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.

Claims

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 (2a, 2b . . . ) 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.

Description

BRIEF DESCRIPTION OF THE INVENTION

[0036] It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered for limiting of its scope, for the invention may admit to other equally effective embodiments.

[0037] FIG. 1 shows the configuration of bioinspired inclined skirted footing with varying spacing and inclination.

[0038] FIG. 2 shows the model foundations: skirted footing (left), bioinspired skirted footing with vertical micropiles with 4D spacing (center) and bioinspired skirted footing with inclined micropiles with 2D spacing (right)

[0039] FIG. 3 shows variation of load-carrying capacity with varying length of micropiles: (a) S=3D, (b) S=4D, (c) S=6D.

[0040] FIG. 4 shows variation of load-carrying capacity with the angle of installation of micropile: (a) L/B=0.5, (b) L/B=1, (c) L/B=1.5, (d) L/B=2.

[0041] FIG. 5 shows variation of load-carrying capacity with spacing between micropiles (S/D): (a) L/B=0.5, (b) L/B=1, (c) L/B=1.5, (d) L/B=2.

[0042] FIG. 6 shows variation of load-carrying capacity with the length of micropiles (L/B): (a) =0, (b) =10, (c) =20, (d) =30

[0043] FIG. 7 shows experimental model load-settlement curves for plate, skirted footing and bioinspired footing with fixed L/B=0.5 and S=3D.

[0044] FIG. 8 shows the experimental model load-carrying capacity with micropile installation angle for bioinspired footing with fixed L/B=0.5.

[0045] FIG. 9 shows experimental model load-settlement curves for bioinspired footing, representing the influence of spacing between the micropiles with fixed L/B=0.5 and =150.

[0046] FIG. 10 shows experimental model load-settlement curves for bioinspired footing, representing the influence of the length of micropiles (L/B) with fixed S=4D and =15.

[0047] FIG. 11 shows the detailed method of construction.

DETAILED DESCRIPTION OF THE INVENTION

[0048] The present invention relates to a system and method for the shallow foundation. An inclined skirted shallow foundation is provided for onshore structures. The system adopts the principles of biogeotechnique. Micropiles serve as inclined skirted foundations. It uses micropiles to mimic the root system of trees and enhance the load carrying capacity of a shallow foundation. Thus the invention provides an effective solution to the method of installation/construction of skirted footings, which are otherwise theoretical and non-practical. Micropiles not only confine the soil but also act as structural members taking tensile, compression and frictional forces.

[0049] Installation is completed readily using the cast in situ or prefabricated micropiles. In case of use of prefabricated micropiles, system would be ready to take the structural loads immediately after the installation. After the insertion 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. In the case of the cast in situ, the casing can be left in the ground permanently to facilitate structural connections, for seismic design considerations, or for other design considerations. The configuration of bioinspired inclined skirted footing with varying spacing and inclination is shown in FIG. 1. A bioinspired skirted footing comprises substructure base (1) square or rectangular or circular or strip footing with closely spaced vertical/inclined micropiles and multiple micro piles (2a, 2b . . . ) of different lengths attached to the base at different inclinations 0 to 90 and at a 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. Thus use of micropiles in place of structural skirts, would be material-efficient, energy-efficient and economical as compared to traditional skirted footing, other ground improvement options as well as deep foundations.

[0050] The substructure herein defines a square or rectangular or circular or strip footing with closely spaced vertical/inclined micropiles. The vertical or inclined closely spaced micropiles are of varying lengths. 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.

[0051] Inclined skirted footings not only increase vertical load carrying capacity but also increase lateral and moment carrying capacities of the footing significantly as compared to vertical skits. However, their installation is very tedious and expensive. The present invention provides an effective solution to the method of installation/construction of inclined skirted footings, which are otherwise theoretical and non-practical. This is a novel method of constructing a new foundation using the number of micropiles, which performs very well in different loading environments.

