Soil Reinforcement Technique Research Articles

A State-of-the-Art Review on Soil Reinforcement Technology Using Natural Plant Fiber Materials: Past Findings, Present Trends and Future Directions.

Incorporating sustainable materials into geotechnical applications increases day by day due to the consideration of impacts on healthy geo-environment and future generations. The environmental issues associated with conventional synthetic materials such as cement, plastic-composites, steel and ashes necessitate alternative approaches in geotechnical engineering. Recently, natural fiber materials in place of synthetic material have gained momentum as an emulating soil-reinforcement technique in sustainable geotechnics. However, the natural fibers are innately different from such synthetic material whereas behavior of fiber-reinforced soil is influenced not only by physical-mechanical properties but also by biochemical properties. In the present review, the applicability of natural plant fibers as oriented distributed fiber-reinforced soil (ODFS) and randomly distributed fiber-reinforced soil (RDFS) are extensively discussed and emphasized the inspiration of RDFS based on the emerging trend. Review also attempts to explore the importance of biochemical composition of natural-fibers on the performance in subsoil reinforced conditions. The treatment methods which enhances the behavior and lifetime of fibers, are also presented. While outlining the current potential of fiber reinforcement technology, some key research gaps have been highlighted at their importance. Finally, the review briefly documents the future direction of the fiber reinforcement technology by associating bio-mediated technological line.

Effect of reinforcement fibers on the collapse potential of clayey sands

The collapse of soils under wetting is a major problem in Geotechnical engineering. The erection of structures on these types of soils, located in arid and semi-arid zones, needs careful treatment of these soils. Soil reinforcement techniques have been rapidly increased during these two decades because of their effectiveness in geotechnical engineering. The aim of this experimental work is to investigate the collapsible soil behaviour in order to improve its characteristics. To achieve this goal, Polyethylene fibers, and Sisal fibers were used as Polyethylene fibers content in mass are varied from 0% (unreinforced samples) to 15%; and Sisal fibers content from 0.5% to 1%. The fiber reinforcement is combined with other processing procedures such as compaction and the addition of CPA cement to decrease the collapse potential.

Effect of reinforcement fibers on the collapse potential of clayey sands

The collapse of soils under wetting is a major problem in Geotechnical engineering. The erection of structures on these types of soils, located in arid and semi-arid zones, needs careful treatment of these soils. Soil reinforcement techniques have been rapidly increased during these two decades because of their effectiveness in geotechnical engineering. The aim of this experimental work is to investigate the collapsible soil behaviour in order to improve its characteristics. To achieve this goal, Polyethylene fibers, and Sisal fibers were used as Polyethylene fibers content in mass are varied from 0% (unreinforced samples) to 15%; and Sisal fibers content from 0.5% to 1%. The fiber reinforcement is combined with other processing procedures such as compaction and the addition of CPA cement to decrease the collapse potential.

Behavior of Geosynthetic Reinforced Soil Foundation Systems Supported on Stiff Clay Subgrade

A series of laboratory model tests was performed to investigate the behavior of geosynthetic reinforced stiff clay foundation systems under circular loading. The footing consisted of a rigid circular steel plate with a diameter of 150 mm. Five different series of tests were performed in both homogeneous (clay or sand) and layered configurations. The tests used planar geogrid and three-dimensional geocell reinforcements. Test results indicate that both types of reinforcements substantially improve the performance of the stiff clay foundation bed. A maximum threefold improvement was observed in bearing pressure, depending on the reinforcement type. However, geocell was found to be the most advantageous soil reinforcement technique, giving maximum performance improvement.

Strength Behavior of Clayey Soil Reinforced with Human Hair as a Natural Fibre

There are various ground improvement techniques available, soil reinforcement technique has been successfully used in recent times to improve the shear parameters of the marginal/weak soils. Among various reinforcing materials, human hair fiber (HHF) can be used as a natural fiber to enhance the shear strength and bearing capacity of a clayey soil for sustainable use of waste material and sustainable development of infrastructures in a rapid urbanization. Human hair fiber is a natural non-degradable waste material, which creates health and environmental problem if not disposed-off in scientific manner. This is available in abundance at a very low cost and can be easily used as a reinforcing material not only to improve poor/unsuitable construction sites for sustainable construction but also to avoid its disposal problems. Therefore, this paper presents some studies on strength properties of clayey soil reinforced with HHF. The HHF randomly distributed in clayey soil samples were tested for its engineering properties by performing CBR and tri-axial test on a number of samples by using the different percentage of fibres and comparing the results with the non-reinforced soil. Fibres of average length 25 mm and average diameter of 50 µm were used. The test result revealed that the strength significantly improves with the inclusion of HHF and also prevents the sample from cracking.

