Full Answer
Why is soil reinforcement important?
Soil reinforcement is fundamental in consolidating the bottom and slope of the landfill to ensure a stable foundation for the lining system. Geogrids can be conveniently used as materials for mechanical support of soil, geotextiles, geonets, and geomembranes ( Koerner, 2012 ).
What is reinforced soil?
Reinforced soil or mechanically stabilized soil consists of soil that is strengthened by tensile elements such as metal strips, geotextiles, or geogrids. The development of polymeric materials in the form of geosynthetics has brought major changes in geotechnical engineering. The beneficiary effects of soil reinforcement are derived from (a) the increased tensile strength of soil and (b) the shear resistance developed from the friction at the soil reinforcement interfaces. So, there is an increase in applications of geosynthetics in geotechnical structures such as foundation, embankments, retaining wall, etc.
What type of protection layer is needed for a geosynthetic soil?
Depending on the particle size, hardness, and angularity of this soil, a geotextile or other type of protection layer will often be necessary. If the covering layer is a geosynthetic, it will generally be a geonet or geocomposite drainage material, which is usually placed directly on the geomembrane.
How to stabilize gypsiferous soil?
In an attempt to stabilize gypsiferous soil, Razouki and Kuttah (2004) used physical stabilization method instead of adding chemicals to stabilize the gypsiferous soil. This physical stabilization is achieved by compacting the gypsiferous subgrade soil at high compaction efforts. Razouki et al. (2005) reported that increasing the compaction effort from 12 to 56 blows/layer causes an increase of 2.3-fold and 6.5-fold in the estimated ultimate bearing capacity for the unsoaked and soaked CBR gypsiferous soil samples for 120 days respectively, indicating that the effect of compaction effort becomes more pronounced as the soaking period increases for highly gypsiferous soil (of about 33% gypsum content).
What type of soil is used for gas drainage?
Equalizing and soil reinforcement will depend on the local situation. Coarse sand or granules are generally used for gas drainage in a 0.3–0.5 thick layer, topped by a 0.5 m layer of compacted clay with k < 10 −9 m/s. A geotextile separates the mineral liner from the gas drainage layer. An HDPE geomembrane of 1.5–2.0 mm is superimposed in direct contact with the surface of the clay liner. The geomembrane is protected by a thick high-density geotextile structured for this purpose. Above the geotextile, a layer of 16–32 mm gravel constitutes the water drainage layer (0.5 m thick). Protective/supporting soil is superimposed over the water drainage layer and a good quality geotextile emplaced to promote filtration. Soil should display good permeability properties with a thickness ranging from 0.5 to 1.0 mm, depending on the overlying vegetative layer (humic soil minimum 0.5 m) and the type of vegetation to be planted.
How does geogrid reduce soil swelling?
The restraints provided by geogrids in the form of tensile reinforcement may reduce swell pressure. Also, more uniform soil swelling may be ensured through the provided paths for the moisture entry by the geogrids. However, the use of reinforcement stabilizers exhibited a dissimilar technique in swelling reduction, as the swelling clay minerals remain the same. They also do not reduce the water deficiency condition of the soil. Furthermore, there is no evidence that those materials can prevent water from reaching the high potential expansive clay minerals.
What are the two criteria for shallow foundation design?
The design of shallow foundation considers two criteria: the bearing capacity and settlement . Bearing capacity generally depends on the strength of the soil while settlement generally depends on the compressibility of soil ( Das, 2007 ). In the case of weak soil, the improvement in bearing capacity and decrease in settlement can be achieved by geosynthetic reinforcement ( Shukla & Yin, 2006 ). The analysis of reinforced foundation is considered in terms of pullout and rupture (break out) failure of geosynthetic reinforcement.
What was soil reinforcement?
In ancient times soil reinforcement consisted of mixing straw with mud, reinforcing with woven reeds, and using branches and other plant material to improve strength and capacity to support greater loads .
When was soil reinforcement invented?
Early versions of “modern” soil reinforcement were developed in the early 1960s with Henri Vidal’s patented Reinforced Earth® for construction of self-supporting retaining walls. These walls were constructed using galvanized steel strips with “ribs” to provide lateral resistance against earth pressures ( Figures 14.1 and 14.2 ). These types of wall (and similarly slope) structures are generically referred to as mechanically stabilized earth (MSE). Construction of earth walls with geosynthetic reinforcing materials was introduced in the 1980s ( Federal Highway Administration, 2011 ). Since that time there has been an explosion of the use of geosynthetic reinforcement for soil structures as well as for many other geotechnical applications.
What are the main parameters of uplift load?
The main parameters of uplift load which may act on soil parameters and reinforcement materials such as GFR layers are those due to unit weight of sand, internal friction, symmetrical anchor plate’s embedded depth and size of symmetrical anchor plates, geogrid width, number of reinforcement layers, depth of first layer of reinforcement top anchor plate, and vertical distance between geogrid layers. In full-scale model analysis, equations of these parameters may be expressed in dimensionless quantities as given below using Eq. 3.9:
How do stone columns improve soil?
As mentioned earlier, the basic mechanisms behind ground improvement using stone columns are (1) soil compaction through the bulging action of the stone columns, (2) soil reinforcement with the inclusion of stone aggregates into the soil mass, and (3) accelerated consolidation of the cohesive soils. The differences between the load carrying mechanism of a pile and that of a stone column are presented in Fig. 6.1. The structural load is mainly carried by the piles only and there is no transfer of stress to the surrounding soil in the case of pile foundations. However, in the case of stone columns, a part of the structural load is carried by the surrounding soil. This is demonstrated in the stress distribution diagram in Fig. 6.1. A single stone column primarily fails by bulging, whereas a group of stone columns may fail by bulging or by shear failure of the soil/columns mass.
