Фундамент для дома на глинистых и суглинистых почвах

Мало какое строительство обходится без устройства фундамента, ведь именно эта конструкция принимает на себя всю нагрузку от строения. При выборе фундамента учитывают не только материалы и особенности будущего строения, но и тип грунта. В частности, это касается участков с глинистой почвой, которая при строительстве может создать некоторые сложности.

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Выбираем правильный фундамент для глинистой почвы

На глине можно соорудить практически любой фундамент. Выбор основания во многом зависит от особенностей участка и пожеланий застройщика. Независимо от того, какой фундамент будет сооружаться, специалисты рекомендуют выполнить ряд необходимых работ.

По всей площади участка выполняется выемка грунта на определенную глубину. На этом месте устраивается подушка из песка или щебня. Стоимость таких работ находится на довольно высоком уровне, но благодаря ним можно повысить надежность и прочность строения.

В особенности это касается участков в районах, где период низких температур довольно длителен.

При выборе основания стоит учесть показатели глинистости и глубину промерзания почвы. Немаловажным является и значение уровня глубинных вод. В том случае, когда подземные воды находятся выше уровня промерзания почвы, необходимо устроить дренаж по периметру основания дома. Дренаж выполняется еще до сооружения фундамента.

На глинистой почве можно возводить такие фундаменты:

• ленточный;
• плитный;
• свайный.

Ленточный фундамент используют на глинистых почвах, где уровень грунтовых вод находится на довольно большой глубине.

Основание представляет собой железобетонную ленту, которая проходит под внешними и всеми несущими стенами. Если в доме предусмотрено устройство подвального помещения или гаража, то данные участки усиливаются монолитной подушкой. К достоинствам конструкции относят долговечность и высокую несущую способность. Конечно, на сооружение такого основание уйдет довольно много времени и денег.

Плиточный фундамент является оптимальным решением для глинистых почв. Он представляет собой железобетонную плиту, которая размещается под всем строением. Еще этот тип основания называют плавающим. В процессе движения грунта конструкция смещается полностью, что предотвращает ее деформацию.

Плита укладывается не на глину, а на специально обустроенную подложку из песка и гравия. Такой фундамент может прослужить полтора века. Он очень легко противостоит просадке и размыванию почвы.

Конечно, чтобы соорудить такую конструкцию, необходимо будет провести трудоемкие земельные работы. Это повлечет за собой немалые денежные и временные затраты.

При сооружении свайного фундамента рассчитывают, какую нагрузку будет нести тот или иной элемент конструкции. Для его сооружения используют винтовые, буронабивные и забивные сваи. К достоинствам такого основания относят скорость возведения, долговечность и низкая стоимость.

Свайный фундамент способен прослужить несколько веков. Конечно, чтобы достичь таких результатов, необходимо провести некоторые расчеты, а также не допустить типовых ошибок.

Типовые сложности с фундаментами на глинистых грунтах

Основные причины деформации основания

Глина состоит из маленьких частиц, которые со временем могут размываться под воздействием грунтовых вод. Благодаря таким свойствам глинистые грунты относят к сильнопучинистым и просадочным.

Особое внимание необходимо уделять суглинкам. Они представляют собой пески, которые имеют примесь глины. Такой состав является причиной низкой несущей способности почвы.

Если на строительном участке есть такой грунт, то стоит учесть некоторые факторы, которые могут негативно сказаться на целостности основания. К основным причинам разрушения фундамента, сооруженным на глинах и суглинках, относят следующие:

• Просадка основания. В данном случае речь идет о постепенном погружении конструкции в почву. Конечно, если речь идет о малоэтажном строительстве, то просадка встречается крайне редко.
• Выпучивание. Возникает в тех случаях, когда основание устанавливается выше уровня промерзания грунта. В основном проявляется на пучинистых грунтах, которые имеют в своем составе влагонасыщенную глину и суглинки.
• Сдвиг основания в сторону. Возникает при движении пластов земли в результате активного передвижения грунтовых вод.

