Soil aeration
Renewal of air in soil pores. Waterlogging expels oxygen from the root zone; drainage restores aeration, reduces root rot, and improves plant development.
Technical terms for agricultural drainage and large infrastructure projects — roads, railways, warehouses, mining and solar energy — explained clearly and aligned with Brazilian reality: soils, climate, standards (DNIT, ABNT, ANM) and products.
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Renewal of air in soil pores. Waterlogging expels oxygen from the root zone; drainage restores aeration, reduces root rot, and improves plant development.
A zone saturated with water in the subsoil. Its fluctuation (rising during rain, falling during drought) is controlled by underground drains, which lower the water level only to the depth at which they are installed.
This is a condition, not a soil type: the upward pressure of groundwater in fine sands or silts prevents soil compaction, reduces its bearing capacity, and compromises the drain’s service life. It requires a stable subgrade and, sometimes, a temporary drain before final installation.
The way drains are laid out in the field: systematic (parallel across the entire area), herringbone (lateral drains oblique to a central main drain, for sloped areas), random (only in wet spots on uneven terrain), and double main (when there are obstacles such as waterways or roads).
Deposition of fine particles (silt and fine sand) inside the pipe, reducing flow. Common in sandy soils and when the drain outlet is submerged for long periods. Self-cleaning speed and settling boxes help prevent it.
A structure that retains sediment carried by the water before it settles in the pipe. Recommended when the slope does not ensure self-cleaning velocity or when there is a risk of silting.
Urban stormwater drainage structures for water collection and inspection. They are found in infrastructure projects, not in subsurface agricultural drainage.
Upward migration of fine subgrade particles into overlying track or pavement layers, caused by repeated heavy loads on saturated soil. Responsible for ~92% of structural railway and road failures. Prevention: drainage geocomposite at the subgrade-ballast interface and deep longitudinal drain with Techdreno KC.
A drainage structure carrying water under a road or railway embankment. Types: reinforced concrete pipe (RCP/NBR 8890), box culvert (DNIT 025/2025-ES) and double-wall corrugated HDPE (DNIT 093/2016-EM). HDPE offers lower roughness (Manning n ≈ 0.009–0.011 vs. 0.013 for concrete), resistance to aggressive soils, and faster installation.
A structure where multiple drains converge, used to connect branches, safely change direction, and facilitate system inspection and maintenance.
A compacted or low-permeability horizon (e.g., the textural B horizon of an Argissol or plinthite) that blocks water flow and causes waterlogging even on high ground. It forms the basis for calculating the spacing between drains.
The amount of water the soil retains after excess water has drained by gravity. It is the practical goal of drainage: to remove excess water without drying out the soil.
Water depth (mm/day) that the system needs to remove, used to determine the pipe diameter in the drainage calculator. Techduto guide references for mineral soils: 9 mm/day (forage and grain crops), 12 mm/day (commercial crops), and 20 mm/day (specialty crops). In regions with concentrated rainfall, a more conservative value is used (“tropical mode”).
Distance from the soil surface to the top of the pipe (different from depth, measured to the bottom of the trench). The minimum cover protects the pipe from machinery loads—generally 600 mm for lateral drains.
Increase in soil density due to reduced porosity, caused by machine traffic or trampling in wet conditions. Restricts air, water, and roots. See wheel ruts.
Geotechnical test measuring relative soil penetration resistance against a standard aggregate, after 96 hours of immersion. A low CBR under saturated conditions indicates a weak subgrade when wet — the core argument for deep drainage in roads and railways.
Fraction of rainfall that becomes surface runoff (dimensionless, 0 to 1). Depends on surface type: metal roof C ≈ 0.90–0.95; asphalt pavement C ≈ 0.85–0.90; lawn C ≈ 0.15–0.40. Used in Q = C·i·A to size collection systems and detention tanks for logistics warehouses and solar farms.
Continuous layer of drainage material (crushed stone or geocomposite) installed horizontally under foundations, slabs-on-grade, tailings piles, or embankments to collect and conduct percolated water to collectors. Relieves base pore pressure and prevents differential settlement and mud pumping.
Longitudinal slope of the drain that ensures drainage by gravity. Insufficient slope reduces self-cleaning; excessive slope can cause excess pressure and internal erosion. Reverse slope (backslope) should be avoided.
