Введение
Процесс, при котором объемы почв уменьшаются.
Soil consolidation refers to the mechanical process by which soil changes volume gradually in response to a change in pressure. This happens because soil is a three phase material, comprising soil grains and pore fluid, usually groundwater. When soil saturated with water is subjected to an increase in pressure, the high volumetric stiffness of water compared to the soil matrix means that the water initially absorbs all the change in pressure without changing volume, creating excess pore water pressure. As water diffuses away from regions of high pressure due to seepage, the soil matrix gradually takes up the pressure change and shrinks in volume. The theoretical framework of consolidation is therefore closely related to the concept of effective stress, and hydraulic conductivity. The early theoretical modern models were proposed one century ago, according to two different approaches, by Karl Terzaghi and Paul Fillunger. The Terzaghi’s model is currently the most utilized in engineering practice and is based on the diffusion equation. In the narrow sense, "consolidation" refers strictly to this delayed volumetric response to pressure change due to gradual movement of water. Some publications also use "consolidation" in the broad sense, to refer to any process by which soil changes volume due to a change in applied pressure. This broader definition encompasses the overall concept of soil compaction, subsidence, and heave. Some types of soil, mainly those rich in organic matter, show significant creep, whereby the soil changes volume slowly at constant effective stress over a longer time scale than consolidation due to the diffusion of water. To distinguish between the two mechanisms, "primary consolidation" refers to consolidation due to dissipation of excess water pressure, while "secondary consolidation" refers to the creep process. The effects of consolidation are most conspicuous where a building sits over a layer of soil with low stiffness and low permeability, such as marine clay, leading to large settlement over many years. Types of construction project where consolidation often poses technical risk include land reclamation, the construction of embankments, and tunnel and basement excavation in clay. Geotechnical engineers use oedometers to quantify the effects of consolidation. In an oedometer test, a series of known pressures are applied to a thin disc of soil sample, and the change of sample thickness with time is recorded. This allows the consolidation characteristics of the soil to be quantified in terms of the coefficient of consolidation and hydraulic conductivity
Clays undergo consolidation settlement not only by the action of external loads (surcharge loads) but also under its own weight or weight of soils that exist above the clay. Clays also undergo settlement when dewatered (groundwater pumping) because the effective stress on the clay increases. Coarse grained soils do not undergo consolidation settlement due to relatively high hydraulic conductivity compared to clays. Instead, Coarse grained soils undergo the immediate settlement.
Консолидация почвы – это механический процесс, при котором объем почвы постепенно изменяется в ответ на изменение давления. Это происходит потому, что почва является трехфазным материалом, состоящим из зерен почвы и поровой жидкости, обычно грунтовых вод. Когда почва, насыщенная водой, подвергается увеличению давления, высокая объемная жесткость воды по сравнению с почвенной матрицей приводит к тому, что вода первоначально поглощает все изменение давления без изменения объема, создавая избыточное поровое давление. По мере диффузии воды из областей высокого давления вследствие фильтрации, почвенная матрица постепенно принимает на себя изменение давления и уменьшается в объеме. Таким образом, теоретическая основа консолидации тесно связана с понятием эффективного напряжения и гидравлической проницаемости. Первые современные теоретические модели были предложены столетие назад двумя различными подходами – Карлом Терзаги и Полом Филлунгером. Модель Терзаги в настоящее время наиболее широко используется в инженерной практике и основана на уравнении диффузии. В узком смысле, "консолидация" относится строго к этой замедленной объемной реакции на изменение давления, вызванной постепенным движением воды. В некоторых публикациях термин "консолидация" также используется в широком смысле для обозначения любого процесса, при котором объем почвы изменяется из-за изменения приложенного давления. Это более широкое определение охватывает общие понятия уплотнения почвы, осадки и вздымания. Некоторые типы почв, особенно богатые органическими веществами, проявляют значительную ползучесть, при которой объем почвы медленно изменяется при постоянном эффективном напряжении в течение более длительного периода времени, чем при консолидации, вызванной диффузией воды. Для разграничения этих двух механизмов, "первичная консолидация" относится к консолидации, вызванной рассеиванием избыточного порового давления, а "вторичная консолидация" – к процессу ползучести. Эффекты консолидации наиболее заметны там, где здание расположено над слоем почвы с низкой жесткостью и низкой проницаемостью, например, морской глины, что приводит к значительной осадке в течение многих лет. Типы строительных проектов, где консолидация часто представляет собой технический риск, включают рекультивацию земель, строительство насыпей, а также прокладку тоннелей и рытье котлованов под фундаменты в глинистых грунтах. Геотехнические инженеры используют одометры для количественной оценки эффектов консолидации. В ходе одометрического испытания серия известных давлений прикладывается к тонкому диску образца почвы, и регистрируется изменение толщины образца во времени. Это позволяет количественно оценить характеристики консолидации почвы с точки зрения коэффициента консолидации и гидравлической проницаемости.
