Bearing Capacity Of Soft Soil Research Articles

Using blast energy as an effective technology to provide subgrade stability in road construction

Drilling and blasting technology is considered to be one of the most efficient and cost-effective ways to increase the bearing capacity of soft soils which form the subgrade of road embankments. This study investigates blast energy as a means of creating vertical sand drains in a section of Moscow-Saint-Petersburg Motorway M-11 (construction 2018) which crosses the Kolomenka River and is located in a swampy area. Geophysical and geological engineering tests were conducted, they included monitoring of pore pressure modification in soft soils as well as geodetic monitoring of settlement levels. The findings showed that the applied technology quickly allowed a large bulk of sandy soils (more than 500 thousand cubic meters) to compact in the subgrade of the road as a result of generation of excessive pore pressure. No other technology could have been used due to the presence of an embedded bulk of soft soils and swampiness of the site. Decreasing deformations of the subgrade and CPTU data revealed that the subgrade of the road embankment was compacted. This fact was also confirmed by geophysical tests. Drilling and blasting technology is very effective from an ecological and economic perspective in comparison with other technologies. In addition, this study highlights the importance of preserving swamp systems in order to protect river sources.

Analytical model for consolidation and bearing capacity of soft soil stabilized by combined PVD-deep cement mixing columns

Analytical model for consolidation and bearing capacity of soft soil stabilized by combined PVD-deep cement mixing columns

Ultimate Bearing Capacity of Soft Soil Improved by DCM Columns: A Comparative Review

Ultimate Bearing Capacity of Soft Soil Improved by DCM Columns: A Comparative Review

Effect of several patterns of floating stone columns on the bearing capacity and porewater pressure in saturated soft soil

One of the common geotechnical problems is the construction on soft soil and the improvement of its geotechnical properties to meet the design requirements. A stone column is one of the well-known techniques used to improve the geotechnical properties of soft soils. Sometimes thick layers of soft soil imposed the designer to use floating stone columns for improvement of such soil; in this case, the designer will be lost the end bearing of the stone column. In this study, the effects of several patterns of floating stone columns distribution under footing on the bearing capacity of soil and the distribution of excess porewater pressure are investigated. The soft soil used in this study has a very low undrained shear strength (cu) of 5.5 kPa and improved by several patterns of stone columns (single, two linear, triangular, square, and quadrilateral). The stone column has a length of 180 mm and a diameter of 30 mm. The material of the stone column is poorly graded sand has an angle of internal friction (48.5°) at a relative density of 65%. The results indicated a significant increase in the ultimate bearing capacity of soft soil when treated with floating stone columns despite the small ratio of area replacement and reducing the excess porewater pressure and settlement. Also, the ultimate bearing capacity of soil calculated from experimental work is compared with the corresponding values obtained from the proposed equations in the previous studies to evaluate the validity of using such equations.

Geocell Reinforced Soil/Subgrade: Comparative Study of Bearing Capacity Evaluation Methods

At present, rapid urbanization results in enormous infrastructure growth, which led engineers to face construction challenges over soft soil or weak sub grade. Many soil stabilization approaches have been established as a viable way to overcome this hindrance. Among all the ground improvement techniques, geocell, being a three-dimensional form of geosynthetics, is often used to enhance the bearing capacity of soft soils. This paper discusses analytical methods developed by researchers Presto (2008) [1], Koerner (2012) [2], Avesani Neto et al. (2013) [3], and Sitharam and Hedge (2013) [4] to evaluate the bearing capacity of soil reinforced with geocell. The paper also compares the results of these methods with those of laboratory experiments conducted by Dash et al. (2003b) [5] and Emersleben and Meyer (2008) [6]. Researcher Dash et al. used cohesive soil in foundation, while Emersleben and Meyer used c-ɸ soil in foundation. The comparisons show that researchers Koerner and Presto underestimate the bearing capacity when compared with experimental results of both Dash et al. and Emersleben and Meyer. Whereas authors Avesani Neto et al. and Sitharam and Hegde offer the best fit with experimental results of Dash et al. But, with Emersleben and Meyer’s experimental results, Avesani Neto et al. gives the overestimated results, while Sitharam and Hegde partially agree for lower geocell aspect ratios beyond settlement equal to 35% of footing diameter.

