Earth pressure on lock chamber walls during construction

Actual observations of earth pressure on retaining walls and laboratory experiments in fl,-,es show that the pressure and its redistribution over the height depend on kinematic displacements caused by external forces and deformation of flexible retaining walls. Consideration of these factors in a theoretical determination of earth pressure on retaining walls is complicated by the fact that depending on its working conditions the backfill is in a state of inhomogeneous stress and it8 physical and mechanical properties are characterized by nonlinear dependences. In connection with this a number of suggestions have appeared in which the properties of soil to change the pressure on retainlng walls during their yielding and deformation are taken into account. The suggestions of G. K. Klein, N. K. Snitko, A. Ya. Budln, G. Ao Dubrov, A. K. Bugrov, V. F. Rayuk, I. K. Semarln, and others are most known. The indlcatedmethods are of practical interest and permSt more reliable calculations, but they are not sufficiently universal. Therefore the development of universal methods of detemlnlng earth pressure on retaining walls is quite important.Engineering methods of the deformation theory of small elastoplastlc deformations [1] can serve as the basis of creating such methods for a wide range of backfill soils. In combination with the flnite-element method (FEM) these methods permit Investlgating the behavior of a retaining structure comprehensively at various stages of construction and operation. In this case the scheme of "instantaneous" construction of the structure, which should be calculated by the method of variable parameters of elasticity (MVP), corresponds to the operating period. The use of the successive loadlngmethod (SLM) permits modeling the conditions of layer-by-layer construction of the structure.The choice of the FEM as the numerical tool for solving the stated problem is explained by its broad possibilities for taking into account the shape of the structure, loads actlng on it, real properties of soils (inhomogeneity, anlsotropy, nonlinearity, etc.), character of constructing the structure, kinematic conditions of its work, and a nmnber of other factors.In the present work calculation of the "structure-soil" system is replaced by an investigation of the interaction of a linearly elastic rough retaining wall contacting a physically nonllnearly deformable (elastoplastic) sol1 medlmn through a l~yer of special one-dlmensional contact elements corresponding to P. L. Pasternak's two-paremeter model of a foundation and simulatlng friction between the wall and backfill [2,3].Taking into account that the solution is obtained on a B~SM-4 computer with the use of magnetic droms, we regard the "structure-soil" system as a set of individual substructures: wall--hypothetlcal foundation-calculated backfill region.Two types of the problem being solved are possible: "instantaneous" or "layerwlse" construction of the wall and backfill. In the calculation scheme the backfill region having height H and length L = 4H is appro...

supporting

confidence: 75%

Effect of displacements of a retaining wall on parameters of the lateral earth pressure diagram

Rudykh¹

1979

“…It was hypothesized [3] that the main cause of this was the presence in the lower part of the fill of a small zone of weakly compacted soil which on flooding caused additional deformations in the overlying backfill. However, in addition to this, the distribution of lateral pressure on walls is affected considerably by nonuniform deformations of the backfill, determined by the technology and quality of placing the soil.…”

Section: Investigations Of Earth Pressure On Walls Of Structuresmentioning

confidence: 99%

Use of the method of centrifugal modeling in investigations of hydraulic structures