[0052] The present invention is based on the use of optimally spaced multiple micro piles, which act as inclined structural skirts fixed to the edges of the foundation. Thus it provides an alternative to skirted/bucketed foundation and can be constructed without much difficulties. The invention describes the novel method of constructing a new foundation using a number of equidistance micropiles, as an alternative to inclined skirted foundation. A radial array of batter-angled micropiles is drilled or driven and resembles the natural tree root structure. The invention uses micropiles to mimic the functioning of the roots of a tree and provide stability to the foundation under all different types of loading. The proposed foundation uses micropiles to mimic the root system of trees and holds the soil, which enhances the load-carrying capacity of a shallow foundation and offers solutions to many challenging problems. These micropiles constrain the soil between them and increase the effective depth of the overall foundation, hence the footing performance. Use of inclined micropiles as compared to vertical micropiles confines much more soil. Thereby, they increase not only the effective depth but also the effective width of a shallow foundation.

[0053] This is an effective solution to the method of installation/construction of skirted footings, which are otherwise theoretical and non-practical. It presents an innovative shallow foundation based on the principles of biogeotechnics. Biogeotechnics is comprised of both bio-mediated and bio-inspired technologies, and offers solutions to many challenging problems. Micropiles serve as the inclined skirted foundation. The proposed foundation uses micropiles to enhance the load carrying capacity of a shallow foundation. The addition of inclined micro piles to the edges of shallow foundations offers significant improvement in the overall performance of existing foundations. Further, micropiles not only confines the soil but also act as structural members taking tensile, compression and frictional forces. These inclined micro piles which replicate the tree root system constrain the soil between them, increase the effective width of a shallow foundation and improve the footing performance. Thus, the proposed invention comes under the domain of bio-inspired getotechniques. Apart from increasing vertical load carrying capacity, the proposed bioinspired foundation also significantly increases the lateral and moment carrying capacity of the footing compared to the strip foundation or existing skirted foundation. The performance of this invented foundation depends on micropile dimensions, spacing between micropiles and the optimum inclination of micropiles.

Method of Construction:

[0054] Micropiles, as well as footing, can be made of reinforced concrete following two methods of construction: Precast or Cast-in-Situ and two methods of installation: Driven and Bored. After the 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 micro piles are very beneficial when micro-piles are to be installed in relatively dense and/or obstruction-laden fill and/or hilly terrains. On the other hand, driven precast concrete micropiles are preferred in loose soils and they also help in rapid installation of the bio-inspired footing. However, they are to be designed to withstand high driving stresses. In fact, forming micropiles through driving, helps in socketing micropiles firmly within the ground, which further enhances the load carrying capacity and stability of the overall foundation. The proposed bio-inspired skirted footing would be material-efficient, energy-efficient and economical compared to other ground improvement options and deep foundations as well as traditional skirted footings. The detailed methods of construction for Cast-in-Situ (Bored/Driven) and Precast (Bored/Driven) are given below:

[0055] Bored Cast-in-Situ: A simple method of construction of a micropile involves a total of eight steps as shown in FIG. 11. Step 1 involves predrilling a hole (with a casing if the hole is collapsible) as per design specification. Predrilling a hole can be done with normal auger if the sites are inaccessible for heavy machinery. The drilling can be done vertical or inclined according to design specifications and requirements using augers or drill bit as per the feasibility as shown in step 2. Step 3 and 4 involves lowering a solid steel-round textured reinforcement bar with centralizers into the bore and filling the cavity with cement grout, typically through tremie methods either under gravity or high pressure. Then the casing is gradually withdrawn, creating a bond zone between the grout and the surrounding soil. In case of loose soils, casing can be left in place and then micropile can be constructed as shown in Steps 5 and 6. The same process of construction is repeated for other micropiles following the spacing and inclination as per design specification and is shown in step 7. Finally, the reinforcement of the micropile cap/footing is placed and concrete is casted as per design specification as shown in step 8.

[0056] Driven Cast-in-Situ: A closed-ended hollow steel casing is driven into the ground. Then the solid steel-round textured bar with centralizers are placed into the casing and filled with concrete to create driven cast in-situ concrete micropiles. The casing can either be pulled out and reused as the concrete is being poured or left in place to form a part of the micropile. The same construction process is repeated for other micropiles following the spacing and inclination as per design specifications. Finally, the reinforcement for the micropile cap/footing is placed and concrete is casted as per design specification.

