The ramps of the grade separators are constructed either as embankments with natural slopes, or as reinforced soil walls. In case of partial walls, where sloped embankments are supported on reinforced soil walls, it is essential that the embankment slopes are given adequate protection against soil erosion, which can otherwise damage the fascia of the underlying reinforced soil wall and also induce seepage into the system.
Conventionally, stone pitching has been the preferred solution to reduce erosion. Availability of stones is posing a great challenge from an environmental and commercial standpoint. Furthermore, quarrying of stones has become an environmental and legal issue making it scarcer. It is imperative that alternate solutions should be implemented.
StrataWeb® provided along the slope surface helps to prevent erosion by effectively confining the top soil within its three dimensional frame. Locally available fertile soil can be used as an infill which can be further vegetated to provide a green finish, thus avoiding the use of expensive stones for slope protection. Installation is extremely simple and five times faster as compared to stone pitching.
Steep Slope / Wall
Conventionally, a highway grade is raised either by constructing a RCC framed structure, a RCC wall or an embankment with natural slopes. In the first two cases, the cost is high and construction is time consuming, while in the third case, large tracts of land have to be acquired which is prone to litigation, requires substantial time and can be expensive based on the region.
Strata reinforced soil solutions are very well suited for use in highway embankments. This is a proven technology the world over and has been extensively used by Strata on national highway projects in India. With the use of reinforced soil solutions embankments can be constructed faster, requiring less land footprint and with savings greater than 20% as compared to conventional RCC walls. Furthermore, reinforced soil technology offer various fascia options which include concrete blocks, concrete panels and more recently vegetated slopes. Global design methods are well established for this technology. MoRTH has addressed the design and construction of reinforced soil structures in adequate details through its specifications and guidelines.
Conventional pavement sections are susceptible to subsoil characteristics. In highway engineering the subsoil capacity to carry loads is measured by its California Bearing Ratio (CBR). Much of the design computations, which are empirical, are based on CBR, besides the expected loads over the lifecycle of the pavement. A low CBR and inadequate section can cause rutting at the surface of the pavement and differential settlements. Expansive soil subgrades can further aggravate the problem.
StrataWeb® reinforcement solutions help in distributing the loads over a larger surface area and helps eliminate rutting and problems arising due to expansive soils. Furthermore, StrataWeb® helps in economizing the pavement sections and reducing the requirement of expensive quarried materials such as GSB, WMM and DBM.
Embankment & ground improvement
One of the toughest challenges faced by highway authorities is to prevent differential settlements along the highway that can lead to operational and maintenance issues. Presence of soft soil along the route can lead to differential settlements if not failure.
StrataWeb® is a well-established solution to improve the bearing capacity of sub-grades and significantly reduces differential settlements. Due to the principles of confinement, StrataWeb® distributes heavy loads uniformly over a larger area thereby reducing the pressure acting upon the sub soil of the embankment.
Besides embankments, StrataWeb provides stability to foundations of reinforced soil structures where the bearing pressures are more intense. This is a more economical option as compared to soil replacement and presents a viable alternative in cases where intermediate improvement is required. StrataWeb® has been permitted for use in highways for ground improvement by Indian Roads Congress (IRC) in its latest codes.
Access roads leading to a highway are generally not well maintained and have low subgrade. Poor access roads lead to lower efficiency and increase in the operational cost.
Strata ground improvement solutions help in improving the bearing capacity of sub grades, reduce differential settlements, are easy and rapid to construct, can be engineered for site specific challenges and can make use of locally available materials.
StrataGrid™ biaxial (PP) works on the principles of interlocking of particles and behaves like a 2D rigid mat. This product can be used for moderate ground improvement challenges.
StrataWeb® is very effective and feasible in cases where the subgrade is very soft or the loads are very high. As it confines the infilled material it provides a stiff base layer for the access road. StrataWeb® facilitates the use of various kinds of infill materials such as construction debris, riprap, recycled asphalt pavement etc.