friction sleeve rasistances. A steady excitation voltage is <br /> supplied to the strain gauges by means of P.n electric cable which is strung through the „ <br /> - push pipes. Till-Is strain gauges return an output signal tin millivolts), according to the � <br /> magiftude of the load cell deformation. The output signal is amplified and oonvortod to <br /> digital data in units of force (tans). { <br /> - r <br /> For this investigation, eloctric friction cones with 15-ton capacity load cells were t a <br /> used. The load cell configuration is the "subtraction type% in which the bottom load <br /> a"measures the cone tip resistance and the top load cell measures the combined tip and <br /> sleeve resistances. Both load cells are loaded in compression. The net sleeve resin ance ; <br /> value is obtained by subtracting the bottom load cell measurement from the top load cell { <br /> _ measurement. This subtraction is performed automatically by the computerized data, <br /> _- acquisition system. <br /> The inclination of the probe was measured with a built-in tilt sensor to monitor the <br /> verticality of the penetration. <br /> _ I <br /> The pore water pressure measurement is made by means of a filter and pressure tra,I==r <br /> assembly which is also built into the probe. <br /> 2.1.2 Piezometric CPT Measurements <br /> The piezometric CPT option can be used to measure pore water pressure, which enables <br /> evaluation of groundwater conditions as well as deriving additional stratigraphic <br /> information. <br /> Piezometric CPT testing is performed using a piozacone (or 4-channel cone), .which is an . <br /> electric friction cone equipped with a filter and fluid pressure transducer, such as shown <br /> in Figure 2. The maximum caracity of the transducer is 500 psig (36 tons/ft2 above <br /> I. <br /> b <br /> I <br /> � I <br /> u <br />