WO2020165815A1

WO2020165815A1 - Augmented foundations using structural grips used for improving pile/anchor properties

Info

Publication number: WO2020165815A1
Application number: PCT/IB2020/051175
Authority: WO
Inventors: Deepu RANJIT
Original assignee: Vijayarajan, Sridhanya Kumary
Priority date: 2019-02-14
Filing date: 2020-02-13
Publication date: 2020-08-20

Abstract

The present invention discloses augmented foundations using Structural Grips used for improving pile/anchor properties. The structural grip is comprising of Sleeve, Piercing Fins / Soil anchors, and Connecting system. The sleeve or the top ring (1) is strengthened with support rods (3) which forms the soil anchors or the piercing fins. Connecting rods (4a) are attached to top ring (1) while connecting rods (4b) are attached to bottom ring (2)and are hinged (5) to one another and will allow them to spread horizontally when the sleeve (1) is pushed down by the jacking system. The connecting system enables the connecting rods to connect top ring and bottom ring by means of swivel joints (6). It can be expanded horizontally by applying downward force by the jacking system, followed by concreting after lowering the reinforcement cage in the bore.Structural grips increase the load bearing capacity of the foundation and act as a reinforcement at reduced cost.

Description

AUGMENTED FOUNDATIONS USING STRUCTURAL GRIPS USED FOR

IMPROVING PILE/ANCHOR PROPERTIES

FIELD OF INVENTION:

The present invention relates to foundations including pile and anchors using“structural grips”. More especially the present invention discloses augmented foundations using Structural Grips used for improving pile/anchor properties and reducing the cost of construction.Conventional foundations including piles and anchors have a plane body (surface) and a flat base. In cases where a shoe is used, it has a pointed base. In such cases interaction between the foundation and soil is through the adhesion/friction of the plane surface/flat base and soil and end bearing. Hence, in the present invention, augmented foundations are introduced which has structural grips. These augmented foundations do not have a plane surface or flat base. Instead they have a surface with structural grips to improve the adhesion/friction interaction with the soil.These structural grips used for foundation are more eco-friendly as the depth of the system is reduced and the total cost involved is also comparatively less than conventional file foundations. These structural grips can be used in isolation or in association with foundation systems such as deep foundations including piles, shallow foundation, anchors or similar etc. This has wider application in foundation system of structures such as in building projects, infrastructure projects, power generation projects (including thermal power projects, hydro power projects and wind turbine projects etc.).

BACKGROUND OF THE INVENTION:

Piling is a usual practice in most of the construction projects throughout the world. It is done to transfer the loads of the structures to the soil thereby holding the structure intact. This will address the transfer of all kind of forces on the structure both the weight of the structure and any vertical, lateral or uplifting forces acting on the structure due to wind load or any other external loads. The regular practice for the design of piles is to calculate the skin frictional resistance and the end bearing to arrive at the capacity of the pile. Piling and anchoring is a major part in any construction project. Where piling is done to improve the load carrying capacity and moment carrying capacity of the structures that are constructed above, anchors are used to improve the strength of free-standing soil masses. In a building project the total cost of foundation system will be around 3-10% depending on the soil below structure. So, savings in the cost of foundation will reduce the total cost of the project very much. Similarly, in anchoring methods also the depth can be reduced by using the structural grips.

The basic concept behind the development of structural grips has come from tree roots. The trees and plants get its strength from the roots to hold it in position during strong winds and similar disturbing forces. The roots are spread in all directions which give the trees their grip to withstand the loads. In the current conventional piling/anchoring techniques the piles/anchors are bored/driven only vertically downwards and no sideways branch like structure is provided in the piles. Through the development of structural grip, the system is strengthened by giving some extra grip to the system thereby improving the compressive, lateral and uplift capacities. The system and the structural grips may be cast in situ, precast, prestressed or pretensioned.

PRIOR ART:

A lot of work had been done in this direction by Some of the patents/patent application and literatures related to the present invention are discussed below.

A known configuration of the foundation of wind turbine towers comprises a base slab, a pedestal (in which the tower is supported) and radial walls extending from the pedestal to the edge of the base slab.

Given the situation away from the urban centres of wind turbine towers and the size of the foundation and its construction by in-situ concreting methods, a conventional gravity foundation poses several problems that have led to a number of proposals of construction methods using prefabricated elements as those described in US 2007/181767 Al, WO 2008/036934 Al and WO 2015/124815 Al. Proposals to reduce the size of the foundation are also known such as that described in WO 2010/138978 Al in which a three-dimensional network of post-tensioning elements to achieve a desirable combination of high stiffness and greater fatigue resistance is used.

Indian Patent application No. 201837025023 refers to a foundation for a wind mill comprising a circular or polygonal pedestal for supporting a wind mill tower and a plurality of ribs radiating radially outwardly from the pedestal, wherein the pedestal is divided into a plurality of circumferential sections, wherein a circumferential section and a rib are each integrally formed with one another as a precast concrete element, wherein the precast concrete elements are made from reinforced concrete comprising a first reinforcement structure, in particular reinforcement bars, embedded into the precast concrete elements.

Further, the invention refers to a wind turbine comprising a mast and a rotor mounted on the mast, wherein the mast is mounted onto a foundation. Improved foundation for a wind mill that is built from precast reinforced concrete elements, but that behaves similar to a monolithic foundation, in order to resist to high static and dynamic loads are also known from prior literatures.

Indian Patent application number 201717024402 provides a wind power installation foundation having a cylindrical central unit, a plurality of steel carriers which are arranged radially around the central unit and which respectively have a first and a second end, and a plurality of foundation piles. The first ends of the steel carriers are fixed to the central unit so that the second ends of the steel carriers are in the form of free ends. The second free ends of the steel carriers are respectively placed on one of the foundation piles. The drawback of such foundation is that the formed foundation may not be a monolithic structure. This may result in an interrupted load path between said structures so that the forces introduced into the foundation are not effectively distributed.