Предотвращаем деформацию фундаментов на суглинках

Существует несколько основных способов, которые используются большинством строителей. Среди них:

• Установка металлического каркаса из арматуры. Укладывается непосредственно в тело конструкции по всему объему. С его помощью производится связка верхней и нижней части конструкции.
• Увеличение ширины подошвы. Ее делают несколько шире верхней части конструкции. Стенки тщательно выравнивают и покрывают скользящим слоем. Его делают из машинного масла или полиэтиленовой пленки, что позволяет снизить боковое воздействие почвы.
• Ленточные фундаменты всесторонне связывают арматурой. Связка должна быть жесткой и надежной. Это позволит предотвратить сдвиг основания в сторону.

• Чтобы уменьшить глубину промерзания грунта, по периметру фундамент утепляется такими материалами, как пенопласт или керамзит.
• Заливается мелкозаглубленный фундамент, который имеет маленькую боковую поверхность. Это позволяет несколько снизить действие боковой силы пучения.

Соблюдение таких рекомендаций позволит соорудить надежное основание для практически любого строения. Конечно, проектирование фундамента лучше доверить профессионалам.

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Загрузка…90000 What type of soil is good for a foundation for buildings or houses? — Soils Matter, Get the Scoop! 90001 90002 90003 Question 90004: What type of soil is good for a foundation for buildings or houses? 90005 90002 90003 Answer 90004: In both cities and the countryside, selection of sites with the best soil is an important engineering decision in the building process. Whether you live in a house, condo, or apartment, your home is connected to the soil. Your school, the building where you work, the stores you shop in-all of them are built on soil, and often with it.90005 90002 Building foundations need to be on stable and strong soils. Soils range in strength. Some soils are able to support a skyscraper, while other soils are not able to support the weight of a human. If the soil under a building is not stable, the foundation of the building could crack, sink, or worse-the building could fall! 90005 90002 The strength and stability of soil depend on its physical properties. Soil with good structure is more stable. Clay textures are often more stable than sand textures because they have better structure.However, a mix of particle sizes (and pore sizes) is best for engineering (just as it is best for growing crops). It is also important that soil is stable through wetting and drying cycles, so that expanding soil does not crack roads or foundations. Some clay minerals, from a family called smectite, are more likely to shrink and expand during wetting and drying cycles than minerals from other families, such as kaolinite. 90005 90002 Good soil should also have the ability to capture precipitation, so that runoff and erosion do not damage structures.Finally, good soils for infrastructure have balanced chemistry so no building material corrosion occurs. 90005 Buildings crack when not placed on soil with proper qualities. Credit: L. Baldwin 90002 How does all this come together? Soil maps are a great tool to help engineers determine the best location for their design. Soil maps are created by soil scientists and present information such as: 90017 — the slope of the land surface 90017 — the soil’s biological, chemical, and physical properties 90017 — the potential for water runoff, drainage, or storage.90005 90002 Soil maps are also available for public access from the USDA Natural Resource Conservation Service at the Web Soil Survey site. 90005 90002 Few building sites start with ideal conditions. Good engineering designs incorporate corrective measures and management practices. For example, drainage can be added or land surfaces reshaped to direct water away from the site. It is important to know what soil properties exist to avoid future problems. 90005 90002 There are some well-known examples of structural failures that resulted from a lack of soil knowledge.One of the most famous is the Leaning Tower of Pisa. The land underneath seemed stable during the dry season when building began, but the soil became unstable during the wet season and sank under the weight of the building. Even worse, it sank unevenly, resulting in a leaning tower. In addition to managing drainage, compacting and stabilizing the soil before construction may have reduced settling problems. 90005 90002 -Answered by: Larry F. Baldwin, CPSS / NCLSS, Land Management Group, Inc.90005 90002 To read more about cracked foundations, read this Soils Matter blog: https://soilsmatter.wordpress.com/2017/10/01/why-is-my-basement-wall-cracked/ 90005 90002 To view SSSA’s video, Soils Support Buildings and Infrastructure, visit https://www.youtube.com/watch?v=zJi-73qeE-0 90005 90002 90003 More educational materials can be found on various SSSA websites: 90004 90005 90002 90003 http://soils4teachers.org/ (K-12 Lesson Plans and Activities) 90004 90005 90002 90003 http: // soils4kids.org (Just for kids!) 90004 90005 90002 90003 http://soils.org/iys (International Year of Soils, with a coloring book and monthly ideas for teachers and scientists!) 