Non-uniform Settlement Research Articles

Tests on a two-layered ballast system

Considerable evidence suggests that ballast is the main cause of uniform and non-uniform settlement of railway track, provided the subgrade is adequately specified. Over a period of time uneven settlement of the ballast will cause voids to form under the sleepers, leading to unacceptable ride quality of the track. Regular maintenance is required to keep the track geometry within acceptable limits and to maintain ride quality. The proposed two-layered ballast system described in this paper would replace the crib ballast by stone of smaller size. The aim is to fill the voids beneath the sleepers as soon as they become unacceptably large and thus to maintain ride quality without the use of tamping or stone-blowing. Preliminary model tests carried out on the system indicate good potential for it. The results of the model tests have been validated by full-scale tests in the laboratory. The tests have shown that by replacing crib ballast by stone of smaller size a void beneath the sleeper will be filled up to less than the void size minus the average particle size of crib ballast. The next logical step is to go for full-scale live track trials, and it is anticipated that these will take place in the near future.

Modeling deformation behaviour of clay liners in a small centrifuge

In modern solid waste landfills, liner systems are essential structural elements that ensure that waste materials are safely separated from the environment. Many liner systems have been developed and used over the past decade. Among impermeable layers, clay liners are regarded as one of the very significant components of liner system and are being used worldwide as a waste containment system in landfills. One of the failures associated with clay liners is the occurrence of nonuniform settlements, resulting from the sudden collapse of waste, or the decomposition of waste materials, and (or) the subgrade over which the liner is laid. This paper deals with the use of a small centrifuge to model the deformation behaviour of clay liners. Model tests were performed in a small geotechnical centrifuge to investigate the behaviour of clay liners in landfills subjected to nonuniform settlements at sharp curvatures. A parametric study was conducted to analyze the influence of parameters like thickness, consistency, and overburden on the behaviour of clay liners. The clay liner without any overburden is observed to experience severe cracking in the form of deep and wide cracks at the maximum curvature zone. The depth and width of the cracks are found to decrease with an increase in clay liner thickness. The cracking failure pattern is suppressed by shearing for a clay liner with an increase in overburden pressure. Based on model test results, the clay liner with an adequate overburden is found to be free from cracking failure even when subjected to sharp curvatures. The effective usage of a small geotechnical centrifuge to model the deformation behaviour of clay liners is demonstrated adequately.Key words: landfills, municipal solid waste, clay liners, centrifuge modeling, nonuniform settlements, model tests.

Buckling of un-stiffened cylindrical shell under non-uniform axial compressive stress

This paper provides a review of recent research advances and trends in the area of stability of unstiffened circular cylindrical shells subjected to general non-uniform axial compressive stresses. Only the more important and interesting aspects of the research, judged from a personal viewpoint, are discussed. They can be crudely classified into four categories: (1) shells subjected to non-uniform loads; (2) shells on discrete supports; (3) shells with intended cutouts/holes; and (4) shells with non-uniform settlements.

Method of Accounting for the Deformability of an Inhomogeneous Elastoplastic Bed in Analyzing Foundation Slabs

The problem of accounting for the actual distributive capacity of a spatially inhomogeneous and nonlinearly deformable soil bed is solved by conversion to a set of conditionally one-dimensional calculations for different points of slab support. A procedure is developed to take nonlinear soil deformations into account; it describes the structural compressive and shear strengths of the soil. Results of calculations are compared with field measurements of nonuniform settlements of a foundation slab on an inclined layered bed.

Causes of the Appearance and Prediction of Nonuniform Settlements of the Foundation Bed Beneath the State Historical Museum

Causes of nonuniform settlement of the building housing the State Historical Museum are examined, and suggestions are developed relative to their stabilization and to prevention of further structural deformation of the building.

Vibration Insulation for Jaw Crushers ― an Effective Means of Reducing Bed and Foundation Deformations

Nonuniform settlements of a primary-crushing mill, which resulted from the operation of three heavy-duty jaw crushers housed in the mill, are described. Test results are cited for foundations with and without vibration-insulated crushers. The high effectiveness of the proposed method of protecting the foundation beds from additional deformations caused by industrial vibration is noted.