WO 2004/101898 reveals a foundation of a wind energy plant which is constructed by prefabricated readymade concrete parts. The foundation has for this purpose a hollow cylindrical base element with a plurality of radially spaced foot modules. The foot modules are braced on the base module as well as with one another.In the case of prefabricated structure, the main difficulty will be the transportation of elements. Also, the structure formed may not behave like a monolithic structure, if adequate care is not taken.

Indian Patent application No. 201617002146 relates to a wind energy plant foundation as well as a corresponding wind energy plant, which consists of a plurality of prefabricated ready made concrete parts and which has improved statics.The foundation segments have a plurality of first and second sheaths which serve to receive tensioning wires for bracing the foundation segments. The foundation segment has an underneath side, an upper side for receiving a lower tower segment, an inner side, an inwardly curved outer side, two side faces and an outer section.As mentioned earlier, Prefabricated structures have a disadvantage of transportation of the parts and difficulty in achieving a monolithic foundation.

Indian Patent application 2577/MUMNP/2014, an upper reinforced concrete slab poured“in situ” is described, having a polygonal or circular footprint, which is made rigid at the bottom by means of reinforced-concrete ribs of a rectangular or trapezoidal cross-section which are arranged radially. The method envisages said ribs being made with concrete“in situ”, or alternatively by means of prefabricated elements, always working integrally with the upper slab.Drawback being difficulty in excavation, construction and compaction. Further, if prefabricated elements are used the above mentioned drawback would also add up

In all the above-mentioned prior arts, prefabricated elements are used. A major disadvantage remains that precast concrete elements must not exceed certain dimensions so that they may be transported from the precast plant to the work site. Another drawback of such foundation that it is made from precast concrete elements is that, in contrast to foundations casted on-site. No monolithic structure is provided, so that technical solutions must be developed for securely connecting the precast concrete elements to each other to simulate a monolithic structure.

European Patent application EP1074663 is known, for example, which discloses an example of a foundation with three stabilizing members arranged symmetrically around a central support, with the drawback of having very little surface for contacting with the terrain, with the subsequent increase in stress applied on the terrain and in settlements.

Patent application PCT W02004/101898 describes a circular foundation based on prefabricated triangular sections. This solution requires completely emptying out the excavated cavity, resulting in an inverted T-shaped concrete section that does not involve any structural advantage because the width of the compressed concrete head is very small. This means that when calculating bending, the neutral axis will be lower and there will be a smaller mechanical arm, the need for reinforcement increasing and sectional ductility considerably is also dropping.

Spanish Patent application ES-2347742 describes a cone-shaped foundation together with a lower planar ring-shaped slab. It is a very complex solution to implement and presents serious questions concerning its structural performance. The type of foundation for these superstructures is a very well-known and easy to calculate and design technical solution, and the simplicity thereof further simplifies the formwork and construction. However, such foundations have the drawback of being quite large, so the use of steel and concrete as well as the volume of earth that is removed is extraordinarily high, all of which noticeably increases the economic cost of the structure. The impact of the cost of the foundation on the cost of the structure is higher the larger the superstructure is.

Indian Patent application No. 10272/DELNP/2014 relates to a modular foundation resistant to ground movement. A module for a foundation characterized in that each space having a height is traversed by at least one integral rigid member capable when in use of transmitting a load from the upper surface to the lower surface. The drawback of this type of foundation is in its difficulty in construction.

Indian Patent Appl No. 8695/CHENP/2014 provides a hybrid foundation structure which is efficient in reinforcing the soft ground as well as preventing the subsidence of the ground and keeps boring equipment from overload. The invention relates to a foundation structure vertically installed on the ground and comprising of an upper support layer formed on the ground in the vertical direction, a lower support layer extended downward from the upper support layer in order to have a narrower width compared to the width of the upper support layer. The upper support layer and the lower support layer provide a hybrid foundation structure formed from solidified soil which is a mixture of earth, sand and a soil -solidifying agent. It is preferable that the lower support layer is formed with deeper depth compared to the depth of the upper support layer. The drawback of this method is that it involves the chemical treatment of the soil surrounding it which could be comparatively laborious, time consuming, costly and undesirable for the ecosystem as such.

Indian Patent Application Number 921/MUMNP/2014 relates to a foundation for antenna mast where expandable piles are used to anchor the slab to the ground firmly. The foundation consists of at least three foundation elements joined at a central portion of the foundation by a central concrete portion. The foundation element each comprise of an elongated body. At least one bar of each foundation element is joined by the central concrete portion. The foundation is arranged in the ground with first end surface substantially at ground level. Each foundation element is provided with a through hole extending through the elongated body. A pile extends through the hole. The pile is secured in the through hole through a concrete filling. Thus, in addition to the foundation providing a wide foot print, the foundation is anchored to the ground by means of piles to provide a stable foundation for the antenna mast. The pile is an expandable steel pile i.e. the pile is driven to the ground in the form of a substantially uniform diameter steel tube. Thereafter an expander device is lowered into the pile and is activated to expand a portion of the pile. In this manner the pile is solidly anchored to the ground. Further piles of the foundation may be of the same kind as pile or of one or more different kinds than pile. Each foundation element is provided with attachment arrangement. The antenna mast is attached to the foundation by means of an attachment arrangement. The attachment arrangement may comprise at least one threaded shaft and nut. The drawback of this foundation is that it uses prefabricated elements hence acquire all the drawback of a prefabricated foundations. Further, driven piles are suggested which is not suitable for all types of soil. In addition to this, expandable steel piles are used, which could be affordable in small projects but in large projects it would increases the cost of the project where huge quantity of piling may be required.

