Geocell can be easily contracted and folded for transportation; and stretched and expanded on job site to cellular structure. When filled with infill materials, such as soil, gravel and concrete, the structure has strong lateral confinement and high stiffness.
Geocell is lightweight, wear-resistant, chemically stable, anti-photo-oxidative aging, and acid and alkaline-resistant, so can be used in different soil environments (for example, deserts).
Geocell is of high lateral confinement, slide-resistant and deformation-resistant, so can effectively increase load bearing capacity and decentralize load distribution in subgrade reinforcement applications.
The geometrical parameters (for example, height of the cellular structure and welding interval) of geocells can be adjusted for different engineering applications.
Geocell can be easily contracted to achieve small transport dimensions; and easily fastened together on site to achieve high engineering efficiency.
Geocell is valued in the engineering industry thanks to their outstanding performance, which can be understood from the basic principle. In foreign research literature, geocells are described as “honeycomb-like three-dimensional confinement systems that can significantly enhance the performance of normal infill materials in such applications as load support and worm corrosion control.” The critical principle is three-dimensional confinement. As it is known to all, an automobile running in a desert will leave two deep ruts, the area under the wheel to settle deeply into the ground and the walls at both sides of the rut to elevate high above the ground. With another automobile, the rut will become deeper and the walls higher. With more automobiles following the same rut, the ground will be deformed to a degree that no more automobile can run along the same rut as the wheel will be trapped by the rut and the rut walls will block the chasis. The reason is that, according to bearing capacity theories developed by Prandtl and Tylor, when an external concentrated load is applied to the earth surface the active zone 1 settles due to the stress and the stress is transferred laterally to both sides to transitional zone 2, which in turn transfers the stress to passive zone 3, which will be infinitely deformed and elevated.
1. Geocell can be easily contracted and folded for transportation; and stretched and expanded on job site to cellular structure. When filled with infill materials, such as soil, gravel and concrete, the structure has strong lateral confinement and high stiffness.
2. Geocell is lightweight, wear-resistant, chemically stable, anti-photo-oxidative aging, and acid and alkaline-resistant, so can be used in different soil environments (for example, deserts).
3. Geocell is of high lateral confinement, slide-resistant and deformation-resistant, so can effectively increase load bearing capacity and decentralize load distribution in subgrade reinforcement applications.
4. The geometrical parameters (for example, height of the cellular structure and welding interval) of geocells can be adjusted for different engineering applications.
5. Geocell can be easily contracted to achieve small transport dimensions; and easily fastened together on site to achieve high engineering efficiency.Put it another way, when a load is applied onto the subgrade, an active zone of triangular cross section will come into being in the subgrade right below the load. The stress will be transferred to the passive zone through the transitional zone and cause the passive zone to elevate. In other words, Deformation of the subgrade is determined by shear force along the direction of sliding and the force on the active zone, transitional zone and passive zone. This is true with not only sandy soils in desert but also any soft soils, the only difference being the degree and speed of deformation. Such lateral movement of subgrade materials also happens with good subgrade materials. Normally a highway is elevated several meters above the ground. For such a highway, frost boiling due to water absorption rarely happens but pavement settlement does happen after some time. One of the major reasons is absorption of rain water, which leads to run-away of soils, and then settlement of the subgrade. Another major reason is lateral movement of soil due to long-time pressure and vibration caused by dynamic load of vehicles. On many provincial country roads, one can feel something an “S” shaped track in the traffic lane. Similarly, on some highways, one may feel that the traffic lane is significantly more jolting than the express lane (due to heavier and more frequent load). This same mechanism can also explain the so called “bridge-head bump”. Such ditch shaped subgrade settlement is a typical example of lateral movement of subgrade material..