90004 90005 90002 90003 Subscribe to SSSA’s Soils Matter blog posts to get monthly answers to common soils-related questions: https://soilsmatter.wordpress.com/ 90004 90005 90002 90003 Become a Friend of Soil Science (no charge) at: https://www.soils.org/membership/friends-of-soil-science/ 90004 90005 90002 90003 Dig in further with a free trial membership at https: // www.soils.org/membership/become-a-member/trial/ 90004 90005 90061 Like this: 90062 90002 Like Loading … 90005 90002 90061 90067 Related 90068 90062 90005.90000 Foundation Systems and Soil Types 90001 90002 Foundation systems and soil types go hand-in-hand as the type of soil you encounter on your plot will inform the best foundation system for you to use for your project. 90003 90002 Neglecting to investigate the ground conditions on your site is one of the earliest and costly mistakes a self builder can make. 90003 90002 If you have not yet purchased your plot, take a look at this building plot checklist to make sure you exercise due diligence regarding various factors (including soil type) as best you can before committing to a purchase.90003 90002 You can either check with your local authority or building inspector, or undertake a soil investigation. A soil investigation could cost as little as £ 500, but would flag any major issues before you start, which could save you £ 1,000s. 90003 90002 It is always a good idea to allocate at least 10% of your budget for a contingency fund should you encounter any unforeseen issues with your soil type. 90003 90002 Here, we explain the soil types you might encounter and the foundation system you should choose.90003 90002 Ready to start laying out? Check out this step-by-step guide to building foundations. 90003 90016 What Soil Types Might I Find on my Plot? 90017 90002 If you do not already know the soil type of your plot, a good starting point is to call your local authority Building Control department. They can give you an idea of ​​the typical soil type in the area you are building, and the sort of foundation that is appropriate. 90003 90002 Most local authorities produce a fact sheet on typical foundation solutions for different soil types commonly found in the area.90003 90002 Another useful source of information is the 90023 Building Regulations Approved Document A: 2004 90024 which lists seven types of soil plus subsoil conditions and practical field tests to help you identify soil type. 90003 90002 90027 Rock 90028 90003 90002 Includes: 90003 90032 90033 limestone 90034 90033 granite 90034 90033 sandstone 90034 90033 shale 90034 90033 hard solid chalk 90034 90043 90002 These rocks have a high bearing capacity. The rock may simply need to be stripped back and levelled off to build from.90003 90002 Rock can be impervious, so topsoil is likely to require drainage as it is not possible to build soakaways to dispose of rainwater or surface water. Off-mains drainage options will also be very limited. 90003 90002 90027 Chalk 90028 90003 90002 Providing the chalk is not too soft, widths of 450mm for low-rise buildings are generally acceptable. The depth of the foundation must be below any frost action (700mm). If the chalk is soft it will need to be excavated until firm chalk is reached.90003 90002 Chalk soils can be prone to erosion so be wary of hollows or caves. 90003 90002 90027 Gravel and sand 90028 90003 90002 Dry compact gravel, or gravel and sand subsoils are usually adequate for strip foundations. Generally a depth of 700mm is acceptable, as long as the ground has adequate bearing capacity. 90003 90002 If the water table is high (i.e. the gravel is submerged), the bearing capacity is halved, so it’s important to keep the foundations as high as possible. A shallow, reinforced, wide strip foundation may be suitable.90003 90002 Sand holds together reasonably well when damp, compacted and uniform, but trenches may collapse and so sheet piling is often used to retain the ground in trenches until the concrete is poured. 90003 90002 90027 Clay 90028 90003 90002 The first 900-1,200mm layer of clay is subject to movement due to expansion and shrinkage depending on moisture content, so it is generally necessary to excavate foundations to a depth where the moisture content of the clay remains stable . British Standard 8004 recommends a minimum depth of 1m for foundations But if there are, or were, trees nearby, depths of up to 3m may be necessary.90003 90002 In clay, prior to concreting the foundations, the trench is often protected from heave by lining it with a compressible layer (e.g. Clayboard). 