Stress-strein state of weak and filled soils reinforced with reinforced concrete and soil piles, respectively

Introduction. The overwhelming majority of construction areas are characterized by difficult engineering and geological conditions, represented by the presence of weak soils at the base. There are construction sites on which a large thickness of fill soil is observed. In these conditions, designers apply: soil consolidation, soil reinforcement, significant deepening of the underground part of buildings, etc. This article presents the formulation and solution of the problems of interaction of reinforced concrete piles with weak soils, as well as the interaction of soil piles with bulk soils as part of a pile-slab foundation, which allow one to determine the reduced deformation modulus and the bedding value. Materials and methods. To describe the change in shear stresses depending on depth, a law was adopted in the form τ(z)=τ0е–αz. The solution is presented by analytical and numerical methods. The results obtained were compared by the analytical solution of the problem with the results obtained in the PLAXIS 3D software package. Results. Regularities of the distribution of the total load on the pile-slab foundation between the pile field and the grillage have been obtained. The analytical solutions in the article are supported by the graphical part, performed using the Mathcad program. Numerical simulation of the problem was carried out in the PLAXIS 3D software package. The dependence of the settlement on the load, calculated by analytical and numerical methods, is shown. An expression is obtained for defining the stresses in different sections of the pile shaft and under the grillage slab. The theoretical and practical aspects of the construction of crushed stone piles are considered. The theoretical substantiation of compaction of bulk soils with crushed stone piles using a special technology is given. A dependence is obtained for determining the reduced modulus of deformation for bulk soil mass reinforced with soil piles. Conclusions. Comparative evaluation of the results of solutions obtained by analytical and numerical methods showed good convergence. The solutions obtained can be used to preliminary determination of the settlement of piles as part of a pile-slab foundation. Selection of the optimal ratio of the pile length and its diameter allows the most effective use of the bearing capacity of the pile. For bulk soils, reinforced with soil piles, it is possible to select the optimal reduced modulus of deformation by varying the pitch of the soil piles.

MODIFIED CAM-CLAY MODELS FOR DYNAMIC ANALYSIS OF GRANULAR METAMATERIALS IN EARTHQUAKE ENGINEERING

the problem of protecting buildings and structures from vibrations of natural and artificial nature is im-portant for modern construction. One of such modern methods of protection is seismic pads. The purpose of this work was to study the effect of adding a layer of granular metamaterial under a slab foundation on the vibration of a building under the influence of seismic shear waves (S-waves). To achieve this objective, the finite element method (FEM) was used in combination with Cam-Clay models. The FE model consists of a ten-story superstructure rested on the slab foundation, under which there is a layer of granular metamateri-als. 16 models were created taking into account changes in the values of these parameters (pad thickness; density; cohesion; critical state strength parameter (M); Young's modulus-Poisson's ratio). The dynamic analysis performed using the software package Abaqus/CAE showed the effectiveness of granular met-amaterials in their ability to dissipate seismic energy and significantly reduce vibration transmitted from the ground to the building.

EXPERIENCE OF CONSTRUCTION OF THE PLATE AND PILE FOUNDATION IN COMPLEX ENGINEERING AND GEOLOGICAL CONDITIONS

Purpose. An urgent issue for the construction of foundations in complex engineering and geological conditions is the development of new technologies for the construction and monitoring of buildings built in deep beams. The purpose of this article is to development a technology for eliminating cavities with the help of vertical rigid soil-cement elements. Methodology. Using the experience gained in designing foundations in complex engineering and geological conditions, it was proposed to implement a new type of pile-slab foundation. It includes reinforced vertical hanging piles based on drilling and mixing technology and a slab foundation. An algorithm for monitoring houses built in deep gorges and pile-slab foundations using a system of wells and marks is also proposed. Findings. Scientific substantiation of construction technology in Solomianskyi District of Kyiv has been performed, where there are areas that, given the variable height and saturation of various wastes, are very difficult to use for construction, especially in the construction of houses with large area and height within 9 … 16 floors. The results of construction of a ten-storey frame-type residential building with an underground length of 102.5 m and a width of 14.0 m are presented. Originality. Based on the performed calculations, the dependences of the deformed state of the pile-slab foundations during the construction of high-rise residential buildings are obtained. It is proved that when applying the technology of creating vertical hanging piles, the values of maximum allowable deformations of the house and the foundation meet the requirements of current regulations of Ukraine. Practical value. The use of pile-slab foundation in complex engineering and geological conditions made it possible to develop the technology of construction of a ten-storey building.

DRUCKER-PRAGER MODELS FOR DYNAMIC ANALYSIS OF GRANULAR METAMATERIALS IN EARTHQUAKE ENGINEERING

Problem of developing methods for protecting buildings and structures from the vibrations transmitted to them from the soil under the action of seismic effects is extremely important to date. One of these modern methods is seismic pads. The purpose of this work was to study the effectiveness of adding a pad of granu-lar metamaterials under the foundation of the building to decrease influence of seismic shear waves. The Finite Element Analysis of Mohr-Coulomb models was used to achieve this goal. The FE model consists of a ten-story superstructure rested on the slab foundation, under which there is a layer of granular metamateri-als. The values of five variables that affect the mechanical properties of these metamaterials were analyzed (density – cohesion – internal friction angle – Young's modulus – Poisson's ratio) for two different pad thicknesses. The dynamic analysis performed using the software package Abaqus/CAE showed the effec-tiveness of the granular metamaterials in their ability to significantly reduce magnitudes of displacements, velocities and accelerations in the building compared to the same values in the absence of these metamateri-als. The analysis also revealed that among the studied variables, the cohesion is the parameter most influenc-ing the effectiveness of metamaterials in their ability to dissipate seismic waves, while no significant effect was observed for the other parameters

