Misplaced Pages

#329670

35-476: Underpinning may be accomplished by extending the foundation in depth or breadth so it either rests on a more supportive soil stratum or distributes its load across a greater area. Use of micropiles and jet grouting are common methods in underpinning. Underpinning may be necessary where P class (problem) soils in certain areas of the site are encountered. Through semantic change the word underpinning has evolved to encompass all abstract concepts that serve as

70-505: A stratum ( pl. : strata ) is a layer of rock or sediment characterized by certain lithologic properties or attributes that distinguish it from adjacent layers from which it is separated by visible surfaces known as either bedding surfaces or bedding planes . Prior to the publication of the International Stratigraphic Guide, older publications have defined a stratum as being either equivalent to

105-632: A bed, a flow should only be designated and named as a formal lithostratigraphic unit when it is distinctive, widespread, and useful for stratigraphic correlation. A band is a thin stratum that is distinguishable by a distinctive lithology or color and is useful in correlating strata. Finally, a key bed, also called a marker bed , is a well-defined, easily identifiable stratum or body of strata that has sufficiently distinctive characteristics, such as lithology or fossil content, to be recognized and correlated during geologic field or subsurface mapping. Soil improvement#Soil Stabilization A soil conditioner

140-436: A few millimeters to several meters or more. A band may represent a specific mode of deposition : river silt , beach sand , coal swamp , sand dune , lava bed, etc. In the study of rock and sediment strata, geologists have recognized a number of different types of strata, including bed , flow , band , and key bed . A bed is a single stratum that is lithologically distinguishable from other layers above and below it. In

175-498: A foundation. Mass concrete underpinning is one of the simplest forms of remedial underpinning at shallow depths. This type of underpinning is done by excavating "bays" along and under the existing foundation and filling them with mass concrete. It is sometimes called a "traditional" method to distinguish it from other types of underpinning like piling and needling. The latter often require underpinning specialists and may use proprietary underpinning systems. Mass concrete underpinning work

210-424: A grid of piles is installed, and a reinforced concrete raft is then constructed over the complete floor level, picking up and fully supporting all external and internal walls. One of the uses of the soil improvement technique of pressure grouting is foundation underpinning especially during excavations like subway constructions. This technique has been used in municipal development projects of significant scope in

245-516: A high slenderness ratio, feature substantial steel reinforcing elements and can sustain axial loading in both senses. The working loads of mini-piles can sustain up to 1,000 kN (100 long tons-force; 110 short tons-force) loads. In comparison to Mass Concrete Underpinning, the engineering aspect of mini-piles is somewhat more involved, including rudimentary engineering mechanics such as statics and strength of materials. These mini-piles must be designed to work in tension and compression, depending on

280-409: A number of ways. Some are worked into the soil with a tiller before planting. Others are applied after planting, or periodically during the growing season. Soil testing should be performed prior to applying a soil conditioner to learn more about the composition and structure of the soil. This testing will determine which conditioners will be more appropriate for the available conditions. While adding

315-619: A regular domestic doorway. They are capable of constructing piles to depths of up to 15 m (49 ft). The technique of minipiling was first applied in Italy in 1952, and has gone through many different names, reflecting worldwide acceptance and expiration of the original patents. The relatively small diameter of mini-piles is distinctive of this type of underpinning and generally uses anchoring or tie backs into an existing structure or rock. Conventional drilling and grouting methods are used for this method of underpinning. These mini-piles have

350-621: A single bed or composed of a number of beds; as a layer greater than 1 cm in thickness and constituting a part of a bed; or a general term that includes both bed and lamina . Related terms are substrate and substratum (pl. substrata ), a stratum underlying another stratum. Typically, a stratum is generally one of a number of parallel layers that lie one upon another to form enormous thicknesses of strata. The bedding surfaces (bedding planes) that separate strata represent episodic breaks in deposition associated either with periodic erosion , cessation of deposition, or some combination of

385-485: A soil can hold, its total negative charge, is the soil's cation exchange capacity. The higher the CEC, the higher the negative charge and the more cations that can be held and exchanged with plant roots, providing them with the nutrition they require. Soil conditioners may be used to improve water retention in dry, coarse soils which are not holding water well. The addition of organic material for instance can greatly improve

SECTION 10

#1732772872330

420-433: A soil conditioner to crops or a garden can seem like a great way to get healthier plants, over-application of some amendments can cause ecological problems. For example, salts, nitrogen, metals and other nutrients that are present in many soil amendments are not productive when added in excess, and can actually be detrimental to plant health. (See fertilizer burn .) Runoff of excess nutrients into waterways also occurs, which

