A MIDDLE ARMOR BLOCK FOR A COASTAL STRUCTURE AND A METHOD FOR PLACEMENT OF ITS BLOCK

Abstract: This invention relates to a middle armor block for a coastal structure and a method of placement of its block with a hydraulic stability of a slope surface and an economical construction cost. The middle armor block of the half-loc comprises a body (10) forming an octagon column with a rectangle side and a perforated hole (12) at the center, a leg (14) integrally formed and attached to alternatively each side of the body (10) and a protruding foot (16) at a lower portion of the leg and each corner of the leg (14) and the foot (16) is chamfered. For a placement type of the blocks, the middle armor block of the half-loc are tilted with a certain angle and each side portion of the leg (14) of the block is contacted to the other side portion of the leg (14) of neighbor block all around directions in series.

Description: A MIDDLE ARMOR BLOCK FOR A COASTAL STRUCTURE AND A METHOD FOR PLACEMENT OF ITS BLOCK BACKGROUND OF THE TNNKNTTON The present invention generally relates to a coastal structure and a method of its placement. More particularly, the present invention relates to a middle armor block for a coastal structure and a method of placement of its block with a hydraulic stability of a slope surface and an economical construction cost. Generally, the coastal structure, which is located inside harbor or leeward, is installed under the protection concept for protecting the facility structures from transportation of wave energy. When the coastal structure is constructed for a breakwater or seawall, an under layer of the coastal structure is used a sandy rock for hydraulically stabilizing on the slope surface, and an upper layer of the coastal structure is used an artificial armor units of a coated block, such as a tetrapeod, a dolos, an accropode or a core-loc to role for dissipating wave energy. Specially, for a design method of the breakwater, a rubble mound breaker is widely adopted to install the artificial armor units for the front slope surface. Recently, Caisson adopted a composite type is used for constructing the breakwater. Due to increasing the amount of trades and the size of surface freighters, there is a tendency to construct the breakwater on the deeper water advanced from the coast. Therefore, it is expected to increase the weight of coating materials for protecting the structure against the big waves. For the design of newly developing harbors, it should be considered the severer weather and the bigger waves than the design conditions of the conventional harbor. For protecting the important facilities on the leeward, the design of breakwater or seawall should be considered the design with over 100 years return period. According to the conventional standard design method for a section, in case of constructing a large size of harbor, or a conventional rubble mound breakwater and the seawall, a weight ratio of an upper layer of coating materials and an lower layer of sandy stones would be 1: 1/10. (Coastal Engineering Research Center, U.S. Army Corps of Engineers, 1984, Shore Protection Manual Pg. 7-228) It is possible to provide a demanded weight of the coating materials because the coating materials could be possibly manufactured by an artificial casting. But, it is not easy to provide enough amount of corresponding weight of the under layer of sandy stones because the natural rocks for under layer of sandy stones are usually provided nearby the construction cite. To solve the problems described above, a conventional artificial armor block or a slightly modified type of block is used instead of the lower layer of sandy rocks for the front slope layer coated block. In this case, it would not clearly be stable for the hydraulic characteristics of the whole section if the lower layer were exposed during a construction or placed together with the front slope layer coated block. On the other hand, the Grovel sea level is raised because of the Laninor phenomenon. As a result, it may not be occurred the expected dissipation of wave energy due to wave breaking in the shallow water zone. However, the current design for the coastal structure does not consider the raised sea level. SUMMARY OF THE INVENTION The objective of this invention is to overcome the problems described above and provide an artificial block (hereinafter "half-loc") to replace the sandy stones. The other objective of this invention is to provide a new form of the middle armor block for improving ability of construction at the construction cite and stability of the breakwater. The other objective of this invention is to provide a safety placement method when a middle armor block is constructed along with the front slope layer coating material. In order to accomplish the above objectives of this invention, the new form of the middle armor block comprises a body having a shape of octagon column with a rectangle side and a perforated