[0057] Bored Precast: Precast micropiles are casted using reinforced concrete at casting yard. The installation process of bored precast micropiles also requires drilling of bore using auger/drill bit similar to bored Cast-in-Situ micropiles. Step 1 involves predrilling a hole as per design specifications. Predrilling a hole can be done with normal auger if the sites are inaccessible for heavy machinery. The drilling can be done vertical or inclined according to design specifications and requirements using augers or drill bit as per the feasibility. Step 2 involves lowering of precast micropile into the pre bored holes. Step 3 involves filling the spaces between the micropile and bored holes with cement grout. The same construction process is repeated for other micropiles, following the spacing and inclination as per design specifications. Finally the reinforcement for cap is placed and the concrete is casted as per design specification as shown in step 8. Alternatively, structural plate or precast concrete slab can also be used as a micropile cap.

[0058] Driven Precast: The installation process of a micropile involves driving/hammering the micropiles to the required depth according to design specifications and requirements using a weight/hammer attached to a tripod arrangement. After insertion of micropiles, footing/cap will be either constructed or placed, such that sufficient reinforcement of micropiles will be lapped within the concrete of the footing. Precast micropiles should be designed to withstand handling and driving stresses.

RESULTS AND DISCUSSION

Numerical Study:

[0059] As mentioned above, bio-inspired skirted footing basically consists of a footing with micropiles placed at optimal spacing. Numerical simulations are carried out to show how closely spaced micropiles on the periphery of the footing are equivalent to a skirted footing. In this study, the capacity of skirted footings resting on cohesionless soils under vertical loading is investigated by means of a finite-element limit analysis (FELA) performed with OptumG3 (OptumCE, 2018). In this evaluation, the square footing width B is set to be 1.95 metre. Five different ratios of skirt depth (L) to footing width (L/B) were employed in the research: 0, 0.5, 1.5, and 2.0. There were five different angles of friction that were taken into account to analyse their influence. A range of inclinations of the micropiles (0, 10, 20 and 30) were tested. Also spacing between the micropiles were varied from S=3D, 4D and 6D. The elastic plate element from the OptumG3 element library was used to mimic the footing, skirts and micropiles. We carried out a convergence analysis considering the different geometries and soil properties to determine the optimal domain size, which wouldn't impact the failure loads and their mechanisms. The movements in all directions are constrained at the base of the model, while only the horizontal movements are constrained on all the side boundaries. In order to examine the load carrying capacity of the footings, elasto-plastic model with Mohr-Coulomb (MC) failure criteria is adopted for modelling the material properties. Young's modulus, and poisson's ratio, unit weight, friction angle and the dilation angle are the considered soil material properties. Considered FEM models results from numerical simulations are presented in FIGS. 3 to 6. It is worth noting from FIG. 6(a) that the load carrying capacity of bioinspired footing (S-3D) is slightly lower than the skirted footing. In other words the load carrying capacity of bioinspired footing (S=3D and L/B=0.5) is just 11% less than the skirted footing. While as for L/B>1, 1.5 and 2 the load carrying capacity of bioinspired footing (S=3D) is just 7-8% less than the skirted footing. Hence, it is interesting to note that, the load carrying capacity of skirted footing is replicated by the bioinspired footing by effectively spacing the micropiles.

[0060] Further for bioinspired footing (S=3D and L/B=0.5) in FIG. 4 (a), it is seen that load capacity varies with , showing an initial increase and peak at =20 followed by a milder increase or decrease with further increase in . It is clear that inclination of micropiles from 0 to 20 resulted in an increase of 29% in load carrying capacity while as for further increase in inclination from 20 to 30, nearly 5% increase in load carrying capacity was noticed for S=3D and L/B=0.5. For S=4D and L/B=0.5 case, inclination of micropiles from 0 to 20 resulted in an increase of 15% in load carrying capacity whileas for further increase in inclination from 20 to 30 nearly a decrease of 4.5% in load carrying capacity was noticed. Similarly for L/B=1.5 and S=3D, (FIG. 4 (c)) the inclination of micropiles from 0 to 20 resulted in an increase of 108% in load carrying capacity whileas with further increase in inclination from 20 to 30 nearly a decrease of 6.5% in load carrying capacity was noticed. For S=4D and L/B=1.5 case, inclination of micropiles from 0 to 20 resulted in an increase of just 29% in load carrying capacity whileas for further increase in inclination from 20 to 30 nearly a decrease of 14% in load carrying capacity was noticed. Main reason for less improvement with the inclination of micropiles in this case is primarily because of the inability of micropiles to confine the soils with an increase in the spacing.

