Load Carrying Capacity Of Soil Research Articles

Numerical Analysis of Piled-Raft Foundations on Multi-Layer Soil Considering Settlement and Swelling

Numerical modelling can simulate the interaction between structural elements and the soil continuum in a piled-raft foundation. The present work utilized a two-dimensional finite element Plaxis 2D software to investigate the settlement, swelling, and structural behavior of foundations during the settlement and swelling of soil on various soil profiles under various load combinations and geometry conditions. The field and laboratory testing have been performed to determine the behavior soil parameters necessary for numerical modelling. The Mohr–Coulomb model is utilized to simulate the behavior of soil, as this model requires very few input parameters, which is important for the practical geotechnical behavior of soil. From this study, it was observed that, as soil is soft and has less stiffness, the un-piled raft was not sufficient to resists and higher loads and exceeds the limits of settlement. Piled raft increases the load carrying capacity of soil, and the lower soil layer has a higher stiffness where the pile rests, decreasing the significant settlement. Further, the effects of (L/d) and (s/d) of the pile and Krs on the settlement are also discussed, detailed numerically under different scenarios. The swelling of expansive soil was also simulated in Plaxis 2D with an application of positive volumetric strain. The above-mentioned parametric study was similarly implemented for the heaving of foundation on expansive soil.

Reduction in Lateral Displacement of Cohesionless Soil at Box Tunnel Face Using Nails in Overburden

The construction of shallow box tunnel underpass below rail/road traffic using jack pushing has become a quite common technique these days to create an uninterrupted flow of traffic in metropolitan cities. During the driving of shallow box tunnel underpass, the overburden cohesionless soil experiences large stresses and excessive lateral displacements at the box tunnel face, which sometime causes an accident leading to loss of lives. In order to overcome this problem, a laboratory model study has been conducted. A steel tank of size 450 mm × 300 mm × 300 mm, filled with cohesionless soil was used, in which a square steel box tunnel of size 34 mm × 34 mm (inner) with 1 mm wall thickness was moved through jacks. This tunnel was slowly pushed into the soil mass with the help of jack. Three vertical offsets from top of soil surface as well as three horizontal offsets from center of loading. To restrict the excessive lateral displacement, the overburden soil above the box tunnel was reinforced with 8 mm diameter tor steel nails prior to pushing of box tunnel. The lateral displacement of soil at tunnel face was found reduced from 6.92 mm in case of ‘without nailed’ to 0.23 mm in case of ‘with nailed’ overburden soil. Further, there was also a gain in load carrying capacity of soil in case of reinforced overburden soil. The study shows that if, overburden soil is reinforced with nails prior to the driving of box tunnel, the chances of collapse or lateral displacement at box tunnel face soil can be minimized for construction of shallow underpass.

Numerical Simulation of the Response of Geosynthetic Encased Stone Columns Under Oil Storage Tank

Geosynthetic encased stone columns (GESCs) are a newly developed technique in which stone columns are wrapped with geosynthetic to overcome some of the limitations of ordinary stone columns (OSCs) through the additional confinement provided by the geosynthetic. This paper presents the behavior of GESCs under circular oil storage tank and its comparison with OSCs under the same in situ conditions using PLAXIS 3D. In this paper, initial studies were carried out to understand the mechanism of load carrying capacity of soils reinforced with stone columns and the later observations from the parametric studies supported the conclusions. The various parameters considered in this investigation include the effect of encasement stiffness and length on settlement and lateral deformation of stone columns. The results show that with an increase in stiffness value, there is a considerable reduction in the long-term settlement and lateral deformation of GESCs. It was found that settlement reduced by up to 55% and lateral deformation by up to 68% with an increase in geosynthetic stiffness from 1000 to 10,000 kN/m. Meanwhile the encasement length up to six times the diameter was found as the optimum encasement length to get the same performance as that of fully encased stone columns. Further a suitable arrangement of encased stone columns in terms of encasement length has been developed to economize the consumption of geosynthetic without compromising the performance of GESCs.

A new technology for strengthening soils as an intangible resource for investment-building projects

The effectiveness of intellectual activity in construction is determined by the relevance and the possibility of practical application of its results in the implementation of investment and construction projects. The investment attractiveness of the territory depends to a large extent, including on the construction site’s ground conditions. Analysis of scientific research conducted by Russian and foreign researchers shows that the solution of this problem is possible due to the strengthening of soils. Areas of application of soil reinforcement technology are identified. The analysis of existing technologies carried out in the field of increasing the load-carrying capacity of soils has been carried out, and the main shortcomings of the methods have been identified. A new technology for strengthening soils with crushed stone piles is proposed. The main problems are researched, and the ways of their solution are considered in case of applying the proposed technology.

Behaviour of square footing on sand reinforced with coir geocell

The use of geosynthetics as a ground improvement technique offers the advantages such as space saving, environmental sensitivity, material availability, technical superiority, higher cost savings and less construction time. Coir geotextiles can be considered as an efficient replacement to its synthetic counterparts due to its economy and excellent engineering properties. The present study aims at exploring the possibilities of utilising coir geocells as a potential reinforcement material for shallow foundations and thereby increasing the load carrying capacity of soil. Geocells were fabricated from coir geotextiles with the aim of providing an additional confinement to the soil. An enumerated parametric study was conducted by varying the relative density, depth of the first layer, width and height of coir geocell. The surface displacement profiles of the non-reinforced and coir geocell-reinforced soil indicate that the footing rotation and heave are considerably reduced with the provision of geocell. The results of the relative density study indicate that bearing capacity characteristics increase with denseness of the soil sample. It was also observed that geocell arrangement and configuration play a pivotal role in the performance characteristics of reinforced soil.

THE STUDY OF DEFORMATION CHARACTERISTICS OF SOIL MATERIALS WITH THE USAGE OF WASTES

Purpose. More often the qualified building materials are replaced by the industrial wastes for environmental improvement. This refers to both metallurgical slags and biological solids of water treatment plants. In order to understand the possibilities of their usage it needs studying deformation properties of composite soil materials with industrial wastes addition. Methodology. The soil of real buildings and structures foundation is in the complicated conditions and the stress-strained state. While studying this state the total deformation modulus Е 0 is used as the deformation characteristic. This one is determined according to the results of sample soil testing in the compression instrument (odometer). This instrument prevents the possibility of lateral expansion of sample soil under the vertical load. Findings. As a result of the testing the compression curves are plotted as the dependence of the porosity coefficient on pressure. These data allow determining the compressibility coefficient and the strain modulus. It is found that a biological solids addition increases the compressibility coefficient four times compared to the clay. The two types of samples are compared. The first type contains 50% of biological solids. The second type contains 50% of biological solids and 50% of slag. The comparison shows that the second type is compressed twelve times less. An addition into the clay of biological solids increases the strain modulus from 7 . 8 to 20 . 3 MPa. The slag increases the strain modulus to 52 . 7 MPa. Originality. While making the composition based clay materials the functional groups of biological solids interact with hydroxyl groups which are placed on the surface of clay particles and form a spatial structure. Besides an addition of biological solids contributes to peptization, soil aggregates destroy themselves, and form contacts between separate particles. It causes the decrease of soil compressibility due to the total porosity decrease. An addition of slag results in formation of optimal structure where particles of less sizes are placed in layers between bigger particles. Practical value. An application of biological solids and slag provides the increased load-carrying capacity of soil, extending of raw material sources while improving the environmental situation in the cities. Also it provides the recycling of reinforced soil.