AU539065B2 - Articulated erosion control system - Google Patents

Description

Descr iption

Articulated Eros ion Control System

Technical Field

The present invention relates to the control of soil erosion especially on the sides of rivers, drainage canals and riverbeds, on levees, beaches and the like. The present invention more particularly relates to an articulated erosion control system comprising a plurality of blocks, each of which is connected to the adjacent block by an interlocking connection provided by the blocks themselves which interlocking connection maintains horizontal block placement yet allows articulated movement in all directions of the blocks with respect to one another allowing conformation of the overall block system to the underlying terrain.

Background Art

Erosion of land is a problem generally accompanied by water flow at the interface of the land and the water such as on the side of a r iverbed or on a beach. Erosion can also occur as a result of rainfall as it proceeds through a particular basin to the river which emσties that area. Erosion is prevented in a natural sense by the growth of trees, grass, vegetation and the like with their root systems functioning to consolidate the underlying soil and prevent the mechanical erosion by both water and wind, but mainly water.

The natural vegetation is removed purposefully in many instances as when streams are channelized, or cleaned, or when levees are reformed. Other times vegetation removal and resulting erosion is natural, caused by flooding or the mechanical action of streams, rivers and generally by natural water flow.

Land which has been stripped of the natural vegetation is highly susceptible to erosion by wind and rain since the consolidation provided by vegetation is missing. This occurs on sloped terrain, as well as on terrain which is flattened.

The erosion problem is compounded by the removal of forrests, overgrazing of land, burning, construction of highways and the like, and the channelization of streams.

Planting rapidly growing vegetation on areas which have been stripped is sometimes successful but usually only where the vegetation grows rapidly and extensively enough so that the soil is protected. In areas where water is continually flowing such as on riverbanks, the growth of vegetation can usually not be done quickly enough to prevent erosion. Various systems of revetment have been used to augment or replace vegetation as an erosion barrier. The art has used loose fill barriers (riprap), continuous paving mats (some with weep holes to relieve pore pressure) and porous paving mats to control erosion.

"Riprap" which is known for control of erosion is basically a barrier or coverage comprising a plurality of large chunks of concrete (obtained, for example, in salvage operations) which are dumped in a particular area. The concrete chunks are usually of random size, with some so large as to not provide protection and washouts occur underneath. Further, the placement is often random, not adequately covering the subject area. Solid continuous paving mats of concrete are highly costly because of the extensive amount of concrete required, the difficulty and costs of installation, and the problems of hydrostatic pore pressure which are created once the concrete is in place.

Paving blocks of concrete and other materials are known. Flexible porous concrete mats have been used as an erosion controlling protective surface.

Different patents directed to using revetment blocks and structures for preventing soil erosion have been issued. U.S. patents 242,689

306,251 314,022 541,815 572,762 984,121

994,999 1,039,579 1,162,499 1,379,440 1,597,114 1 , 636 , 114 1,691,848 1,772,821 1,822,602 1,834,060 1 , 847 , 852 1,927,834 1,939,417 1,991,196 1,993,217 2,008,866 2,047 197 2,143,461

2,159,685

2,221,416

2,295,422 2,454,292

2,577,170

2,662,343

2,674,856

2,876,628 3,096,621

3,176,468

3,210,944

3,301,148

3,343,468 3,344,609

3,386,252

3,421,417

3,597,928

4,227,829 disclose blocks and erosion control systems. The disclosures of the above U.S. patents are incorporated by reference herein.

U.S. Patent No. 4,227,820 discloses a device comprising a matrix of cellular concrete blocks, each of which has internal passageways for cables to pass therethrough and interconnect a matrix of concrete blocks. The free ends of the cables are anchored into the ground after which operation the soil is spread over the blocks to reinforce surface thus controlling soil erosion.

U.S. Patent 4,152,875 discloses a ground covering with adjoining plates which are clamped together by tensioning elements extending through the plates and parallel to them. Nijdorn in U.S. Patent 3,922,865 describes a mattress having a filter cloth with metal bars woven thereinto. Soaced concrete blocks are connect these bars .

Appelton in U.S. Patent 3,903,702 teaches the use of a revetment structure with similar inter f i tting units which form a flexible mattress. The units are provided with a series of interconnected ribs which make opposite sides of the units reflections of each other.