455-436: Is a product which is added to soil to improve the soil’s physical qualities , usually its fertility (ability to provide nutrition for plants) and sometimes its mechanics . In general usage, the term "soil conditioner" is often thought of as a subset of the category soil amendments (or soil improvement , soil condition ), which more often is understood to include a wide range of fertilizers and non-organic materials. In

490-486: Is constructed below, above or in replacement of the existing footing. The beam then transfers the load of the building to mass concrete bases, which are constructed at designed strategic locations. Base sizes and depths are dependent upon the prevailing ground conditions. Beam design is dependent upon the configuration of the building and the applied loads. Anti-heave precautions are often incorporated in schemes where potential expansion of clay soils may occur. Mini-piles have

525-532: Is performed in compliance with the Party Wall Act (in the UK) using plans that are designed with engineering calculations to plan a sequence of excavating bays along and underneath the existing foundation without damaging existing walls. In some cases walls have collapsed because lateral support was inadequate leading to disputes among contractors, subcontractors and architects about where the responsibility lay for

560-581: The Building Research Establishment subsidence database, mass concrete underpinning was the most common underpinning and was often applied only to part of a building. If the soils have a low bearing capacity partial underpinning may increase the risk of differential settlement and localized settlement due to additional load on the soil. The beam and base method of underpinning is a more technically advanced adaptation of traditional mass concrete underpinning. A reinforced concrete beam

595-418: The water quality of nearby rivers and streams. As an nonionic monomer it can be co-polymerize with anionic for example Acrylic acid and cationic monomer such as diallyldimethyl ammonium chloride (DADMAC) and resulted co-polymer that can have different compatibility in different applications. Polyacrylamide is also used in some potting soil . Another use of polyacrylamide is as a chemical intermediate in

630-528: The 1950s, when the chemical hydrolysed polyacrylonitrile was the most used. Because of their ability to absorb several hundred times their own weight in water, polyacrylamides and polymethacrylates (also known as hydroabsorbent polymers, superabsorbent polymers or hydrogels ) were tested in agriculture, horticulture and landscaping beginning in the 1960s. Interest disappeared when experiments proved them to be phytotoxic due to their high acrylamide monomer residue. Although manufacturing advances later brought

665-590: The United States. One of the largest chemical grouting projects was the extension of the Pittsburgh Light Rail Transit subway when the foundations of six large buildings needed to be protected from ground movement and related building settlement. Pressure grouting can be low pressure or high pressure. "Jet grouting" is a general term used for high pressure grouting where the high pressure air, water and cementing grout are injected into

700-473: The classification hierarchy of sedimentary lithostratigraphic units, a bed is the smallest formal unit. However, only beds that are distinctive enough to be useful for stratigraphic correlation and geologic mapping are customarily given formal names and considered formal lithostratigraphic units. The volcanic equivalent of a bed, a flow, is a discrete extrusive volcanic stratum or body distinguishable by texture, composition, or other objective criteria. As in case of

735-691: The context of construction soil conditioning is also called soil stabilization. Soil conditioners can be used to improve poor soils, or to rebuild soils which have been damaged by improper soil management . They can make poor soils more usable, and can be used to maintain soils in peak condition. A wide variety of materials have been described as soil conditioners due to their ability to improve soil quality. Some examples include biochar , bone meal , blood meal , coffee grounds , compost , compost tea , coir , manure , straw , peat , sphagnum moss , vermiculite , sulfur , lime , hydroabsorbant polymers , and biosolids . Many soil conditioners come in

SECTION 20

#1732772872330

770-603: The effective strength and resistance of very soft soils, for example when excavating deep tunnels for underground subway or tunnel construction. The soil stabilization technique of low pressure chemical permeation grouting has also been used for high rise foundation underpinning as an alternative to pile foundations at a residential development over the East River landfill . Pressure grouting can be difficult to apply correctly at sites with waste materials or heterogeneous and coarse soils. Soil conditioners may be applied in

805-418: The form of certified organic products , for people concerned with maintaining organic crops or organic gardens. Soil conditioners of almost every description are readily available from online stores or local nurseries as well as garden supply stores. Polyacrylamides have been widely investigated as soil conditioners. They were introduced as "linear soil conditioner" in the 1950s by Monsanto Company under

840-700: The greatest use where ground conditions are variable, where access is restrictive, where environmental pollution aspects are significant, and where structural movements in service must be minimal. Mini-piled underpinning is generally used when the loads from the foundations need to be transferred to stable soils at considerable depths – usually in excess of 5 m (16 ft). Mini-piles may either be augured or driven steel cased, and are normally between 150 mm (5.9 in) and 300 mm (12 in) in diameter. Structural engineers will use rigs which are specifically designed to operate in environments with restricted headroom and limited space, and can gain access through