Assessment of innovative dented sheet liner on the improvement of hydraulic properties of pervious concrete pile

The Pervious Concrete Pile (PCP) is a technique that has emerged as an innovative method to improve radial consolidation and the bearing capacity of soft soils. The PCP, a stiffer vertical column (pile), has voids on the surface that accelerate the radial consolidation and eventually improve soft soils' bearing capacity. Since the PCP is stiffer material, the performance does not depend on the confined soil, unlike other drains. As the rate of radial consolidation hinges on the drain's hydraulic conductivity, ensuring the permeability of PCP along its total length is essential. An innovative method of dented sheet liner has been introduced in this study to improve the hydraulic conductivity of PCP. This method was introduced to create surface roughness and regular voids along the length of PCP. Malleable material like aluminium has been dented with specified patterns as a liner on the inner surface and introduced along with conventional formwork, which shall be removed after the concrete's final setting time. A series of laboratory experiments such as compressive strength, split tensile strength, porosity, and falling head permeability tests were performed on PCP cast using dented sheet liners. The results were compared with the conventional PCP properties to establish the efficiency of dented sheet liner in improving the hydraulic conductivity of pervious concrete. The results show that using dented sheet liners, the hydraulic properties porosity and permeability of PCP have been increased up to 22.5% and 79%, respectively, with minimum reduction in the strength parameters.

Effects of Curing Time Using Crushed Coconut Shell (CCS) and Coconut Shell Ash (CSA) as Additive to Improve Lateritic Soils

Numerous constructions in Malaysia have encountered the issues where soil cannot fulfil the standard required specification due to the bearing capacity of soft soil is too weak to withstand traffic loading. Recently, there is a lot of defeats related to soil settlement and distorting of the structure effect by the inflated compressibility and low in shear strength of the soil. This research study on the effects of natural additives in crushed coconut shell (CCS) and coconut shell ash (CSA) to enhance the durability of lateritic soil for road pavement. The effects of curing time in the CCS and CSA admixture of soil is examined. Different proportions of 5% and 9% CSA with a constant 8% CCS were used to study the effect on lateritic soil. Series of preliminary tests were performed followed by engineering test of Compaction test in identification on optimum moisture content (OMC) and maximum dry density (MDD) followed by California Bearing Ratio (CBR) for curing day of 4 days, 7 days and 14 days of soil mixtures sample to investigate its enhancement to soil strength. Further review from the previous research has also been carried out and it is pointed out that by using natural CCS and CSA brushed up the soil load-bearing capacity due to the increment of CBR value obtained as compared to the normal mix. Hence, it can be concluded that the combination of natural additives CCS and CSA in the soil also have the capability to improve the soil strength and can be suggest to replace aggregates and cement for use in lateritic soil stabilization subject to road works.

Methodology for calculate bearing capacity of soft soils under cyclic loading

The bearing capacity in soft soils under cyclic loading has not been widely studied as the static bearing capacity. In soft saturated soils under cyclic load, the phenomenon of cyclic softening occurs, this consists of an increase in the generation of pore-water pressure due to the cyclic load and a decrease in effective soil stresses. The purpose of this work was to propose a methodology for calculating the bearing capacity in soft soils under cyclic loading. The research is based on the results of monotonic and cyclic simple shear tests carried out with samples from the PRAT port of Barcelona. From an analysis carried out on all the experimental data, an equation for the generation of pore-water pressure is proposed. This formulation was implemented in the FLAC2D finite difference software and is part of the methodology. The methodology of the proposed calculation process consists of 6 stages and verification under two criteria. This process is iterative in case of not meeting any of the two verification criteria. Under this methodology of the calculation process, charts are proposed to calculate the bearing capacity of soft soils under cyclic loading. This application takes into account the properties of the soil, the static bearing capacity (P he), and the effective load outside the foundation (q). Also, an analysis of the parameters that most influence the bearing capacity of soft soils under cyclic loading was carried out.