90003 90002 90027 Firm clay over soft clay 90028 90003 90002 A traditional strip foundation is sometimes acceptable but it is important not to overdig as this may increase the stress on the softer clay beneath. A common solution is to dig wide strip foundations with steel reinforcement — however an engineered foundation may be necessary.90003 90002 90027 Peat 90028 90003 90002 Peat and loose waterlogged sand are very poor subsoils. If the peat can be stripped back to find suitable load-bearing ground of at least 1.5m depth, strip foundations may be suitable. A reinforced raft foundation will likely be required. 90003 90002 90027 Filled ground 90028 90003 90002 Where ground has previously been excavated and filled, it is generally necessary to dig down to a level beneath the area of ​​the fill. 90003 90002 90027 Sloping sites 90028 90003 90002 Sloping sites require stepped foundations.Guidelines are given in the Building Regulations. 90003 90016 Do I Need a Soil Survey? 90017 90002 Soil investigations can prove very useful but are not a prerequisite. Most sites start without a formal soil investigation, relying instead on either the knowledge of the designer, or the local expertise of the building inspector. 90003 90002 The process involves holes being dug at various points on the site and extrapolating the findings in each hole to assume the subsoil conditions throughout the site.90003 90016 Types of Foundation Systems 90017 90002 The standard routine is to place as little solid concrete as possible into trenches and then to build up from this in blockwork until ground level, where the walls switch to brick or stone or whatever the chosen external cladding should be. This is known as a 90027 strip foundation 90028. 90003 90002 For a single storey building strip foundations will typically be 450mm wide and at least 200mm deep, and for two storeys 600mm wide and 200mm deep.90003 90002 90027 Deep Strip Foundations: 90028 Where strip foundations need to be at a lower level to reach soil with suitable bearing capacity, a wider, deeper trench can be dug to work in, and the strip foundations dug and poured at a lower level. Walls are then built up to ground level in masonry. 90003 90002 90027 Wide Strip Foundations: 90028 Where the soil is soft or of a low load-bearing capacity, wide strip foundations can be used to spread the load over a larger area, reinforced with steel so that the loading per m² is reduced.90003 90002 90003 90023 Diagrams of strip foundations (left) and trenchfill foundations 90024 (Image credit: Homebuilding & Renovating) 90002 A widely used alternative is the trenchfill foundation, where the trenches are filled with ready-mixed concrete to just below ground level. Steel reinforcement may be added in areas close to trees. While this method saves on labour, it will add to the overall cost of your foundations. Just above ground level, the footings are topped with a damp-proof course and then the ground floor is fixed.90003 90002 Compared to deep strip foundations, trench fill minimises the width of the dig and the labour and materials required for building masonry below ground level, offsetting the cost of the additional concrete. 90003 90002 (90027 MORE: 90028 How much will my foundations cost?) 90003 90002 If you have a plot where the ground is deemed to be difficult, then standard strip or trenchfill foundations are unlikely to suit. There are alternative options, but they are considerably more expensive.90003 90002 Digging deeper trenches and filling with more concrete, and potentially adding sheets of polystyrene beside the trenches to act as a slip membrane can be a simple solution. 90003 90002 But if you are having to dig beyond 2.5m in depth, then this solution becomes impractical. Not only will the amount of concrete needed to fill the trench become prohibitively expensive, but working at that depth can prove dangerous. 90003 90002 If the site requires deep foundations in more than a couple of spots, then it is now usual to use a different approach, most often piling, occasionally using concrete rafts.90003 90002 (90027 MORE: 90028 Foundations for difficult sites) 90003 90002 90027 What are Raft Foundations? 90028 90003 90002 As the name suggests, a concrete raft is designed to ‘float’ on the ground beneath. The structure is made up of an extra-thick floor slab, strengthened by masses on steel reinforcing. Rafts have the advantage of providing the base of a ground floor solution, not just wall trenching, but they are reckoned to be rather more complex to construct. 