A drain installed at the upper end of the side ditches or at the edge of the field to capture water that would otherwise flow into the agricultural area.
A drain positioned transversely to the slope to intercept groundwater before it reaches the surface, installed near the impermeable layer, where the flow is concentrated.
A pipe that collects water from the soil and conveys it to the main drain. When installed in parallel, they form the collection network.
A larger-diameter pipe that collects water from the lateral drains and conveys it to the outlet. Its diameter is determined by the drained area, slope, and drainage coefficient.
An open channel without a pipe in clayey subsoil—a technique used in temperate climates. Rarely applicable in tropical Brazil; mentioned only for context.
Controlled removal of excess water from the soil profile using buried pipes, lowering the water table to the depth of the drains and creating a suitable environment for roots. See the complete guide.
Removal of water accumulated on the surface through shallow ditches and land leveling. Reduces the volume that would percolate into the soil and makes the underground system more efficient; recommended in flat areas with fine-textured soil.
Techduto sealing tape used to seal connections (for example, at the internal joint of the Techdreno DW), ensuring a watertight seal against sediment ingress.
Low-pH effluent (typically < 4) generated by oxidation of sulfide minerals (pyrite, FeS₂) exposed to water and oxygen during mining. Produces sulfuric acid and dissolves heavy metals that contaminate water bodies. Prevention: impermeable covers, geomembranes, and controlled drainage to prevent sulfide contact with water and air.
Controlled removal of geotechnical and environmental risk from a tailings dam that will no longer be needed — removal of tailings, demolition of containment structures, and rehabilitation of the site. Brazil’s Law 14,066/2020 required decharacterization of all upstream-method dams. Drainage is a critical component for stability during and after the intervention.
Hydraulic structure installed at the outlet of culverts, drops, and spillways to reduce flow velocity and prevent regressive erosion of the receiving channel. Common types: stilling basin (with concrete blocks) and riprap. Absence of a dissipator is a leading cause of outlet erosion in roads and railways.
Subsurface drainage system with a main collector and oblique laterals (30–60°) forming a herringbone pattern. Installed at shallow depth (0.5–1.5 m), it distributes collection laterally to reduce surface moisture on roads, industrial yards, and fields.
Drain parallel to the road or railway axis, installed ≥ 1.5 m deep (minimum per ISF-210/IPR-724) to intercept and lower the water table at least 1.5 m below grade. Composed of perforated corrugated HDPE pipe (Techdreno KC in fine-grained soil) in a trench with minimum 0.5% gradient.
Method of tailings disposal where material is pre-dewatered by filtration (~75–85% solids) and compacted into stable stacks. Eliminates liquefaction failure risk and allows up to 95% water reuse. Requires robust base drainage blanket (geocomposite + HDPE corrugated pipe) and erosion control on exposed slopes.
A layer (geotextile, synthetic fabric, or graded gravel) that surrounds the pipe to reduce the migration of soil particles into the drain, maintain soil stability, and improve flow. In Brazil, this is often necessary, as many soils have a fine texture (fine sands and silts ranging from 50 to 250 microns), which are susceptible to internal erosion. The Techdreno KC already includes the envelope.
Granular material (gravel or coarse sand) placed over the pipe to facilitate water entry and maintain hydraulic connection with the soil. It differs from the filter material, whose function is to block fine particles.
The transport of particles by water. Proper drainage reduces surface runoff and, with it, erosion and nutrient loss; however, high velocities inside the pipe or at the outlet can cause erosion and require energy dissipators.
Rainwater that runs over the surface instead of infiltrating. A sign of poor drainage or compacted soil.
Synthetic material with filtration, layer separation, erosion protection, and soil stabilization functions. In drainage, it wraps around the pipe as a filter layer. The choice depends on the apparent filtration aperture and soil texture. In fine-textured Brazilian soils, a filter is usually necessary—a function that Techdreno KC already incorporates.
An indicator that relates flow velocity to pipe diameter; values above 1 indicate a steep gradient, requiring design precautions (half-section sections, unperforated pipes, relief wells) to prevent excessive pressure and erosion.
Chimney filter: vertical drain embedded in an earth dam core, with increasing grain-size layers, designed to intercept internal seepage and channel it to a toe drain. Inverted filter: any system of increasing grain-size layers that prevents fine particle migration under seepage. Non-woven geotextile is the modern equivalent of a granular inverted filter.