The Novel Usage of EPS Geofoam as Column Material: A Laboratory Study

The technique of stone column to improve the performance of soft soil is well established. However, an alternative material to enhance the performance of the soft soil by reinforcing with geofoam materials is suggested. Expanded polystyrene (EPS) geofoam is a superlight weight geosynthetic material used in various geotechnical engineering applications. This study deals with the innovative use of geofoam as a column material in soft soil for improving the bearing capacity. The method was developed in small-scale laboratory tests, and a series of loading tests were carried out on various single floating geofoam columns (normal geofoam and hollow geofoam) with two different diameters and the length-to-diameter ratio of 5. Next, a comparison was made with the results of ordinary stone columns and reinforced stone columns to obtain the benefits of geofoam columns. According to the results and by considering the bearing capacity, geofoam columns could be a good alternative material for improving the bearing capacity of soft soils. It was also found that the efficiency of the geofoam columns is almost similar to that of the ordinary stone columns and the usage of the geofoam is easy and economical. However, encasing the stone columns with geotextile results in further growth in the bearing capacity.

Reinforcement Of Soft Soil Using Soil Column Method (Soft Soil + CCR + RHA)

Soil reinforcement method is one of attempt to improve technical characteristic from the soil, such as soil bearing capacity, compressibility and permeability. The Soil Column Method is one of alternatives to enhance physical characteristic by way of stabilization to improve soil bearing capacity. Rice Husk Ash (RHA) contains high silica element, Calcium Carbide Residue (CCR) contains high calcium which is able to form pozzolan when mixed upon silica. This research aims to improve soil bearing capacity by using column soil method with a mixture of soft soil, 3% Calcium Calbide Residue (CCR) and 12% Rice Husk Ash (RHA). Soil column in this research applied a single column variation with a diameter of 3,2 cm which each has 40 cm, 46 cm, and 53 cm in length and each column with diameter of 3,2 cm, 4,2 cm, and 4,8 cm. Based on the research, ultimate Bearing Capacity (qu) of soft soil without soil column was 54,03 kPa and after being given reinforcement had increased the bearing capacity value (qu). The greates increase in soil bearing capacity of the soft soil occurred in soil column variation of 53 cm in lenght with 4,8 cm in diameter where the soil bearing capacity had increased to 75,58 kPa and the percentage increase in BCR was 39,90%. Meanwhile the least of soil bearing capacity occurred in soil column that had 53 cm in length and diameter of 3,2 cm while the soil bearing capacity had increased to 64,47 kPa and BCR only increased to 19,33%

Experimental studies on single reinforced stone columns with various positions of geotextile

Stone columns are used as a technique for improving the strength and enhancing the bearing capacity of soft soils. Due to the low confinement of the soil typically surrounding the stone columns, reinforcement materials like geotextile are needed to improve such weakness. Although the technique is now well established, little research has been undertaken on the use of various positions of the reinforcement materials. In this paper, some small-scale laboratory tests were performed on reinforced floating stone columns with diameters of 80 mm and 100 mm and the length of 400 mm and 500 mm, respectively, to study the influence of various positions of geotextile. They were included vertical encasement stone columns, horizontal reinforcement stone columns and combined vertical–horizontal encasement stone columns. The impacts of the different diameters of the columns, the length of the reinforcement and the spaces of the reinforcement have been studied. Based on the results, by increasing the diameter of the vertical encasement stone column, the benefit of encasement decreases, while in horizontal and vertical–horizontal encasement stone column, the performance of the reinforcement increases. Moreover, the load-carrying capacity of combined vertical–horizontal encasement stone columns increases considerably in comparison with the other types.

