Improvement In Bearing Capacity Research Articles

Numerical Analysis of Bearing Behavior of the Prebored Precast Pile with an Enlarged Base

Prebored precast pile with an enlarged base (PPEB pile) is a new type of green and environmental protection pile foundation developed in China in recent years, which has complex bearing characteristics and many influencing factors. Based on the static load tests and key parameters’ tests in deep soft soil in Shanghai, a three‐dimensional numerical analysis model was established using ABAQUS finite element software. The transfer law of load among the precast pile, cement soil, and soil around the pile and the action mechanism of the enlarged base were analyzed emphatically, and a sensitivity analysis of the main factors affecting the bearing performance was carried out. The calculation results show that the existence of the enlarged base can greatly improve the compressive bearing capacity, increasing the diameter and height of the enlarged base is beneficial to the bearing capacity, and the influence of the diameter expansion ratio is more effective. With the increase of the proportion of nodular piles, the ultimate bearing capacity increases slightly, but the deformation increases obviously. Under the condition of cement soil of the test piles, the spacing of the neighboring nodules of nodular piles has no obvious effect on the bearing capacity, and the 1 m spacing commonly used in engineering applications can be optimized. The increase of cement soil thickness is beneficial to the improvement of pile bearing capacity, but the efficiency is low. Finally, some improvement measures for the construction technology of the PPEB pile were put forward.

Uplift Bearing Capacity of Transmission Tower Foundation in Reinforced Aeolian Sand Using Simplified Model Tests

In order to analyze the uplift bearing capacity of transmission tower foundation in the geosythetic‐reinforced aeolian sand, a series of simplified indoor modeling tests are carried out. A simplified reduced‐scale foundation made according to the prototype and the uplift bearing capacity of transmission tower foundation in geosynthetic‐reinforced aeolian sand is studied. Three kinds of reinforcement materials are embedded in the sand according to five ways of layout spacing. A total of 15 reinforcement schemes are tested. The results show that ultimate uplift bearing capacity of transmission tower foundation can be significantly improved by the reinforcement treatment of geotechnical materials in the aeolian sand. The type and spacing of reinforced materials also have a significant influence on the uplift bearing capacity of the foundation model in reinforced aeolian sand, and the effect of reinforcement works until the end of the loading process. The comprehensive effect is evaluated by the ratio of bearing capacity improvement and the total layer of reinforced materials. Based on the above results, the bearing mechanism of transmission tower foundation in geosynthetic‐reinforced aeolian sand is elaborated and analyzed in detail.

Performance evaluation of construction and demolition waste aggregates as an alternative base course material in highway construction

ABSTRACT Construction and demolition (C&D) wastes are found to be the main source of unwanted materials produced worldwide. Due to the insufficient amount of high-quality fresh limestone aggregates, construction and demolition waste are used as an alternative base course material for highway construction. The stabilization of C&D recycled aggregate waste with ordinary portland cement (OPC) has been repeatedly used by the researchers to improve the performance of the base course in highway construction. The studies related to the geosynthetic-reinforced C&D waste are limited. In this study, the efficacy of geosynthetics reinforced bases was evaluated within the base course with three different base thickness (120, 150 and 200 mm). Two different infill materials, namely, C&D waste and limestone aggregates were used and plate load tests were conducted to simulate traffic loading over geosynthetic reinforced and unreinforced unpaved test sections. This study aims to present the results in terms of load versus deformation and load versus vertical stress distribution. It was observed that the C&D waste improvement factor is more than virgin aggregates (limestone aggregates). Due to the inclusion of geocell and geotextile, the average bearing capacity improvement factor enhances by 62% and the vertical stresses decrease significantly.

Bearing Capacity and Settlement Response of Ordinary and Geosynthetic Encased Granular Columns in Soft Clay Soils: Analysis and Design Charts

This paper discusses the bearing capacity and settlement response of granular columns with and without geosynthetic encasement using the currently available design procedure. The design procedure is modified to include the influence of the geosynthetic encasement. The key parameters influencing the load bearing capacity and settlement are studied through comprehensive parametric analyses. The results portray the advantage of geosynthetic encased granular columns in enhancing the bearing capacity and reducing the settlements compared to granular columns without encasement. Different installation patterns of granular columns were considered in this investigation. The maximum bearing capacity improvement and settlement reduction are observed with granular columns installed in triangular plan arrangement. The hexagonal pattern results in the lowest area replacement ratio and also the lowest improvement factors. It is shown that with geosynthetic encasement, the performance with hexagonal pattern could be improved to match with other more efficient patterns like square and triangular. Some selected results are validated through detailed finite element results. A quick assessment of the settlement improvement with geosynthetic encapsulated granular columns is possible with the design charts presented.