STUDY ON SHEAR STRENGTH CHARACTERISTICS OF COIR MAT REINFORCED SAND

Soil reinforcement technique is one of the most popular techniques used for improvement of poor soils. Metal strips, synthetic geotextiles, geogrid sheets, natural geotextiles, randomly distributed, synthetic and natural fibers are being used as reinforcing materials to soil. Further, the soil reinforcement causes significant improvement in tensile strength, shear strength, other properties, bearing capacity as well as economy. This is a relatively simple technique for ground improvement and has tremendous potential as accost effective solution to many geotechnical problems. The objective of the present investigation is to determine the effect of introducing coir mat reinforced soil layer over soil stratum and effect of size of the opening of coir mat on shear strength characteristics of sand will be analysed.

IMPROVING THE STRENGTH OF SANDY SILT SOILS BY MIXING WITH CEMENT KILN DUST

Egyptian irrigation and drainage system consists of the River Nile, its branches, canals and drains. It is very important to keep them working in good condition to assure efficient water management and distribution process. Water channel embankments made of sandy silt soils are exposed to slope stability problems. These problems are considered one of the common canal embankments problems in the delta of Nile River. Soil improvement is one of the most economic engineering solutions to overcome soil problems. This research studying the improving of sandy silt soils by mixing with cement kiln dust. Laboratory tests were carried out to evaluate the improved soil properties. Three numerical models were built for an embankment of a canal to examine the introduced method to overcome slope stability problems. The natural soil slope stability safety factor was calculated from the first numerical model. The second model used to calculate safety factor after applying the improved soil properties that were determined from the laboratory works. The third numerical model was built to simulate improving natural soil by using the traditional soil reinforcement technique. The results for the two improvement methods were compared. The results showed that the proposed method caused significant improvement for slope stability of the sandy silt soil. The proposed method has the advantage of using with existing or new structures.

Physical Modelling Of Improving Bearing Capacity For Foundations By Geo Fabrics

The objective of the research paper is to develop a new model by which we can improve the bearing capacity of foundation by using geo fabrics. The primary design concerns for a foundation engineer are bearing capacity and settlement. The soil reinforcement technique of the geo synthetic has been taken into account for developing such a model that can be used to reduce excessive settlements on soft soils and prevent the foundation from failing. Hence, this paper summarizes the physical and numerical simulation to verify the results to enhance the performance of the foundation. Motivation: With the rapid increase in globalization, there has been a shortage of land. Deep foundations are required for poor soil conditions, sloping lands and where there is problems regarding site drainage. Besides with rising cost of materials and increased labor and time required for construction, it has become the need of the hour to develop a new model that will do away with the traditional materials, increase the bearing capacity, and reduce settlement to construct the foundations. The geo synthetics are the third revolution in civil engineering materials that has taken the world by surprise. Its increasing usage owing to its non biodegradable ness, durability, increasing the factor of safety and cost effectiveness can be used to develop a model that would increase the bearing capacity of foundations. Besides, in places where deep foundations are used for poor soil conditions and drainage problems, we can use this new cost effective model of shallow foundation with geofabrics that results in increased bearing capacity. I. Introduction: The primary design criteria for a foundation are bearing capacity and settlement. The use of geo synthetic material to improve the bearing capacity and the settlement performance of a shallow foundation has been of much interest to geotechnical engineers. Several research works has been carried out for soil improvement using several geosynthetic materials. Binquet and Lee used metallic strip under strip footing to improve its bearing capacity. Geogrids and geo cells were later on used for such work. From the finding of numerous researchers, it can be concluded that the bearing capacity of soil also changed with various factors like type of reinforcing materials, number of reinforcement layers, ratios of different parameters of reinforcing materials, and foundations such as footing width, location of the 1st layer of reinforcement to width of footing and vertical spacing between consecutive geogrid layer. However, not much appreciable work has been done with geofabrics to improve the bearing capacity of foundations. The ratio of improvement in the bearing capacity can be expressed in a non dimensional form as bearing capacity ratio (BCR) which is the ratio of bearing capacity of reinforced soil to bearing capacity of unreinforced soil. The present study investigates the improvement of bearing capacity of shallow foundations with the utilization of geofabrics. OBJECTIVE: 1. To improve the bearing capacity of foundations with the help of geo fabric 2. To determine the place where the geo fabric should be placed. 3. To determine the reason behind the increase in bearing capacity. 4. To validate the results using physical simulation.