Indian Patent application No. 2473/DELNP/2014 relates to the foundation structure of an offshore plant in particular an offshore wind turbine which foundation structure is to be installed at a low noise level and installation method thereof. This invention relates to a foundation structure for an offshore plant, in particular an offshore wind energy plant, having at least one foundation element which can be anchored to the sea floor, precluding a gravity foundation and precluding a floating foundation, and a support structure which can be attached thereto to fix the offshore plant. The invention also relates to a method for assembling this foundation structure on a sea floor.

In order to provide a foundation for an OWEP in the sea floor the use of so-called piles as foundation elements is known from DE 20 2010 010 094 Ul, these foundation elements having a diameter of about 1.5m to about 6 m depending on the construction. The number of piles used is dependent on the support structure concerned. According to the current state of the art, various steel constructions are known as support structures, being provided with a foundation of piles: monopile, jacket, tripile and tripod. A jacket support structure known from EP 2 067 913 A2 is attached to the sea floor by four piles, while tripiles and tripods require piles with a larger diameter. For a monopile, a single pile will suffice if it has a substantially larger diameter than other foundations. Furthermore, from the document DE 20 2011 101 599 U1 a hexagonal support structure is known, having a foundation of six piles. Depending on the construction and the properties of the floor, the piles are driven up to 65 metres down into the sea floor. They have a weight of about 220 to 700 tonnes depending on the properties of the floor and the support structure selected. The lower ends of the support structure, the support structure feet, can be connected to the foundation piles in such a way that the feet of the support structure are pushed into the driven foundation piles which have a larger diameter. The foundation pile and support structure foot are then connected to each other e.g. by a special cement mixture (grout compound). In addition to the foundation option using piles, gravity foundations are also known as foundations for offshore wind energy plants from DE 10 2010 012 094 20 B3. These consist of reinforced concrete and can weigh up to about 7000 tonnes. Drawback of such foundation being its huge consumption of material and less economical.

Furthermore, from the international patent application WO 2011/030167 Al, attachment of turbines in tidal power generation plants below sea level by means of grouted piles bored vertically into the sea floor is known. The use of grouted piles in relation to offshore wind energy plants is described in the American patent application US 2011/0061321 Al. However, the grouted piles are used together with a gravity foundation as a kind of hybrid solution.Cost of construction of such piles may be higher.

Furthermore, the British patent GB 880 467 describes the use of a driven piles to attach lattice mast-like foundation structures to the sea floor. The Japanese Patent Application Faid-Open (JP-A) No. 10-237866 and JP-A No. 7-11637, In the former invention, an excavation hole is formed at the ground by using an excavation rod to which an extensive excavation bit capable of being expanded in diameter is equipped at the toe thereof. Here, the extensive excavation bit is expanded and rotated at a predetermined depth, a bulb portion is formed with magnitude. There was a problem with expansion amount of an extensive excavation bit for each foundation pile. Therefore, there has been a problem of construction cost increase. Further, there has been a problem of a risk to construct a foundation pile being unable to support required total bearing capacity owing to false setting of a diameter expansion amount of an extensive excavation bit. Further, in an invention disclosed in the later literature, a spiral blade is fixedly arranged at an outer surface of a toe of a pile body (hereinafter, referred to as a "rotary penetration steel pipe pile" or a "screw pile"). Here, an outer diameter of the spiral blade is preferably on the order of 1.5 to 3.0 times of the outer diameter of pile body. In a case where required total bearing capacity is different between one foundation pile and another foundation pile, spiral blades fixedly arranged respectively are required to have different outer diameters. That is, since the outer diameter of the spiral blade is different between one foundation pile and another foundation pile, it has been required to prepare a plurality of kinds of foundation piles with complication of material management and construction procedure for screwing the foundation piles to specified positions. Further, owing to difference of torque generated during construction (during screwing to the ground) corresponding to outer diameter size of spiral blades, construction has been complicated with necessity to prepare construction machines corresponding to magnitude of the torque. Accordingly, there has been a problem of construction cost increase. All this contribute to the drawback of this foundation.

To solve the abovementioned problems, a later invention was made which provides a foundation pile group including foundation piles capable of reliably supporting required total bearing capacity with easy construction. Indian Patent application No. 3578/KOLNP/2012 relates to a foundation pile group, and, relates to a foundation pile group including a plurality of foundation piles to support a predetermined structure. A foundation pile group according to the invention is formed with a plurality of foundation piles which support a predetermined structure, wherein each of the plurality of foundation piles includes a pile body and an approximately spiral-shaped blade which is fixedly arranged at a toe or toe vicinity of the pile body, and respective outer diameters of the blades are approximately equal. Further, in a foundation pile group formed with a plurality of foundation piles which support a predetermined structure, each of the plurality of foundation piles includes a pile body and an extensive foot protection bulb which is formed at a toe of the pile body, and respective outer diameters of the extensive foot protection bulbs are approximately equal. Further, either or both of an outer diameter and thickness of each pile body are determined in accordance with total bearing capacity required for each of the plurality of foundation piles. Further, strength of a material of which each pile body is formed is determined in accordance with total bearing capacity required for each of the plurality of foundation piles. The pile body is made of a steel pipe or concrete. Accordingly, uniformity in construction materials can be improved and construction errors such as mistaking an installation position are prevented. Further, since screwing torque during construction (screwing to the ground) becomes approximately constant, it is not required to prepare a plurality of kinds of construction machines and construction machine operation is facilitated. Further, since outer diameters of the respective extensive foot protection bulbs are approximately equal, it is not required to prepare a plurality of kinds of extensive excavation bits and construction machines. Accordingly, management of construction materials and preparation and operation of a construction machine are facilitated. Further, since it is not required to control a diameter expansion amount of an extensive excavation bit for each foundation pile. Further, false setting of a diameter expansion amount of an extensive excavation bit is prevented for each foundation pile. All claims above as provided in the invention by the inventor. The drawback of this is that the preferred pile is steel pile, this increases the cost of the project considerably in case of large projects.