Intrusion of Geomesh in Gypseous Soil Under Single Footing

Methods to improve bearing capacity of footing resting of collapsing soil can, in fact, take two approaches, improving soil strength properties and intrusion of reinforcing sorces into soil. The footing is modeled by a square steel plate 0.1 by 0.1 m. The footing is loaded as to have a stress of 40 kPa and settlement is receded in dry and in soaking conditions. Two depths of the geo-mesh reinforcement are used, one B (B is width of footing) and 0.5B. For one B depth, three different square sizes of geo-mesh are used, 4B, 6B, and 8B. For the reinforcement depth of 0.5B the three sizes of the geo-mesh used are, 3.5B, 5.5B, and, 7.5B. Results reveal that the best improvement obtained is the case of square geo-mesh width of 7.5B and located at depth of B/2 under footing, with an improvement in terms of collapse settlement of 35%, and a settlement reduction in dry condition of 50%. The least improvement is the case of square geo-mesh with width of 4B and depth of one B, and it was really negligible, about 4% decrease in collapse settlement. Other cases varied between the two mentioned ratios. For findings of study, author recommends not to use geomesh size less than size of footing and not to place it in a depth more than half footing width. As such, in a whole, the effectiveness of geomesh in reducing the settlement of collapsing soil is obvious if used in proper way.

Peat Soil Improvement Method Using Woven Bamboo and Cerucuk

Most of the land in South Sumatera is the problematic soil, one of that is peat. Peat has low soil bearing capacity, and it becomes a problem when construction is built. Before the installation process, it is necessary to handle that soil. Soil improvement that can be done on peat to increase the bearing capacity value is the reinforcement method or physical stabilization. The results of research on woven bamboo and cerucuk are used as reinforcement material, which is expected to be an alternative to improve soil bearing capacity. The research methodology used was on the scale of the laboratory and analyzed by comparing the soil bearing capacity without reinforcement in bearing capacity ratio (BCR). The maximum bearing capacity with cerucuk reinforcement and without woven bamboo is 39.33 kPa with variations of the two outer rods of the left and right sides from 750 angle toward the foundation plane. However, using the 3 layers of reinforcement woven bamboo that is combined with cerucuk, which has diameter 1,5 cm and length 60 cm generates the highest soil bearing capacity value. The maximum of bearing capacity is 58 kPa. The BCR is 10,88 or in percentage is 988,2%, or 10 times greater than bearing capacity without reinforcement. So, it can be inferred that woven bamboo and cerucuk are used as an alternative to improve bearing capacity on peat soil.

Effect of Multi-Directional Reinforcements on the Settlement and Heave Characterstics of Foundations on Sand

Laboratory plate load tests are conducted on model footings resting on sand bed reinforced with plastic multi-directional reinforcements. The bearing capacity, settlement and heave are evaluated and the effect of depth to first layer, spacing between reinforcements in a layer, number of layers and spacing between layers are investigated. The bearing capacity at 25 mm settlement improved by almost 1.3 times for a single layer of reinforcement, placed at an optimum depth of 0.5B. An increase in number of layers beyond four resulted in a reduction in improvement of bearing capacity. Three layers of reinforcement, spaced vertically apart at 0.5B resulted in a maximum increase of 185% in the bearing capacity. For the same area, the multi-directional reinforcing elements provide additional confinement to the soil mass due to the three dimensional projections. Comparing the economic aspects, the multi-directional elements prove to be a viable alternative to the conventional planar geosynthetics. An artificial neural network based model has been developed in order to effectively predict the ultimate bearing capacity and settlements of the model footing, resting on reinforced sand.

Effect of geosynthetic reinforcement on the bearing capacity of strip footing on sandy soil

Due to the increasing presence of problematic soils, expansive clays and highly compressive sand engineers are using a verity of soil improvement techniques to treat such soils. While geosynthetics are extensively used for improving soil characteristics in roads, pavements and embankments, it can also be used to increase the lack of bearing capacity of residential housing or lightweight structures constructed on sandy soils. In order to simulate site conditions in the laboratory environment, a laboratory-scale testing platform has been manufactured to assess the behaviour of geosynthetics reinforced and un-reinforced strip footing. The first group of tests were performed on the unreinforced compacted sandy soils with different densities where the other group of tests were carried out in the soil that has been reinforced individually with three different types of geosynthetic materials having distinct tensile strengths. Furthermore, interface direct shear tests and consolidated undrained triaxial tests have been carried out to determine the shear parameters which is directly influencing the bearing capacity a strip footing. Geosynthetic reinforcement has considerably enhanced the mechanical behaviour of sandy soil in regarding the type of geosynthetic. Furthermore, it was observed that coir geosynthetic has provided increased interfacial friction when compared to other geosynthetic types and improved bearing capacity. Moreover, the adopted testing method found to represent well the behaviour of such materials in the laboratory environment.