90003 90002 A raft is used where the soil requires such a large bearing area that wide strip foundations are spread too far, making it more economical to pour one large reinforced concrete slab.90003 90002 90003 90023 A raft is an alternative to piled foundations and it can be less expensive 90024 (Image credit: Homebuilding & Renovating) 90002 90027 What are Piled Foundations? 90028 90003 90002 Some housebuilders now use piled foundations on every site because the costs are predictable. Piles are driven into the ground and then filled with concrete, and the whole foundation gets topped with a ground beam to build off. 90003 90002 90027 Short bore pile and beam: 90028 Short bore piles are typically 2-3m long and can be reinforced with steel.Each pile is then connected at the top by a precast horizontal beam of reinforced concrete. A suspended reinforced concrete ground floor can then be built using precast components, or cast in situ. 90003 90002 90027 Friction Piles: 90028 A similar concept to short bore pile and beam used in situations where there is no suitable bearing stratum at an acceptable depth. Friction piles rely on skin resistance against the soil. 90003 90002 90003 90023 Short bore piles are typically 2-3m long and can be reinforced with steel 90024 (Image credit: Homebuilding & Renovating) 90002 90027 What are Pad Foundations? 90028 90003 90002 Used when isolated loads need to be supported, for instance to support the columns of a steel or post and beam frame house.The load is concentrated on a small area. 90003 90002 (90027 MORE 90028: How much does it cost to build a house?) 90003 90002 90003 90023 Pad foundations diagram 90024 (Image credit: Homebuilding & Renovating) 90016 What Might Affect my Choice of Foundation System? 90017 90002 Where the foundations are affected by tree roots (or their previous removal), you may be required to employ a fairly deep trench filled with concrete but with a compressible material to one or both sides of the external trenches to counteract any heave or expansion in the ground.90003 90002 Water pipes must enter the building at a depth of at least 750mm but no more than 1.35m below ground. If that means that they pass through a concrete foundation then they must either be laid prior to pouring or, better still, a duct installed for them to be pushed through later. 90003 90002 If sewage pipes leaving the building have to be deeper than the top of the foundation concrete then they should also be ducted; they can not be trapped within the concrete and must be able to move freely.90003 90002 Electricity and gas do not usually need to be ducted or installed at this point as they are normally surface mounted. Finally, the building and warranty inspectors will have to approve the excavated foundations prior to any concrete being poured. 90003 90002 (90027 MORE 90028: How to bring electricity to site) 90003 .90000 Is Clay Soil Acidic? Understanding Clay Soil PH and How to Amend It 90001 90002 Does your garden soil stick to your shoes and gardening tools when wet? Does it also become rock solid in the summer heat? If the answer to these two questions is yes, then it means that you have a clay soil in your garden. 90003 90002 Any soil that contains at least 50% of clay particles qualifies to be clay soil. And although it can be quite difficult to dig clay, it is one of the most fertile soils that you can have in the garden.90003 90002 Clay has both good and negative features, and although it can be stressful and tiring to work with, it can also produce some thriving gardens. But, if you are dealing with it for the first time, the chances are that you are wondering whether clay is acidic or alkaline. 90003 90002 It is right to be concerned about the pH since it determines the plants that you can have in the garden and also the amendments that you should use. 90003 90010 Is Clay Soil Acidic Or Alkaline? 90011 90002 90003 90002 Soil pH is a result of various things with the organic material and mineral composition being some of the main ones.And so the pH of clay soil will always vary from one geographical place to the other. Also, different gardens might also have varying PH levels even if they are one the same location. The different pH is because other factors like fertilizers and water will also affect the pH. 90003 90002 So is clay soil acidic or not? The pH of most clay soils will always be on the alkaline side of the scale, unlike sandy soils which tend to be more acidic. While the high pH of clay soil might be suitable for certain plant types like asters, switchgrass, and hostas, it is too alkaline for most other plants.And so it most cases it will be necessary to lower the pH. 90003 90010 Amending Clay Soil pH 90011 90002 If you have clay in your plot, the best thing would be to find crops that tolerate alkaline soils and instead focus on improving the quality of the earth by breaking clay soil up. But, if you have particular plants in mind that you want to have that prefer acidic soils, you can still amend your soil in a few easy steps. 