Considering all the prior art available and the drawbacks of each of those, the inventor has attempted to develop an optimum solution which counters these drawbacks to the maximum extent possible.

Hence, we have introduced augmented foundations which has structural grips. To obviate the drawbacks of the prior art we have come up with our innovative structural Grip which is an enhanced mechanism where the contact area of the pile is increased or the smooth surface of the pile is made rough by designing suitable mechanisms thereby enabling them to take more loads than conventional piles. These augmented foundations do not have a plane surface or flat base. Instead they have a surface with structural grips to improve the adhesion/friction interaction with the soil. The base of these foundations is also not usually flat but have a grip to enhance the bearing capacity. This structural grips can be used in isolation or in association with foundation systems such as deep foundations including piles, shallow foundation, anchors or similar etc. The basic concept here is to utilize the expanded soil contact area thereby increasing the load and functional capabilities of the foundation system. The extent to which the area is increased depends on how much the grips penetrate the soil. Another option/concept is to enhance the roughness of the pile surface which is otherwise smooth. Here we have come out with various embodiment under the invention for structural grips which can be selected as per the site conditions and load bearing requirements of the structure.

OBJECTIVES OF THE PRESENT INVENTION

The present invention is directed towards improving the efficiency of the foundation system. The first main objective of the invention is to increase the efficiency and load bearing capacity of the foundation system compared to the prior art piling system / foundation system. This will be achieved by using structural grips which can take the same amount of loads, thus reducing the size of the components (such as say of piles, anchors etc.).

The next main objective of the invention is to make the design and installation very simple so that any unskilled workforce can understand and install the foundation system.

Yet another objective is to reduce the use of heavy machineries in sites and to use smaller rigs and machineries to obtain the same result of conventional higher diameter piles and anchors. It is also ensured that no new mechanism is utilised for the installation of the structural grips. This ensures that the installation of these grips in the foundation can be carried out using the existing/conventional machineries and techniques.

One more objective is to use basic or commonly used materials for the entire design so that the cost of the project remains as low as possible.

SUMMARY OF THE INVENTION

According to the invention, augmented foundation system is developed using structural grips. This invention discloses the use of structural grips in isolation or in association with foundation systems such as deep foundations including piles, shallow foundation, anchors or similar etc. here after referred to as“the system”. This means that the structural grips may be used to act as the foundation itself where the design requirements satisfy. It can also be used in combination with Shallow foundation, Piles, anchors or similar where it augments the properties of the parent system. The system is so developed that it shall be applicable for use in foundation system of structures such as in building projects, infrastructure projects, power generation projects (including thermal power projects, solar power projects, hydro power projects and wind turbine projects etc.).

The present invention discloses augmented foundations using structural grips used for improving pile/anchor properties. Conventional foundation system including piles and anchors have a plane body (surface) and a flat base. In cases where a shoe is used it has a pointed base. In such cases interaction between the foundation and soil is through the adhesion/friction of the plane surface/flat base and soil and end bearing. In the present invention, augmented foundations are introduced which has structural grips. These augmented foundations do not have a plane surface or flat base. Instead they have a surface with structural grips to improve the adhesion/friction interaction with the soil. The base of these foundations is also not usually flat but have a grip to enhance the bearing capacity.

Grips are designed basically to form a firm gripping in the soil which will increase the load bearing capacity of the foundation and thereby reduce the costs of conventional practices, mainly the piling and anchoring methods. The grips are made by using anti corroding materials so as to avoid damage to the system in the future. The parts which are exposed to the soil are made by anti-corroding material and those parts which are embedded in concrete can be made by ordinary load carrying materials thus reducing the cost of the system.

The main advantage in this type of grips is that the length and the diameter of the piles and anchors (or any foundation) can be reduced without affecting the capacities. In other words, the same load carrying capacity can be achieved for the foundation with reduced diameter/length through the use of structural grips thereby reducing the total cost of the foundation system. These grips are more eco-friendly as the depth of the system is reduced. According to the invention augmented foundations using structural grips used for improving pile/anchor properties comprising of: a) sleeve or the top ring (1) strengthened with support rods (3), used by the jacking system for pushing the sleeve for expanding the folded connecting rods (4a, 4b) which functions as soil anchors or the piercing fins;b) soil anchors or the piercing fins formed by the connecting rods (4a) attached to top ring, and connecting rods (4b) attached to bottom ring are hinged (5) to one another and will allow them to spread horizontally which forms the soil anchors or the piercing fins when the sleeve is pushed down by the jacking system; and c) connecting system facilitates the connection between the sleeve and the connecting rods wherein anterior part of the connecting rod assembly is joined by means of swivel joints (6) to top ring and the posterior part of the connecting rod assembly is joined by means of another swivel joints (6) to the bottom ring (2) and kept in tension by means spring ( 8) that connects connecting rod (4a) and top ring (1) and are designed in collapsible form, so that it can be folded facilitating easy insertion of the foundation system in the bore and later on it can be expanded horizontally by applying downward force by the jacking system, followed by concreting after lowering the reinforcement cage in the bore. Here the sleeve, soil anchors or the piercing fins and the connecting system may be of different configuration and material depending on the foundation system in which it is used to facilitate the penetration of structural grips depending on the site condition, soil (bearing stratum) and load bearing requirements of the structure.

