cooling tower foundation
cooling tower foundation
(OP)
thread194-260175: Ring Foundation Design for Water Tanks
Hi, I am working on a project consists of the construction of a 30' x 90' cast in place concrete basin with a precast concrete screen wall. There will be 3 cooling tower cells located within the basin. Basin is 2.5 feet deep and is below the grade.
Tower diameter is 25 feet; tower height is about 35-40 feet. Groundwater is about 6-7 feet below the surface. Site is underlain by 2 to 4.5 feet of SM soil, as fine sandy clayey soil, or silty sand. The sandy soil SM is underlain by 50 feet of CL (sandy/silty clay) with thin CH; CL is more compact and less plastic with depth.
The soil boring and lab test (include unconfined compressive test on clay) will be underway in a week.
Is concrete mat foundation 30 ft by 90 ft beneath the water basin a good solution to support the three cooling towers? The mat foundation will be on properly compacted backfill.
What is the mat foundation bearing elevation? I am thinking its bottom elevation being about 6 feet below the ground surface or 3 feet below the water basin. Would bearing elevation near water table adequate?
If not, what is alternative, such as three trapezoidal concrete ringwalls, and sloped inside and covered with a geotextile? The concrete ringwall will be built within the 30 ft x90 ftx2.5 ft water basin.
Hi, I am working on a project consists of the construction of a 30' x 90' cast in place concrete basin with a precast concrete screen wall. There will be 3 cooling tower cells located within the basin. Basin is 2.5 feet deep and is below the grade.
Tower diameter is 25 feet; tower height is about 35-40 feet. Groundwater is about 6-7 feet below the surface. Site is underlain by 2 to 4.5 feet of SM soil, as fine sandy clayey soil, or silty sand. The sandy soil SM is underlain by 50 feet of CL (sandy/silty clay) with thin CH; CL is more compact and less plastic with depth.
The soil boring and lab test (include unconfined compressive test on clay) will be underway in a week.
Is concrete mat foundation 30 ft by 90 ft beneath the water basin a good solution to support the three cooling towers? The mat foundation will be on properly compacted backfill.
What is the mat foundation bearing elevation? I am thinking its bottom elevation being about 6 feet below the ground surface or 3 feet below the water basin. Would bearing elevation near water table adequate?
If not, what is alternative, such as three trapezoidal concrete ringwalls, and sloped inside and covered with a geotextile? The concrete ringwall will be built within the 30 ft x90 ftx2.5 ft water basin.





RE: cooling tower foundation
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RE: cooling tower foundation
RE: cooling tower foundation
UC test and consolidation results will be back about a week. From the nearby boring logs, the soil is SM silty sand from surface to 6 feet below underlain by CL. I will check the settlement with new lab data and consider water loading replacing soil loading within the water basin .
Shall seismic design be concerned for the large mat foundation, adding driven piling / drilled piers?
I am wondering what is coefficient of friction between concrete and SM or CL soil ?
Is allowable foundation bearing pressure of 3,000 psf a little high?
Any reply is appreciated.
RE: cooling tower foundation
If you do decide to use piling / drilled piers the allowable soil bearing pressure is not important for the completed structure; the piling / drilled piers should be designed to carry ALL (100%) of the vertical loads. It is a big mistake to have a portion of the loads from a structure supported by soil and the remainder supported by piles / drilled piers.
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RE: cooling tower foundation
The city 50 mile south of the site had an earth quake in 1947 scale 4.6, this earthquake damaged chimneys in that city, but was felt as intensity II near the site. The boring shows SC (sandy clay) as the dominate soil, and no water table even at 40 feet depth.
If piles are to be drilled, what is the depth? I am thinking to use steel H pile. Hope to use Lpile software for a quick calculation.. the dead load is about 2600 ton.
The real water table is 70 ft below the grade, I am thinking settlement should not be a concern since it is the fully saturated clay stratum, in situ, that displays the lowest strength and greatest compressibility. Beside, the mat foundation is 72 feet wide. However, I will use lab's one dimensional consolidation test result for the settlement calculation.
RE: cooling tower foundation
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