See Filter / geotextile.
Grayish or bluish colors and spots in the soil profile, indicating prolonged saturation and lack of oxygen. It is a field diagnosis of poor drainage, typical of Gleissols and Plintosols.
Geosynthetic product combining a HDPE geonet (drainage core with flow channels) and non-woven geotextile facing(s) (filtration). Replaces crushed stone + geotextile systems at a much smaller thickness (5–25 mm vs. 150–300 mm of aggregate). Used under industrial slabs, at the ballast-subgrade interface in railways, as dam drainage blankets, and in retaining wall drainage.
Impermeable barrier made of textured or smooth HDPE, used to prevent liquid migration between layers. Main application in mining: lining of tailings ponds, heap leach pads, and pile covers. Works in tandem with drainage geocomposite: geomembrane as the barrier, geocomposite/corrugated HDPE pipe as the drain over the barrier.
International standard published in 2020 by UNEP/PRI/ICMM in response to Mariana (2015) and Brumadinho (2019). Defines 6 areas, 15 principles, and 77 specific requirements for tailings management, with mandatory review by an independent dam engineer. Major global and Brazilian miners (Vale, Anglo, Glencore) are committed to full adoption; institutional lenders now require it as a credit condition.
Formula that calculates the spacing between lateral drains under steady-state conditions, based on permeability, depth, and the impermeable layer. It forms the basis for the Techduto guide and the drainage calculator; for concentrated rainfall, it is supplemented by the Glover-Dumm equation.
Metal extraction technique (gold, copper, silver) in which crushed ore is stacked on a HDPE-geomembrane-lined pad and leach solution is sprayed from the top. The PLS (Pregnant Leach Solution — metal-rich solution) is collected by the pad drainage system (geocomposite + corrugated HDPE pipe over the geomembrane) and routed to the recovery plant.
Geotechnical phenomenon where a saturated, unconsolidated soil suddenly loses shear strength and behaves like a fluid, typically triggered by dynamic disturbance (earthquake, rapid surcharge). Main mechanism of catastrophic upstream tailings dam failure — banned in Brazil since 2020 (Law 14,066/2020). Prevention requires tailings consolidation and efficient internal drainage to reduce saturation.
The soil’s ability to absorb rainwater. It is reduced by compaction and by impermeable layers.
Internal cleaning of the pipe with a water jet to remove sediment and unclog the system.
Calculates the flow rate of the pipe based on diameter, slope, and roughness (coefficient n). In corrugated pipe, n ranges from 0.015 to 0.022 depending on the diameter; it is the basis for the diameter selection charts and the drainage calculator.
A calcareous material that is not classified as soil. The installation of underground drains is generally not recommended in marl or in rock stratified at shallow depths.
See gleization.
Empirical equation (V = (1/n)·R²/³·S¹/²) for calculating mean flow velocity in pipes and open channels. The n coefficient represents roughness: double-wall HDPE (smooth interior) n ≈ 0.009–0.011; concrete n ≈ 0.013. A lower n means HDPE conveys the same flow rate with a smaller diameter or lower gradient than concrete.
Correction of small surface depressions to eliminate ponding and provide more uniform percolation. Complements subsurface drainage in flat, fine-textured soils.
Brazilian technical standards applicable to corrugated polyethylene drainage pipes. They define dimensions, ring stiffness classes (SN), and compliance requirements. See the details of NBR 15715.
A deposit of iron oxide that forms inside the drain when iron dissolved in the soil comes into contact with air and oxidizes, often with bacterial involvement. It occurs mainly in very open acidic sands and in floodplain soils with a permanent water table (anaerobic conditions), and is identified by intense reddish deposits at the drain outlets. There is no definitive solution—which is why it is difficult to predict and requires careful design.
Authorization from the managing agency (ANA or state) to intervene in water resources. Relevant when drainage affects water bodies.
A compacted layer just below the implement’s working depth, created by repeated machine traffic. It blocks water and roots; it must be corrected by subsoiling before drainage is considered.
A polymer used in drainage pipes due to its flexibility, chemical resistance, and durability—the predominant solution in Brazil. See the resource on HDPE.
Statistical frequency of a rainfall event (e.g., once every 10 years). Higher-value crops warrant protection against rarer events.
The ease with which water passes through the soil. It determines the depth and spacing of drains.
