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Caisson Foundation

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鲜花(135) 鸡蛋(3)
东南西北人 发表于 2014-10-19 22:19:40 | 显示全部楼层 |阅读模式
Caisson Foundation
  • The foundation system of and the soils beneath the building prevent the complex from moving vertically.
  • When a load is placed on soil, most soils settle. This creates a problem when the building settles but the utilities do not. Even more critical than settlement is differential settlement.
  • This occurs when parts of your building settle at different rates, resulting in cracks, some of which may affect the structural integrity of the building. Conversely, in some rare instances soils may swell, pushing your building upwards and resulting in similar problems.
  • Therefore, the foundation system must work in tandem with the soils to support the building.

鲜花(135) 鸡蛋(3)
 楼主| 东南西北人 发表于 2014-10-19 22:20:55 | 显示全部楼层
WHAT IS CAISSONS?
  • It’s a prefabricated hollow box or cylinder
  • It is sunk into the ground to some desired depth and then filled with concrete thus forming a foundation.
  • Most often used in the construction of bridge piers & other structures that require foundation beneath rivers & other bodies of water
  • This is because caissons can be floated to the job site and sunk into place
  • Basically it is similar in form to pile  foundation but installed using different way
  • used when soil of adequate bearing strength is found below surface layers of weak materials such as fill or peat
  • It’s a form of deep foundation which are
  • constructed above ground level, then sunk to  the required level by excavating or dredging material from within the caisson
  • A caisson foundation consists of concrete columns constructed in cylindrical shafts excavated under the proposed structural  column locations
  • Caissons are drilled to bedrock or deep into the underlying strata if a geotech eng. find the soil suitable to carry the building load
  • It’s created by auguring a deep hole in the ground
  • Then, 2 or more ‘stick’ reinforcing bar are inserted into and run the full length of the hole and the concrete is poured into the caisson hole.
  • The caisson foundations carry the building loads at their lower ends, which are often bell-shaped.
鲜花(135) 鸡蛋(3)
 楼主| 东南西北人 发表于 2014-10-19 22:22:57 | 显示全部楼层
TYPES OF CAISSONS
  • Box Caissons
  • Excavated Caissons
  • Open Caissons
  • Pneumatic Caissons
  • Sheeted Caissons
ADVANTAGES & DISADVANTAGES
ADVANTAGES
  • Economics
  • Minimizes pile cap needs
  • Slightly less noise and reduced vibrations
  • Easily adaptable to varying site conditions
  • High axial and lateral loading capacity
DISADVANTAGES
  • Extremely sensitive to construction procedures
  • Not good for contaminated sites
  • Lack of construction expertise
  • Lack of Qualified Inspectors

鲜花(135) 鸡蛋(3)
 楼主| 东南西北人 发表于 2014-10-19 22:26:18 | 显示全部楼层
Caisson Foundations
  • A drilled pier is a deep foundation system that is constructed by placing fresh concrete and reinforcing steel into a drilled shaft.
  • The shaft is constructed by rotary methods using either a self-contained drill unit or a crane mounted drill unit. The hole is advanced through soil or rock to the desired bearing stratum. Temporary or permanent steel casings may be used to maintain the sides of the drilled excavation if caving soils or water infiltration becomes a problem.
  • Drilled shafts can be used to sustain high axial and lateral loads. Typical shaft diameters range from 18 to 144 inches.
  • Caisson foundations are similar in form to pile foundations, but are installed using a different method. Caissons (also sometimes called “piers”) are created by auguring a deep hole into the ground, and then filling it with concrete. Steel reinforcement is sometimes utilized for a portion of the length of the caisson. Caissons are drilled either to bedrock (called “rock caissons”) or deep into the underlying soil strata if a geotechnical engineer finds the soil suitable to carry the building load. When caissons rest on soil, they are generally “belled” at the bottom to spread the load over a wider area. Special drilling bits are used to remove the soil for these “belled caissons”.
  • Drilled shafts (also called caissons, drilled piers or bored piles) have proven to be a cost effective, excellent performing, deep foundation system, that is utilized world-wide. Typically they are used for bridges and large structures, where large loads and lateral resistance are major factors.
  • Caisson foundations are used when soil of adequate bearing strength is found below surface layers of weak materials such as fill or peat. A caisson foundation consists of concrete columns constructed in cylindrical shafts excavated under the proposed structural column locations. The caisson foundations carry the building loads at their lower ends, which are often bell-shaped

鲜花(135) 鸡蛋(3)
 楼主| 东南西北人 发表于 2014-10-19 22:28:06 | 显示全部楼层
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hongqloi300656 发表于 2014-10-20 08:18:38 | 显示全部楼层
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mikelu 发表于 2014-10-20 22:23:10 | 显示全部楼层
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xmgao9996 发表于 2014-10-20 22:37:38 | 显示全部楼层
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zgb8080 发表于 2014-10-20 23:25:33 | 显示全部楼层
thanks。
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xiaochao 发表于 2014-10-21 01:32:29 | 显示全部楼层
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ease2020 发表于 2014-10-21 07:48:55 | 显示全部楼层
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victor_zeror2 发表于 2014-10-21 08:37:23 | 显示全部楼层
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zspkd 发表于 2014-10-22 13:46:52 | 显示全部楼层
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