Potential of Soil and Groundwater Contamination Due to Mine Subsidence Under a Landfill

Results of a study to evaluate the effects of mine subsidence on the integrity of a clay liner and potential for soil and groundwater contamination below a previously mined landfill are presented. The results show that for the existing site conditions, surface subsidence features are expected to be similar to subsidence troughs, and the site has minimal potential of being contaminated due to deep-sited subsidence in the mine. To further reduce potential for soil and groundwater contamination at the site, it is recommended that the minimum thickness of the compacted clay liner be 4 ft instead of the 2 to 3 ft generally used. Discussion is presented indicating that further study is required to develop an adequate design procedure to determine the effects of nonuniform settlement of foundation soils or refuse on the hydraulic conductivity of landfill clay barriers.

Deformations of buildings on thick soil strata prone to slump-type settlement

Results of inspections of deformed buildings on soils prone to slump-type settlement are examined, and the basic causes of nonuniform settlements analyzed. Measures are proposed for stabilization, and results presented for geodesic observations on the behavior of the buildings inspected.

Deformations of the birth of our lady cathedral in the Suzdal' Kremlin

The causes of the deformation of cultural monuments at the Suzdal' Kremlin are discussed. It is demonstrated that nonuniform foundation settlements are associated, as a rule, with deformation processes in the bed soils, which are caused either by changes in the hydrogeological regime, or by disturbance of equilibrium conditions of the soil bed under the influence of modern construction.

Causes of foundation settlements beneath a sawmill

The foundation oscillations of saw frames prior to and after their paired union and the foundations of the sawmill operated by the Kotlassk Wood-Working Combine are examined. Results of observations on foundation settlements are presented. The causes of additional nonuniform vibration-induced foundation settlements of the saw frames and frame columns are analyzed.

Foundation of a 157 m high transmission tower : J. Farkas & L. Marczal, Periodica Polytechnica: Civil Engineering, 38(1), 1994, pp 29–40

In a city of Hungary known to have a weak subsoil, a microwave transmission tower 157 m high, with a cylindrical reinforced concrete shaft was built. In its design, possibilities of both spread foundation and deep foundation arose. Beyond dead and live loads, also other effects (wind load, seismic effects, uniform and nonuniform settlement, daily and seasonal temperature variations) had to be reckoned with. In case of spread footing, that should be 25-30 m diameter because of the extreme height, uneven settlement and tilting, rather than soil failure, were the main problems. Effects likely to cause eccentricity like wind load and building inaccuracies had to be analyzed. In case of a deep foundation, which is technically much better, the point of the large-diameter bored piles was suggested to be taken in a clay beginning at 25 m below the ground level, which is in a much better condition than the overlying one. At last. the tower was built on spread foundation. During and after construction, stresses under the slab footing were recorded, horizontal and vertical displacements of the tower observed.

Calculation of suffosion deformations in saline soils

A method is proposed for the calculation of nonuniform settlements of a single rigid foundation on an inhomogeneous bed of saline soils, including those in which inclined layers exist.

On the buckling analysis and design of silos and tanks

Buckling considerations arise in the design of steel silos and tanks because the slender shell wall is subjected to compressive stresses, most commonly from the action of wind on the empty structure causing circumferential stresses, and combinations of wall friction forces, roof loads, non-uniform filling and discharge, and non-uniform settlement of the foundation causing meridional stresses. In this paper, recent research work of the author and graduate students relevant to buckling behaviour is briefly reviewed. Problems relevant to buckling behaviour, and which arose in several major tanks and silos with which the author was concerned either at the design stage or arising from operational problems, are discussed. The buckling behaviour and design of slender steel silos and tanks has been reviewed, with particular reference to buckling under wind loading, and under meridional compression. The benefits to be obtained by refined finite element analysis at the design stage have been emphasised, and several examples of buckling phenomena in the design of major structures reviewed. The occurrence of uplift of large emoty tanks under severe wind loadings has been detected. A simplified design method for wind buckling has been given, which includes an approximate consideration of the effects of imperfections, meridional end restraints and form of the wind pressure distributions. Situations under which meridional compression can govern the design have been explored. The beneficial effects of a bulk solid content against buckling have been investigated.

