Geogrid Reinforced Soil Wall Research Articles

Experimental Study on Long-Term Performance of Tiered Geogrid-Reinforced Soil Walls under Sustained Loading

Experimental Study on Long-Term Performance of Tiered Geogrid-Reinforced Soil Walls under Sustained Loading

Experimental study on the performance of geogrid-reinforced soil (GRS) walls under monotonic footing loading

Geogrid-reinforced soil (GRS) is a widely employed compound material in the construction of retaining walls. This paper presents a set of reduced-scale model tests to study the performance of GRS walls with dry backfill under monotonic footing loading, varying parameters such as wall inclination angle and the number of reinforcement layers. Lateral deflections of the retaining wall, bearing capacity of the footing and the failure mode of the soil were analysed. The results indicated that augmenting the reinforcement layers will lessen wall lateral deflections, and increasing the angle of inclination could significantly enhance ultimate bearing capacity of the footing. A linear relationship was found between the overall lateral deflections of the retaining wall and the footing settlement. The failure of geogrid could lead to a breakdown in the connection between the geogrid and the soil, consequently causing local failure. The failure modes of the GRS wall under strip footing was composed of shear failure in the reinforcement layer and spiral failure in the weak layer. At last, the logarithmic spiral analysis method was modified slightly to calculate the ultimate bearing capacity. The analytical solution and the outcomes derived from experimental models exhibit a high level of concordance.

Mechanical Behavior of Geogrid Flexible Reinforced Soil Wall Subjected to Dynamic Load

The geogrid flexible reinforced soil wall is widely used in engineering practice. However, a more comprehensive understanding of the dynamic behavior of reinforced soil wall is still required for a more reasonable application. In order to explore the mechanical behavior of a geogrid flexible reinforced soil wall, the model test was carried out to investigate the dynamic deformation of geogrid reinforced soil wall subjected to a repeated load. The numerical simulation was also conducted for comparison and extension with regards to the earth pressure and the reinforcement strain. The change rules for the deformation of the wall face, the vertical earth pressure and the reinforcement strain subjected to dynamic load with four frequencies (4, 6, 8 and 10 Hz) and four amplitudes (30–60, 40–80, 50–100 and 60–120 kPa) were obtained. The factors that affect the mechanical behavior of geogrid flexible reinforced soil wall were analyzed. The results show that the dynamic deformation characteristics of reinforced soil wall are affected by the number of vibrations, the amplitude of dynamic load and the frequency of vibration. The maximum lateral displacement of the reinforced soil wall occurs on the third to the fifth layer. With an increase in dynamic load amplitude, the development of dynamic deformation gradually increases, and after a cumulative vibration of 200 × 104 times, the cumulative lateral deformation ratio and the cumulative vertical deformation ratio of the wall face is less than 1%. The vertical earth pressure of geogrid flexible reinforced soil wall increases partially along the length of the reinforcement, and the vertical earth pressure of the third layer is basically unchanged when subjected to a dynamic load. With an increase in vibration number, the change in the reinforcement strain of the third layer is more complex, and the change rules of the reinforcement strain of each layer are different. The reinforcement strain is small, with a maximum value of 0.1%.

Evaluation of the Behavior of Geogrid-Reinforced Soil Walls Subjected to Rainfall Through Centrifuge Model Tests

Evaluation of the Behavior of Geogrid-Reinforced Soil Walls Subjected to Rainfall Through Centrifuge Model Tests

DIA of centrifuge model tests on geogrid reinforced soil walls with low-permeable backfills subjected to rainfall

Geogrid reinforced soil walls (GRSWs) constructed using low-permeable backfills often experience failures when subjected to rainfall. The objective of this paper is to employ centrifuge modelling to investigate the effect of geogrid types on the performance of GRSW models constructed with low-permeable backfill, when subjected to rainfall intensity of 10 mm/h. A 4.5 m radius large beam centrifuge facility was used, and rainfall was simulated using a custom-designed rainfall simulator at 40 gravities. Digital Image Analysis (DIA) was employed to understand the deformation behaviour of GRSWs with low stiffness geogrid layers with and without drainage provision subjected to rainfall. Additionally, the effect of varying stiffness of geogrid reinforcement layers across the height of GRSW was also investigated. The interpretation of DIA helped to quantify displacement vector fields, face movements, surface settlement profiles and geogrid strain distribution with depth. Irrespective of drainage provision, GRSWs reinforced with low stiffness geogrid layers experienced a catastrophic failure at the onset of rainfall. However, GRSW reinforced with geogrid layers of varying stiffness was observed to perform well. This study demonstrates the effective use of DIA of GRSWs subjected to rainfall along with centrifuge-based physical model testing.