Is GFR constant with reinforcement layers?
Since the GFR length and GFR angle with reinforcement layers are constant, thus they are constant although ∅ is a dimensionless unit, thus
What is soil reinforcement?
In simple terms, soil reinforcement is a technique used to improve the stiffness and strength of soil using geo-engineering methods. It is particularly useful in areas with soft soil as it cannot provide adequate support to any construction or building.
What is soil R/F?
Soil r/f is the act of improving soil strength to enable its support & to carry more load.
How is bamboo used to reduce soil erosion?
In old ways, it used to reduce soil erosion at marshy land and river boundary sand. It is done by placing a bio-fabric i.e, bamboo , in the pattern of the network in soil with a mixture of aggregate-sand to make it stiff and compacted mass.
Why is natural fibre important?
It is particularly useful in areas with soft soil is present. Because soft soil and not provide adequate support to any type of construction.
Is soil reinforcement visible?
Soil reinforcement generally invisible in the cornerstone of any structure built on soil with the very poor mechanical characteristics.
How to reinforce soil?
Soil reinforcement techniques have always been used, whether to reinforce existing soils (Figure 1) by adding beaten or dark vertical inclusions in the soil, or to create retaining walls (Figure 2) by using soils remodelled and reinforced with horizontal reinforcement (strips, slicks, cellular structures, etc.) or short or continuous fibres.
How to improve soil mechanical properties?
Two major techniques can be used to increase the mechanical characteristics of soils: by modifying the internal structure of the existing soil and by reinforcing the soil by adding inclusions. More specifically, soil improvement techniques can increase the compactness of the existing soil, either by reducing the volume of voids, for example by applying an overload to saturated soil and allowing it to settle by expelling the overpressure water, in this case consolidation, either by imposing vibrations in the soil so that it densifies by rearranging the grains dynamic compaction technique allowing to densify the soil to a depth of less than 10m, under the impacts of a mass of 15 to 150 tonnes falling from 20 to 40 m). Soil reinforcement techniques themselves involve vertical or horizontal reinforcement elements in the soil. The objective of all these techniques is to allow the construction of a structure without excessive surface deformation or stability defects.
Why are reinforcement techniques not visible to laymen?
Not very visible to the layman because they are buried in the ground, reinforcement techniques are very widespread and surround us on a daily basis (foundations, retaining walls, road embankments, railways, etc.).
What are soils made of?
Soils are complex materials made of a more or less compact mineral skeleton with a natural porosity where air and water circulate freely. Soil grains result from the more or less coarse fragmentation of rock into pebbles, gravel, sand or silt, but also from the chemical decomposition of some rock compounds into microscopic clay particles. In permeable soils, such as pebbles, gravel and sand, water circulates easily. This is not the case in low-permeability or even impermeable soils, such as silt and clay. Water circulates 1 million times less quickly in clay than in gravel. In addition, as a result of external stresses such as water inflows, drought or earthquakes, the mechanical characteristics of soils may change and no longer be adapted to their intended use.
Which vector allows the transmission of forces from the ground to the reinforcement?
It should be remembered that the interface zone between the ground and the reinforcement is the preferred vector that allows the transmission of forces from the ground to the reinforcement, a totally smooth interface resulting in a non-transfer of forces and therefore in zero reinforcement.
Why is poor quality land development important?
Certain types of soil, hitherto neglected because of their poor mechanical characteristics, must be reinforced to ensure the stability of the buildings and the civil engineering infrastructure they are required to support. Not very visible to the layman because they are buried in the ground, reinforcement techniques are very widespread and surround us on a daily basis (foundations, retaining walls, road embankments, railways, etc.). More than a technological challenge, the construction of infrastructure in classified unbuildable areas represents a real strategic, economic and environmental challenge in many common cases such as:
Why is soil reinforcement used?
Soil reinforcement techniques is commonly used in area with soft soil as it doesn’t provide sufficient support to any building/ construction. These types of soil are highly susceptible to numerous natural and environmental factors such as poor shear strength, high compressibility and temperature changes.
Who developed soil reinforcement?
In modern times, the concepts and principles of soil reinforcement was first developed by Henri Vidal.
Why are geotextiles placed on land?
Layers of geotextiles are placed methodically on the land to steepen soil slopes. This achieves overall increase of tensile strength without the risks of soils sliding or rotating.
Why is soil used as a backfill?
The soil is utilised as backfill in cases where the soil is granular with less than 15% fines to allow the development of large friction between the soil and reinforcement. The most often used reinforcement is steel strips as they have large tensile strength and low extensibility.
What happens when soil is pressured?
When pressure is applied on the soil mass, it causes a strain on the reinforcement, creating a tensile load which can now resist soil movement and provide additional support . By doing this, soil is reinforced and provides much greater shear strength than the soil mass alone.
How much higher is land filling than soil reinforcement?
The cost required for traditional land filling can be up to 50% higher than the cost of soil reinforcement with geotextiles. Geotextiles can be utilised to disperse the load uniformly within the soil and reduce the displacement of small soil particles.
What is soil nailing?
Soil nailing is a technique commonly used to reinforce and strengthen the ground adjacent to an excavation by installing closely spaced steel bars or “nails”, as construction commences from top down. Vertical or steeply inclined cuts can be made for open excavation using rigid soil nails as reinforcement.
