The invention relates to foundation pilings. More particularly, the present invention relates foundation piling with a self-expanding footing that takes the place of areas of soil recession near the bottom of the piling.
Pile or caisson supported foundations have been used commonly for construction on loose or unstable soils, sinking soils, hillsides, cliffsides, seasides and earthquake zones. Loss of soil support at the base of the caisson can occur with soil erosion in most areas, and with soil liquefaction in earthquakes. Pile design practice is based on preventing or mitigating a bending mechanism, wherein lateral loading due to soil loss, movement or spreading induces bending failure in the pile. Less common are considerations necessary to avoid buckling of a pile due to axial load acting on it during a soil liquefaction event.
Gravel and stone can be added to the bottom of a hole dug for a foundation piling to allow rainwater to drain through around the piling base, but this merely underlines the existence of expansive and collapsible soils at the base of many foundation pilings. Where bedrock cannot be reached, the piling relies on upward forces from side friction with the soil and the relatively narrow contact between piling base and soil at the depth of the base, which can be expected to contract and expand.
Preparing the foundation piling hole at depth with soil and gravel can slow or mitigate soil settling and water movement, but cannot truly prevent them. What is sought, then, is a method and apparatus that acknowledges the problems of water and soil movement at the base of a foundation piling or caisson and incorporates structures to take advantage of said water and soil movement in ways that improve stability of the piling at depth. Specifically, such a structure would passively use rain or ground water movement to expand into compressed or vacated soil at depth. It would passively use soil movement to solidify this expanded structure. It would incorporate sensors for monitoring the soil conditions at depth. And, it would allow for active addition of concrete material at depth in instances where soil sensors indicated that passive measures were insufficient.
A Smart Caisson incorporates an expandable balloon-like body at depth under the base of a vertical piling or foundation member. The self-expanding balloon-like footing matches and counteracts soil erosion by expanding to fill areas of soil recession.
A pipe or through-hole in the vertical piling admits surface rainwater into the balloon footing at the same time the rainwater is contributing to sub-surface erosion. The user can also actively pump water downward through the piling through-hole to fill the balloon footing during times of low rainfall or following short-duration erosion events, such as earthquakes.
The through-holes are designed to capably admit cement, concrete and other fill materials without clogging or corroding. A metal mesh surrounding the balloon footing expands with the balloon, providing structure and a matrix to trap and hold shifted sub-surface earthen material and concrete previously pumped into the balloon footing.
An array of sensors running from the bottom to the top of the Smart Caisson warn the user of sub-surface soil conditions and the condition of the balloon footing, metal mesh and piling.
The pictured prior-art piling is driven into sloped soil 3, such as occurs when a house is supported on a hillside. The upper end 4 of the piling extends above the soil surface 5 and the lower end 6 of the prior art piling as pictured is not deep enough to reach bedrock 7.
Soil shifting, water erosion and earthquake liquefactions cause recession 8 of the soil from the piling, illustrated by stylized soil separation from the downhill side of the vertical surface of the prior art piling. Soil recession results in increased potential for pile settlement, horizontal displacements and bending moment under lateral load. Water buildup 9 in the recessed area shown near the base of the piling creates further problems with erosion and settling.
The vertical foundation member is typically situated such that it extends into earthen material 12 such that friction between the vertical surface 11 and earthen material 12 results in some upward force on the vertical foundation member. The vertical foundation member lower end 10 often ends at or above bedrock 13. The vertical foundation member upper end 9 is typically extended above the soil surface 14 to at least some distance.
A stylized foundation member through-hole 15 is illustrated having an upper opening 16 and a lower opening 17. The foundation member through-hole extends from the upper end of the vertical foundation member, down through the vertical foundation member and to the lower end of the vertical foundation member. The foundation member through-hole can simply be a hole 18 formed in the vertical foundation member, but in the preferred embodiment is an open downpipe through such a hole formed in the vertical foundation member.
The pipe of the foundation member through-hole in the preferred embodiment is formed of a metal or durable plastic suitable for use with a concrete foundation piling. The pipe of the foundation member through-hole in the preferred embodiment is also able to withstand repeated exposure to rainwater or pumped water.
Suitable metals for through-hole downpipes include steel, galvanized steel, iron, galvanized iron, copper, brass and bronze. Aluminum or other metals subject alkali reactions with concrete would not be suitable. Suitable plastics include some PVCs not subject to alkali reactions or PEX materials having enough hardness for plumbing pipes of thirty feet or more.
Adjacent the vertical foundation member lower end 10 and foundation member through-hole lower opening 17 is illustrated a puncture-resistant foundation footing balloon member 19 having a first balloon exterior surface 20, a first balloon interior and a first balloon upper surface 21 adjacent the vertical foundation member lower end 10.
The foundation footing balloon member will typically be globular, lozenge shaped or other rounded shape extending wider than the diameter of the vertical foundation member in at least one dimension. The foundation footing balloon member is of a flexible, inflatable material that holds water and resists puncture by stones, shards, sticks, rubble and other buried materials. Examples of puncture-resistant balloon structures will include flexible fuel bladders and fuel cells such as found in U.S. Pat. No. 3,622,035 “PUNCTURE-RESISTANT FUEL CONTAINER” or U.S. Pat. No. 4,574,986 “FLEXIBLE CONTAINER SYSTEM”.