U.S. Patent 3 , 597 , 928 discloses the use of porous flexible supporting sheets with mat of blocks which are placed on these sheets. Each mat consists of a plurality of blocks with drainage passageways therethrough and the blocks are secured to the sheets by adhesive means.

Nelson in U.S. Patent 3,386,252 discloses a riprap structure for waterways, comprising rectangular blocks interconnected by a rod which extends through the blocks to provide for hooking the blocks at d iagonally opposite corner ends and forming a matrix. Dixon, U.S. Patent 2,876,628 discloses a rapidly sinking articulated revetment for riverbanks compr is ing rigid blocks interconnected by flexible cables. The upper surface of each block has recesses from which openings extend through the whole block to provide for water passageways. Louckes in U.S. Patent 2,674,856 teaches the use of a similar flexible revetment mat which flexibility comes from the use of reinforced wires extending continuously from one concrete block to another to form a mattress for protection of river banks from erosion. U.S. Patent 2,159,685 describes a concrete riprap consisting of precast units connected by interlocking bars which pass through the orifices in the body of each unit.

A revetment in U.S. Patent 2,008,866 comprises a number of rectangular concrete blocks arranged diagonally and hooked together by crossed rods to form a mat. Mason in U.S. Patent 1,987,150 teaches the use of a revetment containing filled asphalt in a certain proportion. A mat of such asphalt is placed adjacent a mattress consisting of slabs interlocked by cables or clips passed through the rings at each corner of a slab.

U.S. Patent 1,359,475 describes a seawall construction comprising concrete panels with mating tongues and grooves at their edges and locked together by metal rods passing through the notches in the tongues and grooves.

Edinger in U.S. Patent 1,164,708 discloses an enbankment protection construction composed of interlocking rectangular concrete slabs with integrally made hook flanges and interengaging keys and sockets for locking the slabs in a mattress.

Edinger's U.S. Patent 1,164,707 discloses a flexible concrete slab revetment construction composed of concrete slabs with integrally formed concrete joints interlocking the slabs, these slabs being preferably of a triangular contour.

U.S. Patent 763,171 teaches the use of enbankment linings consisting of brick or stone blocks interlocked by wires passing through the perforations in the block bodies.

Villa in U.S. Patent 554,354 discloses a covering for protecting banks from erosion, this cover ing comprising cement or terra-cσtta prismatie plates interconnected by wires which pass through the plates to form rows of units adapted to cover riverbeds and banks, and free ends of wires are fastened to trees or piles driven into the bank.

Flexible mats, though generally more expensive than riprap or continuous paving barriers, are usually more stable. Flexible mats are not as prone to undercutting erosion, by water, and provide greater relief for hydrostatic pressure. Flexible mats do exhibit failure, however, when individual elements of the mat are displaced by hydrostatic pressure or wave action, for example.

Applicant has provided an improved flexible mat structure which relieves hydrostatic pressure, conforms to the underlying surface, and retains its structural integrity. The noted advantages may be achieved at a cost which is competitive to known structures.

Disclosure of Invention The present invention provides a lock block and key block system which allows articulated connections to be formed between the lock block and the key block so that a mat of the key blocks and lock blocks can be formed in the field by the interlocking of the blocks themselves without extraneous connectors, wires, cables, and the like. A mat formed with the preferred embodiment of the apparatus of the present invention retains its interlocking integrity even after temporary connections which might be used in placement of a mat assembly have been eroded or corroded away. The preferred embodiment provides at leas t a lock block having sockets spaced around the periphery thereof which can be connected in two radial directions to an adj acent pair of blocks . The connect ion between blocks is provided by a socket on one block and an enlarged head on the ad jo ining block which occupies the socket and allows the two blocks to articulate with respect to one- another in a pivotal fashion. The sockets and locking heads provide narrowed protions which discourage disassembly by horizontal movement once the blocks are in the position. Sidewalls of the sockets and locking heads can be bevelled to allow for the surfaces of adjoining blocks to form angles with respect to one another as when the blocks occupy a curved contour, dome, valley, or like irregularity in terrain. In the preferred embodiment, the lock block is hexagonal having rounded sockets outcropping on three of the peripheral sides. The remaining two sides can have immediately inside their surface vertical openings or passageways which might allow for hydraulic flow, the passage of vegetation, and the accumulation of soil and silt. The key block in the preferred embodiment is a three-armed key block having a central hub with three locking arms projecting radially (preferably equiradially-spaced) with enlarged locking heads being provided at the tip of each arm. The center of each locking head and the center of each locking arm form respectively equilateral triangles of identical dimension on each key block and on each lock block. In the preferred embodiment, the equilateral triangluar geometric placement of the key block socket centers and the lock block locking head centers insures interlocking points- of articulation between adjacent blocks. Flexibility in each direction is provided and in an alternative embodiment a twist-in lock assembly is provided which allows easy assembly- of adjacent blocks yet discourages substantial vertical relative movement therebetween thereafter which might result in disassembly. The present invention provides an articulated erosion control system having at least one lock block and a pair of key blocks. The key blocks are connectable to the lock block independently in an interlocking fashion with each of the lock blocks, with the key block-lock block connections being in separate directions and in an articulated fashion. This allows multi-directional flexibility which allows an entire mat system formed of the blocks to conform easily to changes in terrain both with regard to curvature and irregular size.