The traditional subgrade engineering is nothing but to increase the shear strength and frictional force of subgrade materials and reduce or delay lateral movement of the subgrade materials under load or vibration, which is known to all and need not be further elaborated. Therefore, there are strict requirements for materials used in such applications. If such materials cannot be obtained locally, then they have to be purchased. The acquisition cost and transportation cost of such materials accounts for a very high percentage of engineering project budget. With geocells, materials available locally, even those materials that traditionally are deemed inferior or not appropriate for such an application, can be used. Consequently, material acquisition and transportation cost can be drastically reduced. Why? Under a concentrated external load, the active zone still transfers the stress to the transitional zone. The stress, however, cannot be transferred from the transitional zone to the passive zone owing to the lateral confinement of cell wall, the passive resistance of the neighboring cells, and the lateral resistance formed by the frictional force between the infill materials and cell walls. As a result, the load bearing capacity of subgrade has increased. Some experiment results show that, with confinement of geocells, the apparent cohesion of medium dense sand can increase by more than 30 times. Obviously, the bearing capacity of subgrade can be improved when the shear strength of subgrade materials can be increased and the lateral movement of stress from active zone 1 to transitional zone 2 and to passive zone 3 can be contained. This is just the confinement principle of geocells. As a new geosynthetical material, geocells have been studied in many research projects from late 1980s and early 1990s and, as demonstrated by laboratory tests and field trials, are very effective to improve bearing capacity of normal infill materials and protection of subgrade. China started introducing Western know-how and developing geocells from early 1990s, and has made breakthroughs in correction and prevention of roadbed defects and stabilization of loose subgrade materials. With further understanding of geocells, it is found that they have advantages that are not available with other geosynthetical materials (for example, geotextile, geomembrane, geogrid, geobag, and geonet) and are a promising material in many areas of applications.
Cut and Fill Subgrade
When the slope of natural terrain is higher than 1:5, steps should be constructed on the subgrade and width of the step should be at least 1 m. When a road is expanded or constructed in a phased manner, steps should be constructed on the side slope of old embankment (at the side of new embankment) and the step width for high-class roadways is normally 2 m. Geocell is then constructed on the level surface of each step, which has been proven an effective solution to differential settlement of subgrade thanks to the lateral confinement and reinforcement effect of geocells.
Embankment in windy and sandy regions
Embankment in windy and sandy regions is usually less than 0.3 m in elevation. However, the bearing capacity required of roads in such regions is usually high. Geocell is a good solution to resolve this conflict, able to achieve high stiffness and strength of loose local infill materials in such slightly elevated embankment and thus high bearing capacity thanks to the lateral confinement of geocells.
Reinforcement of Subgrade near Bridge-Head
Geocell can be used to reinforce the subgrade near bridge head as the high frictional force between geocell and infill materials can reduce the differential settlement of subgrade and bridge and thus alleviate the so called “bridge-end jump” and the damage to bridge caused by such bumps.
Embankment over Perennially Frozen Soil
Embankment over perennially frozen soil should be elevated to a certain height, in order to prevent frost boiling and settlement of the upper layer of frozen soil, which may lead to excessive settlement of the embankment. With geocells, the embankment need not be alleviated that high but still can achieve the required strength and stiffness thanks to the vertical reinforcement and three-dimensional confinement enabled by geocells.
Subgrade over Collapsable Loess
The advantages of geocells can be especially manifested in engineering subgrade of highways and Class 1 roads over collapsable and non-collapsable loess (or when bearing capacity of embankment is less the sum of dynamic load of vehicles and weight of embankment).
Subgrade over Saline Soil or Expansive Soil
For highways or Class 1 roads over saline soil or expansive soil, the road shoulder and side slopes should be reinforced. Geocell is the best reinforcement materials in terms of vertical reinforcement performance. Besides, Geocell is erosion-resistant and thus a good choice for road construction work over saline soil and expansive soil.
Subgrade of road and rail track.
River embankment and shallow riverbed
Multi-purpose retaining wall (for slide-resistance and load support)
Construction over soft soil (Geocell can significantly reduce construction labor intensity, subgrade thickness and engineering cost and improve construction efficiency and performance)