Bioinspired skirted footing and its method of installation

Abstract

The present invention relates to the field of bioinspired geotechnics to provide an alternative to conventional vertical and inclined skirted footings and their method of installation. The invention provides tree root inspired substructure with improved load carrying capacity and a method of installation. Tree root inspired substructure herein defines a square or rectangular or circular or strip footing with closely spaced vertical/inclined micropiles. This hybrid substructure takes advantage of depth effect, width effect, arching effects, compaction and relative ease in installation on level and sloping grounds as compared to conventional skirt/bucket foundation. The micropiles attached to the traditional footing are spaced such that the trapped soil in-between behaves as a plug and major load shearing/transfer takes place at the level of tip of micropiles. Some load distribution also takes place along the micropiles and underneath the footing. The uplift, moment, lateral and vertical load carrying capacity gets enhanced due to the increase in the depth of foundation without much efforts on excavation. The proposed foundation can be cast-in-situ or precast or hybrid. Micropiles of the footing could be installed by either driving or boring. Micropile material can be solid/hollow steel or reinforced/unreinforced concrete, while the footing can be made up of steel plate/frame or reinforced/prestressed concrete. Appropriate selection of a bioinspired skirted footing saves a lot of material and construction time as compared to conventional skirted footing, leading to cost savings.

We claim: 
     
         1 . A bioinspired skirted footing comprises substructure base ( 1 ) square or rectangular or circular or strip footing with closely spaced vertical/inclined micropiles characterized in that the solid/hollow steel or reinforced/unreinforced concrete, footing of steel plate/frame or reinforced/prestressed concrete and multiple micro piles ( 2   a ,  2   b  . . . ) of different lengths attached to the base at different inclinations 0° to 90° and at different spacing from each other which is in ration of 1D to 6D, where “D” represents the diameter of micropile, which act as inclined structural skirts fixed to the edges of the foundation wherein closely spaced micropiles to a footing helps in plugging the soil and making it as a part of the footing, yields comparable load carrying capacity to the footing with structural skirts and thus replaces the structural skirts. 
     
     
         2 . The bioinspired skirted footing and its method of installation, as claimed in  claim 1 , wherein the method of installation includes the following steps:
 predrilling a hole, vertical or inclined (with a casing if the hole is collapsible) as per design specification.   then lowering a solid steel-round textured bar with centralizers into the bore.   then filling the cavity with cement grout, typically through tremie methods either under gravity or high pressure.   the casing is gradually withdrawn, creating a bond zone between the grout and surrounding soil or bedrock.   
     
     
         3 . The bioinspired skirted footing and its method of installation, as claimed in  claim 1 , wherein the method includes following steps:
 After insertion/construction of micropiles, the footing will be either constructed or placed, such that sufficient reinforcement of micropiles will be lapped within the concrete of the footing.   Drilled pre-cast/cast-in-situ micropiles are particularly useful in limited-access situations adjacent to vibration-sensitive structures, where driving of micropiles is not feasible.   Further, the drilled mircopiles are very beneficial when micro-piles are to be installed in relatively dense and/or obstruction-laden fill and/or hilly terrains.   
     
     
         4 . The bioinspired skirted footing and its method of installation, as claimed in  claim 1 , wherein precast installation process of a micro pile involves driving in case of loose and soft soils, or drilling a bore through soils, rocks, overburden, etc. and then placing and after insertion of micropiles, footing will be either constructed or placed, such that sufficient reinforcement of micropiles will be lapped within the concrete of footing. 
     
     
         5 . The bioinspired skirted footing and its method of installation, as claimed in  claim 1 , wherein in case of loose soils, the casing can be driven and then micropile can be constructed. 
     
     
         6 . The bioinspired skirted footing and its method of installation, as claimed in  claim 1 , wherein forming micropiles through driving, helps in socketing micropiles within the firm ground, which further enhances the load carrying capacity and stability of the over all foundation. 
     
     
         7 . The bioinspired skirted footing and its method of installation, as claimed in  claim 1 , wherein the skirt action by closely spaced micropiles increases vertical load, lateral load and moment carrying capacities of the footing. 
     
     
         8 . The bioinspired skirted footing and its method of installation, as claimed in  claim 1 , wherein the load carrying capacity also depends on the spacing of micropiles, length of micropiles, the optimum inclination of skirts/micropiles.