EFFECT OF REPLACING CRUSHED STONE IN STONE COLUMNS BY WASTE MATERIAL ON SOIL IMPROVEMENT RATIO

Many researchers’ studies have shown that stone column is the best material to use to improve the bearing capacity of clayey soils. There are millions of waste volumes resulting from daily human activities. This excess waste leads to disposal problems and also causes environmental contamination and health risks. Demolished concrete is such one waste material that is produced from building demolition in Baghdad, Iraq. This paper describes experimental work conducted at the University of Technology that was carried out to investigate the improved bearing capacity of soft clay using crushed stone, followed by replacing crushed stone with concrete waste with the same relative density and grain size. The replacement was carried using waste concrete with different percentages corresponding to 25%, 50%, 75%, and 100%. The main conclusion drawn is that the bearing capacity increased to 119% by using crushed stone column, while the bearing capacity increased to 155% by using 100% of crushed concrete waste.

Phase morphology and tribological properties of PI/UHMWPE blend composites

Polyimide/ultrahigh molecular weight polyethylene (PI/UHMWPE) blends with different mass ratio were produced. A ratio-image method was adopted by plotting the ratio of Raman peak intensity of a typical band of PI with that of UHMWPE as a function of position, Raman Mapping images with a relatively high accuracy and enhanced visualization were obtained. Two-phase distribution morphologies of the blends were studied using Raman Mapping. Effects of blend phase morphology and phase distribution on the tribological properties of blend composites were investigated. The results indicated that both the phase structures and their distribution are obviously different for the PI/UHMWPE blends with different mass ratios, which significantly influence the tribological properties of the blends. PI phase disperses in an island form in the UHMWPE matrix phase when the mass ratio of PI/UHMWPE is relatively small (10/90). The scattered PI dispersed phase effectively reduces the friction coefficient of the blend and improves the wear resistance. For the PI/UHMWPE blend composite with the mass ratio of 30/70, layered PI phase forms and distributes in the UHMWPE matrix phase, improving bearing capacity and wear resistance of the blends. Large continuous area structure and phase separation occurs in the blend when the mass ratio of PI/UHMWPE increases to 50/50, resulting in a significant reduction in the wear resistance of the blend composite.

Numerical analysis of bearing characteristics of composite foundation with variable diameter rigid pile

Variable diameter rigid pile composite foundation are proposed for the multi-layer foundation. The bearing characteristics of composite foundation with variable diameter rigid pile under vertical load are numerically calculated and analysed. The research content of this paper focuses on the variation law of load and settlement of composite foundation, pile axial force, pile lateral friction resistance and distribution law of soil internal force between piles under different diameter ratios etc. The results showed that Variable diameter of rigid pile composite foundation can effectively improve bearing capacity and control settlement and reduce the stress level of soil; negative skin friction section at the top of pile decreases with variable diameter ratio D/d increases, Zero skin friction section in diameter produced and increases with variable diameter ratio D/d increases; Optimal diameter ratio of pile in the variable diameter rigid pile composite foundation should be at about 1.75.

Sustainable Soil Bearing Capacity Improvement Using Natural Limited Life Geotextile Reinforcement—A Review

Geotextiles are commercially made from synthetic fibres and have been used to enhance bearing capacity and to reduce the settlement of weak soil foundations. Several efforts have been made to investigate the possibility of using bio-based geotextiles for addressing environmental issues. This paper attempts to review previous studies on the bearing capacity improvement of soils reinforced with bio-based geotextiles under a vertical static load. The bearing capacity of the unreinforced foundation was used as a reference to illustrate the role of bio-based geotextiles in bearing capacity improvement. The effects of first geotextile depth to footing width ratio (d/B), geotextile spacing to footing width ratio (S/B), geotextile length to footing width ratio (L/B) and the number of reinforcement layers (N) on the bearing capacity were reviewed and presented in this paper. The optimum d/B ratio, which resulted in the maximum ultimate bearing capacity, was found to be in the range of 0.25–0.4. The optimum S/B ratio was in the range of 0.12–0.5. The most suitable L/B ratio, which resulted in better soil performance against vertical pressure, was about 3. Besides, the optimum number of layers providing the maximum bearing capacity was about three This article is useful as a guideline for a practical design and future research on the application of the natural geotextiles to improve the short-term bearing capacity of weak soil foundations in various sustainable geotechnical applications.