[0061] Thus, the ultimate load capacity of bioinspired footing as shown in FIG. 4. was affected by both and S. The combined effect of micropile inclination and spacing was however significant, and it was observed from FIGS. 3 and 4 that the values of the ultimate load of bioinspired footing were greater for smaller values of spacing(S) and with inclination angle () between 10-20.

[0062] From FIG. 5 and FIG. 6, it was observed that the values of the ultimate load of bioinspired footing were greater for larger values of L/B when micropiles are placed at optimal spacing (i.e S=3D). The maximum capacity in all the cases is attainted at S=3D. It is clear from FIG. 6a that an increase in the L/B of micropiles from 0.5 to 1 resulted in an increase of 101% in load carrying capacity and also an increase in the L/B of micropiles from 0.5 to 1.5 resulted in an increase of 230% and nearly 400% for L/B=2 in load carrying capacity.

[0063] From FIG. 3a, it can be noted that for S=3D and L/B>1 the load carrying capacity increases with the inclination from 0 to 20, whileas it decreases with further increase in the inclination from 20 to 30. For S=4D, the maximum load carrying capacity is achieved at =10. For S=6D the maximum load carrying capacity is achieved at -0.

[0064] Also from FIG. 3b the micropile groups constructed with a S-3D displayed a stiffer response than the groups constructed with S>3D. In addition, for S=3D, groups constructed with =20 displayed an increase in capacity compared with groups constructed with -0, 10 and 30. This demonstrates the benefit of using S=3D and =20 when a larger capacity or stiffer response is required.

[0065] The above results confirm that both inclination and spacing between the micropiles plays an important role in improving the load carrying capacity. Therefore by using micropiles at optimum inclination and with optimum spacing, the load carrying capacity enhances significantly particularly at higher L/B. It's worth to note that the load carrying capacity of skirted footing is replicated by the bioinspired footing by using micropiles at an optimum inclination and with effective spacing between the micropiles.

Experimental Study

[0066] An experimental study has also been carried out to verify the numerical findings of the study. The load carrying capacity and settlement of physical bioinspired foundation models resting on the sand were determined using a laboratory setup consisting of a test tank, sand raining hopper, and loading system. The 2.10 m1.20 m1.10 m tank had a see-through wall on one side, where the experiments were carried out. The boundary effects were nullified by keeping a safe distance between the boundary and the foundation. A servo-hydraulic linear actuator (double acting, double ended) with a 3T capacity that was installed there to supply the reaction forces required for vertical loading. A displacement transducer is installed within the servo hydraulic linear actuator to monitor settlements.

[0067] Table 1 provides the details of all the experimental tests conducted in this study and the tests are designated by the alphanumeric characters in their names. The letter BF indicates bioinspired footing with either vertical or inclined micropile cases. Whileas letter SKF indicates a skirted footing case and SF indicates surface footing. The number after letter BF/SKF/SF represents the inclination, designated as 0, 15 and 30. 0 represents vertical micropiles and 30 represents micropiles are inclined at 30. The last number indicates the L/B (length of micropiles or skirts wrt width of footing. Width of footing (B) is 200 mm for all the cases.), designated as 0, 0.5, 1 and 1.5. (0 represents there are no micropiles or skirts attached while 1.5 represents 300 mm micropiles/skirts of length). Specially for bioinspired footing cases spacing between the micropiles is indicated by xD (x=2, 3, 4 or 6). D represents the diameter of micropiles, which is constant as 16 mm. So 2D represents that the micropiles are spaced 32 mm from each other. Hence, BF4D-10-1.5 represents Bioinspired footing spaced four times the diameter of micropiles (416-64 mm) from each other with 10 inclined micropiles with the length of micropiles as 1.5 times the width of footing (1.5200=300 mm).

TABLE-US-00001 TABLE 1 Details of experimental model tests carried out Inclination Spacing Length Type () (S) (L/B) SF SKF-0-0.5 0 0.5 BF2D-0-0.5 0 2D 0.5 BF2D-15-0.5 15 2D 0.5 BF2D-30-0.5 30 2D 0.5 BF3D-0-0.5 0 3D 0.5 BF3D-15-0.5 15 3D 0.5 BF3D-30-0.5 30 3D 0.5 BF4D-0-0.5 0 4D 0.5 BF4D-15-0.5 15 4D 0.5 BF4D-15-1 15 4D 1 BF4D-15-1.5 15 4D 1.5 BF4D-30-0.5 30 4D 0.5 BF6D-0-0.5 0 6D 0.5 BF6D-15-0.5 15 6D 0.5 BF6D-30-0.5 30 6D 0.5

