Page - 1413 - in Book of Full Papers - Symposium Hydro Engineering

5.1. PROCEDURE IN-SITU TESTS Plate load test aims to determine the elasticity modulus of the bed with regards to: Es=qB(1-υ2)lw/∆ and other geotechnical properties such as the Poisson ratio of the bed, internal friction angle and cohesion values, as a control test and in order to find out anomalies in pressure meter tests. To attain this objective and perform the test, a number of pits have been tested in different locations and points including the spillway slope, based on the lithological and geological changes of test places in the right and left abutments of the spillway, so that the results are controlled in a number of aspects. The plate loading test of the soil has been carried out in ASTM-D 1159 method. Steel plates of 30 and 50 cm diameters and a hydraulic jack to implement the load have been used in the tests. At least 3 gauges of 0.01 mm sensitivity have also been used for measurement of plate settlement. The considered tests have been carried out as cyclic loading, in three consecutive cycles, in accordance with the above-mentioned test method. Table 3 shows the plate loading test results and maximum settlement (St), modulus of elasticity and mean Poisson ratio in the concerned layer have been also been provided for the maximum stress implemented in each cycle, at the end of each phase of loading and unloading cycle. A considerable point in this regard is the fact that the bed reaction modulus is not a fixed number for the soil and varies due to following the plate diameter and stress. It can be considered equal to the above-mentioned values, considering an appropriate safety factor in the foundation and superstructure calculations. Delineating the stress-strain curve and calculating total settlement and the residual settlement (in zero bar), elastic settlement at each phase of loading has been obtained. Then the maximum stress diagram of each loading cycle against its corresponding elastic settlement has been delineated. Elastic sub grade reaction (CU) of the soil has been calculated from the delineated diagram. Thus, based on the test, the CU has been calculated from the following relationship: Cu = q/Se (kg/cm3) In this regard, more investigations carried out by Barkan shown that Cu is a function of the load plate area. So that, if Cul and Cu2 are steady elastic pressure factors for the mats with Al and A2 contact areas, respectively, then the following relationship would be applicable: Cu2 = Cu1√(A1/A2) But here, the objective of the test has been controlling the values of the elasticity modulus obtained from the pressure meter tests in the concerned levels. In the plate loading tests carried out, the values of this parameter in 7 cases out of the 8 tests having been carried out, have been calculated and their first rates have been provided (in test PLT-2 and in the dry state, it has been rejected as the 1413