Polymer grid reinforced pavement on soft clay grounds

This paper deals with model and field tests for investigating the mechanism of reinforcement by a polymer grid in suppressing non-uniform settlement of pavements constructed on soft clay ground. A series of laboratory tests on reinforced and unreinforced model pavements in a soil tank indicates that the polymer grid is useful for suppressing non-uniform settlement of pavement under cyclic loading. Deformation analysis by FEM is carried out to make clear the reinforcement effect of a polymer grid in a model pavement. To investigate the performance of a polymer grid in practice, a test road of 300 m length with six sections of different kinds of pavement is constructed on soft clay ground. The function of a polymer grid is discussed by comparing the pavements made by conventional and reinforced methods.

Sealing device for wide expansion joints

The unreliability of the work of shaft waterbars of wide expansion joints of high-head hydraulic structures, the complexity of their design, and the labor intensity of their manufacture compel searching for ways to simplify them without loss of reliability. One such way is to replace the costly and complex designs of shaft waterbars by more simple and reliable membranes of rubber and polymer materials. However, these membranes as a consequence of a limited load-bearing capacity cannot cover expansion joints with a width of more than 4 cm. The author developed a design of a sealing device for expansion joints of high-head hydraulic structures, consisting of a sealing membrane in which this shortcoming is eliminated. The sealing device (Fig. 1) is installed in adjacent sections 1 of the hydraulic structure and includes a watertight elastic membrane 2 and a flexible netting 3 (for example, Rabitz wire netting). The transition part of the waterbar 4 between sections 1, made with a bend, increases the reliability of the work of the seal at high heads and considerable displacements of the sections of the structure. To protect the membrane 2 from mechanical damages by floating objects, a protective plate 5 performing the role of a contour permeable waterbar is installed on the upstream side. During construction of the hydraulic structure, at the time of preparing the blocks of the first section the concrete-embedded netting 3 and membrane 2 are passed through the formwork and secured on it by means of rods, bolts, or anchors. After concreting and striking the formwork from the blocks of the first section the embedded elements of the seal are staightened and put into the blocks of the second, adjacent section with the use of templates duplicating the prescribed bend of the membrane and netting, providing in so doing joining of the netting to the elastic membrane. They are fastened to the formwork of the second section in the same way as to the first. The sealing device works in the following way. The watertight elastic membrane 2 is pressed by the seepage pressure of water against the concrete surface of sections 1 of the hydraulic structure and against netting 3. Netting 3, embedded into the concrete of the sections 1 being joined, absorbs the seepage pressure of the water being transmitted by elastic membrane 2 performing the role of a seal in the device. The netting 3 made in the cavity of the joint with a bend duplicating the bend of the elastic membrane has a considerable degree of freedom of deformation, which enables it to work without breaking during nonuniform settlement of the sections 1 of the hydraulic structures. The presence of netting 3 makes it possible to cover expansion--settlement joints by means of rubber or polymer membranes of any required width. In addition to this, it is possible to use less strong, but more elastic membranes made from comparatively cheap rubber or polymer materials. As shown by the experience in using rubber and polymer membranes in the USSR and abroad (in foreign countries elastic membranes have been used since 1935), in such seals the reliability against seepage of water increases and the seals are simpler to make, which affects the quality of making them, and also the operating expenses are reduced to a minimum. Laboratory investigations conducted before the industrial use of rubber membranes on the Imperial Dam (USA) determined that the increase of stiffness of the rubber after 20-yr operation of the seal did not exceed 10% and during long operation all rubber seals worked satisfactorily. In hydrotechnical construction practice there is a tendency toward replacing complex, expensive, and not always reliable asphalt waterbars by simpler and more reliable elastic membranes. Example of Calculation. Use of the proposed device instead of the Nos. 12 and 14 shaft waterbars of the Lower Kama hydrostation. The cost of 1 m of shaft waterbar of the Lower Kama hydrostation according to catalog No. 4-77 of additional unit price rates, referred to the local conditions of the construction of the Lower Kama hydrostation, is equal to 243 rubles (collection No. 37, price list No. 37-Dy-12-72). The cost of 1 m of the vertical seal of an expansion joint made of a rubber membrane according to building code SNiP V-5-82, p. IV, collection 41, chap. 5, price list 41-51 is equal to 12.65 rubles.