90003 90022 Read more: Best Electric Tillers To Till Your Garden In The Right Way 90023 90024 Test The pH 90025 90002 90003 90002 Before you decide to acidify your clay soil, the first move should be to examine it to determine the exact pH.By knowing the level of alkalinity, you can choose an acidifying compound that will not only lower it but also be gentle on your soil. 90003 90002 A pH test by a professional is always the best since you get an exact number, but you can still get reliable data by doing it at home with the use of a pH meter or pH strips. However, if you are a serious grower / gardener, it is advisable to use the services of an extension officer or to send a soil sample to your local laboratory. Doing this ensures you get a detailed analysis and recommendations on the best amendments for your clay soil.90003 90024 Amend The pH 90025 90002 90003 90002 Once you determine just how alkaline your clay soil is, the next step is to amend it. However, it might also be necessary to test the water pH before this to ensure that is not too alkaline because it can raise the soil pH. When amending the clay soil, it is important to make sure that you do not work on wet soil because this leads to compaction. 90003 90002 The pH test results should guide you on what to use and the amounts. Organic matter is always the best solution for most clay soils as it not only helps to lower the pH but will also assist in breaking it up and ensuring that your plants get proper nutrients.90003 90002 If the pH test results show that your soil is very alkaline, you should use compounds like sulfur, cottonseed meal, and iron sulfate. And this is because they are more efficient in acidifying soil and also work way much faster than the organic compounds. Gypsum can also be very helpful, and this is more so in places where the soil is also very salty. 90003 90024 Maintaining The pH 90025 90002 90003 90002 It is important to amend the pH several months before you plant in the clay soil because most of these acidifying compounds will require a lot of time to work.And once you get it to the level that you want it is still important to make sure that you maintain it at between 6.3 and 6.8 on the pH scale because this is what most plants prefer. You can do this by applying manure, compost, and other organic compounds every other season. 90003 90002 90049 90050 90003 90010 Conclusion 90011 90002 Clay soil will in most cases be alkaline without any amendments. While this might be good enough for some plants to thrive, most others will require you to acidify the soil.For this, organic compounds, sulfur, iron sulfate and ammonia-based fertilizers are an excellent choice. But, it is always important to remember that there is no permanent pH change and so you need to maintain the clay soil at the level that you desire. 90003.90000 How To Improve Clay Soil And Improving Sandy Soil 90001 90002 Gardeners ask 90003 how to improve clay soil 90004 more often than about 90003 improving sandy soil 90004, but the reasons are generally the same, and the main reason has to do with water. 90007 90002 In many gardens, clay does not infiltrate and drain fast enough and sand drains too fast. 90007 90002 One of the most commonly given pieces of advice on how to improve clay soil is to add sand. When it comes to improving sandy soil, the advice is often to add clay.90007 90002 Both of these are poor organic gardening practices. Before we go into why, we need to take a quick look at how water moves through the soil. 90007 90002 Trust me, this is really good to know and quite interesting. 90007 90016 How Water Moves Through Clay And Sandy Soil 90017 90002 Water moves downward after rain or irrigation and upward to eventually evaporate from the soil surface. 90007 90002 This water flows through the open «pores» between soil particles. In any soil that is not dominated too much by sand, silt or clay, approximately half the soil volume is pore space.Water and air share this pore space. 90007 90002 When soil is entirely saturated with water, gravity forces the water to move very quickly through the big pores, but the rest of the time, gravity does not play as big a role in how water moves through the soil. 90007 90002 The rest of the time, adhesion (how water molecules tend to stick to other surfaces) and cohesion (how water molecules tend to stick together) govern the movement of water in the soil. Interestingly it moves out in all directions fairly equally — up, down and horizontally.It moves downward only slightly more due to gravity. 90007 Adhesion and cohesion in action 90002 So let’s say it’s a beautiful Saturday morning and you are doing some organic gardening. 