DESC:Field of Invention:
The present invention is in field of High Strength Boulder Net (HSBN) for rockfall protection. More particularly, the present invention relates to a locking device for holding the two steel wire ropes crossing each other at a junction.

Background of Invention:
A rockfall protection safety net structure is generally installed on the sloping hills or the like. The safety net structure is installed at the site throughout the year and being a metal part it is prone to corrosion. Forces acting on the steel net structure vary round the year. In monsoon there is heavy rain and chances of land slide and/or rockfall. During winter extreme cold temperature and in summer the hot conditions may deteriorate the quality of the netting as well as of the clamp.

Typically, the main component that holds the two steel wire ropes, which are crossing each other at a junction, is a metal clamp. Conventionally, the metal clamps which are being used are coated with anti-corrosion coating which may get damaged during installation. Further, the anti-corrosion coating may also get damaged over a period of time, leading to corrosion which may increase the chances of a fatal accident. The clamps are the main component and it is noticed that most failures occur at the junction. Therefore, a strengthening of the junction requires provision of corrosion free and stronger clamps. The current invention provides stainless steel clamps which is a stronger corrosion resistant material.

EP3063334 described a rockfall wire mesh safety net, wherein the wire mesh is woven from bent wires or wire strands of high tensile steel and is held on to the soil surface with the help of spike plates. The spike plates are pressed against the soil surface by means of nuts or the like. The nuts used as anchoring elements. The spike plates are distributed on the wire mesh and hence pressed against the soil surface along and across the wire mesh. There is however, a problem in this arrangement of spike plate. There might be catastrophic failure if the nut comes out of the soil causing the wire mesh and the rocks/debris to fall down.
KR100859209B1 described a shock absorbing rockfall safety net, wherein the wire ropes with springs are used to form a shock absorbing network between two successive meshes. Additionally, in the mesh where the shock absorbing springs are installed, the wire ropes are passed through a cylindrical tube, wherein there are clamps and shackles which are used to secure the arrangement. There is however, a problem when using too many types of equipment. This increases the complexity, installation time and costs.

KR200141791Y1 describes a rockfall protection net, wherein the steel wire ropes pass over each other. The steel wires ropes passing over each other are secured by fixtures and U bolts. This steel ropes passing through the fixture, wherein there are grooves engraved in the fixture and there are holes to pass the U bolt. There is however, only one U bolt which is tightened at two points. As a result in situations of heavy loading the fixture and U bolt may not sustain the load and complete system might fail. Also there are chances of rope slippage during extreme loads.

DE202014101406U1 discloses a safety net mesh structure without any clamps and comprises of a plurality of non-metallic (UHMPE) strands, wherein the strands cross through each other at alternate crossover points.This may lead to a situation where the strands may slide over each other and hence joint may shift. There is no clamp to prevent the slippage of clamps passing through each other.

In EP2260150B1 discloses a rockfall protection safety net designed to suit the variation in the slope of rock masses by providing wound wire seizing at variable intervals depending on the slope and the impact. The rockfall protection method described here, wherein the wire net comprises an array of longitudinal wires arranged side by side and each intertwined with at least one respective adjacent longitudinal wire, the rope members being intertwined or interlaced with at least one adjacent wire material of the wire net. Though the crossing wires are interlaced, there is risk of slippage.

KR2002528910000 discloses an assembly for prevention of rockfall whereby, the junction or crossing point of wire is enclosed in a clamp-like assembly comprising grooves for horizontal and vertical ropes. However, the intersection point or crossing point of the steel ropes appears to be a simple overlay of the steel ropes. The intersection may be a weak intersection since there is likelihood that the steel ropes might slide over each other and destabilise the intersection leading to an overall weak net. Further, it appears that the clamp-like assembly is made of iron, which is prone to corrosion. The corrosion may lead to weakening of the entire structure and eventual failure of said structure.

Significant work to overcome above issues has been done in the past. However, despite significant advancement in technology, the need continues for efficient ways to obtain further improvement in this field. Such a need is met by present invention described herein.