Experimental measurement on friction performance of PDC bearings for oil drilling under different working conditions

Abstract As a kind of superhard material, the polycrystalline diamond compact (PDC) has been extensively used in engineering with its high strength and high wear resistance. Meanwhile, PDC has been increasingly used in bearing design to improve bearing capacity and service life. However, as a bearing material, its friction coefficient under different working conditions is not clear although it is a very important parameter. In this paper, the authors proposed a theoretical model of friction measurement and design a set of measurement rig to investigate the friction characteristics of the PDC bearing. The measurement equipment is developed based on the Coulomb friction model, with the three measurement environments taken into consideration: dry, water and drilling mud. A pair of thrust ball bearing was used in the measurement equipment to equilibrium axial load. But the friction coefficient of thrust ball bearing is proved far less than that of the PDC bearing in the experiment. The frictional coefficient of PDC bearings can be stabilized at about 0.12 under dry friction or water lubrication conditions and increase to 0.2 when tested under drilling fluid environment. Measuring the friction coefficient of PDC bearing -especially under drilling fluid environment can not only provide support for the design of the downhole tool where the bearing friction coefficient obviously affects the feasibility and agility of the tool but also help people to deepen the understanding of PDC materials.

Controlling collapsibility potential by improving Iraqi gypseous soils subsidence: A Review study

Gypseous soils classified as the most difficult soil due to their complex and unexpected behaviour. Gypseous soils around the world, formed mainly in arid and semi-arid lands. In Iraq, gypsum soil covers 20-30% of total area of Iraq specifically, in western, south and southern west areas. For the soil engineer, it is of great importance to know properties of soil before designing and building any structure. Since the gypseous soil can collapse when the water run through, therefore, many Iraqi researchers have worked out to find the best methods to improve this kind of soil. This paper summarizes most of these studies and present chemical and physical treatment applied to gypsum soils in Iraq to improve bearing capacity of gypsum soils and reduce settlement and collapsibility, improve the Bearing capacity in present study improved AL Fallujah Gypseous soaked soil after using geogrid increase the Bearing capacity about (51)%.

Performance of encased single stone column in layered soil

Stone columns were found to be effective, economical and widely-used ground improvement technique in soft grounds. It is important to understand the behavior of stone columns when they are installed in layered soils. This paper presents results from a series of small scale laboratory model tests carried out in unit cell tank to investigate the behavior of floating and end bearing stone columns in layered soils with and without encasement, consisting of loose sand overlying a soft soil. Tests were conducted with loading only the stone column area to estimate the limiting axial capacity of stone column. Laboratory tests were carried out on a column of 10 cm diameter surrounded by layered soil. Test results indicated that the bearing capacity of layered soil has been improved in all cases of stone column applications. The non- encased floating stone columns gave better results than non-encased end bearing stone column. The inclusion of geotextile encasement resulted in further improvement of layered soil and the encased floating stone column had superior bearing capacity improvement.

Effect of aspect ratio of footing on behavior of two closely-spaced footings on geogrid-reinforced sand

This paper presents the results of laboratory model tests carried out on two closely-spaced interfering footings resting on the surface of geogrid-reinforced and unreinforced sand bed. The effect of aspect ratio (or shape) of the footing on interference behavior is studied by adopting three pairs of model footings of different sizes. The length (L) to width (B) ratio (i.e., aspect ratio) of the footings is varied from 1.0 to 2.0. The effects of single layer of geogrid on footing interference and bearing capacity improvement are investigated. The optimum depth of the geogrid layer for both interfering and isolated footings is found to be one-third of the footing width and it is not dependent on the aspect ratio of the footing. The optimum spacing between the interfering footings is found to be 1.5 times the width of the footing. Lower efficiency factor is observed for interfering footings resting on the reinforced sand compared to the unreinforced sand. Higher bearing capacity ratio (BCR) is observed for isolated footing than that of interfering footings when BCR is measured based on ultimate bearing capacity values of reinforced and unreinforced cases and BCR value increases as the aspect ratio of the footing increases.

