Experience in studying technogenic unloading in construction pits

Conclusions

• 1. The thickness and character of the technogenic unloading zone depend on the degree of jointing and crushing of the mass, its weathering, depth of excavating the pit, and blasting method.

• 2. A study of the character and thickness of the technogenic unloading zone formed during excavation of pits in rock foundations of hydraulic structures is carried out with the use of geological and geophysical methods.

• 3. The results of studying technogenic unloading made it possible: to regionalize the foundation according to the degree of unloading and jointing of the rocks; to construct a model of jointing with unloading zones characterizing various parts of the mass and serving as the basis for calculating the stability of rock slopes and foundations of concrete structures; to refine the contours of the cut for concrete structures at the site of the Krapivinskii hydropower project; to develop stabilization measures (anchoring of the pit sides), which saved 400,000 rubles (Dnepr-II).

The results of the investigations are being used for refining the parameters of contact grouting and the grout curtain, siting drainage structures, and installing monitoring equipment in the rock foundation of concrete structures.