[0068] FIG. 2 shows the detailed configuration of the plate, skirted footing and bioinspired model foundations, all of which were made of stainless steel. Three square-shaped plate with widths of 200 mm with 16 mm thickness were fabricated and used. Additionally, tests are also conducted using simply square plate alone to obtain the load capacity of the footing without any skirt and micropiles. For the micropile foundations, three installation angles () of 0, 15 and 30 and three pile spacing(S) of 2, 3, 4, and 6 times the micropile diameter (D) were considered. The diameter of the micropiles for all cases was 15 mm.

[0069] Loads were applied using a servo hydraulic linear actuator with the load increment 0.02 kN/s. The results from the experimental study are presented in FIGS. 7 to 10.

[0070] The load-settlement curves of the surface footing (SF) in FIG. 7 show that the ultimate state is reached after a certain settlement beyond which no further increase in the load capacity is observed. For bioinspired footing with inclined micropiles, the load-carrying capacity increased continuously without a clear indication of yielding or failure. These footings couldn't be tested till the ultimate state due to the limitation of the reaction frame. Hence, in the present study, the load capacities of all the model foundations are compared, corresponding to 10% of raft width settlements.

[0071] The behaviour of skirted footing and bioinspired footing were studied with the help of load-displacement curves. In FIGS. 7, 9 and 10, the horizontal dashed lines indicate 10% of raft width settlements. It was seen from FIG. 7 that the load carrying capacity of skirted footing is 18.5 kN which is slightly higher than bioinspired footing (S-3D) as 17.2 kN. In other words, the load carrying capacity of skirted footing is just 7% more than the bioinspired footing with S=3D. It is interesting to note that the load carrying capacity of skirted footing is replicated by the bioinspired footing by effectively spacing the micropiles. Also inclination of micropiles will further increase the overall performance of the foundation. As seen from FIG. 7, in bioinspired footing with a micropile inclination of 15, the load carrying capacity is increased significantly as compared to bioinspired footing with vertical micropiles. The load carrying capacity of BF3D-15-0.5 is 25% more than BF3D-0-0.5. However, further increase in micropile inclination from 15 to 30 doesn't help much in increasing capacity. These findings are well supporting our numerical findings, where we have clearly seen an increase in bioinspired footing capacity increases significantly with an increase in micropile inclination upto about 20 and thereafter only a slight increase in capacity.

[0072] The ultimate load capacities for bioinspired footing with fixed L/B=0.5 and with varying S/D were obtained from FIG. 7 and plotted in FIG. 8 as a function of installation angle ().

[0073] The ultimate load capacity of bioinspired footing as shown in FIG. 8 was affected by both and S. These observations are also similar to our numerical findings.

[0074] Further for bioinspired footing with S=3D, in FIG. 8, it was seen that load capacity varies gently with , showing an initial increase at =15 followed by a milder increase with further increase in and reaches a peak at =30. It is clear that the inclination of micropiles from 0 to 15 resulted in an increase of 25% in load carrying capacity whileas for further increase in inclination from 15 to 30 nearly 8% increase in load carrying capacity was noticed.

[0075] From FIG. 9 and FIG. 10, it was observed that the values of the ultimate load of bioinspired footing were greater for smaller values of S and higher values of L/B. It was interesting to note from FIG. 9 that the decrease in spacing from 3D to 2D leads to an increase of 23% in load carrying capacity for fixed L/B=0.5 and =15. Also, it is clear from FIG. 10 that an increase in the L/B of micropiles from 0 to 0.5 resulted in an increase of 36% in load carrying capacity and an increase in the L/B of micropiles from 0 to 1 resulted in an increase of 84% in load carrying capacity.

[0076] The above results from the experimental study also confirm that both inclination and spacing between the micropiles play an important role in improving the load carrying capacity. Therefore by using micropiles at an optimum inclination and with optimum spacing the load carrying capacity enhances significantly, particularly at larger micropile lengths and all the benefits of an inclined skirted foundation can be replicated by the bioinspired foundation.

[0077] Numerous modifications and adaptations of the system of the present invention will be apparent to those skilled in the art, and thus it is intended by the appended claims to cover all such modifications and adaptations which fall within the true spirit and scope of this invention.