hole at the center of the top of the body. Four legs are integrally formed to the body and has a shape of rectangle column on four sides of the body alternatively. A protruding foot is formed at each of a lower portion of the legs and each corner of the legs and the foot is chamfered. The other objectives and features of this invention will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS Figs. 1A and IB show a half-loc of embodiments of this invention. Fig. 2 shows a top and front views of the half-loc of one embodiment of this invention in Fig. 1A. Figs. 3 to 5 show a method of placement of the half-loc of the embodiment of this invention. Fig. 6 shows a graph representing a relationship between the Hudson stability coefficient and the rate of damage depending on the placement of the half-loc. Fig. 7 shows a graph representing a relationship between the Hudson stability coefficient and the rate of damage for the placement of the half-loc shown in Fig. 3 to Fig. 5. Fig. 8 shows a graph representing a relationship of the stability depending on the rate of weigh of the half-loc. The detailed description of this invention would refer the attached drawing. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A new form of the middle armor block of a half-loc (hereinafter "half-loc") of an embodiment of this invention is shown in Figs. 1A and IB. The half-loc mainly comprises a body 10 and a leg 14. The body 10 is formed a shape of octagon column with a rectangle side and a perforated hole 12 at the center of the top surface. The perforated hole 12 has a shape of rectangle or preferably a square. Four legs 14 are integrally formed and attached alternatively to the side of the body 10. Also, a protruding foot 16 is formed at a lower portion and/or upper portion of the leg 14. The protruding foot 16 is disposed upward or downward direction at each of top and bottom of the legs. Each corner of the lower portion and upper portion of the leg 16 and the foot 14 is chamfered. The perforated hole 12 at the center of the body 10 is designed to pass the water upward or downward to disperse an up-lifting force. The perforated hole 12 has a shape of square. Each side of the perforated hole 12 is parallel to the side of the body, which does not have a leg. The perforated hole 12 is disposed at the center of the top of the body in order to avoid the concentration of the stress. Each foot 16 formed on the top and bottom of the leg 14 will be locked in the upper and lower coated layer rocks of the breakwater or seawall and minimize the slippage. Therefore, it will improve the reinforcement of the upper and lower coated layer rocks and increase the stability of the hydraulic characteristics. Also, the corners of the leg 14 are chamfered to disturb the water flows over the blocks. The detailed dimensions of the half-loc of an embodiment as shown in Fig. 1A are shown in Fig. 2. The maximum length of the half-loc is shown in Fig. 2, i.e., a dimension C measured from an outside of the leg 14 to the opposite side of the leg 14 that is assumed a scale of 100. It is favorable dimension of the half-loc having a thickness of the leg 14 approximately 20, a width of the leg 14 approximately 40, a thickness of the body 10 approximately 30 for the desirable stability and ability of the construction. Also, it is desirable dimension for one side length of the perforated hole 12 approximately 20, and the height of the protruding portion of the foot 16 from the body 10 approximately 5. (Herein after the block having above dimension is called "block I") For a convenient construction of the block, as an alternative embodiment of a half-loc without a top foot as shown in Fig. IB, a modified form of the half-loc is considered to remove the upper extruding foot 16 of the leg 14 during the casting of block. (Herein after the block without the upper foot is called "block II") The volumes of these blocks using the scale "C" for a standard dimension are representing; V = 0.2134 x C 3 (Block I) V = 0.19145 x C 3 (Block II) — (1) The important factor of construction of the half-loc is a placement type. The placement type is closely related to the stability of the block and dominantly depended a degree of interlocking and a porosity of the half-loc. Therefore, Figs. 3 and 5 of the present invention shows the arrangement methods for the placement type. The placement type of Fig. 3 (herein after "Type I") shows a method of half interlocking. This method of half interlocking arranges blocks to contact an pro- outside of leg 14 of one block to an aft-outside of leg 14 of a neighbor block each other in a serial line, and the left-outside or right-outside of leg 14 of the blocks in a second serial line contacted the right-outside or left-outside of leg 14 of the blocks in the neighbor serial line by disposing inside a concave area which is created by a serial line, and be coated over the blocks. The arranged blocks of half-interlocking looks like