Thus, it is an object of the present invention to provide a three dimensional interlocking mat assembly for erosion control.

Still another object of the present invention is to provide an articulated erosion control system having flexibility in every direction. Another object of the present invention is to provide an interlocking mat for use in erosion control system with the interlocking connections being spaced in an equilateral triangular fashion.

Still another object of the present invention is to provide a twist-in lock for attaching adjacent blocks which allows easy assembly but discourages disassembly due to relative vertical movement of adjacent blocks.

A further object of the present invention is to provide an articulated erosion control mat system which can be easily adapted to disposable sling type lifting and placement. Another object of the present invention is to provide an alternative wire interconnecting system for assembling a plurality of adjacent blocks forming an overall articulated erosion control system.

Still another object of the present invention is to provide an articulated erosion control system useful in the controlling of waves at seashores, surfs, and the like. It is another object of the present invention to provide an articulated erosion control system having a plurality of blocks which can be interconnected on sight without the use of further connection devices than the blocks themselves. Still another object of the present invention is to provide an overall articulated erosion control system which easily conforms to changes in terrain relief and shape.

Still another object of the present invention is to provide an articulated erosion control system which allows vegetation to grow through the system.

Another object of the present invention is to provide an articulated erosion control system which can use but does not rely upon a mat or other interconnection between adjacent blocks for its long term performance.

Brief Description of the Drawings

For a further understanding of the nature and objects of the present invention, reference should be had to the following detailed description, taken in conjunction with the accompanying drawings, in which like parts are given like reference numerals and wherein:

Figure 1 is a perspective view of the lock block portion of the preferred embodiment of the apparatus of the present invention; Figure 2 is a perspective view of the key block portion of the preferred embodiment of the apparatus of the present invention;

Figures 3A-3C are sequential views illustrating assembly of the key block and lock block portions of the preferred embodiment of the apparatus of the present invention and further illustrating the wave control embodiment of the key block portion;

Figures 4A, 4B are sectional schematic views illustrating the bevelled sidewall portions of the key block and lock block;

Figure 5 is a top view of the wave control cone embodiment of the lock block portion of the preferred embodiment of the apparatus of the present invention;

Figure 6 is a top view of the wave control cone embodiment of the key block portion of the preferred embodiment of the apparatus of the present invention;

Figure 5A is a sectional view taken along lines 5A- 5A of figure 5;

Figure 6A is a sectional view taken along lines 6A- 6A of figure 6;

Figure 7 is a top view of the art iculated erosion control mat system of the present invention illustrating a plurality of key blocks and lock blocks interconnected;

Figure 8 is a perspective view of a plurality of key blocks and lock blocks interconnected to provide the articulated erosion control system of the present invention and illustrating the vertical support system portion thereof;

Figure 8A is a perspective view of the hanger portion of the preferred embodiment of the apparatus of the present invention useful in the embodiment of figure 8;

Figure 9 is a sectional view of the preferred embodiment of the apparatus of the present invention during lifting;

Figure 10 is a schematic view illustrating lifting of the preferred embodiment of the apparatus of the present invention using a flexible mat to lift.

