The erosion of soil due to the flow or movement of water, such as experienced on beaches, lake shores, waterways, channels and water shed areas is a significant concern both as to the deterioration of the land, as well as the soil contamination of the water. The expense and cost to repair such type of erosion can be substantial, often raging in the millions of dollars. Further, the repair of such type of eroded properties includes not only the rebuilding of the land, but often the subsequent removal of the soil which has been washed or carried down stream and settled in the navigation waterways. Also, eroded soil carried by run off water often finds its way into city and municipal drainage systems, thereby causing other concerns and expenses of removal.
Revetment or erosion control blocks have been developed to limit or control the erosion of soil due to the movement of water. A number of different styles of revetment blocks are currently available for satisfying particular needs. For example, U.S. Pat. No. 4,875,803 by Scales discloses blocks having interfitting tongues and cavities to prevent relative movement of one block with respect to the other. Because of the construction of the tongues and cavities, such blocks cannot be utilized in a curved path, although such blocks do provide a degree of flexibility to conform to vertical contours and curvatures of the ground. When the area to be protected with such type of blocks is curved, pie-shaped sections of grout between sections of blocks must be installed to accommodate corners and the like. A serious disadvantage of the Scales revetment block system is that, depending upon the arrangement, blocks with two tongues and four cavities are utilized, blocks with three tongues and three cavities are utilized, and blocks with four tongues and two cavities are utilized, as noted in FIG. 9 of the patent. Because of the different styles of blocks utilized, each block must be selected and studied briefly in order to determine how it should be oriented before being installed with the other blocks. Because of the difficulty in installing each block, the entire installation of a number of such blocks necessarily takes longer. Another severe disadvantage of the Scales blocks is the replacement of one or more blocks after the matrix of blocks has already been installed. Because of the nature of the interfitting tongue and cavities, the blocks cannot be lifted out of the matrix and replaced with another block. Rather, the replacement requires entire rows or sections to be removed in order to replace a single block. More practically, if a block is broken, the relevant area is simply grouted or cemented, which compromises the vertical flexibility of the matrix. Additionally, because of the nature of the tongues and cavities in the various blocks, they cannot be block cast, but only can be made by wet casting techniques.
U.S. Pat. Nos. 4,227,829 and 4,370,075 respectively by Landry, Jr. and Scales describe other revetment blocks that are cabled together so as to maintain a system of such blocks in a group to control the erosion of soil.
U.S. Pat. No. 4,372,705 reissued as Re. U.S. Pat. No. 32,663 describes an articulated erosion control system utilizing two entirely different types of blocks that are interlocked together. A "lock block" is constructed entirely of a number of sockets, and a "key block" is constructed only with a number of locking arms. The lock blocks and key blocks are interlocked together and can be cabled to facilitate installation. Although the lock and key blocks are structured so that a number of them can be installed in a curved path, the arrangement has certain disadvantages. For example, since two entirely different types of blocks are necessary, the different types of blocks must be available and alternately selected by the installer during installation thereof. Also, if one type of block is broken, during or before installation, then it must be replaced with an identical type. It can be appreciated that the installation, inventory and manufacture is thus more complicated, due to the necessity of two different types of blocks. Further, the arms of the key block are susceptible to breakage when installed in the socket of a lock block, and rotated or angled sideways. Because such type of blocks are constructed of concrete, the material is susceptible to breakage at the thinned portion of the arm, when such portion engages the edge in the opening of the socket and when rotated sideways to the fullest extent. The installation of a system of such blocks is also more complicated, in that the blocks are installed in a diagonal manner, rather than along the x-y laterals of a matrix. Lastly, the cabling of such blocks is more of a necessity to prevent dislodgement due to flowing water because the key blocks are lighter in weight than the lock blocks, and thus have a tendency to be more easily lifted out of place and carried with flowing water. Because of the structure and arrangement of the key and lock blocks, the cabling thereof is substantially more difficult. The entire disclosures of the foregoing patents are incorporated herein by reference.
French Pat. No. 75 32233 discloses a terrain erosion control block that is interlocking and requires only a single type of block. However, because of the length of the arms that extend substantially away from the block itself, a high likelihood exists that one or more of the arms will be broken during transportation, handling or installation. Also, rotation of blocks with respect to each other a maximum amount can exert a cross-sectional or transverse strain on the arms, thereby increasing the probability of breaking the thin and elongated arms.
From the foregoing, it can be seen that a need exists for an interlocking erosion control block that substantially reduces or eliminates many of the foregoing disadvantages. In particular, a need exists for a structurally strong interlocking block that is flexible with respect to other such blocks. A further need exists for a block of only which one type is required, is more easily manufactured, as well as installed. A further need exists for an interlocking type of block where the breakage of the exposed arms is less likely, especially when arranged to follow a curved path. A further need exists for a simplified erosion control block that can be constructed by either the wet cast or block cast techniques.