a honeycomb. The pro- or aft-outside leg 14 of the neighbor blocks contacted each other in a serial direction are contacted perpendicular to the left or right outside legs 14 of the blocks in the second serial line, and formed a zigzag arrangement. This method of placement type is perfectly linked each other to be almost static. The placement type of Fig. 4 (herein after "Type II") shows another arrangement method that the chamfered portions of the legs of the block are contacted to the chamfered portions of the legs of the neighbor blocks all around the blocks in the series. The blocks of type II are disposed individually without a linkage relationship each other, and has a high porosity. The placement type of Fig. 5 (herein after "Type III") discloses another arrangement method that the side portions of the legs of the block are tilted and contacted to the side portions of the legs of the neighbor blocks in the series. Figs. 3 to 5 disclose an ideal arrangement of the placement type. In reality, there are limitations to construct the ideal arrangement of the placement type at the construction cite. However, the actual construction should not deviated from the selected ideal arrangement of the placement type. Using the half-loc block shown in Fig. 1, the number of required blocks can be calculated from a given area of the construction site depending on the selected placement types of Type I, Type II, Type III. The porosity can be calculated by counting a height of the top and bottom of the blocks. Using the placement types described above, an experiment for the exposure stability can be performed to apply the actual construction. The data of exposure stability is obtained though the experiments because the coated block would be exposed to the wave during the construction. An experiment section of model is determined by considering the parameters related to the size of block, expected stability, size of model and source of a wave and reservoir. Table 1 is shown the relationship of the above parameters based on the given experimental conditions. ε .SP > 0) a tΛ .^; > ^ From each of the parameters described above, a weight of the half-loc could be calculated, then the height of wave corresponding to the value of the expected stability could be calculated for the design of experiment conditions. The volume of the half- loc could be calculated from the equation 1 by using the basic scale of "C". After the volume is determined, the corresponding weight of the half-loc could be calculated. The significant wave height H 1/3 could be calculated based on the Hudson's stability coefficient K D . (For the Hudson's stability coefficient K D , refer "Laboratory Investigation of rubble mound breakwater" 1969, Proc. ACSE, vol. 85) Hudson suggests an equation for the Hudson's stability coefficient K D as shown below. K D = γ(H 1/3 )7W(S r - l) 3 cot θ (2) Wherein; W is the weight of armor block. γ is the specific weight of concrete in the air. (2.657 g/cm 3 for granite, 2.5 g/cm 3 for concrete) S r is the specific gravity of concrete against the seawater. cot θ is the slope. The K D value is set up a range of 3 to 12. This range of the value is quoted from the blocks used for other purposes because there is no previous examples or data available for the middle armor block. An X-block, such as an all side slope coating material or a solid block developed by a apanese company TETRA, is suggested the K D value of 10. It is hard to estimate the hydraulic stability because the rate of porosity varies depending on the placement types. For the smooth slope, the K D value is estimated the range of 4 to 5 based on the K D value of 10 based on the X-block as a standard value. This invention of the half-loc is designed to use the block on slope rate of 1:1.5. Therefore, the K D value is in the stable range for the smooth slope. From the TABLE 1, the value of H 1 3 is in the range of 9.60-13.03cm. An equation having a relationship between the maximum wave height EL ^ and the significant wave height H 1/3 is introduced in the "Random Sea and Design of Maritime Structures" 1990, 16 section, by Yoshimi Goda. The equation of the wave height ratio is given; (H^/H,^ = 0.706{[In N 0 ] 1/2 + γ (2[In N 0 ] 1/2 )} (3) wherein; N 0 is a frequency of wave and is used 1,000 waves. The water depth of the breakwater is estimated based on the calculation of HL ^ using the equation 3 in order not to break the wave. In this experiment, a possibility of breaking wave by the standing waves is considered and used the value of D s = IL ^ /0,61 instead of using the value of D s = EL ^ /0,78 which is shown in the McCowan's "On the Solitary Wave" (Philosophical magazine, 5 th series, vol. 32, No. 194, PP 45-58) and related to a limitation of wave breaking of a solitary wave and a water depth. Also, the run-up height R υ is estimated in order to determine the height of free board R L . The value of the run-up height R υ is refereed from the