Best Mode for Carrying Out the Invention In figures 1 and 2 there is seen respectively the lock block 20 portion of the preferred embodiment of the apparatus of the present invention (Figure 1) and the key block 50 portion of the preferred embodiment of the apparatus of the present invention (Figure 2). As will be described more fully hereinafter, each block 20, 50 can be integral and blocks 20, 50 attach together by interlocking. The blocks 20, 50 so provided interlock to form an enlarged articulated mat 10 which can be seen in figures 7-8, which mat allows articulation of the individual blocks and some relat ive vertical movement, yet maintains horizontal spacing thus allowing the mat 10 to conform to the underlying terrain.

The assembled articulated erosion control system 10 can be l if ted (as during installation) by a spreader bar or crane and assumes a curved position characteristic of a flexible sheet supported at its ends (see figures 9 and 10).

Figures 1 and 2 show more particularly the construction of lock block 20 and key block 50. In figure 1 can be seen lock block 20 which provides upper and lower coplanar and preferably parallel surfaces which terminate at a peripheral terminal sidewall. A hexagonal shape is preferable with hexagonal sidewalls 21-26 being shown in figure 1. Three alternate sidewalls 22, 24, and 26 provide sockets 30-32 which are open recesses at surfaces 20S of block 20 as well as being open recesses at sidewalls 22, 24, and 26 and at the bottom 20B of block 20. As will be described more fully hereinafter, each socket 30, 31 and 32 provides a place for the interlocking connection of key block 50 thereto with three key blocks being attachable respectively at sockets 30-32 of each lock block 20 to form the articulated erosion control system 10 as shown in' figures 7 and 8. The upper surface 20S of block 20 provides an etching of radial V-shaped channels 39 and circular Vshaped channels 40 which provide recesses that will during operation gather soil allowing natural vegetation to grown on the surface of block 20 further enhancing erosion control and aesthetics.

A plurality of vertical preferably cylindrical channels 34-37 are provided through block 20 which allow hydrostatic flow through block 20 as well as allowing the growth of vegetation therethrough which enhances the anchoring of block 20 to its final position.

Figure 2 shows more particularly the construction of key block 50. Key block 50 comprises a central hub 52 from which extend radially a plurality of spaced locking arms 55-57 with three being shown in the embodiment of figure 2.

Each locking arm 55-57 has attached at outermost tip portion to an enlarged locking head 60-62 respectively with each being slightly smaller than but correspondingly sized to register and fit within one of sockets 30-32 provided on lock block 20. Vert ical channels 65-67 are provided respectively through heads 60-62 to allow fluid flow therethrough for hydraulic relief. Also vegetation can grow through channels 65- 67 to aid in securement of block 50 to its underlying terrain. Each socket 30-32 may provide at its lowermost portion an annular rib 45 with a corresponding annular recess 68 being provided around the bottom of each locking head 60-62. This combination provides a stop which disallows a drop through of locking heads 60-62 through its respective socket. This connection is seen in figure 8 and once this assembly is completed the upper surface 20S of block 20 and the upper surface 51 of key block 50 would be substantially coplanar as shown in the drawings in figure 8. An additional feature, not shown in the drawings, may be used to retain the assembled lock blocks 20 and key blocks 50 joined in the desired coplanar relationship. A flexible adhesive may be placed in the joint formed by locking heads 60-62 and sockets 30-32, for example, at the point of contact between annular ribs 45 and annular recesses 68. A continuous bead may be used or the application of adhesive could be discontinuous. Any suitable rubber-like or flexible adhesive could be used. A one-component polyur ethane adhesive manufactured by Sika Corporation, Lyndhurst, N.J. under the trademark SIKAFLEX has been found to be satisfactory.

Figures 3A-3C show more particularly the assembly of a single key block being placed into three lock blocks 20.

In the embodiment of figures 3A-3C and in those sequential views shown, note the key block being provided as designated by the numeral 80 with key block 50 having a wave control cone 90 portion which extend upwardly a distance of, for example, three times the overall height of the key block 80 itself. Wave control cone 90 can provide a truncated top 92 which gradually contours to meet locking heads 95-97 with each locking head being provided with a vertical channel 100-102. Though the wave control is shown, in Figures 3A-3C, as a truncated cone 90, it will be appreciated that another equivalent shape could also be used, such as a cone, a cylinder, a pyramid, a truncated pyramid or other polyhedron.

