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Retaining structures
Published in Rodrigo Salgado, The Engineering of Foundations, Slopes and Retaining Structures, 2022
Retaining structures are often needed to create temporary or permanent space. Temporary space is needed to create the conditions for construction and foundation installation activities at construction sites. Permanent space is needed for underground parking, subway stations, and various other purposes. Retaining structures retain soil in place when the natural tendency of the soil would be to slide due to self-weight or existing loading. When the ground needs to be built up, the space behind a retaining wall is backfilled with soil. A clear example of this use of retaining walls is the construction of bridge abutments, nowadays most frequently done using mechanically stabilized earth (MSE) walls.
Soil Mechanics
Published in P.K. Jayasree, K Balan, V Rani, Practical Civil Engineering, 2021
P.K. Jayasree, K Balan, V Rani
Mechanically stabilized earth (MSE) is soil constructed with artificial reinforcing. It can be used for retaining walls, bridge abutments, sea walls, and dikes. The reinforcing elements used can vary but include steel and geosynthetics. MSE is a term usually used in the USA to distinguish it from the name “Reinforced Earth.” A trade name of the Reinforced Earth Company, but elsewhere Reinforced soil is the generally accepted term. MSE wall stabilizes unstable slopes and retains the soil on steep slopes and under crest loads. The wall face is often precast, segmental blocks, panels, or geocells that can tolerate some differential movements. The walls are in-filled with granular soil with or without reinforcement, while retaining the backfill soil. Reinforced walls utilize horizontal layers typically of geogrids.
Earth retention and earth anchors
Published in Alan J. Lutenegger, Soils and Geotechnology in Construction, 2019
Mechanically stabilized earth (MSE) walls are earth-retaining structures consisting of reinforced and compacted soil placed behind facing elements that form a composite structure. The wall is constructed by placing layers of compacted fill with horizontal reinforcement in layers. MSE walls are gravity structures, but because they are constructed of soil, they are more flexible than concrete walls and can tolerate settlement and horizontal displacement without problems. Figure 7.19 shows the three main components of an MSE wall: (1) reinforcement; (2) compacted fill; and (3) facing.
Experimental study of the effect of different backfilled soils on the stability of mechanically stabilized earth walls
Published in Journal of the Chinese Institute of Engineers, 2020
Wen-Yi Hung, Truong-Nhat-Phuong Pham, Chung-Chi Weng
Mechanically stabilized earth (MSE) walls are commonly used worldwide because they are inexpensive, easily constructed, and are able to accommodate multiple types of deformations (Allen and Bathurst 2015). Geosynthetic reinforced earth walls (GREW) are often used as retaining walls for the construction of paved roads in mountainous regions and on sloped land. Such walls can have just one tier (vertical geosynthetic reinforced earth wall – VGREW) or several tiers (superimposed geosynthetic reinforced earth wall – SGREW) (Berg, Christopher, and Samtani 2009; Elias, Christopher, and Berg 2001; Huang, Yin, and Hsu 2017). The SGREW is selected as a more desirable alternative to the traditional retaining wall because of its reduced construction cost, long-term stability, simplicity of construction, and esthetic appeal (BSI 2010; Huang 2000; Hung 2008). Engineers often favor a two-tiered design because it is simple to construct and design.
Comparison of FEA and analytical methods for determining stability of a RAP supported MSE wall
Published in DFI Journal - The Journal of the Deep Foundations Institute, 2018
Emily C. Reed, Daniel R. VandenBerge
Mechanically Stabilized Earth (MSE) is a general term for reinforced soil placed in multiple layers (Federal Highway Administration 2009). Reinforced soil can be used for both reinforced slopes and retaining walls. A reinforced slope rises at an incline not exceeding 70 deg and requires two zones of reinforcement layers: a dense zone near the face of the slope and a well-spaced zone across the cross sectional width of the slope. Retaining walls with reinforced soil will rise at an angle exceeding 70 deg and tend to have only one zone of reinforcement (Federal Highway Administration 2009). These walls are usually backfilled with a coarse-grained soil. The geotechnical design at work in these walls is often overlooked by the public because the soil is hidden behind a “facing” usually made of decorative concrete panels or blocks. These walls are often chosen over a typical reinforced concrete retaining wall because they can be much more cost effective. Global stability is one important failure mode that must be considered for MSE walls. Global stability is a rotational type of failure mechanism that passes through the retained backfill, behind the reinforced zone, and through the foundation soil.
Performance of MSE walls with sustainable backfills subjected to differential settlements
Published in International Journal of Geotechnical Engineering, 2022
Large scale infrastructural development is going on worldwide. Mechanically stabilized earth (MSE) walls or reinforced soil structures have become very popular these days and are extensively used in approach roads for highway flyovers, slope stabilization works, bridge abutments, etc. Various standard codes and guidelines such as FHWA (Federal highway authority), NCMA (National Concrete and Masonry Association), IRC (Indian Road Congress, IRC:SP:102), AASTHO (American Association of State Highway Transportation Officials), BS-8006 (British Standards), etc. specified the requirements of ideal backfill material for reinforced soil applications. Ideally, freely draining granular materials such as sand are used as the backfill material in MSE walls. Most of the design guidelines mandated the usage of soil with less than 15% fines (passing 75µ). However, NCMA (2010) guidelines permit up to soil with less than 35% fines (passing 75µ) with proper drainage considerations. A comprehensive summary of the requirements mandated by the standard specification for the structured fill of MSE walls was reported by Prasad and Ramana (2016). Granular soils or ideal backfill materials ensure proper interaction and load transfer from the soil to reinforcement. But, the scarcity of ideal granular materials necessitated the utilization of locally available marginal soil which does not meet the requirements of an ideal backfill material (Koerner and Koerner 2013, 2018; Vibha and Divya 2019, 2020, 2021). Also, the cost of backfill constitutes about 50–75% of the total cost of the wall (Koerner and Koerner 2011). Another alternative, gaining popularity these days is the utilization of waste materials such as pond ash, bottom ash, copper slag etc. (Ghosh, Ghosh, and Bera 2005; Pant, Datta, and Ramana 2019; Prasad and Ramana 2016; Thakur et al. 2012)