Large-scale experimental investigations of failure of an embankment slope under dynamic loads

Abstract

Experimental collapsing of the slope of a 35-m embankment under the effect of seismic shooting was carried out at the construction site of the Nurek hydroelectric station for refining the characteristics of the mechanical properties of the soils.

Concerning the problem of the seismic stability of the Nurek dam

“…Contrary to the statements of the authors of [6], the standards [8-10] call for taking into account all components of seismic inertia loads (accelerations) actually acting on the structure, for example, when calculatingthem for an inclined (directed at angle 30 ~ to the horizon) seismic action; when determining two or three components of seismic accelerations of On the other hand, the authors of [6] conduct a physical experiment for determining the angle of shear @ and it is obvious that in this case all forces, including those due to horicontal accelerations, which exceed the horizontal by twofold, actually acting on the investigated object (experimental embankment) should be taken into account.…”

“…The authors of [6,7] conducted investigations to select "seismic actions of low probability," to determine the strength (shear strength) of the gravel-pebble materials of the dam shoulders, including on the basis of the data of large-scale tests, and also to select the designs and layout of antiseismic collars and evaluate the seismic stability of a reinforced dam.…”

“…To determine the shearing resistance (strength) of the gravel-pebble soils of the shoulders of the dam, large-scale failure tests were conducted at the construction site of the Nurek hydroelectric station by means of blasting an experimental embankment with a height of 35 m placed from these soils on the upstream slope within the design counter of the dam [6]. When determining the angles ~ by means of this equation a number of assumptions were made, according to which the duration of the vibrations excited by the explosions was considered sufficient for realization of shear and flattening of the slope to a state of stable equilibrium; cohension in the soil during large displacements caused by seismic actions is absent; when determining the angle ~ only the horizntal component acceleration ~h is taken into account (just as, according to the statement of the authors [7], in calculations of the seismic stability of the slopes of dams according to the standard SNiP [8]); with consideration of the two components of accelerations ~h and ~v the angle ~ is determined with the use of accelerograms.…”

“…However, the assumptions made in [6] are unfounded. Actually, the records of the accelerations of the experimental embankment (Fig.…”

“…Actually, the records of the accelerations of the experimental embankment (Fig. The method under consideration [6], in principle, is unsuitable for determining the total (with consideration of cohesion) shear strength of soils and cannot give any information about the presence or absense of cohesion in soils ("engagement" in coarse-fragmental materials), since the equation given above for determining the angle ~ does make possible a determination of the values of @ and c separately. The assumption that during large displacements caused by seismic actions, cohesion is absent in soils is incorrect and is not confirmed by the results of experiments.…”