A MATHEMATICAL MODEL FOR MONITORING THE ROCK-EARTHEN DAM OF THE HOA BINH HYDRAULIC POWER SYSTEM

摘要

The Hoa Binh hydraulic power system (Fig. 1) of power 1920 MW erected on the Da river (Socialist Republic of Vietnam) in cooperation with the USSR is the largest hydraulic engineering object in South-East Asia. The hydraulic power system (HPS) is composed of a rock-earthen dam with a central core (material ― gritty-clay) and side retaining prisms (unsorted rock mass). The dam core is flanked on both sides by transition sections that connected it to the retaining prisms. The material of one of the prisms (nearer to the core) was alluvial sandy gravel, and the other one ― pit gravel. The top height of the dam is 128 m, the crest length ― 600 m, and the crest width ― 20 m. The core foundation width is 50 m, and the core crest width ― 10 m. The axis of the dam has an arch-like profile; the forebay bending radius is 350 m. The upstream slope ratio in the upper part of the dam is 1:2.75, and in the lower part ― 1:4.5. The downstream slope ratio varies from 1:1.75 to 1:3. The dam was erected in a U-shaped valley with bank slopes varying from 20 to 40°. The dam foundation at the river bed has an over-deepening of 50 - 60 m filled with gravel-and-pebble deposits; the abutments are underlain by massive rocks. The dam on its left side is adjacent to a spillway. In the core zone, the unconsolidated deposits in the overdeepening were grouted, through an array of special holes drilled to a depth of 80 m, with clay-cement and clay-silicate mortars to produce a screen. The massive rocks at the foundation and abutments were reinforced by grouting. Standard physicomechanical properties of materials of the foundation and the body of the dam are summarized in Table 1.