Damage to the soil surface caused by animal hooves on waterlogged ground; a sign of poor drainage in pastures.
An iron-rich material that hardens with alternating moisture. Common in Brazilian soils and associated with poor drainage and the formation of ochre.
A structure installed at the base of steep sections to relieve excess hydraulic pressure in the drain and prevent erosion-induced collapses.
Distance from the soil surface to the bottom of the trench. For soybeans, depths around 80 cm are usually sufficient; in sandy soils, the depth should not exceed 750 mm. See drain cover.
Device installed at the top of steep sections to prevent negative pressure (vacuum) in the drain.
Vertical pipe that carries surface water into the underground drain; may be equipped with flow restriction devices.
Detention basin (dry pond): stores stormwater runoff peak volume and releases it slowly at the restricted flow rate. Operates dry between events. Retention pond: maintains a permanent water surface. Detention basins are required by São Paulo’s Law 12,526/2007 for impervious areas > 500 m².
Resistance of a corrugated pipe to diametric deflection caused by soil pressure and traffic loads. ABNT NBR 15073 classification: SN2 (agricultural, no heavy traffic), SN4 (moderate), SN8 (heavy-vehicle highways, truck yards, railways). Techdreno DW is manufactured to SN8, with burial depth of 0.8 to 6.0 m under heavy traffic.
Point where the main drain and laterals discharge into the ditch or body of water. It is the most critical part of the system—it must be well constructed and well maintained; a clogged outlet is the number one cause of failure. Protected by a rigid end pipe and energy dissipators.
Fine sandy and silty soils that, at the depth of the drain, allow particles to migrate into the pipe. They require testing to determine the need for a filter and, in general, a filter sleeve (Techdreno KC).
Soils that make up the majority of agricultural areas; the primary focus of the drainage recommendations in the Techduto guide.
Peat-type soils, which typically do not drain well and may collapse when drained. Subsurface drainage is usually not economically viable; the best option is typically pasture or grasses.
Groundwater management in which the same system alternates between draining and raising the water level to irrigate from below. Requires specialized design, a water source, and a water withdrawal permit.
An operation that breaks up the compacted layer (plow pan) with deep rods, restoring infiltration. It often precedes or complements drainage.
Techduto’s line of corrugated drain pipes with an integrated filter sleeve, developed for the unstable, fine-textured soils typical of Brazil—eliminates the need for separate geotextile application and has been validated by UFLA.
Techduto’s double-wall pipe line (smooth on the inside, corrugated on the outside), recommended when higher flow rates and greater strength are required; its internal joint is sealed with DutoSeal tape.
Soil condition capable of supporting machinery without getting stuck or compacting. Drainage extends the planting and harvesting window—a direct economic benefit in mechanized agriculture.
Drain installation equipment (trencher/plow type) that opens the trench, shapes the bottom to the pipe’s diameter, and lays the pipe with slope control. Requires caution in fine, moist soils to avoid compromising drainage.
A section of rigid, continuous, and unperforated pipe used at the drain outlet to protect the discharge point from erosion, weather, fire, animals, and crushing.
Reference train type for structural design of heavy-haul railways in Brazil, with 36 t per axle. Pipes and culverts under TB-360 railways must have their structural stiffness verified for this load — justifying the use of Techdreno DW (double-wall, SN8). DNIT ISF-210 permits “pipe + manufacturer-standardized drainage fabric” as an integrated solution.
Time required for water precipitated at the most remote point of a catchment to reach the control section. Defines the design storm duration: tc equals the storm duration that puts the entire catchment in simultaneous contribution. Impervious areas like warehouse yards have low tc (5–20 min) — higher rainfall intensities and larger peak flows.
An open channel for conducting water; it may serve as the outlet for subsurface drains.
Floodplain. In irrigated rice fields, drainage is part of management practices, involving alternating soil saturation; floodplains with a permanent water table are prone to ochre.
The flow velocity inside the pipe that prevents sediment deposition. The Techduto guide recommends designing for 0.45 m/s whenever possible; where sedimentation is not a risk, a minimum of 0.15 m/s is acceptable.
Maximum outflow rate from a developed area to the public drainage system, equal to the pre-development flow rate (before imperviousness). Detention basins must not exceed this limit when releasing stored runoff. In São Paulo, Decree 41.814/2002 and Law 12,526/2007 require detention/retention structures for impervious areas > 500 m².
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