The parts which are exposed to the soil are made by anti -corroding material and those parts which are embedded in concrete can be made by ordinary load carrying materials, such as Steel or similar material thereby reducing the cost of the system and the anti -corroding material includes stainless steel, rubber coated steel members and fluoropolymer coated steel members.

An additional soil reinforcement (4)to increase the piercing length into the soil is provided to the connecting rod attached to the bottom ring (2) and will spread horizontally as jacking is done by pushing the sleeve, resulting in piercing the soil anchors into the soil around it completely and, facilitating the concreting the reinforcement cage that is lowered in the bore. According to one aspect of the invention said assembly / mechanism can be used as reinforcements in under reamed pile bulbs and can be used as soil anchors independently in ordinary piles and once the hole is dug the above assembly / mechanism is lowered to the bottom of the hole before pushing the sleeve downwardly by the jack.

in the case of under reamed piles, the horizontal spread of the mechanism isso designed to match the dimensions of the under reamed bulb area so that it will act as a reinforcement in the under reamed bulb area which is unreinforced in the conventional under reamed, squeezed or any other conventional piles in use.

According to an embodiment under the invention additional soil reinforcement (4) is provided to the connecting rod attached to the bottom base plate (2a) and a central rod (7) connected to the bottom base plate (2a) which will rest at the excavation/bore bottom or any other desired location through which the elongated sleeve (la) in the form of an outer pipe that surrounds the central road (7) slides down freely when the elongated sleeve (la) is pushed down by jacking.

According to another aspect of the invention, height of the elongated sleeve(la) will be less than the central rod (7) so that it facilitates positioning the steel grip assembly centred around the central rod (7), and acts as guide during the installation of the elongated grip.

This invention also discloses a method of installation of the augmented foundations using structural grips. It is comprising the steps of: a) carry out the excavation/boring out as required at the site; b) insert the structural grips in collapsible form, lower to the bottom of the hole and then expanded into the soil using suspended jacking system;c) insert the reinforcement cage; d) carry out concreting; and e) backfill the foundation.

According to another embodiment under the invention the method of installation of the augmented foundations comprising the steps of: a) carry out the excavation/boring out as required at the site; b) insert the structural grips having the elongated sleeve (la) provided with connecting rod (4a), bottom base plate (2a) provided with connecting rod (4b) attached with additional soil reinforcement (4) and a central rod (7) while said bottom plate (2a) will be resting at the excavation/bore bottom; c) expand the structural grip into the soil by downward pressing of the elongated sleeve (la) by the suspended jacking system so that the elongated sleeve(la) will slide down slowly over the central rod (7) and spread the structural drip horizontally ;d) insert the reinforcement cage by lowering into the bore and carry out concreting; and e) backfill the foundation.

According to one more aspect of the invention, protrusions are provided in the elongated sleeve (la), such that it does not interrupt the working of the mechanism by getting a proper grip of this mechanism to the concrete that is placed. BRIEF DESCRIPTION OF DRAWING

These and other features, aspects and advantages of the present invention will become apparent to those skilled in the art upon reading the detailed description is read with reference to the accompanying drawing.

Fig.1 - Isometric view of the first exemplary embodiment under the invention.

Fig. 2 Expanded position of the first exemplary embodiment under the invention, before inserting the cage for filling concrete.

Fig. 3- Isometric View of the second exemplary embodiment under the invention.

Fig. 4-Expanded position of the secondary exemplary embodiment under the invention, before inserting the cage for filling concrete.

Fig.5-Isometric View of the third exemplary embodiment under the invention.

Fig.6-Expanded position of the secondary exemplary embodiment under the invention, before inserting the cage for filling concrete.

Fig. 7- Shows connecting system pertaining to the top ring as an exemplary embodiment under the invention.

Wherein 1. Top ring(Sleeve) ; la. elongated sleeve; 2. Bottom ring; 2a. Bottom base plate; 3. Support rods of the ring; 4a. connecting rod attached to top ring; 4b. Connecting rod attached to bottom ring;4. Soil reinforcement ;5. Hinges joining the connecting rods ; 6.Swiveljoint for the connecting rod and the top/ bottom ring; 7. Central rod; 8. Spring that connects the connecting rod (4a) and top ring (1).

DESCRIPTION OF THE INVENTION:

The augmented foundations using structural grips used for improving pile/anchor properties according to the invention is directed towards improving the efficiency of the foundation system. The augmented Foundations using Structural Grips developed according to the invention improves pile/anchor properties and as such it is a cost-effective foundation system. Structural grips are designed basically to from a firm gripping in the soil which will increase the load bearing capacity of the foundation and thereby reduce the costs of conventional practices, mainly the piling and anchoring methods. The grips are made by using anti corroding materials so as to avoid damage to the system in the future. The parts which are exposed to the soil are made by anti-corroding material and those parts which are embedded in concrete can be made by ordinary load carrying materials such as Steel or similar material thereby reducing the cost of the system. According to an exemplary embodiment under the invention anti corroding material includes stainless steel and rubber coated steel members. One can give anti corrosion coatings to steel member like LAM-P/FR coating, LAM-V/FR coating or Fluorokote#l, a unique fluoropolymer coating.

The main advantage in this type of grips is that the length and the diameter of the piles and anchors (or any foundation) can be reduced without affecting the capacities. In other words, for a reduced diameter and length of pile/anchor we will obtain the same compressive and tensile properties/capacities and thereby reducing the total cost of the pile/anchor. These grips are more eco-friendly as the depth of the system is reduced.

