Reinforcement Tension per Layer (Geogrid)
Calculate the required tensile tension in a geosynthetic reinforcement layer in a reinforced-soil wall or slope, T_req = K_a·γ·z·S_v, from the active earth pressure coefficient K_a, the soil unit weight γ (kN/m³), the layer depth z (m) and the vertical spacing between layers S_v (m). In a reinforced-soil wall (geogrid walls, mechanically stabilized earth, reinforced steep slopes), each geosynthetic layer must resist the horizontal force the soil, under active pressure, tends to push out over that height band. The required tension grows with DEPTH (z), since lateral pressure increases with the vertical soil stress above — so the lower layers of a reinforced wall are the most stressed and sometimes get stronger geosynthetics or smaller spacing. The vertical spacing S_v sets each layer's 'influence area' (closer layers → less force each). Comparing T_req with the geosynthetic's allowable strength (and checking pullout), the reinforcement is designed: type, strength, spacing and length of each layer. It is the central calculation in reinforced-soil wall and slope design. Enter the active earth pressure coefficient, unit weight, depth and vertical spacing.
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Tensão de reforço por camada (geogrelha)
A tensão de tração requerida em uma camada de reforço em um muro ou talude de solo reforçado é T_req = K_a·γ·z·S_v, a partir do coeficiente de empuxo ativo K_a, do peso específico do solo γ, da profundidade da camada z e do espaçamento vertical entre camadas S_v. Em um muro de solo reforçado (muros de geogrelha, terra armada, taludes íngremes), cada camada de geossintético precisa resistir à força horizontal que o solo, sob empuxo ativo, tende a empurrar para fora naquela faixa de altura. A tensão requerida cresce com a profundidade (z), pois o empuxo lateral aumenta com a tensão vertical do solo acima — por isso as camadas inferiores de um muro reforçado são as mais solicitadas, e às vezes recebem geossintéticos mais resistentes ou espaçamentos menores. O espaçamento vertical S_v define a 'área de influência' de cada camada (quanto mais próximas, menor a força em cada uma). Comparando T_req com a resistência admissível do geossintético (e verificando o arrancamento), dimensiona-se o reforço: o tipo, a resistência, o espaçamento e o comprimento de cada camada. É o cálculo central do projeto de muros e taludes em solo reforçado, uma técnica que permite estruturas de contenção esbeltas, flexíveis e econômicas. Informe o coeficiente de empuxo ativo, o peso específico, a profundidade e o espaçamento vertical.
Related Tools
Number of Reinforcement Layers
Calculate the number of geosynthetic reinforcement layers needed in a reinforced-soil wall or slope, N = H ÷ S_v, from the structure height H (m) and the vertical spacing between layers S_v (m). In a reinforced-soil structure, the geosynthetic layers (geogrid or geotextile) are installed horizontally between compacted soil lifts at regular vertical intervals. The total number of layers is simply the height divided by the spacing. The vertical spacing S_v is a crucial design decision: SMALLER spacing (more layers) better distributes stresses, allows weaker geosynthetics and gives a more homogeneous, stable reinforced mass, but increases installation operations (slower and costlier). LARGER spacing (fewer layers) builds faster but needs stronger geosynthetics and may allow localized deformations between layers (face bulging). Typically S_v ranges 0.3-0.8 m, often adopting multiples of the soil compaction lift thickness (0.15-0.20 m). This calculation is essential for the quantity take-off (total geosynthetic area = N × each layer's area) and budgeting, and defines the construction sequence. Enter the structure height and the vertical spacing.
Allowable Geosynthetic Strength
Calculate the allowable (design) tensile strength of a geosynthetic, T_adm = T_ult ÷ (RF_cr·RF_id·RF_cd), from the ultimate strength T_ult (kN/m, from a short-term tensile test) and the reduction factors for creep RF_cr, installation damage RF_id and chemical/biological degradation RF_cd. Geosynthetics (geotextiles, geogrids, geomembranes) used as soil REINFORCEMENT in walls, slopes and embankments on soft soils must work for decades, and their design strength is far below the lab value from quick tests. The reduction factors discount: CREEP (polymers under constant load deform and lose strength over time, RF_cr typically 2-5, the largest factor); INSTALLATION DAMAGE (compacting gravel fill over the geosynthetic causes abrasion and punctures, RF_id ~1.1-2); and chemical/biological DEGRADATION over the service life (RF_cd ~1.1-2). Their product can reduce the allowable strength to 20-40% of the ultimate. This is the basis of designing any reinforced-soil structure, and underestimating the reduction factors (overestimating strength) is a cause of reinforced wall and slope failures. Enter the ultimate strength and the three reduction factors.
Geogrid Anchorage Length
Calculate the anchorage length (embedment in the resistant zone) needed for a reinforcing geogrid, L_a = T ÷ (2·σ_v·tan φ·C_i), from the layer tensile force T (kN/m), the vertical stress σ_v (kPa) on the geogrid, the soil friction angle φ (degrees) and the soil-geogrid interaction coefficient C_i (~0.6-1.0). In a reinforced-soil wall or slope, each geosynthetic layer must be anchored beyond the potential failure surface, over a length enough for soil-reinforcement friction to mobilize the tensile force without the reinforcement being PULLED OUT. The factor 2 appears because the geogrid has friction on BOTH faces (top and bottom). The pullout resistance per unit length is friction (σ_v·tan φ) times the interaction coefficient C_i, which measures how well the geogrid 'interlocks' with the soil (geogrids, with their apertures, have high C_i since soil passes through the mesh and generates passive resistance, better than smooth geotextiles). The anchorage length adds to the length within the active zone (varying with height) to give each layer's TOTAL length. Insufficient anchorage leads to pullout and progressive wall collapse. Enter the tension, vertical stress, friction angle and interaction coefficient.
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