JPH08165652A - Foundation construction method of maritime structure - Google Patents

Abstract

PURPOSE: To carry out the work of a friction member simply, by composing a friction increasing member provided between the upper side of a riprap foundation and a caison by an asphalt mastic layer, when a maritime structure is constructed by loading the caison on the riprap foundation. CONSTITUTION: A riprap foundation 5 is constructed on a sea bottom ground 2, and a caison 3 and the like is loaded on the upper side of the riprap foundation 5 so as to compose a maritime structure 1. In this maritime structure 1, an asphalt mastic layer is provided instead of using a conventional asphalt mat, in order to increase the friction coefficient between the lower side of the caison 3 and the upper side of the riprap foundation 5. The asphalt mastic layer is thrown in by a bucket and the like in the condition to make the upper side of the riprap foundation even almost in a plain surface, and a layer of the even thickness is formed by utilizing the fluidity of the asphalt. And even though the surface is uneven a little, it is formed flat by pressing by the caison 3, so as to exercise the maintaining function of the caison 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a marine structure such as a breakwater constructed by constructing a rubble foundation at a predetermined height above the seabed ground and installing caisson or the like on the rubble foundation. The present invention relates to a method of constructing a foundation for a marine structure in which a friction member arranged between the upper surface of the foundation and a caisson is constructed by asphalt mastic.

[0002]

2. Description of the Related Art Offshore structures, such as breakwaters and quays, have a substantially uniform level on the seabed, and then stones are dumped on the ground to form a rubble foundation of a predetermined height. It is generally practiced to mount a structure such as a caisson in a state where the top is flattened. As the caisson that constitutes the offshore structure, a box-shaped member integrally formed of concrete, a box-shaped structure made of steel plate, and the like formed by coating concrete with a predetermined thickness on the surface is used. . Since the coefficient of friction between the caisson as described above and the upper surface of the rubble foundation is relatively small, a sheet member for increasing friction is arranged on the lower surface of the caisson.

For example, in the example disclosed in Japanese Examined Patent Publication No. 5-19617, a rubber mat is integrally attached to the lower surface of the caisson to increase the friction coefficient between the caisson and the rubble foundation by the rubber mat to prevent the caisson from undulating waves. It constitutes a means for preventing sliding due to pressure. Further, the rubber mat is relatively expensive,
Because of its workability and the like, a relatively thin one having a thickness of about 3 to 5 cm is often used, and therefore, when leveling the upper surface of the rubble foundation, it is necessary to configure the unevenness to a value as small as possible. On the other hand, as shown in Japanese Patent Laid-Open No. 4-176913, an asphalt mat is integrally attached to the bottom surface of a caisson. When the asphalt mat is used, the price of the mat is relatively low and the thickness of the mat can be arbitrarily formed. Even if there is some unevenness on the upper surface of the rubble foundation, the caisson support It is possible to exhibit the advantage that the above can be performed satisfactorily.

As described above, the offshore structure constructed by disposing the asphalt mat on the lower surface of the caisson is constructed, for example, as shown in FIG. In the offshore structure 1 shown in FIG. 9, the surface of the seabed 2 is leveled substantially flat, and then the rubble foundation 5 is constructed at a predetermined height.
The asphalt mat 4 is laid after the upper surface is leveled flat, and the caisson 3 is placed on the asphalt mat 4. The asphalt mat 4 arranged between the rubble foundation 5 and the caisson 3 has a predetermined length and width, and
Often used is a method of manufacturing a thick thing on land and laying it on a rubble foundation using a crane ship. On the other hand, when manufacturing a caisson, it is also possible to use a construction method in which an asphalt mat is integrally attached to the lower surface of the caisson and the caisson is towed and sunk to the construction site.
This is performed as shown in the above-mentioned Japanese Patent Laid-Open No. 4-176913. When the caisson integrally attached with the asphalt mat is submerged at the site, it is possible to easily perform the site installation work of the offshore structure.

[0005]

As described above, when an asphalt mat is manufactured at a harbor construction site or a construction method of laying it on the upper surface is used, the asphalt mat is manufactured near the construction site. It is necessary to provide vacant land, asphalt plant and equipment for mat production. Also, after manufacturing the asphalt mat,
After storing them temporarily and constructing a rubble foundation,
It is necessary to use a crane ship to construct the asphalt mat immediately before constructing the caisson. However, at breakwaters and jetty construction sites on remote islands, there is often no large open space near the construction site to manufacture asphalt mats.In such sites, asphalt mats are produced near the caisson manufacturing site. Means are used to produce each caisson. Then, the caisson can be towed by a ship while floating on the sea, transported to the construction site, and poured into the caisson to sink it.