Objects of Invention:
The object of the present invention is to provide a novel High Strength Boulder Net (HSBN) for rockfall protection with improved safety features which would overcome the problems as described above.
The present invention seeks to overcome the problems above by maximizing the area of contact between the steel wire ropes (which face the initial loading) and the bolted clamps to whom the load is transferred.
Summary of Invention:
In accordance with above object, the present invention provides a High Strength Boulder Net (HSBN) for securing falling rock masses, with improved junction security and reduced maintenance of the rockfall protection safety net.

In an aspect of invention, steel wire ropes are placed vertically and horizontally wherein the wire ropes are tucked in each other forming a joint, wherein the joint is secured by a corrosion resistant locking device which improves the overall safety and joint strength of the net and the maintenance at the site due to corrosion being drastically reduced.

Brief Description of Drawings:
Fig. 1 illustrates typical terrain where road is being constructed.
Fig. 2 illustrates an array of high strength boulder netting.
Fig. 3 illustrates the tucking of the wire ropes.
Fig. 4Aillustrates the locking device wherein the ropes pass through it.
Fig.4Billustrates another view of the locking device where groove for passing the ropes is visible.

Detailed Description of Drawings:
Fig. 1 illustrates a typical terrain consisting of a hill or mountain and through those mountains a road (1) is being constructed. For the road construction one must have fairly levelled portion (2). The cut face (3) typically comprises of earth and/or rocks. To make road through the hill it requires that rocks and/or earth be cut and moved to another place, as result of which there is weakening of the integrity of the cut face (3). The resultant weakening increases chance of rockfall which may lead to fatal accident. This rockfall may be prevented by using High Strength Boulder Netting (HSBN) (4) made of steel wire ropes. The High Strength Boulder Netting (HSBN) (4) is secured at the hill top (5-6) using an anchor or spike (7).

The High Strength Boulder Netting (HSBN) (4) is illustrated in Fig. 2. The High Strength Boulder Netting (HSBN) (4) comprises of a plurality of vertical steel wire ropes(8) and horizontal steel wire ropes (9) whereby the vertical (8) and horizontal (9)steel wire ropes intersect or overlap on to each other at intersection point (10). The intersection point(10) is further secured with a locking device (11).The locking device (11)overlays the intersection point(10) thereby securing the intersection and/or overlap point (10).

With reference to Fig. 3, the intersection point 10 comprises ofvertical (8) and horizontal (9) steel wire ropes crossing each other at single point forming a joint (10) wherein at the joint the ropes are tucked in or overlap on each other

Now referring to Figs. 4A and 4Bwhich illustrate the locking device (11) which overlays the intersection point(10). The locking device (11) is manufactured using stainless steel, wherein the locking device is constructed using two different plates viz. Upper plate (15) and lower plate (16) as shown in Fig. 4B.The two plates (15) and (16) are joined together using nuts (13) and bolts (12). The bolts (12) can be tack welded or non-welded to the upper plate (15). This eases the prefabrication process wherein the alignment of upper plate (15) and the lower plate (16) is highly important. The locking device is designed in circular shape wherein at each quadrant of the circle there is one nut (13) and bolt (12). However number of nuts and bolts may vary per quadrant depending on the size and strength requirement PCD of the clamp may vary from 40mm to 45mm and plate thickness from is 1mm to 1.5mm based on strength requirements, Socket Head Allen Bolts M6X20, Hex Nuts, Plain Washer Spring Washer are of M6(Range can be covered of M-4 to M8).

The arrangement of nuts and bolts is shown in Fig. 4A. Instead of nut-bolts, rivets could also be used for fastening the upper plate (15) and lower plate (16). The nuts (13) are torque tightened appropriately. This kind of locking device arrangement saves time of fabricating the steel wire rope net.

Detailed Description of Invention:
Described herein is a High Strength Boulder Net (HSBN) for securing falling rock masses and preventing rockfall, with improved junction security and reduced maintenance cost.