According to the invention the structural grips are used in isolation or in association with foundation systems such as deep foundations including piles, shallow foundation, anchors or similar etc. The system so developed shall be applicable for use in foundation system of structures such as in building projects, infrastructure projects, power generation projects (including thermal power projects, hydro power projects and wind turbine projects etc.).

The structural grips are generally designed to have broadly three main subassemblies or parts in common.

1. Sleeve

2. Piercing Fins / Soil anchors

3. Connecting system

The sleeve and piercing fins with connection system may be of different configuration and material depending on the foundation system in which it is used to facilitate the penetration of structural grip into the soil (bearing stratum). According to different embodiment under the invention three different configurations of the structural grips are explained herein by way of examples. Any other configurations designed in conjunction with the above-mentioned parts for use as structural grip to augment the foundation system will also form part of this invention. The sleeve is that part of the structural grip which is used to connect to the jacking system used for pushing the sleeve for expanding the folded piercing pin. The sleeve holds the piercing fins.

The piercing fins are that part of the structural grip which pierces through the soil (or bearing layer) to facilitate griping. The fins are designed to be in a collapsible form, so that it can be folded facilitating easy insertion of the foundation system and later on it can be expanded using jacking system. Both the sleeve and the fins may be of different configuration and material depending on the foundation system in which it is used.

The third part“connecting system” facilitates the connection between the sleeve and the fins. Sleeve and fins may be of any configuration to facilitate the penetration of structural grip into the soil (bearing stratum).

There are optional connecting system (means) provided such as soil reinforcements (4); central rod (7); and base/ bottom plate (2a) which replaces the bottom ring.

Piling is a usual practice in most of the construction projects throughout the world. It is done to transfer the loads of the structures to the soil thereby holding the structure intact. This will address the transfer of all kind of forces on the structure both the weight of the structure and any vertical, lateral or uplifting forces acting on the structure due to wind load or any other external loads. The regular practice for the design of piles is to calculate the skin frictional resistance and the end bearing to arrive at the capacity of the pile.

Structural Grip is an enhanced mechanism where the contact area of the pile is increased, or the smooth surface of the pile is made rough by designing suitable mechanisms thereby enabling them to take more loads than conventional piles. Similar is the mechanism for other foundation systems such as shallow foundations, anchored foundations, other deep foundations etc. where it is integrated with structural grips.

The basic concept here is to utilize the expanded soil contact area thereby increasing the load and functional capabilities of the foundation system. The extent to which the area is increased depends on how much the grips penetrate the soil. Another option/concept is to enhance the roughness of the pile surface which is otherwise smooth. In this invention, many models/options for structural grips have been provided which can be selected as per the site conditions and load bearing requirements of the structure. The sleeve or the top ring (1) strengthened by supporting rod (3) is used to connect to the jacking system. The sleeve holds the piercing fins / soil anchors assembly of the structural/ pile grip. The fins are that part of the structural grip which pierces through the soil (or bearing layer) to facilitate griping. The fins are designed to be in a collapsible form while inserted into the foundation system and later expanded using jacking system. In a conventional foundation the construction of the foundation is carried out in the following steps

1. Excavation/boring is carried out first.

2. Reinforcement cage is then inserted/arranged.

3. Concreting is then carried out

4. This is followed by backfilling of the foundation.

Whereas in the case of augmented foundations using structural grips the construction procedure is as explained below.

1. Excavation/Boring is carried out first as required.

2. Structural grips are inserted in collapsible form and then expanded into the soil using suspended jacking system.

3. Reinforcement is inserted/arranged as required. As an option, structural grips may be attached to the reinforcement in collapsible form for later expansion into soil (or bearing layer). In this case the suspended hydraulic ram for jacking is inserted after the cage is inserted and load is applied for the grips to expand. This makes sure that the reinforcement cage is connected to the grips.

4. Concreting is then carried out

5. This is followed by backfilling of the foundation.

The sleeve and piercing fins / soil anchors assembly and the connection system may be of different configuration and material depending on the foundation system in which it is used to facilitate the penetration of structural grip into the soil (bearing stratum). Three different configurations of the structural grips are explained herein by way of examples though any other configurations designed in conjunction with the above-mentioned parts for use as structural grip to augment the foundation system will also form part of this invention.

These and other features, aspects and advantages of the present invention will become apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments, in conjunction with the accompanying drawings/figureswherein like reference numerals have been used to designate like elements. Any other configurations designed in conjunction with the above-mentioned parts for use as structural grip to augment the foundation system will also form part of this invention.

Example 1:

According to an exemplary embodiment under the invention constructional details of the structure and assembly of one such model of the augmented foundations using structural grips is explained below.

Fig.1 shows an isometric view of the first exemplary embodiment under the invention and the Fig. 2 shows the expanded position of the first exemplary embodiment under the invention, before inserting the cage for filling concrete.

Referring to Fig -1 and Fig-2, this model consists of sleeve comprising of top ring / sleeve (1) with support rods of the ring (3) and soil anchors or the piercing fins formed by Connecting rod (4a) attached to top ring and connecting rod (4b) attached to bottom ring by means of Swivel joints (6). Connecting rods attached to top ring and connecting rod attached to bottom ring are joined by means of hinges (5).This assembly/ mechanism as a whole can be termed as structural grip. The Other part used here is the reinforcement cage. Once the hole is dug the above assembly / mechanism is lowered to the bottom of the hole. Then using a suspended jacking system, the top sleeve is pushed. As the jacking is done the soil anchors/ piercing fins will spread horizontally as the middle portion of the soil anchors are hinged to one another and will allow spreading horizontally. As the soil anchors pierce into the soil around it completely and is in horizontal position, reinforcement cage is lowered into the hole and concreting is done. Since the area of the spread soil anchors are more, the pile mechanism will yield better properties than the original piles having the same diameter and depth.