Numerical simulation of the performance of GRS walls considering freeze-thaw cycles

In practice, little attention has been paid directly to freeze-thaw (FT) cycles during the design and analysis of geogrid-reinforced soil (GRS) walls due to a lack of relevant literature. This study investigates the pavement vertical deformation (s), panel lateral deformation (d), lateral earth pressure (σh), and geogrid strain (ε) of a field GRS wall using an ABAQUS-based numerical model considering variations of the recorded five-year ambient temperature (TR). Numerical results show that the s distribution follows a convex shape instead of the initial concave shape after FT cycles and can be divided into high, transition, and stable deformation zones. FT action alters both location and amplitude of the maximum d within the first two cycles, making the d distribution evolve from a J-shaped curve into an S-shaped one. During freezing, the developments of s and d are coordinated and can be described using a unified model; σh is larger than the Rankine active earth pressure; ε state depends on the interplay of two factors resulting from d and frost heave force. Furthermore, the hysteresis of s, d, σh, and ε with TR was discussed and several beneficial suggestions were proposed for GRS walls to avoid such FT destruction.

Determining performance of two-tiered GRS walls subjected to traffic cyclic loading

This study evaluates the performance of two-tiered geogrid-reinforced soil (GRS) walls subjected to traffic cyclic loading considering several influencing factors. These factors herein include the offset distance (D) of walls, the number (N), amplitude (Pmax), and frequency (f) of applied cyclic loading. Seven GRS walls with a reduced scale of 1 : 3 were prepared in the laboratory and employed to investigate their (i) vertical foundation pressures during construction, (ii) load-induced settlements, (iii) facing lateral displacements, (iv) vertical and horizontal earth pressures, and (v) geogrid strains under the action of cyclic loading. Experimental results demonstrate that GRS walls constructed in tiered configurations can effectively reduce vertical foundation pressures. The increasing D, as well as the decreasing N and Pmax, introduces a reduction to the above five mechanical and deformation properties. However, increasing f results in the decrease of wall settlements and facing lateral displacements, and in the increase of others. Performance of several empirical equations for predicting the vertical foundation pressures, location of maximum geogrid strains, and failure surfaces inside walls was examined using the experimental data obtained in this study. Comparisons were also performed to describe the deformation and failure surface modes of the walls after loading.

Effect of a two-tiered configuration on the seismic behaviour of reinforced soil walls

Shaking table tests were performed on reduced-scale models of integrated and two-tiered mechanically stabilised earth (MSE) walls to evaluate the effect of a tiered configuration on the seismic behaviour of metal-strip and geogrid reinforced soil walls. The results showed that, although inextensible reinforcements could reduce the fundamental period, acceleration amplification and lateral deflection and improve wall stability, these benefits declined with the use of a tiered configuration and gradually faded with an increase in the offset distance. This made changing the degree of extensibility a low-impact factor in two-tiered MSE walls with a sufficiently large offset distance (D > (0.4–0.5)H). In order to benefit from the advantage of a tiered configuration, it was found that 0.22H should be considered as the minimum offset distance. The findings indicated that preventing the development of a slip surface in the lower half of the wall, improving the seismic stability by increasing the failure threshold acceleration, mitigating acceleration amplification and decreasing the reinforcement load were the main advantages of a tiered configuration. Moreover, it was concluded that the Mononobe–Okabe method could be used to find the upper bound for estimating the reinforcement forces in two-tiered MSE walls.

Numerical study of the impact of climate conditions on stability of geocomposite and geogrid reinforced soil walls

Geosynthetic-reinforced soil (GRS) walls using marginal soils can operate under unsaturated conditions depending on climate conditions and drainage inside the reinforced zone. Geocomposite reinforcements have been suggested to act as internal drainage layers, but their hydraulic behavior can also be strongly affected by climate conditions. Numerical analyses were conducted to observe the impact of four distinct tropical climate conditions (arid, semi-arid, humid subtropical and humid tropical) on suction profiles and stability of reinforced soil walls constructed using geogrid and geocomposite reinforcements. The climate simulation involved the incorporation of a soil-atmosphere interaction on water balance and on the unsaturated transient infiltration. Results indicate the GRS walls can operate under relatively high suction levels under arid climates in which cumulative evaporation overcomes infiltration. Any climate that has rainy seasons with consecutive rainfalls with intensities close to the infiltration capacity of soil and/or monthly cumulative precipitation higher than 200 mm/day led to critical conditions in terms of soil water saturation and stability. Under unsaturated conditions of soil, the drainage effectiveness of geocomposites is significantly reduced and adverse capillary break effects become critical.