Soil consolidation refers to the mechanical process by which soil changes volume gradually in response to a change in pressure. This happens because soil is a three phase material, comprising soil grains and pore fluid, usually groundwater. When soil saturated with water is subjected to an increase in pressure, the high volumetric stiffness of water compared to the soil matrix means that the water initially absorbs all the change in pressure without changing volume, creating excess pore water pressure. As water diffuses away from regions of high pressure due to seepage, the soil matrix gradually takes up the pressure change and shrinks in volume. The theoretical framework of consolidation is therefore closely related to the concept of effective stress, and hydraulic conductivity. The early theoretical modern models were proposed one century ago, according to two different approaches, by Karl Terzaghi and Paul Fillunger. The Terzaghi’s model is currently the most utilized in engineering practice and is based on the diffusion equation. In the narrow sense, "consolidation" refers strictly to this delayed volumetric response to pressure change due to gradual movement of water. Some publications also use "consolidation" in the broad sense, to refer to any process by which soil changes volume due to a change in applied pressure. This broader definition encompasses the overall concept of soil compaction, subsidence, and heave. Some types of soil, mainly those rich in organic matter, show significant creep, whereby the soil changes volume slowly at constant effective stress over a longer time scale than consolidation due to the diffusion of water. To distinguish between the two mechanisms, "primary consolidation" refers to consolidation due to dissipation of excess water pressure, while "secondary consolidation" refers to the creep process. The effects of consolidation are most conspicuous where a building sits over a layer of soil with low stiffness and low permeability, such as marine clay, leading to large settlement over many years. Types of construction project where consolidation often poses technical risk include land reclamation, the construction of embankments, and tunnel and basement excavation in clay. Geotechnical engineers use oedometers to quantify the effects of consolidation. In an oedometer test, a series of known pressures are applied to a thin disc of soil sample, and the change of sample thickness with time is recorded. This allows the consolidation characteristics of the soil to be quantified in terms of the coefficient of consolidation and hydraulic conductivity
Clays undergo consolidation settlement not only by the action of external loads (surcharge loads) but also under its own weight or weight of soils that exist above the clay. Clays also undergo settlement when dewatered (groundwater pumping) because the effective stress on the clay increases. Coarse grained soils do not undergo consolidation settlement due to relatively high hydraulic conductivity compared to clays. Instead, Coarse grained soils undergo the immediate settlement.
Глины подвергаются осадке от консолидации не только под действием внешних нагрузок (дополнительных нагрузок), но и под собственным весом или весом вышележащих грунтов. Глины также подвергаются осадке при понижении уровня грунтовых вод (накачке), поскольку эффективное напряжение в глине увеличивается. Крупнозернистые почвы не подвергаются осадке от консолидации из-за относительно высокой гидравлической проницаемости по сравнению с глинами. Вместо этого, крупнозернистые почвы подвергаются немедленной осадке.