Analytical Study of Load-Settlement Behavior of Soil Treated with Stone Columns have Different Sectional Shape

Stone columns have been used widely to improve the engineering properties of the weak soil. Most of the previous works considered a circular section for the stone columns. In the present study, finite element analysis has been carried out to investigate the effect of stone columns shape and length on the settlement and bearing capacity of soft soil. Accordingly, three types of cross sectional shape for stone columns have been selected which they are circular, rectangular, and square sections with equivalent area. Various length of columns are adopted with diameter of 0.75m that achieved length to diameter or equivalent diameter ratios (L/d=2, 4, 6, 8, and 10) of columns spacing (S/d=3). The results show that the stone columns has tangible effects on the settlement of the soil while has minor effects on the bearing capacity. The settlement of the treated soil with stone columns have L/d=2, reduces by 18.0, 17.3, and 19.3% for circular, rectangular , and square sections respectively. With increasing length of the columns to L/d=10, further reductions in the settlement obtained of (27.1, 28.1, and 27.0%). Bearing capacity of the soil increased slightly with length of the stone columns. Almost all cross sectional shapes of the columns give bearing capacity about same. The increased in the bearing capacity of the treated soil with stone columns have L/d=2, not exceeded 10% for all sectional types. The average increments in bearing capacity when L/d=10 are 12 and 15% at settlement 50 and 100mm respectively. Insignificant changes in bearing capacity upon increasing length of columns from L/d=2 to 10 of maximum 5%. The plastic zone recedes with the increasing length of the stone columns. Finally, from the results obtained, it can be concluded that the stone columns shape has negligible effects on the settlement and bearing capacity of the soil.

Experimental Study of Natural Materials Utilization as a Stabilization Agent on Soft Soil

Chemical soil stabilization is known as the most economical method compared to others. The development of stabilization materials has led to studies of the utilization of natural materials and waste materials to replace cement and lime which has become the most popular binder agent ever known. This research utilizes natural minerals such as overboulder, zeolite and Palm Oil Fuel Ash (POFA) as its binder agents. The amount of natural material varies at intervals 3% - 15% by the weight of soil. Additional of natural materials is done to increase bearing capacity as a subbase layer, which is based on FHWA standards CBR minimum is 20%. California Bearing Ratio (CBR) tests were carried out to see the effect of each material for increase bearing capacity of soft soil. Curing periode is varies at 7 days, 14 days and 28 days. The results shows, by adding natural minerals such as overboulder, zeolite, and POFA increasing the CBR value up to 5 times, 6 times and 5 times compared to untreated soil and close to the CBR value of cement stabilized soil. Referring to FHWA standards, we can conclude that natural materials can be used for stabilization materials on subbase layer.

Bearing capacity of foundation on soil reinforced by deep mixing columns

ABSTRACT An analytical calculation of the bearing capacity of soft soil reinforced by the deep mixing method is presented. A comparison between this result and the homogenization method using the mechanism of Prandtl is also discussed. Comparison between the results shows that the direct calculation with the kinematic approach by a rigid mechanism leads to an upper bound of the bearing capacity factor BCF larger, but very slightly, than that obtained from the approach of homogenization considering the Prandtl mechanism. The method of homogenization allows estimating the influence of the reinforcement width beyond foundation while the direct method cannot provide this estimation. It was concluded that the upper bound increases rapidly for a width ratio (width of reinforcement to width of foundation) l ≤ 1 (l is the ratio between the total width of the reinforcement and the width of the foundation), against this, the increase becomes less significant for 1 ≤ l ≤ 2, a little less steep for 2 ≤ l ≤ 3. Then, it becomes stable when l ≥ 3 which shows that ground next to the foundation is the most concerned in increasing the bearing capacity. Comparison with the homogenization method showed that the upper limit increases proportionally with the substitution factor η.

Investigation of the effect of water repellents on the rolling border and the yield stress of clay soils of the base and subgrade of the road

During the construction of roads, the main factor affecting the operational characteristics of a linear facility is the climatic conditions of a particular area where the future road will pass. In the article, the authors consider the problem of building roads on weak soils with insufficient strength characteristics, such soils cause difficulties in the design and operation of the structure. The purpose of this study is to change the physical properties of cohesive soils to increase their strength characteristics. The authors systematized information on existing methods for stabilizing clay soils of the base and subgrade of the road. The results of experimental laboratory studies performed by the authors of the article on the influence of water repellents on the physical properties of clay soil are presented. According to laboratory studies, it can be concluded that with the optimal selection of hydrophobic materials, it is possible to increase the bearing capacity of soft soils, which in turn will lead to an increase in the technical and operational characteristics of the structure and an increase in turnaround times. The main conclusions are formulated based on the analysis of laboratory tests.