In the embodiment of figures 3A-3C, the axis of each locking head 95-97 is skewed as shown in figure 4A. This requires that the assembly of key block 80 into lock blocks 20 be in downward and rotational

(spiral) fashion which is shown by the curved arrow 81 in figures 3A-3B. Sockets 30-32 of lock block 20 aresimilarly skewed with the inner curved sidewall 42-44 of each socket 30-32 being angularly disposed with respect to the bottom 20B of lock block 20. The connection between the lock blocks 20 and key block 80 is accomplished by joining a key block 80 simultaneously to three lock blocks 20. The three lock blocks 20 are placed in an array having the proper spacing and key block 80 is positioned over the array and joined thereto by a vertical helical motion, as shown in figure 3C. To assemble an entire mat 10, two rows of lock blocks 20 are laid out in an array similar to that shown in figure 7, a row of key blocks 80 is then assembled into the array by helical joining, as shown in figure 3C. An adjacent third row of lock blocks 20 is then laid and a second row of key blocks 80 is assembled into the lock block 20. Subsequent laying of additional rows of lock block 20 and key block 80 is repeated until construction of the mat 10 is complete. In figure 4A there can be seen a g ap G which is provided due to the differing angular orientations of the inner curved wall 42 of socket 30 as compared with the angular orientation of the outer wall portion of enlarged locking head 96. This gap G allows for adjustment when an entire mat 10 of assembled lock block 20 and key blocks 50 are lifted as shown in figures 9 and 10. Another embodiment of this adjustable feature when the mat 10 is lifted is seen in figure 4B where the locking head 96 of key block 50 would be of a shorter height H2 than the height HI of the lock block 120 with the gaps G being also shown between and arrows 110 illustrating movement of the upper portion of adjacent lock blocks 20 toward the locking head 96 of key block 80. The presence of the gaps G allow flexible articulated movement of the mat 10 to conform to the shape of the substrate or support on which the mat 10 is placed. The mat 10 can often accommodate to hills, curves and depressions without the necesity of forming special arrays to fill or fit within spaces in the total array.

Figures 3C illustrate a completed connection of key block 90 into three lock blocks 20. Once this combined downward and rotational connection (actually a spiral or helical movement) is completed, it will be apparent to one skilled in the art that vertical movement between key block 80 and lock block 20 will be difficult or at least discouraged. Arrow 111 in figure 4A illustrates the problems which locking head 96 would have in moving upwardly from socket 30. The rotational movement as illustrated would be easy to achieve manually upon assembly, but the same helical movement of locking head 95-97 would not normally be duplicated by nature as by hydraulic action, waves or the like to a mat 10 once it is in place. In figure 5 and 6 are illustrated top views of the wave control embodiment 125 of lock block 120 as well as the wave control cone embodiment 90 of key block 80. In the embodiment of figures 5-6, each recess 30-32 is generally circular providing a center with an equilateral triangle "T" being formed by passing a line through the center of each recess and parallel to the adjacent face 22, 24, 26. The articulated connections between adjacent blocks 20, 50 or 20, 80 or 120, 80 would also fall on these sides of equilateral triangles. In figure 6, T-2 designates an equilateral triangle formed by intersecting each locking head 95-97 at its center with a line perpendicular to the radial center line of each locking arm 82-86. These triangles T and T-2 will have common sides when the lock block and key block are assembled with the interlocking connections of an entire mat forming an array of equilateral triangles.

In figures 5A and 6A are seen sectional views illustrating more particularly the construction of each of lock block 120 and key block 80 with lock block 120 in figures 5 and 5A providing a wave control cone 125 having a truncated top 126.

Figures 7 and 8 illustrate a connected assembly 10 of articulated erosion control system 10 with a plurality of lock blocks 20 being shown assembled with a plurality of key blocks 50. Note that an articulated erosion control system is formed which allows slight relative movement of the blocks 20, 50 with respect to one another allowing it to conform to irregularities in the terrain and allowing slight degrees of vertical and horizontal movement between each block. While three-way locking is shown here, two-way and four-way locking could also be used. For example, lock blocks with four sockets and key blocks with two locking tips could be used.

