METHOD OF HARDENING OF NON-RIGID ROAD CLOTHES

The article discusses the method of strengthening the subgrade and non-rigid road pavements, in areas with weak soils. The use of geosynthetic materials has a positive effect on the condition of the roadbed and pavement, especially in the conditions of the increased traffic load in recent years. The work performed allows us to reduce the cost of operating highways since the construction of the pavement will last longer when used in the difficult natural and climatic conditions of our country.

ANALYTICAL AND NUMERICAL METHODS FOR DETERMINING THE CARRYING CAPACITY OF A PILE BARETT ON WEAK SOILS IN DEEP PITS

The article provides an analysis of the bearing capacity of barrett piles in difficult geological conditions at a construction site in the city of Hanoi, Vietnam based on the results of analytical calculations according to Russian building codes, mathematical modeling and field full-scale tests. The paper describes a numerical test of a single barrette for Mohr-Coulomb and Hardening Soil models in the Midas GTS NX software package. The bearing capacity of a barrette in soft soils is also proposed to be determined by an analytical solution for calculating the settlement of a single pile, taking into account the unloading of the pit after soil excavation. The results of full-scale tests at the site of future construction, graphs of "load-settlement" of the barrette head from the applied vertical load and the general assessment of the bearing capacity of the barret pile by various methods are shown.

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.

Improving bearing capacity of weak soils: A review

Weak soils, such as soft clay and loose sand, have a poor bearing capacity, making them incapable of bearing the load of superstructures that will be imposed on them. As a result, engineers must have a solution to the issue of poor bearing capacity in weak soils before embanking into building on them. This paper reviewed the use of stone columns, piled rafts, and geogrids for improving the bearing capability of weak soils. Important findings from recent research are also discussed. From the review of the previous researcher’s findings, it was found that modelling approaches such as physical modelling (full scale, centrifuge, laboratory scale) and numerical modelling are used to study bearing capacity improvement.

Roadbed Sedimentation on Folded Bases with Weak Soils

Purpose. The main purpose of the work is to construct accurate analytical dependences of the sedimentation of the roadbed base on its coordinates and the trapezoidal external load applied to the upper limit of the base. This will allow the foundation settlement profile to be calculated within and outside the embankment using the layer-by-layer stacking method. Methodology. Theoretical studies of geomechanical processes using analytical and numerical mathematical methods were applied to achieve the purpose, as well as analysis and generalization of the results of theoretical research. Findings. Analytical dependences of vertical and horizontal normal deformations on the half-plane coordinates to the upper limit of which the trapezoidal load is applied were obtained within the framework of the base model in the form of a linear elastic isotropic medium and the calculated scheme of planar deformation. On this basis, an algorithm for constructing a profile of a roadbed sedimentation made of soil materials has been developed. Originality. Analytical dependences of vertical normal deformations in the roadbed base with a trapezoidal profile on its coordinates are obtained. Practical value. The research materials presented in this work make it possible to construct the design profile of the roadbed of soil materials, taking into account the strong compressibility of the soil. In addition, the results obtained can be used to determine the lower limit of the compressible strata of the bases, to the upper limit of which a distributed load of either a triangular or a trapezoidal form is applied.

Numerical investigation of stability multi-storey buildings on weak ground based on their non-linearity

The problems of loss of stability and collapse of high-rise buildings located on weak soils are studied numerically. The problem is solved in a nonlinear formulation using a bilinear model of the soil base. From the point of view of construction mechanics, the critical state of the «ground base – structure» system is considered as an indifferent state. To solve this problem, the perturbation theory is used in combination with the method of successive loadings. Based on the results obtained, a variant of strengthening the foundation is proposed.

Effects of Synthetic Foam on the Properties of Stabilized Lateritic Bricks

Managing the production costs of construction projects is crucial especially in the aspect of material management. The use of lightweight materials reduces the dead load in structures, thus the reduction in the use of reinforcement and concrete in the foundation. To this end, this study examined the effect of synthetic foam on the properties of stabilized lateritic brick with a view to producing lightweight stabilized laterite brick for use on weak soils with low bearing capacity. Laboratory tests were conducted on the bricks produced to determine the density, compressive strength, and water absorption properties at 7, 14, 21, and 28 days. Preformed foam using synthetic foaming agent was used at 0%, 25%, 50%, 75% and 100% to replace the water in the experiment. One hundred twenty samples of stabilized foamed lateritic bricks were produced at a mixed ratio of 1:4 (cement: laterite) using a 0.6 water/cement ratio. The result showed that the bricks at all percentages of foam content meet up with the minimum requirement of compressive strength of 1.6N/mm2, 2.0N/mm2 and 3.5N/mm2 recommended by the Nigerian Building code, Nigerian Building and Road Research Institute, and the third class brick of the BS 3921:1985 respectively. The water absorption is within the limits of bricks specified in standards as 15%. The highest compressive strength was recorded at 25% foam inclusion (4.839N/mm2) on 28th day hence concluding that foaming agent stabilizes the characteristics strength of laterite bricks and also reduces its density.

Field investigation of shallow soft-soil highway subgrade treated by mass carbonation technology

The innovative carbonation technique based on reactive MgO and CO2 has been identified as an environmentally friendly and efficient method in the improvement of weak soils. Previous laboratory studies have indicated that carbonated MgO-admixed soils had significant improvement in mechanical properties. However, there are to date limited investigations on the soft-soil field application of this technique. In this study, a field trial was conducted to ascertain the feasibility of the MgO mass carbonation technique in improving shallow soft-soil subgrades. A series of field tests, including temperature, dynamic cone penetrometer, and light-weight deflectometer tests, were undertaken. The results indicated that compared with uncarbonated soil layers, there was two to three times increase in dynamic resilient moduli and soil resistances of carbonated MgO-admixed soils. The outcomes of this field investigation will contribute to the utilization of the combined stabilizer of MgO and CO2 and the mass carbonation technology in subgrade improvement.