Height Geocell – A Cost-Effective Soil Stabilizer
Our popular 2″ Height Geocell confines and stabilizes soils to reduce weather and traffic impact, and is ideal for roads, driveways, parking lots and trails. It also improves slope and embankment stability.
Laboratory scale loading tests were performed to investigate the effects of lime stabilization and geocell (with different heights) reinforcement on increasing the shear strength of unpaved road test sections. The results indicate that the pocket opening size and aspect ratio significantly influence the increase of shear strength.
Reinforcement
The use of geocells is a very important element in the design and construction of embankments. It is a cost-effective method to improve soil strength and increase the bearing capacity of the ground. Moreover, geocells can also help to prevent car rutting by keeping the infill material compacted within its cells. The height of the geocells is determined according to the project requirements.
In order to determine the influence of geocells on the shear strength of the soil, laboratory scale loading tests were carried out in a test box. Different lime contents and heights of geocells were used in the testing process. The results showed that the shear strength of the soil increased as the height of the geocell was increased.
The results of the experimental and modeling studies indicated that the shear strength of the soil increases as the cell opening diameter decreases. In the case of the geocell with the smallest pocket opening size, the shear strength of the soil was increased by up to 31%. When the shear stress-horizontal displacement curves were measured, it was found that the shear strength of the soil remained stable when the failure plane passed through the middle of the geocell height.
The ABAQUS software was used to simulate the test results. The results of the ABAQUS model showed that the shear strengths of geocell-reinforced clayey soil increased with increasing lime content. It was also found that the shear strengths of geocell-reinforced soil with different pocket opening sizes exhibited similar behavior.
Flexural Strength
Several studies have shown that the shear strength of granular soils increased when it was reinforced by geocell. This improved the bearing capacity of the footing, particularly for a geocell mattress with a smaller pocket opening size. However, when the shear test was performed on a larger geocell with a greater number of cells per unit area, it showed a less significant increase in shear strength.
The improvement in shear resistance was largely dependent on the geometry of the geocell pocket. Specifically, the shear resistance increases more when the failure plane passes through the center of the geocell height rather than through its edge. It also increases when the shear test is conducted on a geocell with a smaller pocket opening diameter. In fact, the most increment occurs when the predetermined failure plane crosses through a geocell with a pocket opening of 25 mm.
When the shear test is simulated using Height Geocell ABAQUS, the shear stress-horizontal displacement curves show that shear failure occurs with a slight decrease in shear stress and a Height Geocell subsequent increase in horizontal displacement. This is likely due to the loss of cohesion between the soil and the geocell.
In addition to the geometry of the pocket opening, the flexural strength of the geocell is an important factor in improving shear resistance. This is because the geocell is able to transfer loads more evenly throughout the embankment. This allows the shear stress to be transferred more evenly across the entire surface of the footing, which results in a lower total shear stress and a more stable foundation.
Lateral Resistance
In general, the higher the geocell height, the more lateral resistance it provides. It is due to the honeycomb structure of geocells that offer a three-dimensional lateral limitation (LL) system, thereby increasing soil cohesion and preventing lateral displacements [7]]. The increased rigidity offered by the geocell-reinforced bed also increases its load-carrying capacity, reducing foundation settlements and heave.
In addition to the lateral resistance, the height of the geocells plays an important role in determining the shear strength of the soil-geocell interface. It has been shown that the shear strength of the soil significantly increases when the failure plane passes through the middle of the geocell height. On the other hand, shear strength decreases when the failure plane is tangential to the middle of the geocell height.
The high shear strengths of the geocell-reinforced soil can reduce significant heave in the sand cushion, which results in surface uplift around the footing. This heave is a result of the lack of cohesion in the sand or aggregate, a critical factor contributing to the heaving of unreinforced beds. The lateral shear resistance of the Height Geocell can restrain this phenomenon.
In the heave test, the shear strengths of the geocell-reinforced sand were significantly higher than those of the unreinforced one, resulting in a lower heave. The shear strengths of the geocell-reinforced bed were also significantly higher when the geocell height was higher. This was mainly because of the greater number of pockets in the geocell, which resulted in the higher shear strengths of the soil-geocell interface.
Stability
During construction, it is important to control the limit bearing capacity of an embankment in order to prevent excessive settlement. This can be achieved by increasing the geocell height or reducing the welding spacing. Among these two techniques, the former has a better effect.
The effects of dimensionless changes in the geocell placement related to the failure plane have been simulated by using ABAQUS software, and it was found that a higher shear strength increment can be obtained by positioning the middle height of the geocell closer to the failure plane (see Fig. 8b).
When the failure plane passes through the middle height of the geocell, the shear strength increment is 5% greater than that of the unreinforced soil. In contrast, when the failure plane passes away from the middle height of the geocell, the increment is less than 5%.
In addition, it was found that the modulus of subgrade reaction increased with the increase in geocell height, but it stopped at a certain level. It is possible that at this point, the geocell begins to interfere with the behaviour of the base soil. Therefore, it is necessary to consider the performance of the base soil and the stability of the road with respect to both the height of geocell and the lime content. Then, it is possible to determine which improvement technique should be used.