In figures 8-8A there can be seen the use of hangers 150 which are substantially U-shaped providing parallel side rods 151, 152 each of which is provided at its upper portion with an eyelet 154, 155 with each eyelet providing an opening 156 through which a suitable hanger line 200 can be placed with a network of hanger lines being used to interlace the provided hangers 150 in such a fashion as to allow the entire mat to be supported as shown in figure 9, during lifting of mat assembly 10. Alternatively, mat 10 could be supported from below using a continuous flexible sheet or net which would support mat 10 in a vertical direction with the interlocking connection taught herein maintaining horizontal spacing. In figures 7 and 10 an underlying supportive sheet

(preferably perforated to allow for fluid flow therethrough) is schematically shown as 210.

Figure 10 schematically illustrates a support cable 160 attaching to beam B at eyelet 162 with bottom eyelets 164, 165 also being provided with side support cables 166, 168 wh ich would attach to hanger l ine 200 and thus support mat 10 during lifting and installation onto an area which needs erosion control.

Since blocks 20 , 50 provide themselves the interlocking necessary to maintain the integrity and connections of mat 10, erosion control in a particular area will be maintained even after sheet S or cable 200 with hangers 150 have corroded away as occurs. Thus, the utility of sheet S or hangers 150 and cable 200 could be primarily for installation, assembly, transportation and l ifting , wi th the interlocking mat above taught serving by itself to control erosion and wave action.

Because many varying and different embodiments may be made within the scope of the inventive concept herein taught, and because many modifications may be made in the embodiments herein detailed in accordance with the descriptive requirement of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.

What is claimed as invention is:

Claims (22)

Claims

1. An erosion control mat having: a. a first block having a plurality of open-ended sockets spaced about the periphery thereof; b. a second block connectable to the first block, the second block having a plurality of locking arms spaced about and integrally formed with a central hub; c. connection means including at least one of the sockets and a corresponding one of the locking arms cooperating to form a connection between the first block and the second block, the connection maintaining horizontal spacing of the blocks.

2. The erosion control mat of claim 1, wherein the first block is hexagonal and has three sockets spaced about the exterior edge portions thereof.

3. The erosion control mat of claim 2, wherein the second block has three locking arms.

4. The erosion control mat of claim 3, wherein the locking arms on said second block are equiangularly spaced.

5. The erosion control mat of claim 1, wherein each of the sockets has, at least in part, a recess portion adjacent to the periphery of the first block, the socket being narrowed at its intersection with the edge of the block, and each of the locking arms having, at least in part, a locking head portion at its periphery and a neck, narrower than the head, connecting the central hub with the head portion, the head portion cooperating to occupy the recess with the narrowed neck occupying a position at the narrowed portion of the socket.

6. The articulated erosion control mat of claim 1, wherein the first block has an integral body defined by upper and lower surfaces and a peripheral terminal wall, and wherein each of the sockets are open-ended and communicate with said upper and lower surface with the terminal wall.

7. The articulated erosion control mat of claim 6, further having relieved means on the surface of the first block for collecting soil on the surface of the first block during use thereof.

8. The articulated erosion control mat of claim 6, further having at least one vertical channel formed through the first block.

9. The articulated erosion control mat of claim 1, wherein the second block has an integral body defined by upper and lower surfaces and a peripheral wall, the body having an inner central hub portion with the locking arms projecting radially therefrom.

10. The articulated erosion control mat of claim 9, further comprising at least one vertical channel formed through the second block.

11. The articulated erosion control mat of claim 9, further having relieved means on .the surface of said second block for collecting soil on the surface of the second block during use thereof.

12. The articulated erosion control mat of claim 1, wherein the sockets and the locking arms cooperate to provide an outer locking head similarly sized, but differentially smaller, than its corresponding socket, wherein generally vertical movement of a locking head into a corresponding socket effects an interlocking of the second block on the first block with subsequent substantial horizontal movement being prevented.

13. The articulated erosion control system of claim 1, wherein the connection means is responsive to vertical movement of the second block to the first block when the locking arm and the socket are vertically aligned, the blocks having means to position the blocks with the block surfaces substantially coplanar.