Improvement of the Gypseous soil properties by using Copolymer and Styrene-butadiene rubber

Gypseous soils are spread in several regions in the world including Iraq, where it covers more than 28.6% [1] of the surface region of the country. This soil, with high gypsum content causes different problems in construction and strategic projects. As a result of water flow through the soil mass, permeability and chemical arrangement of these soils vary over time due to the solubility and leaching of gypsum. In this study the soil of 36% gypsum content, is taken from one location about 100 km (62 mi) southwest of Baghdad, where the sample is taken from depth (0.5 - 1) m below the natural ground surface and mixed with (3%, 6%, 9%) of Copolymer and Styrene-butadiene Rubber to improve the engineering properties of the gypseous soil including collapsibility, permeability and shear strength. Results of the experimental work show noticeable improvement of collapsibility, permeability, and bearing capacity in soil treated with Copolymer and Styrene-butadiene Rubber compared to untreated soil.

Behavior of Geotextile-Encased Single Stone Column in Soft Soils

Stone columns have become a widely used method of increasing bearing capacity of soft soils. This study investigates floating stone columns with and without encasement in soft soils. Although the stone columns in single-layered soil have been studied extensively, stone columns constructed in a base of varying soil layers are not fully understood. In the present study, the behavior of both single-layered soft soil and layered soil consisting of loose sand overlaying the soft soil was investigated by using small-scale laboratory pilot tests. The bearing capacity of soft soil was improved in all cases of stone column application. The contribution of stone columns on the bearing capacity of soft soil was presented by the term bearing improvement ratio (BIR). With a non-encased stone column in single-layered soft soil, the BIR was about 3.3-fold and with geotextile encasement in the same soil, the improvement ratio increased to 3.4-fold. For a non-encased stone column in layered soils, the BIR was about 2.0-fold and with geotextile enhancement in the same soil, this improvement ratio increased to 4.0-fold. The inclusion of geotextiles resulted in improved bearing capacity by distributing the induced stresses over larger areas. The maximum bulging of non-encased stone column in single-layered soft soil was observed at the depth of 1.5 times the original diameter of the stone column from the top, whereas for encased stone column in single-layered soft soil, the maximum bulging was transferred to a depth of 3.0 times the original diameter of the stone column.

Theoretical and experimental study on steel open-web sandwich floor with flanged cruciform section shear key

Abstract Steel open-web sandwich floors (SOSFs) have been applied in several pioneering industrial and public buildings. The traditional square tube shear key (STSK) is changed into a flanged cruciform section shear key (FCSK) to further improve the bearing capacity of SOSFs. A half-scale test model is designed. A graded static loading test is performed to measure deflection and strain. The calculation formula of the intersection beam analogy method (IBAM) considering the influence of shear stiffness is proposed. A finite element (FE) analysis was also performed. The results of the test, IBAM and FE method are compared. The maximum deviation of the deflection obtained by them is less than 5%, and the maximum strain error is less than 7%. These figures prove that all three methods have high precision in the elastic range. Compared SOSFs use a different shear keys with the same grid size and chords, the maximum Mises stress is reduced by 55.9% and the maximum displacement is reduced by 36.1%. The new shear key imparts the structure with improved bearing capacity and safety margin.

Behavior of grouped stud shear connectors between precast high-strength concrete slabs and steel beams

This study aims to examine the interface shear behavior between precast high-strength concrete slabs with pockets and steel beam to achieve accelerated bridge construction (ABC). Twenty-six push-out specimens, with different stud height, stud diameter, stud arrangement, deck thickness, the infilling concrete strength in shear pocket (different types of concrete), steel fiber volume of the infilling concrete in shear pocket concrete and casting method, were tested in this investigation. Based on the experimental results, this study suggests that the larger stud diameter and higher strength concrete promoted the shear capacity and stiffness but with the losing of ductility. The addition of steel fiber in pocket concrete would promote the ductility effectively, but without apparent improvement of bearing capacity or even declining the initial stiffness of specimens. It can also be confirmed that the precast steel-concrete composite structure can be adopted in practice engineering, with an acceptable ductility (6.74 mm) and minor decline of stiffness (4.93%) and shear capacity (0.98%). Due to the inapplicability of current design provision, a more accurate model was proposed, which can be used for predicting the interface shear capacity well for specimens with wide ranges of the stud diameters (from13 mm to 30 mm) and the concrete strength (from 26 MPa to 200 MPa).