Seismic behavior of tiered geogrid reinforced soil (GRS) using treated backfill soil

As the use of geogrid reinforced soil (GRS) walls increases, appropriate solutions should be considered to improve their performance. In recent years, wall construction in the multi-tiered configuration has improved both static and post-earthquake behavior, and become an appropriate approach to building high-reinforced soil walls. In addition to the above approach, treatment of the soil used as the wall backfill is also a suitable solution to enhance the wall performance. In this study, a combination of the two above concepts has been employed for better understanding the GRS wall behavior by developing a series of reduced-scale physical models. One-meter-high models in one- and multi-tiered fashion were tested backfilled with untreated and treated (by adding a combination of cement and polypropylene fibers) silty sand mixture. A comparison of the 1g shaking table tests among wall models subjected to seismic waves indicated the influence of the treating solutions on the dynamic response of the walls. The findings suggest that use of the two proposed approaches in the GRS walls construction has a notable effect on the wall stability after construction and during an earthquake. It also improves the essential seismic parameters such as displacement and acceleration responses.

Seismic response of geogrid-reinforced fiber-cement soil walls using shaking table tests

Improving the characteristics of local low-strength soils at the construction site is one of the appropriate approaches to employ the soils as a backfill of geogrid-reinforced soil (GRS) walls. In this study, the fiber-cement-treated sand–silt mixture was used as the backfill of walls. The post-earthquake performance of the walls was evaluated by applying the sinusoidal waves on 1 m high reduced-scale physical models and conducting a series of 1g shaking table tests. A comparison of the wall models constructed with treated and untreated backfill indicated the advantages of geogrid-reinforced fiber-cement-treated soil walls subjected to strong ground motion. The results revealed the better behavior of the wall models backfilled with treated soil mixtures under dynamic loading. Such improved performance was more evident in (i) deformation responses, including the lateral displacement of wall facing, deformation mode, failure surfaces, and settlement of backfill surface and (ii) acceleration response in different locations, including facing, reinforced, and retained zones of walls.

ソイルネイルと組み合わせたジオグリッド補強土壁の耐震性

ソイルネイルと組み合わせたジオグリッド補強土壁の耐震性

Use of Centrifuge-Based Physical Modelling for Understanding the Performance of Geostructures

Centrifuge-based physical modelling is widely adopted for understanding the performance of geostructures, like levees subjected to flooding and drawdown and geogrid-reinforced soil walls subjected to seepage. In this paper, an attempt has been made to bring out the advantage of centrifuge-based physical modelling to understand (i) the performance of levees subjected to flooding using a custom-designed and developed in-flight flood simulator at 30 gravities with and without chimney drain and (ii) the performance of geogrid-reinforced soil walls with and without chimney drain subjected to seepage at 40 gravities. In both the cases, silty sand was used to model soil and fine sand was used in chimney drain. All centrifuge model tests were performed using the 4.5-m-radius large-beam centrifuge facility available at IIT Bombay. Models were instrumented with linearly variable differential transformers for measuring surface settlements and pore pressure transducers to measure raise in pore water pressure within the soil at the onset of flooding for levees and at the onset of seepage for geogrid-reinforced soil walls. Additionally, digital image analyses of photographs of front elevation of levee models and geogrid-reinforced soil wall models were carried out to obtain face movements, movements of markers embedded within the levee, markers stuck to geogrid layers of reinforced soil walls at the onset of flooding and seepage. The developed in-flight flood simulator was found to be capable of generating the flood rate ranging from 2.2 to 7 m/day. Further, results of centrifuge model tests conducted on levees without any chimney drain were noticed to undergo catastrophic failure within 4.25 days of flooding-induced seepage, whereas a levee with chimney drain was found to sustain flooding-induced seepage of 37.5 days. Geogrid-reinforced soil wall was constructed with silty sand as a structural as well as backfill, without any drainage system experienced catastrophic failure. Contrary to this, geogrid-reinforced soil walls with chimney drain as an external drainage system helped in averting catastrophic failure. However, probability of piping failure near the toe region of the wall cannot be ruled out. Further, the use of geocomposite layers as an internal drainage system within the reinforced zone also explored and the placement of geocomposite layers at one-third portion of height from bottom was found to be effective.