Example 2

According to another exemplary embodiment under the invention constructional details of the structure and assembly of one such model of the augmented foundations using structural grips is explained below. Fig. 3 shows isometric view of the second exemplary embodiment under the invention and Fig. 4 shows the top view of this model, before inserting the cage for filling concrete.

Referring to Fig -3 and Fig-4, this model consists of sleeve comprising of top ring (1) with support rods of the ring (3), a bottom base plate (2a), and soil anchors or the piercing fins formed by the connecting rods (4a and 4b) and connection system which connect top ring(l) and bottom Ring(2). Here an additional soil reinforcement (4) is provided to the connecting rod attached to the bottom ring. The other part used here is the reinforcement cage. The above assembly / mechanism can be used as reinforcements in under reamed pile bulbs and can be used as soil Anchors independently in ordinary piles. Once the hole is dug the above assembly / mechanism is lowered to the bottom of the hole. Then using a suspended jacking system, the top ring is pushed. As the jacking is done the Soil Anchors having the additional soil reinforcement (4) will spread horizontally and will allow spreading horizontally. As the soil anchors pierce into the soil around it completely and is in horizontal position, reinforcement cage is lowered into the hole and concreting is done. In the case of under reamed piles, the horizontal spread of the mechanism is so designed as the dimensions of the under reamed bulb area. This will act as a reinforcement in the under reamed bulb area which is unreinforced in the conventional under reamed piles. This gives extra strength to the bulb and thus piles compared to the conventional under reamed piles. By doing so the piles can take extra loads both compression and uplifting forces. Since the area off the spread soil anchors are more, the pile mechanism will yield better properties than the original piles having the same diameter and depth.

Example 3

According to yet another exemplary embodiment under the invention constructional details of the structure and assembly of one such model of the augmented foundations using structural grips is explained below.

Fig. 5 shows isometric view of the third exemplary embodiment under the invention and Fig. 6 shows the isometric view of this model in open position, before inserting the cage for filling concrete. Referring to Fig.5 and Fig. 6, this model consists of an elongated sleeve (la) in place of top ring (1), a bottom base plate (2a), and soil anchors or the piercing fins formed by the connecting rods (4a and 4b) and connection system which connect elongated sleeve (la) and bottom base plate (2a). Here an additional soil reinforcement (4) is provided to the connecting rod attached to the bottom plate. A central rod (7) is provided which is connected to the bottom base plate (2) that rests at the excavation/bore bottom or any other desired location. The elongated sleeve (la) which is in the form of an outer pipe surrounds the central road (7) and can slide down freely when the sleeve is pushed down by jacking. The height of the elongated sleeve and the central rod will be almost the same, but less by 3 to 4 cm so that while assembling the steel grip assembly centred around the central rod. The central rod will act as guide during the installation of the augmented foundation.

Once the pit is dug the entire assembly / mechanism is placed at the bottom of the pit then the model is jacked down at the sleeve top. As the jacking is done the load is transferred from the elongated sleeves(la) assembled just above the central rod, resulting in spreading the additional soil anchors/ reinforcements (4) connected to the connecting rods (4a,4b)spread horizontally as the other end is fixed at the base plate which restricts its downward movement. The connection in the base plate is such that it allows the horizontal movement and restricts the vertical movement. Once the elongated top sleeve nears the base plate, the soil anchors would have completely pierced into the soil and will be in fully open position / horizontal open position. Once the soil anchors are fully open, reinforcement cage is lowered into position and concrete is done as in usual practice. For getting a proper grip of this mechanism to the concrete that is placed, protrusions may be provided in the elongated sleeve (la), such that it does not interrupt the working of the mechanism. Fig 6 shows the mechanism in open position.

Fig.7 illustrates connecting system under an exemplary embodiment under the invention which connects the top ring or sleeve (1) and the connecting rod (4a) / soil anchors or the piercing fins formed by the connecting rods. Similar connecting system is provided for the bottom ring (2) and the connecting rod (4b). Here the swivel joint (6) connects the top ring (1) and the connecting rod (4a). The spring (8) provided therein maintains the required tension so that structural grip has the right shape before installing in the bore , but at the same time it allows to spread horizontally as jacking is done by pushing the sleeve, resulting in piercing the soil anchors into the soil around it completely, after inserting the structural grip inside the bore.

ADVANTAGES OF THE INVENTION

1. As these structural grips assembly / mechanisms the models are designed to increase the base area of the pile, every example given above will get the advantage of the soil above the spread area.

2. In an alternative option, the roughness of the pile surface is increased, which was otherwise relatively smooth, thus increasing the frictional resistance and thus the load carrying capacity.

3. These structural grips assembly/ mechanisms will have better load carrying capabilities than their counter part models, and hence the depth and diameter of the piles required will be lowered thereby reducing the cost of the piles considerably. Further in the bulged area of the pile, structural grip will act as a reinforcement.

4. The uplift in the piles are also increased considerably which makes it suitable for wind turbine piles, Buildings, and all known structures that are subject to high uplift.

5. The operation requirement for the placement of these structural grips assembly/ mechanisms is very simple which reduces the time taken, cost, machineries requirements (huge boring rigs) etc which will again reduce the cost of the pile.

6. These structural grip systems can be used in any complex areas like offshore, deep sea projects as the operation is much simplified.

7. As the mechanism is very simple and cost effective, no complicated installing procedures are required and hence can be taught to unskilled laborers also very easily.

8. According to a preferred feature of the invention, unlike most precast foundations, the gripping structure is coupled to the first reinforcement structure, which allows an unintermpted load path between said reinforcement structures so that the forces introduced into the foundation are effectively distributed.