Load capacity of the mixed bench and slab foundation. Numerical simulations and analytical calculation model

The paper presents results of a numerical investigation on load capacity of the mixed bench and slab shallow foundations (often used in the process of the modernization of the old, antique buildings, which are suffering from lack of the load capacity). The main trouble with use of existing analytical approaches is a non-unique foundation level of the bench and slab, they could even be founded on different geotechnical layers. Proposed analytical model based on Brinch Hansen (EC-7) approach could deal with such a problem. Results of 2D and 3D numerical modelling (ultimate load of the foundation) are compared to the obtained by using the proposed approach. Influence of the soil above the foundation level is also investigated. Different width to length ratios of the foundation are analyzed (from “short” to “long” foundations). Usability of the proposed analytical model in engineering practice is proved by numerical simulations; the obtained results are on the safe side with quite acceptable margin of additional safety.

EXPERIMENTAL-THEORETICAL CALCULATION OF THE STRESS-DEFORMED STATE OF THE BAR ON THE ELASTIC BASIS

Any strip foundation, and sometimes a slab foundation can be consideredas a be a mon an elastic base. And if with calculation of a beam – the tape base problems practically do not a rise because loading on the tape base as a rule is evenly distributed, and means and the base be haves, a sabsolutelyrigid beam. Then when considering a section of the foundation with unevenlyapplied load, some problems may arise. Today there are many publications on studies of the use of beams with an elastic base in the field of construction and the application of the features of the method of calculating the stress-strain state in the field of design. As is known, from classical soil mechanics, when a load is applied to a flexible slab, its center gives a draft of 1.24-1.57 times greater than the edges. Note that this effect can be explained by the contour work of the base and its uneven stiffness in the central and peripheral zone of the slab foundation. It should be noted that today in most cases the method of BN Zhemochkin [6] is used as the basis for the analytical solution of the problem of the interaction of the beam with the elastic base, which combines an engineering approach and strict solutions of the theory of elasticity. According to research, the method is based on the replacement of the continuous problem of the interaction of the foundation beam with the soil base, discrete, with a limited number of calculated sections within the beam and approximation of the smooth reactive pressure curve stepped with a constant value within a single section. Such simplifications allow to calculate various engineering problems on interaction of beams and plates, including with difficult geometry with the set degree of accuracy, bypassing difficult differential and integral calculations.

Feasibility study of the construction of foundations with a convex upward curved shape of the contact surface

In the article the comparison of the two technologies of foundations: the traditional technology of cast-in-situ solid slab Foundation and the alternative technology foundations with the upward-convex curved shape of the contact surface. The foundation with an upward curved contact surface is a geometrically complex structure consisting of monolithic belts (support contours), united by flat cylindrical shells convex upwards with respect to the ground, made along the curved surface of the soil mass with an undisturbed natural structure. Due to the joint work of monolithic belts and a reinforced concrete shell located in the span of the foundation, made along the curved contact surface of the ground mass, this foundation structure is an alternative to a solid slab foundation. When the support contours are drained under load, the reinforcement of the shell is tensioned, the soil under the shell is compressed and thus the soil is involved in the work, which allows increasing the strength characteristics of the foundation and reducing the overall draft of the building. The author of the article describes the structural and technological features of this type of foundation. Due to the complex geometric shape of the foundation under study, the total labor costs and the duration of the work increase in the construction practice. As part of the study, two types of foundations were compared according to technological and economic indicators, using the example with the specified geometric parameters. As a result of the obtained data, an increase in labor costs for performing manual molding of the soil mass and the device of a monolithic convex up shell of the foundation in comparison with the traditional technology of the device of a solid slab foundation was revealed. But at the same time, a reduction in direct costs by 30 % was revealed in the construction of a band-shell foundation, due to a reduction in the consumption of steel and concrete, which determines the effectiveness of this type of foundation and expands its scope in the construction of buildings and structures.

Development and Testing of Structurally Independent Foundations for High-Speed Containment Concrete Barrier

This paper presents the development and testing of single slope barriers with independent foundations that can be installed at a wide range of site conditions. The researchers developed designs of barriers with foundation systems by conducting a series of finite element simulations and performing full-scale vehicle impact tests under the American Association of State Highway and Transportation Officials’ (AASHTO) Manual for Assessing Safety Hardware ( MASH) Test Level 5 (TL-5) and Test Level 4 (TL-4) conditions. In this process, foundation designs were developed for site conditions that may require shallow foundations, or foundations that have a smaller footprint. Depending on the site conditions and the presence of underground structures, designers could select the most fitting option from these designs. Impact performance of the developed barrier and foundation systems was evaluated using full-scale finite element impact simulations under MASH TL-5 and TL-4 impact conditions. Two critical systems were selected for full-scale crash testing: a 54 in. tall single slope barrier with drilled shaft foundations, and a 36 in. tall single slope barrier with moment slab foundation. The barrier with the drilled shaft foundation system was tested to MASH Test 5-12 conditions, and the barrier with the moment slab foundation system was tested to MASH Test 4-12 conditions. Both systems performed acceptably with respect to the MASH criteria. This paper presents the various barrier and foundation designs that were developed, key results from the simulation analyses, and details of the crash testing performed on the two selected systems.