Geocomposite Drain Flow
Calculate the drainage flow of a drainage geocomposite, q = θ·i·b, from the transmissivity θ (m²/s), the hydraulic gradient i (dimensionless) and the drain width b (m). This is the practical application of transmissivity: it estimates how much water a drainage geocomposite (geonet between geotextiles, or drainage geotextile) can convey in its plane, to check whether it adequately replaces a gravel layer or conventional drain. The flow is the product of transmissivity (the drain's in-plane 'conductivity' at the work's confining pressure), the hydraulic gradient (the head-line slope driving the flow) and the drain width (the drainage front). It is Darcy's law applied to in-plane flow in the geosynthetic. This calculation is essential to size drainage systems with geocomposites: gas and liquid drainage in landfills and mining, drains behind walls and cutoffs, green-roof and buried-structure drainage, and road and railway drains. The flow the geocomposite provides is compared with the design flow (the water to drain, with a safety factor); if insufficient, a higher-transmissivity geocomposite is chosen or the width increased. Enter the transmissivity, hydraulic gradient and width.
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Geocomposite drain flow
The drainage flow rate of a drainage geocomposite is q = θ·i·b, from the transmissivity θ, the hydraulic gradient i, and the drain width b. This is the practical application of transmissivity: it estimates how much water a drainage geocomposite (a geonet between geotextiles, or a drainage geotextile) can carry within its plane, to verify whether it adequately replaces a gravel layer or a conventional drain. The flow is the product of the transmissivity (the in-plane 'conductivity' of the drain, at the confining pressure of the works) times the hydraulic gradient (the slope of the head line driving the flow) times the width of the drain (the drainage front). It is Darcy's law applied to in-plane flow through the geosynthetic. This calculation is essential for sizing drainage systems built with geocomposites: gas and liquid drainage in landfills and mining, drains behind retaining walls and diaphragm walls, drainage of green roofs and buried structures, and road and railway drains. The flow the geocomposite supplies is compared against the design flow (the water to be drained, with a safety factor); if insufficient, pick a geocomposite of higher transmissivity or increase the width. Enter the transmissivity, the hydraulic gradient, and the width.
Related Tools
Geotextile Transmissivity
Calculate a geosynthetic's transmissivity, θ = k_p·t, from the in-plane permeability k_p (m/s) and the thickness t (m); the result, in m²/s, is the transmissivity. Transmissivity characterizes the geosynthetic's ability to convey water WITHIN its own plane (longitudinally, like a planar drain), and is the key property in the DRAINAGE function. While permittivity measures flow THROUGH the geotextile (perpendicular), transmissivity measures flow ALONG it (parallel). It is the fundamental property of drainage geocomposites and geonets — products with a 3D open core (geonet) between filtering geotextiles, used to drain water replacing gravel layers: drainage behind retaining walls, under landfills (leachate and gas collection), in roads, sports fields and gardens (subsurface drainage), and in foundations. Transmissivity depends strongly on confining PRESSURE (the more compressed, the less space for water to flow and the lower θ) and on gradient, so it is specified at the work's real load conditions. Times the gradient and width, it gives the drained flow. Enter the in-plane permeability and the thickness.
Geotextile Permittivity
Calculate a geotextile's permittivity, ψ = k_n ÷ t, from the cross-plane permeability k_n (m/s) and the geotextile thickness t (m); the result, in s⁻¹, is the permittivity. Permittivity characterizes the geotextile's ability to let water pass PERPENDICULAR to its plane (through the fabric), and is the key property in the FILTRATION and cross-plane DRAINAGE functions. It is defined as permittivity (not simply permeability) because a geotextile's thickness is small, variable and hard to measure precisely under load — so permeability is normalized by thickness, giving a property (ψ = k/t) measurable directly from flow per unit area and gradient, without knowing the thickness. In a geotextile filter (replacing the traditional graded sand filter in drains, behind retaining walls, under riprap), the geotextile must be permittive enough to let water pass freely (without damming and building pore pressure), but with pores small enough to RETAIN the soil particles (without clogging or letting soil escape — the retention criterion). The balance between permittivity and retention is the heart of geotextile filter design. Enter the cross-plane permeability and the thickness.