In an embodiment of the invention, the High Strength Boulder Net (HSBN) is made of horizontal and vertical wire ropes spaced in such a way that they cross each other at a point forming a net-like structure. The crisscrossing steel ropes form intersections, said intersections/overlap are secured by a locking device. The locking device prevents slipping of ropes over each other thereby increasing the life of the net, improving joint strength and ensuring safety.

The overall area of contact between wire rope and the clamp is far higher than that available in the prior art which prevents slippage and provides high degree of safety for the rockfall protection net. Furthermore this arrangement provides for a simple arrangement which can be implemented with ease at the project site.

In accordance with above embodiment, the intersection point of the horizontal and vertical steel rope is overlaid with an appropriately shaped locking device. In shape of the locking device can be designed based on the requirements of strength and size, preferably the shape of the locking device is circular.

The locking device consists of an upper plate and a lower plate. The upper and lower plates are torque tightened together using a nut and bolt fastening arrangement. The bolts may be welded on to the upper plate. The welding reduces the chances of misalignment of the upper and lower plate which is essential for efficient securing of the intersection. The nut is then screwed or torque tightened onto the threaded portion of the bolt. Alternatively, the upper plate can be provided with a plurality of built-in bolt like threaded portion over which the nuts can be fastened by screwing or by torque tightening.

In accordance with one of the embodiments, the locking device is divided in four quadrants. Each of said quadrants is provided with a bolt tack welded onto the upper plate. However, the number and position of boltscan vary depending on size and strength requirements.

The locking device is provided with grooves for passing the horizontal and vertical steel ropes. The grooves tend to hold the vertical and horizontal ropes tightly thereby preventing any slippage of ropes hence securing the intersection point of the vertical and horizontal steel ropes.

In accordance with above embodiment, the locking device is fabricated from stainless steel.

In accordance with above embodiment, at the intersection point the crisscrossing horizontal and vertical ropes form a rope-in-rope connection. Accordingly, the horizontal and vertical rope is tucked-in or overlaps on to each other to form a non-slipping joint.

Example
The invention will in the following be described with reference to the enclosed figures, where the steel wire ropes tucked in or overlapped into each other forming a joint, wherein the joint is secured by a stainless steel locking device. The steel wire ropes and the locking device are the parts of High Strength Boulder Net (HSBN) for rockfall protection.

The joint in the rockfall protection net was established by using steel wire ropes of 9mm each passing through the clamp. The joint was tested using IS 2266 and the breaking strength of the wire rope estimated to be 47kN(± 2%). The locking device is manufactured of 1mm/1.5mm thick stainless steel plates with one 6mm bolt in each quadrant

Tensile tests were carried out on locking device of thickness 1mm to1.5mm. Two ends of the first rope fixed in jaw of the tensile testing machine and other two ends of the second rope fixed at the opposite end. The ropes were pulled till the failure occurs. During the test it was observed that steel wire ropes were broken and locking device was successful in securing the joint. Slight bending of the plates of the locking device was observed. Average breaking strength of the locking device was observed to be 4127 kgf.
,CLAIMS:
1. A high strength boulder net (HSBN)(4), for securing falling rock masses, comprising of vertical ropes (8) and horizontal ropes (9) which crisscrossing each other to form a net like structure, wherein, at the intersection point (10), the crisscrossing vertical (8) and horizontal ropes (9) form a rope-in-rope connection to form a non-slipping joint

2. The high strength boulder net (HSBN) as claimed in Claim 1, wherein, the intersection point (10) of vertical (8) and horizontal (9) ropes is overlaid with a locking device (11) to prevent slipping.

3. The high strength boulder net (HSBN) as claimed in Claim 2, wherein, the locking device comprises of an upper plate (15) and a lower plate (16) joined together with nuts (13) and bolts (12).

4. The high strength boulder net (HSBN) as claimed in Claim 3, wherein the bolts (12) are optionally tack welded.

5. The high strength boulder net (HSBN) as claimed in Claim 3, wherein the bolts (12) are optionally non-welded to the upper plate (15).

6. The high strength boulder net (HSBN) as claimed in Claim 1, wherein, the locking device comprises of an upper plate (15) and a lower plate (16) which are optionally joined together with rivets.