14. An articulated erosion control block mat comprising: a. a first lock block having an upper surface and a lower surface spaced therefrom with a peripheral terminal wall defining the edge portion thereof; b. a plurality of locking sockets spaced peripherally about said lock block with each of said sockets being open and communicating respectively to said upper surface, the lower surface and the peripheral terminal wall, the portion of the wall at the edge of the socket defining a narrowed portion of the socket; and c. at least one key block having an upper surface and a lower surface spaced therefrom and further comprising a central hub with a plurality of locking arms extending radially from said hub with each of said arms providing at its terminal end portion an enlarged head having a thickened portion which is thicker than the narrowed portion of the sockets, the locking head and the socket being similarly sized and the locking head being slightly smaller allowing the placement of the head into the socket and vertical movement therebetween, but disallowing substantial horizontal movement once the head is placed within the socket.

15. The mat of claim 14, wherein the axis of the sockets and the heads are skewed with respect to the surfaces of the first block, forming means to connect the first block and the second block by a helical motion, thereby limiting further relative vertical movement between the first block and the second block.

16. The erosion control mat of claim 14, wherein the blocks have projections extending upwardly from the upper surfaces thereof to absorb wave energy.

17. The erosion control mat of claim 14, wherein the blocks are formed of cast concrete and contain wire reinforcing, the wire reinforcing extending outwardly beyond the walls of the blocks and forming loop means for joining adjacent blocks.

18. The erosion control mat of claim 14, wherein the mat is provided with wire loops supporting the blocks therein and wherein the loops have eyelet through which may be threaded supporting cables for lifting and installing the mats.

19. The erosion control mat of claim 14, wherein the mat has a flexible adhesive joining the blocks at the socket connection between the lock block and key block.

20. The erosion control mat of claim 14, wherein the blocks are mounted on a water permeable sheet.

21. A system of interlocking blocks for an erosion control mat wherein the blocks are connected by interfitting head-in-socket joints formed as integral parts of the blocks and wherein successive blocks are linked together through connections to common blocks to form a contiguous mat, the head-in-socket joints being sufficiently flexible to allow articulated movement of the mat to conform to a supporting surface, but preventing substantial displacement of individual blocks in the mat.

22. The mat of claim 21, wherein the blocks include a plurality of hexagonal lock blocks having upper and lower surfaces, the upper and lower surfaces being bounded by six equally sized perpendicular walls, three alternate walls of the lock blocks having sockets therein, the sockets extending perpendicularly through the upper and lower surfaces and communicating through the alternating walls at the periphery of the lock blocks, the sockets being narrow at the point of communication with the perpendicular walls and enlarged in the interior area of the lock blocks, the lock blocks having relieved channels on the upper surfaces of the lock blocks which can accumulate dirt and vegetation when the mat is in place, the lock blocks also having at least one channel extending and communicating through the upper and lower surfaces of the blocks for accumulating dirt and vegetation in use and allowing hydrostatic pressure underneath the block to be relieved, the lock blocks having reinforced wires embedded therein, the wires extending beyond the periphery of the block in the walls alternating between the socket containing walls, the wires being formed into loop means for attachment to and cooperation with like wires on adjacent lock blocks in the mat, the sockets in the lock blocks having annular ribs extending around the periphery of the socket at a lower location thereof, forming a vertical stop means, the blocks also including a plurality of key blocks having a central hub and three equiangularly spaced locking arms, each locking arm terminating in an enlarged locking head, the locking heads being sized and adapted to communicate with and fit within the sockets in the lock blocks and being adapted and forming means to interconnect a plurality of lock blocks and key blocks into a contiguous mat, the locking head being engagable with the sockets by relative vertical movement therebetween, the locking heads being narrowed at the portion remote from the end thereof, the narrow portion cooperating with the narrowed opening through the wall of the lock block forming means cooperating between the enlarged head and the socket of the locking block to restrict horizontal movement between the lock block and the key block when joined, the enlarged head having an annular relieved portion near the bottom thereof forming means cooperating with the annular rib in the socket of the lock block and cooperating to form a stop restricting vertical movement between the lock block and the key block, the key block having vertical openings forming channels therethrough for collecting dirt and vegetation in use and forming means relieving hydrostatic pressure from beneath the key block, the locking heads also having vertical channels therethrough for collecting dirt and vegetation in use and relieving hydrostatic pressure from beneath the key block.