Solids Mass Flow (Dredge)
Calculate the mass flow of solids transported by a dredge or pipeline, ṁ_s = Q·C_v·ρ_s, from the total slurry flow Q (m³/s), the solids volumetric concentration C_v (fraction) and the solids density ρ_s (kg/m³). Solids mass flow is the MASS of useful material transported per unit time (kg/s, or tonnes per hour), the production indicator used when TONNAGE matters — the typical case of ore transport by pipeline (measured in t/h of dry ore) and mineral processing. It is the product of three factors: the slurry flow (pump capacity), the solids concentration (how 'loaded' the slurry is) and the solids density (iron ores, for example, are very dense, ~5000 kg/m³, so little volumetric concentration already gives high tonnage). Mass flow, integrated over time, gives the total transported tonnage, the basis of billing and operational mass balance. Optimizing it — maximizing tonnage per unit pumping energy — is the central goal of pipeline operation, which moves hundreds of millions of tonnes of ore per year over long distances far more energy-efficiently than trucks or trains. Enter the slurry flow, the volumetric concentration and the solids density.
Geosynthetic Seam Strength
Calculate the strength of a geosynthetic seam (sewn or welded), T_seam = (E ÷ 100)·T_ult, from the seam efficiency E (% of base material strength) and the geosynthetic ultimate strength T_ult (kN/m). Geosynthetics come in limited-width rolls, and on large works (reinforced walls, embankments, geomembrane-lined ponds) must be SEAMED to cover the whole area — by sewing, thermal welding (geomembranes) or simple overlap. The seam is almost always the WEAKEST POINT of the system: a sewn seam has efficiency typically 50-80% of the base fabric strength (the needle punctures and weakens the material, and the thread can be the weak link), while well-made thermal welds in geomembranes can reach 80-100%. So in REINFORCEMENT geosynthetics, seams perpendicular to the main tension are avoided or reinforced, and in barrier geomembranes (landfills, ponds) welds are rigorously tested (dual-channel air pressure, vacuum, destructive tests), since a leak from a bad seam compromises the whole lining. Knowing the seam strength is essential for design and quality control. Enter the seam efficiency and the ultimate strength.
Steam Turbine Power
Calculate the mechanical power generated by a steam turbine, P = ṁ × (h₁ − h₂), multiplying the steam mass flow (kg/s) by the enthalpy drop between turbine inlet and outlet (kJ/kg). The result, in kW, is the shaft power delivered to the generator, accounting for the expansion of high-pressure, high-temperature steam down to condenser pressure. It is the core calculation in sizing thermal power and cogeneration plants: the larger the enthalpy drop, the more power per kg of steam. Enter the steam flow and the inlet and outlet enthalpies.
Landfill Methane Flow (Scholl Canyon)
Computes the methane flow generated by one batch of landfilled waste using the Scholl Canyon first-order decay model, Q = k × L₀ × M × e^(−k×t), where M is the mass of that batch, L₀ is the total methane potential per tonne, k is the annual decay constant and t is the age of the batch. The model assumes generation peaks right after placement and falls exponentially from then on, with k between 0.04 and 0.09 per year in wet climates and L₀ typically 50 to 170 m³ of methane per tonne of wet waste, 170 being the LandGEM default. Since the model is linear in mass, a real landfill is summed batch by batch, each with its own age. Enter the decay constant, the methane potential, the waste mass and the age of the batch.
The results provided by this tool are for general informational and educational purposes only and do not constitute professional, financial, medical, legal, tax or accounting advice. Always confirm important decisions with a qualified professional and official sources.