Application of the Modified Goodman Model in Soil Nailing

AbstractSoil nailing is an in situ soil reinforcement technique used for enhancing the stability of slopes, retaining walls, and excavations. Nails work predominantly in tension, but may also work in bending and/or shear under certain circumstances. To accurately simulate the interaction mechanism between soil mass and nails, it is necessary to study the behavior of their contact interface. The Goodman element is one of the interface elements used extensively in geotechnical contact problems. However, larger normal stiffness values are needed in the application of the Goodman element, which often leads to larger numerical error. In this paper, the Goodman element model was modified by adding two rotational degrees of freedom. Then, a finite-element program was written based on the modified Goodman element model and was applied in analyzing a foundation pit. Compared with the actual monitoring results, it shows that the modified Goodman element model developed in this paper is reasonable and feasible.

Influence of slope geometry and nail parameters on the stability of soil-nailed slopes

Soil nailing is one of the in-situ soil reinforcement techniques that have been used for the past four decades. The stability of a soil-nailed slope is closely related to slope geometry and nail parameters. This paper presents a parametric study on various factors influencing the overall stability of soil-nailed slopes. Stability analysis was performed to study the effect of slope geometry, nail parameters and effect of rising water surface within the slope on the overall stability of soil-nailed slopes. The stability of soil-nailed slopes is considered in terms of a factor of safety. The slope geometry varied for the present study includes slope inclination and back slope inclination while the nail parameters include nail inclination, nail length, nail length pattern, and nail layout (horizontal spacing). The study shows that with horizontal back slopes, the optimal nail inclination (α_<i>opt</i>) increases with the decrease in slope inclination but it increases with an increase in back slope inclination. Two nail length patterns: Pattern 1, nail length decreasing with depth of the slope and Pattern 2, nail length increasing with depth of the slope have been studied. Pattern 1 is found to be effective for a 10.2 m high slope whereas Pattern 2 is found to be effective for 7.2 m high slope. Rising water surface within the slope, increase in horizontal spacing and decrease in length of the nail reduce the overall stability of a soil-nailed slope. Contribution of nails to the overall stability of soil-nailed slopes is different and found to be dependent on their location and inclination with respect to the slip surface.

Effect of Coir Fiber on the Stress–Strain Behavior of a Reconstituted Fine-Grained Soil

The heterogeneous nature of the soil poses great challenge as well as opportunity to geotechnical engineers all over the world. As the availability of good sites is becoming difficult, active research is going on throughout the world to improve the engineering properties of the soft soils. Among all the ground improvement techniques, the soil reinforcement is emerging as an attractive alternative. Addition of natural fiber to the soil is a very good soil-reinforcement technique in the context of sustainable development. Coir fiber can be effectively used to tackle many short-term stability issues in geotechnical engineering related to shear strength, permeability, etc. In the present study, comprehensive experimental work has been conducted to investigate the effect of coir fiber on the stress–strain characteristics of a reconstituted cohesive soil. Laboratory model studies are conducted to study the effect of length and amount of fiber on the shear strength of soil. Tests were carried out using fiber contents varying in the range of 0%–2% by dry weight of the soil. The unconfined compressive strength of soil is significantly increased when coir fiber is added to it. The increase is directly proportional to the quantity of the fiber used. The peak compressive strength of the fiber-reinforced soil with 1.5% fiber content is more than twice that of the un-reinforced soil. Mixing of fiber of length 15 mm is found beneficial from laboratory experiments on 38-mm (diameter) × 76-mm (height) samples. Triaxial compression tests results showed that the fiber content in the range of 1.5%–2% is highly beneficial to enhance and strength of the fine-grained soil. Also, it is observed that peak deviator stress increases with increase in fiber content for all confining pressures. A remarkable increase in cohesion and friction angle values has been observed with the addition of fiber, and they increases nonlinearly with the fiber content. Moreover, the stiffness and ductility of the soil are quite improved with the use of natural fiber.

Effect of reinforcement form on the bearing capacity of square footings on sand

This paper presents the results of laboratory model loading tests and numerical studies carried out on square footings supported on geosynthetic reinforced sand beds. The relative performance of different forms of geosynthetic reinforcement (i.e. geocell, planar layers and randomly distributed mesh elements) in foundation beds is compared; using same quantity of reinforcement in each test. A biaxial geogrid and a geonet are used for reinforcing the sand beds. Geonet is used in two forms of reinforcement, viz. planar layers and geocell, while the biaxial geogrid was used in three forms of reinforcement, viz. planar layers, geocell and randomly distributed mesh elements. Laboratory load tests on unreinforced and reinforced footings are simulated in a numerical model and the results are analyzed to understand the distribution of displacements and stresses below the footing better. Both the experimental and numerical studies demonstrated that the geocell is the most advantageous form of soil reinforcement technique of those investigated, provided there is no rupture of the material during loading. Geogrid used in the form of randomly distributed mesh elements is found to be inferior to the other two forms. Some significant observations on the difference in reinforcement mechanism for different forms of reinforcement are presented in this paper.

