Discussion of construction norms: Earth pressure on lock chamber walls

Abstract

1. Upward deflections of lock chambers in winter (observed everywhere) are the principal cause of additional earth pressure, which considerably increases the active earth pressure according to Kulon. 2. An analysis of lock operations under wintertime conditions shows that standard requirements [11] should be revised to account for chambers undergoing repair, since the calculated load on the wall has increased to passive pressure as determined by Eq. (1) with respect to wall friction. The angle of friction should be considered in accordance with the observed data at 2–5° less than the angle of internal earth friction. 3. The direction of overall resultant earth pressure on the wall as the chamber tends to rise coincides with the direction of the active earth pressure, exceeding it by 2–3 times. 4. The increase in earth pressure on the chamber walls as noted from soil dynamometer readings is, to a considerable extent, compensated for by friction along their rear faces. This causes stresses in calculated cross sections of the walls to increase slightly, but the load on the bottom increases correspondingly, which conforms to the observed data. 5. For unloaded lock chambers (and for wide chambers, dry docks, for example) it is difficult to ensure a standard safety factor against floating. A calculation of passive pressure by Eq. (1) solves this problem and permits one to obtain additional savings from a decrease in the amount of concrete in the chambers and from a more simplified drainage system. 6. Calculation methods for lock chambers constructed as docks, allowing for deformations in the wall and bottom, and earth friction resistance along the rear faces of the walls, gave earth pressure values close to the actual.