90007 90002 Let’s look at what happens when you have layers in your soil. 90007 90016 How To Improve Clay Soil 90017 90002 Let’s say you have a clay or silt loam soil that does not infiltrate or drain well. 90007 90002 What happens if you add 6 inches of a coarser soil such as a sandy loam on top of the soil? 90007 90002 When it rains, the water slows down when it hits that fine soil layer as you might imagine, although it does continue to move through.90007 90002 Still, it slows down, which is the opposite of what you were going for. If you instead rototill the sand into the clay, it does not create a nice soil texture like you would think. 90007 90002 The sand just gets embedded in the clay and often forms a soil environment that is like concrete. 90007 90002 When deciding how to improve clay soil, adding sand is not the answer. 90007 90016 How To Improve Sandy Soil 90017 90002 This part is really interesting. Let’s reverse it and say you have a sandy soil that does not hold water.90007 90002 What happens if you add 6 inches of a finer soil on top of a coarser soil below? This also may happen if the builder brought in some topsoil that was clay based and put it on top of your sandy subsoil. 90007 90002 When it rains, you might think the water would speed up when it hits the coarse sandy layer, but in fact, water movement stops until the soil becomes nearly saturated above. 90007 90002 Even more interesting, if the finer soil is on extremely coarse sand or even gravel, the finer soil must become very wet before water will move down through the coarse layer.90007 90002 In this case, the overlying soil can hold two or three times as much as it normally would. 90007 90002 These same principles are often used when making golf greens. A layer of gravel is used underneath the sandy soil for the green in order to create a situation where water will stay in the upper layer of sandy soil and be available to the short roots of the grass on the green, rather than draining away. 90007 90002 But doing this in a home organic garden is dangerous because you may create the opposite problem, which is a very waterlogged soil, or you may make a soil that is like concrete if you rototill the coarse and fine soils together.90007 90016 Improving Clay Soil And Improving Sandy Soil 90017 90002 The answer is the same for both: organic matter. 90007 90002 Compost is what I’m generally referring to. Amend soil with 6 inches of good compost. Work it right into the top of clay soil and it will improve infiltration and will probably improve the amount of air and water available to your plants. 90007 90002 (I should mention that no amount of organic matter, rototilling and aeration will fix a serious drainage issue such as flooding.That needs to be addressed by installing drainage, or even better, work with nature and put in a pond.) 90007 90002 Back to compost. Improving sandy soil with 6 inches of good compost will drastically improve the water-holding capacity of the soil. 90007 Improving clay soil with sand will not help, but compost will 90016 Other Organic Gardening Implications 90017 90002 Since we’ve been learning about how to improve clay soil and improving sandy soil and specifically about water moves through the soil, I’d like to mention a couple of other important organic gardening implications of what we’ve learned about amending soil.90007 90002 Take patio pots for example. Gardeners will often put a layer of gravel in the bottom of a container to improve drainage, but as we have seen it actually does the opposite. 90007 90002 The soil on top has to be very saturated before the water will drain through. This is not necessarily a bad thing with the right plants, but it is important to know how this works. 90007 90002 The other main implication is with regard to organic matter. If you amend soil by turning in (burying) coarse organic matter such as leaves or straw and they end up buried in a layer, or if you drop 6 inches of soil on top of a big layer of coarse material such as sticks or straw, you could be creating a coarse layer underneath a fine layer.90007 90002 This is the same situation where that soil will get very wet before water will drain out. If straw is incorporated very well, this will not occur, but if it is just turned under, it will. 90007 90002 If you need to bring soil into your yard in order to build your garden, you must make sure to rototill it into the existing soil extremely well. If you just drop it on top, you are inevitably creating an interface that will slow drainage. 90007 90002 And try to find a soil that has a similar texture to your exiting soil (i.e. if your soil is clay, bring in more of a clay topsoil than a sandy topsoil). Also, use compost for perhaps 25% of the mix. 90007 90002 Is there anything organic matter can not do? 90007 90002 If you want to learn more about amending soil, here’s my post on double digging. 90007.