Vutsel¹,

Oskolkov²,

Щербина³

1973

Self Cite

Investigations of the bearing capacity of foundations, earth pressure on walls, slope stability and others carried out on conventional models with real soil have an essential shortcoming: the stresses from the structure dead load are many times less than in nature. At the same time, as investigations show, the physical and mechanical properties of many soils (deformability, dilatancy, strength, etc.) change depending both on the magnitude and character of stresses and on the history of stresses. Therefore, model investigations with small loads produce only a qualitative picture of the phenomenon in most cases.Broader opportunities are offered by the use of the method of centrifugal modeling which permits obtaining not only qualitative but also in many cases quantitative evaluations of the working conditions of a structure. The main virtue of the centrifugal modeling method is that stresses close to natural can be created in the model. This is of great importance in cases when the dead weight factor is determining for the operation of a structure (earth dams, retaining wails, soil slopes, etc.). Such investigations are being carried out in the research department of the S. Ya. Zhuk State Planning, Surveying. and Research Institute (Gidroproekt) on a large centrifugal stand which, technically is among the most modern machines. The maximum acceleration which can be created on this machine at a speed of rotation of 340 rpm is 322 g. The hydraulic system of the centrifuge allows filling the model with water and draining it during the experiment and transmitting an additional horizontal shearing force of up to 10 tons to the model by means of jacks.The design of the centrifuge machine is shown in Fig. 1, its main elements being: a rotating arm with two detachable carriages in which the invesitgated modeis are placed, a verticaI shaft, lower support, reducing gear changing the direction of rotation, and a drive.The carriages of the centrifuge weigh 800 kg each. Their inside dimensions, which determine the dimensions of the investigated model, are: length 900 ram, width 400 mm, and height 400 ram. The side walls of the carriages have glass planes for observing deformations of the model by means of television or motion-picture apparatus. Two hydraulic jacks producing horizontal shear in the model are installed in the end walls of the carriages.Measurement System. The problem of transmitting information is most complex in investigations on the centrifuge. First, the measuring instrument located on the model is subjected to the same accelerations as the model and, second, the signal from the transmitter to the recorder passes through the rotating system of the current collector, creating additional varying errors in the circuit. Therefore, special measuring apparatus was developed in the research department for investigations in a centrifugal force field.A special set of instruments was created for measuring deformations of the models. This set includes 12 twocomponent deformation sensors, amplification unit, switchboard, f...

Determination of the additional earth pressure on the chamber walls of twin locks

Moshkov¹

1983

Prior to 1964 differences did not exist in a determination of the loads on single-lane and twin locks. It was considered that each lane operated independently if the width of the space between the locks exceeded the double width of the sliding wedge of the backfill. There were no recommendations on taking into account the interaction of closely spaced chambers.During comprehensive on-site observations of the work of the Votkinsk lock in May-June 1964 the effect of transmission (through the soil in the interlock space) of pressure from the lock chamber being filled to the adjacent one was discovered. This effect consists in that, during filling of one of the chambers of a twin lock with a small width of the interlock space, the relatively flexible wall of the chamber being filled, bending toward the backfill, compresses the soil filling this space so much that it begins to press the wall of the adjacent chamber. This pressure was called the additional earth pressure [i, 2]. After the discovery of this effect the additional pressure in combination with other external actions began to be taken into account in calculations of the chambers of twin locks.The "Instructions on the Design of Navigation Locks" SN 303-65 recommended determination of the extent of the additional earth pressure by means of laboratory investigations on models. When the width of the interlock space was greater than (or equal to) 1.5-heights of the chamber walls the additional earth pressure was allowed to be disregarded.The pressure from the chamber being filled on the adjacent empty chamber is transmitted through the soil of the interlock space, decreasing in intensity with increase of the distance between lock chambers by virtue of the distributing ability of soil. Therefore the additional earth pressure on the inner wall of the empty chamber depends on the width of the interlock space (L) and is always less than the value of the pressure being transmitted by the inner wall of the chamber being filled. However, in design practice of recent years, owing to the absence of substantiated notions about this phenomenon, the additional pressure on the empty chamber in calculations of the chambers of twin locks was assumed equal to the reaction of the backfill on the wall of the chamber being filled, For example, when designing the Lower Kama lock a calculation scheme (Fig. la) was used in which the resistance of the soil to compression from the outer and inner chamber walls was approximated by concrete elastic bars with longitudinal stiffness, expressed in terms of the area of the bar F and modulus of subgrade reaction K = 2000 kN/m 3 equal behind both chamber walls. The area of the support bars is linearly related to their length Z by means of the relation where bd is the cross section of the soil wedge replaced by the concrete support bar; d = i m, width of the calculated strip along the axis of the lock; b, distance between support bars, m; E, modulus of elasticity of concrete, kPa. The calculated length of all support bars except XI-X7 was assum...