Performance of Geosynthetic Reinforced MSE Walls with Marginal Backfills at the Onset of Rainfall Infiltration

In the present study, performance of geosynthetic reinforced MSE walls backfilled with locally available marginal lateritic soil at the onset of rainfall infiltration was investigated. Two different types of geosynthetics reinforcements were used. One was a conventional type of geogrids usually used in MSE walls, and the other was composite geogrids. Seepage analysis, stability analysis and strength and deformation analysis were carried out on MSE walls with rainfall simulated for a duration of 3 days. In case of geogrid reinforced soil wall (GR-W), the suction within the backfill was lost completely at the end of 2.176 days of rainfall, whereas suction was maintained even at the end of 3 days of rainfall in walls reinforced with composite geogrids (CGR-W). From the stability analysis, it was observed that the factor of safety of GR-W decreased at the onset of rainfall infiltration with time and reached less than the desirable value of less than 1.5 in 2.125 days of rainfall. The factor of safety of CGR-W was maintained at 1.88 throughout the period of rainfall. The facing deformation in GR-W was found to increase, with a maximum of 3.2 times increase at the end of three days of rainfall. Similarly, there was an increase in maximum tensile load mobilized in the reinforcements in GR-W, whereas in the case of CGR-W, the influence of rainfall was negligible. From the present study, it can be concluded that the presence of composite geogrids improves the overall performance of MSE walls backfilled with marginal lateritic backfills.

A Case Study on the Reinforcement of Existing Damaged Geogrid Reinforced Soil Wall Using Numerical Analyses

A Case Study on the Reinforcement of Existing Damaged Geogrid Reinforced Soil Wall Using Numerical Analyses

Study on the Mutual Influence of Back-to-back Geogrid Reinforced Soil Wall by Finite Element Method

Study on the Mutual Influence of Back-to-back Geogrid Reinforced Soil Wall by Finite Element Method

Experimental investigation on the performance of multi-tiered geogrid mechanically stabilized earth (MSE) walls with wrap-around facing subjected to earthquake loading

Construction of mechanically stabilized earth (MSE) walls in multi-tiered configurations is a promising solution for increasing the height of such walls. The good performance of this type of walls after recent major earthquakes was reported in a number of technical studies. In the present study, an experimental approach was adopted to compare the seismic performance of single-tiered and multi-tiered MSE walls using physical modeling and through conducting a series of uniaxial shaking table tests. To do so, several geogrid-reinforced soil walls with wrap-around facing (i.e., three-, two-, and single-tiered) with a total height of 10 m were designed in the form of prototypes of 1-m-height wall models. The step-wise intensified sinusoidal waves were applied to the models in 14 typical forms. Comparing the shaking table test results confirmed the post-earthquake advantages of multi-tiered MSE walls. The results revealed that tiered walls exhibited better behaviors under earthquake loading in terms of the seismic stability of the wall, displacement of the wall crest, horizontal displacement of the wall facing, deformation mode and failure mechanism of the wall, settlement of backfill surface, and seismic acceleration responses.

GRS bridge abutments under cyclic lateral push

During earthquakes, the bridge abutments can undergo large displacements that are required to develop high passive earth pressures behind the abutment walls. In the present study, a finite element (FE) model of a Geogrid Reinforced Soil (GRS) wall has been developed to study the passive earth pressure induced under cyclic lateral loading. An advanced constitutive model has been used as VUMAT to characterize the soil elements. Uniform lateral displacement is applied to the abutment wall. Pushing and pulling of the wall is repeatedly done with small increments of lateral displacement towards the soil in each cycle. The loading is continued until the passive resistance of the soil doesn't increase much or stands almost at the same value. The improvement in the pushover capacity because of the provision of reinforcement is about four times that of the unreinforced abutment. Well compacted backfills show a peak capacity, which then decreases to a residual capacity with further push, indicating the dilation of the dense backfill. Whereas the relatively less compacted backfills attain a maximum capacity after being compacted more due to the initial intruding movement of the wall.

Laboratory study on geogrid reinforced soil wall with modular facing under cyclic strip loading

This paper compares the behavior of four geogrid reinforced soil walls with modular facing under cyclic strip footing loading. Four types of reinforcement schemes were used in the laboratory tests on 150 cm × 100 cm × 126.5 cm (length × width × height) walls. Strip plate was used to simulate the foundations for bridges. The settlement of the footing, deflection of the wall facing, lateral and vertical stresses below the centerline of the footings, strains in reinforcement layers, and acceleration in the soils were monitored during the cyclic loading tests. It was found that the layout of reinforcement layers greatly affects the bearing capacity, earth pressure coefficient, and dynamic responses of the walls.

Deformation Behaviour of Geogrid Reinforced Soil Walls under Strip Loading

Deformation Behaviour of Geogrid Reinforced Soil Walls under Strip Loading