Geocell Configuration: Comparison
Please note this is a comparison between Version 1 by Gali Madhavi Latha Latha and Version 2 by Sirius Huang.

Geocells, which are polymeric interconnected cells filled with soil, provide excellent support to loads through all-round confinement and a beam effect; hence, they are extensively used in various geotechnical applications such as embankments, foundations, pavements, slopes, railways, and reinforced earth (RE) walls. 

  • geocells
  • geometry
  • reinforcing parameters
  • pavements

1. Introduction

Since the 1970s, geocells are being widely used in various applications of geotechnical engineering. The idea of a cellular confinement system was originally developed by US army corps of engineers for the ease of transport of military vehicles over weak subgrades [1]. The first cellular confinement systems were made of paper, which were later replaced by aluminum and wooden cells [2][3][2,3].
The modern form of geocells came into existence since 1980s. Unlike planar textiles and grids, geocells, which are three-dimensional networks of cells filled with a choice of soil, provide added benefits such as all-round confinement through hoop stresses developed in the cells and a beam effect resulting from their stiff-mat configuration. Geocells, by virtue of their shape and depth, provide greater load-bearing capacity and reduce lateral deformations in soils confined by them under static and cyclic loading scenarios [4][5][6][7][4,5,6,7]. The inclusion of geocells in various structures has additional benefits such as stability improvement, climate resilience, higher resistance to cyclic loads, erosion control, basal support, and savings in time and cost [4][8][4,8]. Because of these merits, geocells are extensively used in pavements, slopes, foundations, embankments, and reinforced earth (RE) walls. Recently, geocells have also found application in heavy-duty highways and high-speed trains [5][6][5,6]. The mechanism of geocell reinforcement has been investigated by many researchers through experimental, numerical, and analytical studies. In a network of geocells, each cell is surrounded by several neighboring cells, and all the cells are filled with soil. With the application of external load, the soil inside the geocell pushes the cell wall, resulting in the development of an additional confining stress along the wall [4][8][9][10][4,8,9,10]. The additional confinement is translated into apparent cohesion, thereby increasing the shear strength of the soil, and preventing its lateral spread [11]. Furthermore, the extension of cell walls is opposed by the lateral stresses from the neighboring cells, causing the interconnected network of geocells to act as a cushion or stiffened mattress with higher strength and stiffness. This beam action redistributes the externally applied loads over a wider area and, thus, reduces the magnitude of stresses acting on the underlying soil [12]. This stiffened soil–geocell composite also hinders the propagation of the failure surface into the underlying soil [13]. Furthermore, at large displacements, the geocell layer acts as a tensioned membrane, providing sufficient upward resistance to the applied loads and, thus, reducing the stresses on the underlying soil [12][14][12,14]. A schematic representation of a geocell-reinforced soil bed is shown in Figure 1. In this figure, B represents the width of the foundation, u represents the depth of the geocell layer from the ground surface, and H, d, and b represent the height, pocket size, and width of the geocell layer, respectively. Various mechanisms responsible for the reinforcing action of geocells are presented in Figure 2. In this figure, θ represents the angle of load dispersion.
Figure 1.
Schematic representation of geocell reinforced foundation bed.
Figure 2. Mechanisms of geocell reinforcement: (a) confinement effect (plan view); (b) stress dispersion effect (sectional elevation); (c) lateral resistance effect on a single geocell (front view); (d) membrane effect (sectional elevation).
Figure 3 shows a photograph of the latest form of commercially available honeycomb-shaped geocells available at the Indian Institute of Science, Bangalore. Figure 3a shows the collapsed form of geocells, which helps in stacking large volumes of geocells in a compact form. In Figure 3b, an expanded form of a geocell layer is shown, and the cell wall, junctions, and perforations are marked. Geocells took almost five decades to evolve geometrically to their current versatile configuration. Historically, geocell layers were fabricated onsite using planar geosynthetics such as geotextiles and geogrids by strategically connecting the cells and filling them with granular soils [15]. Initially, resins and additives were used to connect the cells, which were chronologically replaced by bodkin joints, photo lamination, and ultrasonic welding in the most recent form of commercial geocells. Similarly, the geometric shape of the geocells has also undergone several transformations from square, circular, rectangular, diamond, and hexagonal to honeycomb. Furthermore, the cell material also evolved from paper, aluminum, and wood to polymer [3]. Currently, solid or perforated high-density polyethylene (HDPE) and novel polymeric alloy (NPA) are the commonly used polymers to manufacture geocells. However, the latter is more popular due to its greater flexibility, thermo-plasticity, and surface texture [16].
Figure 3.
Commercially available geocells: (
a
) collapsed form; (
b
) expanded form.
The present-day configuration of honeycomb geocells enables them to enclose maximum infill with a minimum perimeter of cells [8]. While manufacturing geocells, surface texture is imparted to the geocells, as shown in Figure 3, to enable them to mobilize greater interfacial shear strength when they are in contact with soils [17]. The postmortem analysis of geocells from various model tests showed that the junctions of the geocells remained intact even when local straining and buckling were observed in geocell walls [18][19][18,19]. Furthermore, the perforations present on the geocell walls (refer to Figure 3) facilitate easy drainage to dissipate pore pressures that develop inside the cells. These perforations also provide adequate interlocking between infill soils of adjacent geocells so that the geocell-reinforced soil behaves like a stiffened composite mass [20]. The perforations on cell walls also facilitate root growth within the cells, which is beneficial when vegetation is grown on geocell walls and slopes. The total pore area of the perforations is typically 6–22% of the unit area of the geocell wall. Table 1 presents the typical range of geometric and mechanical properties of commercial geocells reported by earlier studies [8][16][8,16] and geocell manufacturing companies.
Table 1.
Typical properties of commercial geocells.
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