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.

Settlement Behaviour of Soft Soil Reinforced with Geogrid Encased Stone Column under Sustained Loading

The use of stone columns in improving the bearing capacity of soft soil is well researched, but the understanding of settlement requires further studies. This paper presents the results of a series of laboratory tests carried out to study the settlement behavior of soft soil bed reinforced with ordinary stone column (OSC) and Geogrid encased stone columns (GESC). Kaolin was used as the soft soil and stones of size from 2.5 to 10 mm were used as column material. The stone columns of four different diameters were installed, by the method of replacement, into the soil having undrained shear strength of 22.5 kPa. The OSC and GESC test beds were subjected to pressure of 250 and 300 kPa. Each pressure was sustained for 24 hours and the settlement of the composite soil with time was noted. It is found that Geogrid encased stone columns have small settlement than the corresponding ordinary stone columns. The SRR (settlement reduction ratio) being a measure of ground improvement, is found increasing with the area replacement ratio. Further, at a particular sustained pressure SRR is found more for GESC than the corresponding value for OSC.

Numerical Study on Uniaxial Compression Behavior of Geobags

Geobags have been used as coastal erosion control and flood preventing measures during the last decades. More recently engineers have used geobags to improve the bearing capacity of soft soils. In this paper, a study was performed to investigate the behavior of geobags under compression loadings utilizing a finite element computer software. The numerical modeling was verified by simulating reported laboratory compression test results. The effects of various parameters such as geobag’s dimensions, mechanical characteristics of filling soil and bag material properties on the ultimate bearing capacity of geobags were investigated. It was shown that increasing the friction angle of filling soil and the tensile strength of textile lead to an increase in the geobag ultimate compressive load capacity. On the other hand, an increase in dilation angle of filling soil, Poisson's ratio and the height of geobag lead to a decrease in the ultimate compressive load capacity of geobags.

The use of natural fiber from oil palm empty fruit bunches for soft soil stabilization

The use of natural fiber as a construction material, especially soil stabilization continues to grow. This paper focuses on the use of natural fiber to increase shear strength and bearing capacity of soft soil. The fiber used is obtained from oil palm empty fruit bunches (EFB) as a by-product of palm oil mills. Soft soil mixed with fiber with a composition of 5, 6, 7, and 8% fiber in the mixture. Some tests such as the standard compaction test, unconfined compression test, laboratory vane test, and California Bearing Ratio test were carried out. The results show that the soft soil used in this study can be compacted at fiber content higher than 5%. The maximum density obtained is 0.92 g/cm3 at 7% fiber content. The compacted soil-EFB mixtures successfully increase the shear strength and bearing capacity of the soft soil shown by the results of the UCT, laboratory vane, and CBR tests. The soil consistency changes from soft to medium soil. The maximum qu, su, and CBR obtained are 0.8 kg/cm2, 0.65 kg/cm2, and 6%, respectively at optimum fiber content of 6 to 7%.

Effect of aspect ratio of footings on settlement response of geosynthetic-reinforced granular fill-soft soil system

In this paper, a simple mathematical model is used to study the effect of aspect ratio of footings on settlement response of unreinforced or geosynthetic-reinforced granular fill-soft soil system. The length-to-width ratio (aspect ratio) of footings is varied from 1.0 (square) to 3.0 (rectangular). The foundation model is formulated for single layer of reinforcement. Parametric studies are carried out for a range of shear modulus values of granular fill and ultimate bearing capacity values of soft soil. It is observed that the aspect ratio has significant effect on settlement response and mobilised tension in geosynthetic layer. Both settlement and mobilised tension below the loaded area increase with an increase in the aspect ratio of footing for a particular loading intensity with constant width of the footing and constant soil parameters. The effectiveness of the reinforcement in terms of settlement reduction decreases due to increase of aspect ratio. The settlement decreases with an increase in ultimate bearing capacity of soft soil or shear modulus of granular fill. However, the rate of reduction of settlement with an increase in ultimate bearing capacity or shear modulus decreases as the aspect ratio increases.