The foundation footing balloon member will have, for each foundation member through-hole, a neck opening in its upper surface 21 operatively mated to its foundation member through-hole lower opening 17 so as to provide an open path via the foundation member through-hole and through the neck opening into the balloon interior. The neck-hole mating will, in the preferred embodiment, have the foundation member through-hole lower opening extending inside the balloon member neck opening, screwed together or otherwise fixatively attached such that water, cement or concrete aggregate can fit through the through-hole and balloon neck opening connection without obstruction.
Some embodiments of the invention will also include, as depicted, an expansible foundation mesh body 22, capable of expanding to at least the maximum volume of the foundation footing balloon member. The expansible foundation mesh body functions as a net of tough material surrounding the balloon member. The expansible foundation mesh body material may be of durable plastic or corrosion-resistant metals as seen in braided steel automotive hoses. In most embodiments, the expansible foundation mesh body will be strongly affixed to the lower end of the vertical foundation member, using, for example, eyebolts, bent rebar or welded rebar.
The balloon member is depicted in an expanded stated, having expanded to fill in areas of displaced or eroded earthen material below the vertical foundation member. The balloon member is depicted as globular in shape, but other balloon or bladder shapes may be used according to availability. When first installed, the balloon member will typically be mostly or entirely deflated, in anticipation of later displacement of adjacent soil.
Each foundation member through-hole upper opening extends vertically through the foundation member cap in order to be capable of admitting rainwater passively. The foundation member cap may be made concave in order to channel rainwater to the through-hole. The passive environmental rainwater thus helps fill the foundation footing balloon member to press outward against adjacent areas of soil recession, sometimes also caused by concurrent environmental rainwater.
In the first embodiment of the invention, the expansion of the foundation footing balloon member occurs passively due to admission of rainwater via through-holes. However, expansion of the foundation footing balloon member can be performed actively, by pumping or pouring water into the upper opening of a through-hole. Active pumping of water into the foundation footing balloon member may be needed where, for instance, soil liquefaction occurs in absence of significant passive rainwater.
Further, in additional embodiments of the invention, the expanded shape of the foundation footing balloon member can be solidified using cement, aggregate or concrete. The through-holes can be used to pour dry cement powder or concrete mix into the foundation footing balloon member, followed by pressurized water to prevent cement adhering to the inside of the through-holes. Once the cement mixture has cured, the foundation footing will be improved even over initial installation, even if the balloon member is later torn.
For the foundation member through-holes to reliably transmit cement and aggregate, the diameter of the through-holes should be at least three times the diameter of the largest aggregate materials intended to be used.
Where practical, pumping of wet concrete directly into the foundation footing balloon member via the through-holes can be performed. In practice, this means that through-holes can have a diameter of as little as three inches for use with peristaltic concrete pumps, or up to eight inches for use with direct action, piston type concrete pumps.
The expansible foundation mesh body having lattice-like openings 33 between the mesh elements 34, adjacent earthen material 35 is admitted to the interior 36 of the expansible foundation mesh body through the lattice-like openings as the exterior surface of the balloon member deflates and recedes. The adjacent earthen material sifts into the expansible foundation mesh primarily body from above and from the uphill side, but can also sift in during soil shifting events. The admitted earthen material 37 is trapped inside the expansible foundation mesh body by the combination of exterior earthen material, mesh body and deflated balloon body, anchoring the mesh where otherwise would have been shifting soil. The mesh elements are depicted as latitudinal and longitudinal, but can be diagonal.
As with the through-holes, a larger mesh opening allows for sifting in of larger aggregate material in the adjacent soil. For use in clumping clay soils or where large stone aggregate is mixed in with the soil, a loose mesh with openings of two inches in diameter or greater can be used. For dry soils, sandy soils or smaller particulates, a tighter mesh with openings of one inch in diameter or lower can be used. A looser mesh can be used on the top side of the mesh body and a tighter mesh on the bottom half, to help retain admitted earthen material.
As the expansible foundation mesh body is expanded by the balloon member, sliding locking structures 39 lock open so as to resist reversion of the expansible foundation mesh body 22 to its unexpanded state. During shifting or deflation of the balloon member 19, the sliding locking structure of the expansible foundation mesh body holds the expansible foundation mesh body apart from the balloon member exterior surface, allowing admitted earthen material to fill the space between the expansible foundation mesh body and the balloon member.
In the illustration, sliding locking structures are arrayed in a single equatorial line around the expansible foundation mesh body. The indicated sliding locking structures slide and lock vertically, resisting vertical flattening of the expansible foundation mesh body. In other embodiments of the invention, additional latitude lines above and below the equatorial line will have sliding locking structures, further resisting vertical flattening.
Depending on location, embedded condition sensors can be used to measure movement, bending or stresses on the vertical foundation member; movement, recession or liquefaction of earthen material adjacent the vertical foundation member or footing; soil moisture; the volume, interior pressure or exterior pressure of the footing balloon member; contents analysis of the foundation footing balloon member—for example, by temperature or pH; and, distance between two sensors, so as to measure the expansion or collapse of the foundation footing balloon member or its mesh.
The condition sensor receiver unit can be accessed wirelessly by smart-phone, or by a local terminal, in order to read embedded condition sensor data. The embedded condition sensor data can help to determine the history and stability of the foundation piling, and whether it is warranted to add water, cement or pumped concrete via the through-holes. Portions of the connections between sensors and receiver can be made wireless, particularly where above ground.
Although the present invention has been described in connection with certain specific embodiments for instructional purposes, the present invention is not limited thereto. Accordingly, various modifications, adaptations, and combinations of various features of the described embodiments can be practiced without departing from the scope of the invention as set forth in the claims.
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Number | Date | Country | |
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20190078283 A1 | Mar 2019 | US |