Structure settlements at the Atommash plant as a result of prolonged soil wetting

1. In the 14 years that have elapsed since the start of construction on the Atommash plant, deformation phenomena, which have not, however, lowered the strength of the structure in the production buildings, have developed as a result of nonobservance of waterproofing requirements at the site in areas where surface-water domes that had developed as a result of prolonged wetting of the stratum from above have been detected. The design solutions for these foundations have ensured reliable operation under a rising GWT. The absolute settlements, exceeding those permitted by the Construction Rules and Regulations, affect less than 1% of the total number of columns in the buildings at the Atommash plant, while the relative settlements are within allowable limits. Cracks have formed in some auxiliary buildings primarily because their superstructures were built disregarding possible nonuniform foundation settlements. 2. The causes of pile-foundation settlements that had exceeded the standard values with respect to absolute magnitude are not associated with their bearing capacity, but are the result of deformations of the underlying soil layers that are not prone to slump-type settlement and to the development of deformation phenomena. This hypothesis explains the development of additional deformations in the stratum due to the compression of soils beneath the surface-water dome. 3. The deformation phenomena that develop at the site of the Atommash plant as a result of the wetting of the soil stratum from above do not affect the foundation settlements induced by live loads, and should be accounted for in design as a possible displacement of the area. It is possible to eliminate the effect of probable relative settlements on a structure by taking structural measures and observing waterproofing measures. 4. Under conditions favorable to the development of the deformation phenomenon, it is recommended to predict possible compressive deformations in a portion of the stratum underlying the stratum prone to slump-type settlement within the limits of the layers with a relative compression of more than 3% under a pressure equal to the natural pressure in compression devices. 5. Studies directed toward the nature of the processes explaining the development of the deformation phenomenon must be continued.

Some specific problems of wetted loessial soils in civil engineering

Bally, R.J., 1988. Some specific problems of wetted loessial soils in civil engineering. Eng. Geol., 25: 303–324. Loessial soils, wetted above the limit of collapsibility, remain in the category of difficult foundation grounds. Some case histories are presented herein: surpassing soil bearing capacity and non-stabilized settlements of buildings after initially dry loess wetting; slow but nondamped settlements or damped but great and, eventually, non-uniform settlements of structures erected on wet loess; supplementary settlements by water level lowering in loessial ground; great settlements of deep foundations passing through the collapsible loess to the underlaying wet but noncollapsible loess. Research on wetted loess performed in the laboratory (oedometer, triaxial) or in situ (full-scale experiments or real constructions) have emphasized the dependence of the soil structural resistance, deformability (compressibility and deformation under constant volume) and final resistance on both the moisture content or stress-state and on their history; the depth propagation of the active zone of surface loadings on wetted loess is different from that of the linear elastic theory; some suggestions to estimate the depth of the active zone are presented. The usual foundation systems on wetted loessial grounds, or in their vicinity, adopted in Romania include: loessial or gravel cushions; surface compaction (very efficient results of intensive dynamic compaction); foundation “stamping” or loessial ground “reinforcing”. It is recommendable to take into consideration: surveyed wetting under construction until maximum moisture content of the loessial ground; in situ columns of stabilized loess; the efficiency of geotextiles for filter-drainage and antierosional functions in loessial soils.

Consideration of the nonlinearity of bed deformation in computing nonuniform settlements of occupied buildings

Consideration of the nonlinearity of bed deformation in computing nonuniform settlements of occupied buildings

Maximum permissible values of nonuniform settlements of agricultural buildings

1. For single-story agricultural buildings with a complete framework and yielding-type attachment of panels to the frame, it is recommended to adopt, at the next revision of Construction Norms and Regulations (SNiP) II-15-74, a maximum differential settlement of 0.01 mm.