In-service field observations on structures at the Hoa Binh hydroproject (Socialist Republic of Vietnam)

1. Data derived from field observations have confirmed correspondence between working parameters obtained for the basic structures and the results of analysis, model investigations, and basic positions taken in the design of the hydroproject. Results of analysis of the stress-strain state of the rock-and-earthfill dam are in satisfactory agreement with respect to the character of deformation development, the magnitude of bench and crest settlements, vertical displacements, the value of the structural settlement, and manifestation of the "hang-up" effect of the core with values measured during field observations. The decision concerning stepwise impoundment of the reservoir was a critical positive moment; this contributed to the creation of favorable conditions for development of the stress-strain state of the rock-and-earthfill dam. 2. Satisfactory agreement between data derived from field observations and the operating parameters estab lished in design for all anti-filtration measures in the basic structures of the hydroproject should be noted. 3. On the whole, results of field observations conducted during the period from 1983 through 1996 provide complete grounds for us to assume that operational requirements for the basic structures, which were assigned in design, have been fulfilled: operational reliability has been provided; and. the condition of the structures entering into the thrust front of the hydroproject is satisfactory. The measured parameters and performance indicators of the structures do not exceed the limiting allowable values representing the safe condition of the structures. 4. The formulation of observations and the installation of monitoring-measuring equipment has supported the solution of problems involving the technical diagnostics of basic structures of the hydroproject. In addition, it is possible to point out the insufficient number of pressure transducers along the front and in the foundation bed of the dam’s core, as well as measurement facilities for determination of the displacements and deformations of the contours in the working for the machine gallery. On evaluating the results of. and experienced gained with 14 years of field observations, their significant place in supporting reliable operation of the hydroproject should be noted.