Performance of different geosynthetic reinforcement materials in sand foundations

This paper presents the results of laboratory model tests carried out to study the relative performance of different forms of reinforcement (i.e. geocell, planar and randomly distributed mesh elements) in sand beds under strip loading. The results demonstrate that geocell reinforcement is the most advantageous soil reinforcement technique of those investigated. With the provision of geocell reinforcement, failure was not observed even at a settlement equal to about 45% of the footing width and a load as high as eight times the ultimate capacity of the unreinforced soil, whereas, with planar reinforcement, failure took place at a settlement of about 15% of the footing width and a load of about four times the ultimate capacity of the unreinforced soil. For the case with randomly distributed reinforcement mesh, failure was recorded at a load of about 1.8 times the ultimate capacity of the unreinforced soil and at a settlement of about 10% of the footing width.

Experience with soil nailing in Brazil: 1970–1994 : J. A. R. Ortigao, E. M. Palmeira & A. C. Zirlis, Proceedings - ICE: Geotechnical Engineering, 113(2), 1995, pp 93–106

This paper addresses soil reinforcement techniques employing semi- rigid inclusions called nails, hence the term soil nailing. It was intuitively applied for the first time in Brazil in 1970 by tunnel contractors in Sao Paulo. Since then, several soil nailed structures have been constructed successfully. The development of methods of analysis in Europe and North America is reviewed; the application of those methods in Brazil has led to more economical and safer structures. This paper briefly presents the historical development and the use of soil nailing in Brazil. Differences and similarities with traditional techniques are discussed and some examples are given. (A)

EXPERIENCE WITH SOIL NAILING IN BRAZIL: 1970-1994.

This paper addresses soil reinforcement techniques employing semi- rigid inclusions called nails, hence the term soil nailing. It was intuitively applied for the first time in Brazil in 1970 by tunnel contractors in Sao Paulo. Since then, several soil nailed structures have been constructed successfully. The development of methods of analysis in Europe and North America is reviewed; the application of those methods in Brazil has led to more economical and safer structures. This paper briefly presents the historical development and the use of soil nailing in Brazil. Differences and similarities with traditional techniques are discussed and some examples are given. (A)

Soil and rock reinforcements in tunnelling: Pelizza, S; Peila, D Tunnlg Underground Space TechnolV8, N3, July 1993, P357–372

Abstract Soil and rock improvement and reinforcement techniques are used to permit safe tunnel excavations in difficult geological conditions. The main methods are ground reinforcement, grouting, jet grouting, drainage, freezing, and mechanical precutting. The improvement methods are divided into two basic groups—improving interventions and preserving interventions. A critical analysis is of these methods given and a technical comparison between the main improvement techniques adopted in tunnelling is shown. Several ground reinforcement schemes are discussed. Examples from Italy of the various types of ground improvement and reinforcement techniques are given.

Soil and rock reinforcements in tunnelling

Abstract Soil and rock improvement and reinforcement techniques are used to permit safe tunnel excavations in difficult geological conditions. The main methods are ground reinforcement, grouting, jet grouting, drainage, freezing, and mechanical precutting. The improvement methods are divided into two basic groups—improving interventions and preserving interventions. A critical analysis is of these methods given and a technical comparison between the main improvement techniques adopted in tunnelling is shown. Several ground reinforcement schemes are discussed. Examples from Italy of the various types of ground improvement and reinforcement techniques are given.

Kinematical Limit Analysis for Design of Soil‐Nailed Structures

Soil nailing is an in situ soil reinforcement technique that has been used during the last two decades mainly in France and Germany to retain excavations or stabilize slopes. Design of nailed-soil systems has been traditionally done using slope-stability analysis methods. These methods have been developed to incorporate the effect of the available tension and shear resistance of the passive reinforcements on the slope stability. However, they provide only a global safety factor. This paper presents a kinematical limit analysis design approach that provides a rational estimate of maximum tension and shear forces mobilized in each reinforcement. To verify the applicability of the method, the predicted forces are compared with those measured in both laboratory models and full-scale structures. The proposed design approach is also used to analyze the various failure mechanisms observed on model walls and predicted critical model heights are compared with experimental results.

Soil reinforcement technique for control of heave : Srinivasa Murthy, B R; Sridharan, A; Bindumadhava; Revana Siddappa, K Proc 6ht International Conference on Expansive Soils, New Delhi, 1–4 December 1987P195–199. Publ Rotterdam: A A Balkema, 1988

Soil reinforcement technique for control of heave : Srinivasa Murthy, B R; Sridharan, A; Bindumadhava; Revana Siddappa, K Proc 6ht International Conference on Expansive Soils, New Delhi, 1–4 December 1987P195–199. Publ Rotterdam: A A Balkema, 1988