Wallingford, "Hydraulic Experiment Station", 1970, "Report on Tests on Dolos Breaker in Hong Kong", and the experimental data of the run-up height for Dolos from Gunbak A. R.. ("Estimation of incident and reflected waves in random wave experiments 1977, Div. Port and Ocean Engineering, Rep. No. 12/77, Tech, Univ. of Norway, Trondheim) The maximum cycle of 2.5sec is selected for a cycle T The model section and the wave height are finally decided after verify the sum (95.91cm) of the height of the block (DS+RU = 74.41cm) and the mound height (21.5cm) is less than the height of a water tank (120cm). The water depth of the front surface D s for the experiment model of 43cm and the front slope of 1:1.5, which is widely used, for construction of the coated slope breakwater of the tetrapod is selected. The thickness of the front slope of 2.16cm which is corresponding to 40 percent of C = 5.3cm and the weight ratio of the first lower layer and the second lower layer of 1 :20 are selected. The thickness of the standard section of the lower layer is corresponding to the thickness of the second lower layer. Based on these relationship, the model is used a natural rock having 1.4cm thickness corresponding to the average diameter and the height of free board R L 32cm. The model width of the upper layer is decided by an experimental proportion because the model is not a real block, there is no proportional simulation available. The purpose of this experiment is to determine the weight ratio and develop the middle armor block of the half-loc instead of using the natural stones of sandy rock nearby the construction site. The Froude equation is related the weight ratio and length ratio of Wr = 1 r 3. The estimated proportion ratio of 1:28.85 is calculated based on the 77.29g of block, 0.7m 3 of sandy Rock and 1.855 ton of the corresponding weight. (2.65 ton/m 3 of specific volume-weight is used for calculation) By this time, a space of 6m (= 3m x 2 way) for two-way traffic would be provided on top of the block. Therefore, the size of the model would be 20.8cm. The width of road 3.0m is used according to the Standard Design of Harbor Facility. The middle armor block of the half-loc is coated double raw in case of the upper layer of the block is coated with the front slope coating material such as T.T.P. Rear slope ratio is 1 : 1.5 same as the front slope ratio. In this experiment, only the core sandy rocks are used due to the non-overtopping test. There are two kinds of wave generators; Position Type and Absorption Type used in the experiments. Absorption Type of wave generator is used for this experiment. Due to the non-overtopping test, the waves which have the significant wave height (H 1/3 ) and spectrum are generated corresponding to the theoretical value of the spectrum at the location of the disposed block. Each of the experiments is classified depending on the kind of waves by using the data from TABLE 1. T 1/3 is tested between the range of 1.0 ~ 2.5 sec with 0.5 sec increment for the range of 6 ~ 14cm of wave height with 2cm increment. The experiment is performed for total 20 kind of waves by fixing the water depth (43cm) of the all slope surface D s and varies the values ofT 1/3 and H 1/3 . A locking and displacement of the middle armor block of the half-loc is mainly observed continuously by increasing the wave height for each period of experiment. The experiment is continued by increasing the wave height for each period until the model of the breakwater or the lower portion of the sandy rock is got damaged. Then, the wave height is recorded when the model gets damages. A calculation of damage ratio is the total number of blocks divided by the accumulated number of blocks which is correspond to the Hudson's stability coefficient K D and the significant wave height H 1/3 . The equation would be; D = n/N x l00 (%) (4) Wherein: D is a damage ratio n is accumulated number of blocks until the highest wave. N is the total number of the blocks. Fig. 6 represents the stability obtained from the experiments for Block I and Block II. According to the test result shown in Fig. 6, the Block I is more stable than the Block II in all range of waves. Specially, the Block II coated with Type I, the damage ratio would be reached 4 percent. It is revealed that the Block I coated with Type I has the highest damage ratio. Except the Type I, all other models has approximately 11.0 of the K D value. Block II is easier to construct but less stability than Block I. Therefore, Block I has advantage of the stability and anti-slip when all slope coated block is placed on the upper layer. Fig. 7 represents the test results obtained from the experiments for Block I, Type I, Type II and Type III. According to the test result, Type I and Type III have got the damage ratio of 1 percent corresponding to 4.96 K D of the wave height. Type II has no damage until the waves reach corresponding to 11.38 K D of wave height. Each porosity of 33.3%, 