875-422: The ground at high velocity. This can be doing with single tube systems to mix the grout with in situ soil to form a grouted "column" in the ground. Double tube systems and triple tube systems using air and water remove some of the soil to create larger grouted bulbs or columns. Low pressure chemical injection grouting is used to underpin structures in sandy soils. Stratum In geology and related fields,

910-535: The inside of a building, and require the construction of tension and compression piles to each cap. These are normally linked by a beam. The pile and beam system usually involves constructing pairs of piles on either side of the wall and linking them with a pile cap to support the wall. The pile caps are usually linked by reinforced concrete beams to support the entire length of the wall. Piled raft underpinning systems are commonly used when an entire building needs to be underpinned. The internal floors are completely removed,

945-589: The mistake. Mass concrete underpinning is commonly used when permanent support is needed to comply with the Party Wall Act of 1996 in the construction of a new basement during a restoration, rehabilitation or redevelopment. In the United Kingdom most subsidence claims are for buildings at least 40 years old with shallow strip foundations . This is one of the most common types of foundations suffering from subsidence-related damage and according to

980-492: The monomer concentration down below the toxic level, scientific literature shows few successes in utilizing these polymers for increasing plant quality or survival. The appearance of a new generation of potentially effective tools in the early 1980s, including hydroabsorbent polymers and copolymers from the propenamide and propenamide- propenoate families, opened new perspectives. In the context of construction there are some soil improvement techniques that are intended to improve

1015-476: The orientation and application of the design. In detail, attention with design must be paid analytically to settlement, bursting, buckling, cracking, and interface consideration, whereas, from a practical viewpoint, corrosion resistance, and compatibility with the existing ground and structure must be regarded. Mini-piled underpinning schemes include pile and beam, cantilever pile-caps and piled raft systems. Cantilevered pile-caps are usually used to avoid disturbing

1050-793: The production of N-methylol acrylamide and N-butoxyacrylamide. The most common use of soil conditioners is to improve soil structure. Soils tend to become compacted over time. Soil compaction impedes root growth, decreasing the ability of plants to take up nutrients and water. Soil conditioners can add more loft and texture to keep the soil loose. For centuries people have been adding things to poor soils to improve their ability to support healthy plant growth. Some of these materials, such as compost, clay and peat , are still used extensively today. Many soil amendments also add nutrients such as carbon and nitrogen, as well as beneficial bacteria. Additional nutrients, such as calcium, magnesium and phosphorus , may be augmented by amendments as well. This enriches

1085-424: The soil, allowing plants to grow bigger and stronger. Soil amendments can also greatly increase the cation exchange capacity (CEC) of soils. Soils act as the storehouses of plant nutrients . The relative ability of soils to store one particular group of nutrients, the cations . The most common soil cations are calcium , magnesium , potassium , ammonium , hydrogen , and sodium . The total number of cations

Underpinning - Misplaced Pages Continue

1120-535: The trade name Krilium. The soil conditioning technology was presented at a symposium on "Improvement of Soil Structure" held in Philadelphia, Pennsylvania on December 29, 1951. The technology was strongly documented and was published in the June 1952 issue of the journal Soil Science , volume 73, June 1952 that was dedicated to polymeric soil conditioners. The original formulation of poly acrylamide soil conditioners

1155-497: The two. Stacked together with other strata, individual stratum can form composite stratigraphic units that can extend over hundreds of thousands of square kilometers of the Earth 's surface. Individual stratum can cover similarly large areas. Strata are typically seen as bands of different colored or differently structured material exposed in cliffs , road cuts, quarries , and river banks. Individual bands may vary in thickness from

1190-715: The water retention abilities of sandy soils and they can be added to adjust the pH of the soil to meet the needs of specific plants or to make highly acidic or alkaline soils more usable. The possibility of using other materials to assume the role of composts and clays in improving the soil was investigated on a scientific basis earlier in the 20th century, and the term soil conditioning was coined. The criteria by which such materials are judged most often remains their cost-effectiveness, their ability to increase soil moisture for longer periods, stimulate microbiological activity, increase nutrient levels and improve plant survival rates. The first synthetic soil conditioners were introduced in

1225-548: Was difficult to use because it contained calcium which cross-linked the linear polymer under field conditions. Krilium was abandoned by Monsanto. Water-soluble soil conditioners offer the following benefits: Consequently, these translate into The cross-linked forms of polyacrylamide, which strongly retain water, are often used for horticultural and agricultural under trade names such as Broadleaf P4 and Swell-Gel. In addition to use on farm lands, these polymers are used at construction sites for erosion control , in order to protect

#329670