Strength of reinforced-concrete retaining walls

Abstract

Onsite observations of reinforced-concrete retaining structures in recent years in our country and abroad [1, I 1 ] show deviations in their behavior in comparison with the design premises and primarily intense cracking not predicted by the standards. In a number of eases this requires immediate conduction of costly repair works [2, I 1 ].Comprehensive research works on an analysis of the experience of the 40=year operation of hydraulic structures of the Moscow canal were performed in the research department of the All-Union Planning, Surveying, and Scientific-Research Institute (Gidroproekt). The work was carried out also with consideration of the forthcoming reconstruction of the canal related to the social development program of Moscow and specifying, in particular, the possibility of increasing the delivery of water into the canal for improving water supply.It was established during the works that one of the causes of the unfavorable character of cracking of the lock chamber walls was an increase of earth pressure above the calculated, pressure of the frozen layer of soil, especially in the spring, and also the insufficiency of longitudinal steel, and the absence of transverse steel on practically all lock walls. The Moscow canal management took measures in good time, which consisted in installing upper tie rods and pins [1, 2], which provided safe operation. Reinforcement of the walls by installing additional longitudinal and transverse steel is specified in connection with the forthcoming reconstruction for greater reliability and further long-term safe operation.For determining the scheme of reinforcement and the amount of steel, it was required to conduct specia~ theoretical and experimental investigations, since according to the existing standards transverse steel is not required; at the same time, the intense development of inclined cracks on the prototype structures shows the need for it. This is explained by the fact that in the standards [3] a method of calculation is used which is based on the results of tests of mainly beam elements~ However, its use for reinforced=concrete hydraulic structures clearly not of the "beam" type can lead in some eases to a decrease of reliability and in others to an overconsumption of steel.Unlike beams, retaining walls have: a more complex geometry, extremely low percentage of reinforcement, nonuniform effect of the loads, presence of transverse and longitudinal block joints, and presence of extended zones of structural reinforcement.In the "beam" method adopted in the building code SNiP the calculation reduces to finding an unfavorable inclined section, determining either the slope angle of this section or its projection. In this case, the critical crack is assumed rectilinear. In complex hydraulic structures failure cracks propagate, changing the slope angle from 90 ~ practically to 0", encompassing a considerable part of the structure. Failure cracks do not have a definite location of the mouth and, consequently, calculation of their projections loses physical si...

Stress-strain state of reinforced concrete structures of the LN-1 and LN-2 retaining walls of Zagorskaya PSPP taking into account the opening of interblock joints and the formation of secondary cracks

“…Для определения НДС подпорных стен ЛН-1 и ЛН-2 водоприемника Загорской ГАЭС разработаны математические конечно-элементные модели. При этом учтен отечественный и зарубежный опыт численных исследований подпорных стен и стен камер шлюзов [1][2][3][4][5][6][7][8][9][10][11][12][13].…”