37% and 33% for Type I, Type II and Type III, the exposure stability is analyzed and compared each other. The test result reveals that Type III is the most stable placement type. Beside the stability depending on the placement type of the half-loc block, the other important factor is that a weight calculation of the half-loc block for the lower layer coating material. According to the conventional standard design, a weight ratio of each section is suggested. For example, a weight ratio 1 : 10 is used for all side slopes coating material block. In this invention, the weight ratio has determined through the experiment to establish the stability for the all side slopes coating material block To determine the weight ratio, the experiment is performed for the stability of the all side slope coated block using Type II that is the most stable placement type and Type III which is the least displaced type and easy construction. The reason why Type III is selected is that it maintains the most stability for the half-loc coated block and the lowest porosity of the placement type. If the blocks would be displaced, it will affect the stability of the all side slope coated block. The tetrapod is used for all side slope coated block. According to this invention, the weight ratio of the half-loc coated block are 3.36, 5.25, 6.70 and 10. Fig. 8 represent the test result for the four cases of non-breaking, K D =10.2 for Hudson's stability coefficient, corresponding to 150% of the biggest wave based on the normal wave. As shown in Fig. 8, the four kinds of the weight ratios are all stable. The bar graph of Fig. 8 represent that for example, Run Group 2, the tetraped and the bottom portion of the half-loc coated block of this invention is impacted 1,000 waves of 2.0 cycles, after then repeated the impact of 1,800 waves of 2.5 cycles. As a test result, each wave of the continuation time excess more than 1,000 waves. The breakwater would be usually impacted 1,000 waves of 3 ~ 4 impacting hours during a rainstorm. Therefore, this experiment chooses the stable condition of four cases estimating at least 1,800 waves and 2.0 - 2.5 cycles. The half-loc coated block of this invention, which is coated by the tetraped using 3 to 10 times of weight, is in stability condition. According to the test result, the half-loc coated block of this invention could be replaced for the natural stones conventionally used in the slope type breakwater. The half-loc coated block of this invention could be improve the efficiency and standardized for the placement type, the lower layer and upper layer coating blocks, and construction method. The half-loc coated block of this invention could be solved problems comes from the conventionally slope type breakwater, calculated the stability depending on the placement type and provided the new concept of the coastal structure The scope and spirit of this invention is not limited in the description of this invention. It is possible for one who has a skill in this art modifying or deviating scope and spirit of this invention.

Claims: What is claimed is- 1. A middle armor block of a half-loc comprising: a body having a shape of octagon column with a rectangle side, said body having a perforated hole at the center; four legs having a shape of rectangle column on four sides of said body alternatively, said legs being integrally formed to said body; a protruding foot formed at each of a lower portion of said legs, each corner of said legs and said protruding foot being chamfered. 2. The middle armor block of half-loc as claimed in claim 1, further comprising a protruding foot formed at an upper portion of said legs. 3. The middle armor block of half-loc as claimed in claim 2, wherein said legs is measured with a basic dimension of C, a thickness of said logs is 0.2 C, a width of said legs is 0.4 C, and a thickness of said body is less than 0.4 C. 4. The middle armor block of half-loc as claimed in claim 2, wherein said perforated hole is designed to pass the water upward or downward for dispersing an up- lifting force, a shape of said perforated hole is square, and each side of said perforated hole is parallel to the side of said body which does not have said legs. 5. A method of placement of the middle armor block of half-loc as claimed in claim 2, said method of a placement comprising the steps of : tilting said block with a certain angle; and contacting each left or right side of said legs to other right or left side of neighbor legs all around direction in series. 6. The method of placement of the middle armor block of half-loc as claimed in claim 5, wherein a weight ratio of said half-loc to an artificial armor block is 1 :3-10 when said half-loc is disposed under the artificial armor unit.

Inventors: KWEON HYUCK-MIN, LEE DAL SOO, KWEON, HYUCK-MIN, LEE, DAL, SOO
Applicants: KWEON HYUCK MIN, LEE DAL SOO, KWEON, HYUCK-MIN, LEE, DAL, SOO
Application year: 1999
Main classification: E02B3
IPC codes: E02B3