Soil consolidation refers to the mechanical process by which soil changes volume gradually in response to a change in pressure. This happens because soil is a three phase material, comprising soil grains and pore fluid, usually groundwater. When soil saturated with water is subjected to an increase in pressure, the high volumetric stiffness of water compared to the soil matrix means that the water initially absorbs all the change in pressure without changing volume, creating excess pore water pressure. As water diffuses away from regions of high pressure due to seepage, the soil matrix gradually takes up the pressure change and shrinks in volume. The theoretical framework of consolidation is therefore closely related to the concept of effective stress, and hydraulic conductivity. The early theoretical modern models were proposed one century ago, according to two different approaches, by Karl Terzaghi and Paul Fillunger. The Terzaghi’s model is currently the most utilized in engineering practice and is based on the diffusion equation. In the narrow sense, "consolidation" refers strictly to this delayed volumetric response to pressure change due to gradual movement of water. Some publications also use "consolidation" in the broad sense, to refer to any process by which soil changes volume due to a change in applied pressure. This broader definition encompasses the overall concept of soil compaction, subsidence, and heave. Some types of soil, mainly those rich in organic matter, show significant creep, whereby the soil changes volume slowly at constant effective stress over a longer time scale than consolidation due to the diffusion of water. To distinguish between the two mechanisms, "primary consolidation" refers to consolidation due to dissipation of excess water pressure, while "secondary consolidation" refers to the creep process. The effects of consolidation are most conspicuous where a building sits over a layer of soil with low stiffness and low permeability, such as marine clay, leading to large settlement over many years. Types of construction project where consolidation often poses technical risk include land reclamation, the construction of embankments, and tunnel and basement excavation in clay. Geotechnical engineers use oedometers to quantify the effects of consolidation. In an oedometer test, a series of known pressures are applied to a thin disc of soil sample, and the change of sample thickness with time is recorded. This allows the consolidation characteristics of the soil to be quantified in terms of the coefficient of consolidation and hydraulic conductivity
Clays undergo consolidation settlement not only by the action of external loads (surcharge loads) but also under its own weight or weight of soils that exist above the clay. Clays also undergo settlement when dewatered (groundwater pumping) because the effective stress on the clay increases. Coarse grained soils do not undergo consolidation settlement due to relatively high hydraulic conductivity compared to clays. Instead, Coarse grained soils undergo the immediate settlement.
История и терминология
Первые современные теоретические модели для уплотнения грунтов были предложены в 1920-х годах Терзаги и Филлунджером, основываясь на двух принципиально различных подходах.
Аналогия с весной
Процесс консолидации часто объясняют идеализированной системой, состоящей из пружины, емкости с отверстием в крышке и воды. В этой системе пружина представляет собой сжимаемость или структуру самой почвы, а вода, заполняющая емкость, представляет собой поровой раствор в почве. Емкость полностью заполнена водой, а отверстие закрыто (полностью насыщенная почва).
A load is applied onto the cover, while the hole is still unopened. At this stage, only the water resists the applied load. (Development of excess pore water pressure)
As soon as the hole is opened, water starts to drain out through the hole and the spring shortens. (Drainage of excess pore water pressure)
After some time, the drainage of water no longer occurs. Now, the spring alone resists the applied load. (Full dissipation of excess pore water pressure. End of consolidation)
На крышку прикладывается нагрузка, пока отверстие остается закрытым. На этом этапе сопротивление нагрузке оказывает только вода (развитие избыточного давления порового раствора).
A load is applied onto the cover, while the hole is still unopened. At this stage, only the water resists the applied load. (Development of excess pore water pressure)
As soon as the hole is opened, water starts to drain out through the hole and the spring shortens. (Drainage of excess pore water pressure)
After some time, the drainage of water no longer occurs. Now, the spring alone resists the applied load. (Full dissipation of excess pore water pressure. End of consolidation)
Как только отверстие открывается, вода начинает вытекать через него, и пружина сжимается (дренаж избыточного давления порового раствора).
A load is applied onto the cover, while the hole is still unopened. At this stage, only the water resists the applied load. (Development of excess pore water pressure)
As soon as the hole is opened, water starts to drain out through the hole and the spring shortens. (Drainage of excess pore water pressure)
After some time, the drainage of water no longer occurs. Now, the spring alone resists the applied load. (Full dissipation of excess pore water pressure. End of consolidation)
Через некоторое время дренаж воды прекращается. Теперь сопротивление нагрузке оказывает только пружина (полное рассеивание избыточного давления порового раствора. Окончание консолидации).
A load is applied onto the cover, while the hole is still unopened. At this stage, only the water resists the applied load. (Development of excess pore water pressure)
As soon as the hole is opened, water starts to drain out through the hole and the spring shortens. (Drainage of excess pore water pressure)
After some time, the drainage of water no longer occurs. Now, the spring alone resists the applied load. (Full dissipation of excess pore water pressure. End of consolidation)