We have bought out the novel features of the invention by explaining some of its preferred embodiments, by way of examples, thereby enabling any person skilled in the art to understand and visualize our invention. It is also to be understood that the above invention is not limited in its application to the details set forth in the above description or illustrated in the drawings. The phraseology and terminology employed herein are for the purpose of description only and should not be regarded as limiting. Although the invention has been preferred embodiments thereof, variations and modifications can be affected within the spirit and scope of the invention as described herein above and as defined in the appended claims.

Claims

We Claim:

1. Augmented foundations using structural grips used for improving pile/anchor properties characterized in that the structural grips comprising of:

a) sleeve or the top ring (1) strengthened with support rods (3), used by the jacking system for pushing the sleeve for expanding the folded connecting rods (4a, 4b) which functions as soil anchors or the piercing fins;

b) soil anchors or the piercing fins formed by the connecting rods (4a) attached to top ring (1), and connecting rods (4b) attached to bottom ring (2) are hinged (5) to one another and will allow them to spread horizontally which forms the soil anchors or the piercing fins when the sleeve is pushed down by the jacking system; and c) connecting system facilitates the connection between the sleeve and the connecting rods wherein anterior part of the connecting rod assembly is joined by means of swivel joints (6) to top ring and the posterior part of the connecting rod assembly is joined by means of another set of swivel joints (6) to the bottom ring (2) and kept in tension by means spring ( 8) that connects connecting rod (4a) and top ring (1) and are designed in collapsible form, so that it can be folded, facilitating easy insertion of the foundation system in the bore and later on it can be expanded horizontally by applying downward force by the jacking system, followed by concreting after lowering the reinforcement cage in the bore.

2) The augmented foundations using structural grips as claimed in claim 1, wherein the sleeve, soil anchors or the piercing fins and the connecting system may be of different configuration and material depending on the foundation system in which it is used to facilitate the penetration of structural grips depending on the site condition, soil (bearing stratum) and load bearing requirements of the structure.

3) The augmented foundations using structural grips as claimed in claim 1, wherein the parts which are exposed to the soil are made by anti-corroding material and those parts which are embedded in the concrete can be made by ordinary load carrying materials, such as Steel or similar material thereby reducing the cost of the system and the anti-corroding material is selected from stainless steel, rubber coated steel members and fluoropolymer coated steel members.

4) The augmented foundations using structural grips as claimed in claim 1, wherein an additional soil reinforcement (4) is provided to the connecting rod attached to the bottom ring (2) to increase the piercing length into the soil and will spread horizontally as jacking is done by pushing the sleeve, resulting in piercing the soil anchors into the soil around it completely and, facilitating the concreting the reinforcement cage that is lowered in the bore.

5) The augmented foundations using structural grips as claimed in claim 4, wherein said assembly / mechanism can be used as reinforcements in under reamed pile bulbs and can be used as soil anchors independently in ordinary piles and once the hole is dug the above assembly / mechanism is lowered to the bottom of the hole before pushing the sleeve downwardly by the jack.

6) The augmented foundations using structural grips as claimed in claim 5, wherein in the case of under reamed piles, the horizontal spread of the mechanism isso designed to match the dimensions of the under reamed bulb area so that it will act as a reinforcement in the under reamed bulb area which is unreinforced in the conventional under reamed, squeezed or any other conventional piles in use.

7) The augmented foundations using structural grips as claimed in claim 1 , wherein an additional soil reinforcement (4) is provided to the connecting rod attached to the bottom plate (2a) and a central rod (7) connected to the bottom base plate (2a) which will rest at the excavation/bore bottom or any other desired location through which the elongated sleeve (la) in the form of an outer pipe that surrounds the central road (7) slides down freely when the elongated sleeve (la) is pushed down by jacking.

8) The augmented foundations using structural grips as claimed in claim 7, wherein the height of the elongated sleeve(la)will be less than the central rod (7) so that it facilitates positioning the steel grip assembly centred around the central rod (7), and acts as guide during the installation of the elongated grip. 9) Method of installation of the augmented foundations using structural grips comprising the steps of:

a) carry out the excavation/boring out as required at the site;

b) insert the structural grips in collapsible form, lower to the bottom of the hole and then expanded into the soil using suspended jacking system by hydraulic ram;

c) insert the reinforcement cage;

d) carry out concreting; and

e) back fill the foundation.

10) The method of installation of the augmented foundations as claimed in claim 9, wherein in the case where, structural grips in collapsible form are attached to the reinforcement cage for later expansion into soil (or bearing layer), the suspended jacking system is inserted after said reinforcement cage with structural grips is inserted and load is applied later on the sleeve, to expand the steel grips making sure that the reinforcement cage is connected to the grips prior to concreting.

11) The method of installation of the augmented foundations as claimed in claim 9, wherein

a) carry out the excavation/boring out as required at the site;

b) insert the structural grips having the elongated sleeve (la) provided with connecting rod (4a), bottom base plate (2a) provided with connecting rod (4b) attached with additional soil reinforcement (4) and a central rod (7) while said bottom plate (2a) will be resting at the excavation/bore bottom;

c) expand the structural grip into the soil by downward pressing of the elongated sleeve (la) by the suspended jacking system so that the elongated sleeve(la) will slide down slowly over the central rod(7) and spread the structural drip horizontally ;

d) insert the reinforcement cage by lowering into the bore and carry out concreting; and

e) back fill the foundation. 12) The method of installation of the augmented foundations as claimed in claim 1 1, wherein protrusions are provided in the elongated sleeve (la), such that it does not interrupt the working of the mechanism by getting a proper grip of this mechanism to the concrete that is being filled.