STRESS-DEFORMED STATE OF THE FOUNDATION OF HYDRAULIC STRUCTURES AT CONTROLLED COMPENSATION DISCHARGE

Nnumerical simulation of the process of injection of mortar into the thickness of the sandy base during the work on lifting and leveling the structure by the method of compensatory injection is carried out. An author's program has been developed that implements the finite element method (FEM) in a spatial formulation, taking into account the elastic-plastic nature of soil deformation, in which a special element in the form of a spheroid has been developed to describe the expanding area at the location of the injector, which changes its volume during the injection of mortar. During the verification of the program, the results of mathematical modeling were compared with the data of a physical experiment conducted by PhD Luca Masini from the University of La Sapienza (Rome, Italy). Numerical modeling of the stress-strain state of the base of the structure during repair work is considered by the example of lifting the foundation plate of the Zagorskaya PSPP-2. A number of tasks are being solved related to minimizing the number of injection columns, their location, the pitch of the cuffs, the selection of portions of the injected solution, taking into account the requirements for uniform lifting of the foundation plate in order to avoid additional cracking.

Nonlinear Elastic Foundation Plate Model Study on Overlying Strata Movement in Working Face with Solid Backfilling Mining

Although solid backfilling materials are featured with obvious nonlinear stress-strain properties, for a long time, they have been usually simplified as linear elastic materials for approximate calculation in mechanical analysis, so it is difficult to accurately reflect their deformation process. Based on test results of solid backfilling materials’ compaction characteristics, this paper provides a solution method to generate their elastic foundation coefficient. One multiparameter elastic foundation has been used to reflect stress-strain characteristics of solid backfilling material. In addition, the paper establishes a thin plate on a nonlinear elastic foundation model by adopting semianalytical and seminumerical method and obtains the relational expression between roof deflection, roof stress, and backfilling material’s compressive deformation. In combination with geological conditions in a specific mine, the paper probes into what influence both backfilling material’s particle size and the initial compaction force that the backfilling material bears could exert on roof subsidence and stress. Finally, the proposed model has been verified with measured data from industrial tests.

Pile-Soil Stress Ratio and Settlement of Composite Foundation Bidirectionally Reinforced by Piles and Geosynthetics under Embankment Load

The settlement calculation of composite foundation bidirectionally reinforced by piles and geosynthetics is always a difficult problem. The key to its accuracy lies in the determination of pile-soil stress ratio. Based on the theory of double parameters of the elastic foundation plate, the horizontal geosynthetics of composite foundation are regarded as the elastic thin plate, and the vertical piles and surrounding soil are regarded as a series of springs with different stiffness. The deflection equation of horizontal geosynthetics considering its bending and pulling action is obtained according to the static equilibrium conditions. The equation is solved by using Bessel function of complex variable, and the corresponding deflection function of horizontal geosynthetics is deduced. Then, the calculation formula of pile-soil stress ratio and settlement of composite foundation is derived by considering the deformation coordination of pile and soil. The results of engineering case analysis show that the theoretical calculation results are in good agreement with the measured values, which indicates that the proposed method is feasible and the calculation accuracy is good. Finally, the influence of composite modulus of horizontal geosynthetics, tensile force of geosynthetics, and pile-soil stiffness ratio on pile-soil stress ratio and settlement is further analyzed. The results show that the pile-soil stress ratio increases with the increase of the composite modulus of the horizontal geosynthetics, the tensile force of geosynthetics, and the pile-soil stiffness ratio, and the settlement decreases with the increase of the composite modulus of the horizontal geosynthetics, the tensile force of geosynthetics, and the pile-soil stiffness ratio. When the flexural stiffness of the horizontal geosynthetics is small, the influence of the tensile action of the geosynthetics on the pile-soil stress ratio and settlement of the composite foundation cannot be ignored.

An approach to increasing the load-bearing capacity of drilled injection piles

The problem of strengthening weak or overloaded bases is an important objective of underground space development. It is especially urgent if there are alternating weak layers in the base. The paper presents a practical geotechnical case of strengthening the overloaded base of a reinforced concrete foundation plate for a 25-storey residential building under construction. Combined soil piles that consist of Jet (type 1) soil concrete piles reinforced along the longitudinal axis with drilled injection piles made by electric discharge technology (EDT piles) are used as buried structures. This method of arrangement of a combined buried reinforced concrete structure is conditioned by the need to increase the load-bearing capacity of a pile in soil by two or more times.

Load distribution influence on the mechanical state of reinforcement concrete structures of a port storage facility

The stress/strain state of reinforcement concrete walls and foundation plate of a storage facility in the seaport of Klaipeda (Lithuania, the EU) is investigated, considering the distribution of loads from stored bulk materials. At the first, a simple test problem has been calculated: reinforcement slab 21´35 m in plane on 24 columns, which are located by a regular step. During creating the combinations of all 15 possible loadings of each „cell“, increased internal forces and reinforcement results to +20 % have been obtained. Next, a storage facility of bulk materials with dimensions 36´120 m in plane has been considered, when expected 16 loadings, 1/4 for each of four storage sectors, has been used in the FEM model. The results of the comparison with the ordinary calculation, in which each of sectors could be fully filled or be empty, have presented. The investigation results can be used for developing of industrial recommendations for the designing of storage facilities.

RESEARCH OF THE “FLOATING” BASE METHOD FOR SEDIMENTATION ON THE MODEL OF THE FOUNDATION PLATE

In the article, the authors propose the application of a one-dimensional problem of the theory of compression compaction of soils for the calculation of sediments of Foundation slabs of large area. The authors analyzed the existing methods for determining the depth of the compressible thickness. The author suggests an original technique to determine the depth of compressible strata and settling of the Foundation. A test bench (tray) was developed and a laboratory test was performed. The results of an experimental study of the depth of compressible thickness under slab foundations are presented. The analysis of experimental data is made. The method of calculation of compressible thickness depth, previously proposed by the authors, is confirmed.

Elimination of Uneven Settlements During the Construction of Buildings in Complex Hydrogeological Conditions

The main factors influencing the occurrence of uneven settlement of buildings and structures are given. Since the existing methods of calculation of bases and foundations are not sufficient to ensure the guaranteed stability of buildings built on weak clay water-saturated soils, when designing it is necessary to assess the possibility of uneven settlements and provide ways to eliminate them at minimal cost. Based on the analysis of previously performed work on this issue and the conducted research, the designs of the foundation plate and the plate pile grillage are proposed, which make it possible to produce additional pressing or indentation of composite piles through holes in the plate when occurring a roll. The method of pressing composite piles using a support frame is described and the main measures that need to be carried out during the production of works are formulated. The use of the proposed method will reduce the cost of straightening the rolls by an order of magnitude and virtually eliminate the performance of these works at the stage of operation of the building.