However, since it is necessary to transport the asphalt mat to the site by a barge or the like and to lay it on a rubble foundation using a crane ship, many large and small ships are to be constructed at the construction site of the offshore structure. It is necessary to use it, and there is a problem that the construction unit price will increase. In addition, port construction on remote islands, etc. requires construction in relatively rough seas, and small stones should be used when constructing rubble foundations in places with fast tidal currents. There is also the problem that it cannot be done. In addition, when laying an asphalt mat on a rubble foundation, construction is performed in consideration of the situation of the sea area at the site, and port construction is carried out under a great many constraints. In addition to the problems mentioned above, it is often difficult to secure large stones for use as rubble foundations on remote islands, and for that reason means such as transporting from a distant mining site by ship is used. There is.

Further, as described above, when the seabed is a relatively soft ground such as sand or mud, the ground is improved before the rubble foundation is constructed, but the seabed is rock. For example, the construction method as shown in FIG. 10 is used. In the example shown in FIG. 10, an excavation portion 2b having a predetermined depth D is constructed on a rocky seabed 2a, a rubble foundation 5 is constructed in the excavation portion, and caisson 3 and the like are used asphalt mat 4. It is mounted via the above to construct an offshore structure. However, when the above-mentioned construction method is used, there is a problem that it takes a lot of time and labor to excavate a strong rock mass and the construction cost also increases. Also, for rock mass that has the strength to withstand the load of caisson, etc., it is difficult to flatten the support base by the conventional method, although it is not necessary to construct a rubble base. Therefore, there is a problem that it takes a lot of trouble to construct a support base for caisson by constructing a rubble foundation after excavating the bedrock once.

[0008]

The object of the present invention is to solve the above-mentioned problems of harbor construction on remote islands and the like. By directly placing asphalt mastic on the surface of a rubble foundation, the fluidity of the asphalt mastic naturally causes Utilizing flattening, an asphalt mastic layer that replaces the asphalt mat is built, and a caisson is placed on it to provide a construction method that enables the construction of offshore structures. To enable the construction of rubble foundations using small stones in fast-moving waters and to facilitate the construction of offshore structures, and, if the seabed is rock, asphalt mastic on the rock. The purpose of the present invention is to provide a foundation construction method for an offshore structure that can easily construct a support base by constructing a layer of.

[0009]

DISCLOSURE OF THE INVENTION The present invention is a breakwater constructed by constructing a rubble foundation at a predetermined height on the seabed and placing a caisson or the like on the rubble foundation via a friction member. Related to offshore structures. In the present invention, the asphalt mastic that has been heated and fluidized is poured onto the upper surface of the rubble foundation, and the fluidity of the asphalt mastic is used to provide a substantially uniform thickness and a substantially uniform flatness. An asphalt mastic layer is formed, and a structure such as caisson can be positioned on the asphalt mastic layer. Further, in the present invention, it is also possible to form an asphalt mastic on the slope of the rubble substrate to form a slope protection layer and to position a structure such as caisson on the asphalt mastic layer. .

Further, in the present invention, a construction is carried out in which the rubble foundation is divided into a plurality of layers, and the upper surface of one layer of the rubble foundation is heated and coated with asphalt mastic having fluidity. Each time it is constructed and the layer of the rubble stone foundation is constructed, the asphalt mastic is repeatedly cast to build the rubble stone foundation of a predetermined height, and after the rubble stone foundation is constructed The asphalt mastic is cast on the surface to form an asphalt mastic layer having a substantially uniform thickness and a substantially uniform flatness,
A structure such as a caisson may be positioned on the asphalt mastic layer. In addition to the above configuration, in the present invention, when the seabed that constructs the offshore structure is rock, work is performed to correct the unevenness or slope of the rock, and the insufficient strength of the rock is removed. It is also possible to carry out the work described above to form an asphalt mastic layer having an upper surface having a substantially uniform flatness on the rock, and to position a structure such as a caisson on the asphalt mastic layer.

[0011]

As described above, in the present invention, the asphalt mastic layer is formed by flowing the asphalt mastic to the upper surface after the rubble foundation is constructed by flattening the upper surface and forming the asphalt mast layer. By placing a caisson on the mastic layer, it is possible to set a large friction coefficient between the caisson and the rubble foundation. Further, asphalt mastic flowing on the rubble foundation as described above, due to the fluidity in the state of being heated to a high temperature, in addition to the state where large unevenness does not occur, due to the pressing action when placing the caisson, Since it is naturally formed flat, the asphalt mastic layer uniformly contacts the lower surface of the caisson and can exhibit the function as a friction increasing member. Furthermore, in the present invention, in the sea area where the tidal current is fast,
It is possible to construct a rubble foundation by laminating small-diameter stones, cover the surface with asphalt mastic, and prevent stones from sticking to each other by asphalt mastic and flowing by the tidal current. Therefore, it is possible to construct a rubble stone foundation on which relatively small stones are piled up, and it is possible to easily construct a marine structure even at a construction site where large stones cannot be obtained.

Further, according to the method for constructing a foundation for a marine structure of the present invention, in a sea area where the tidal current is fast, the rubble foundation is divided into a plurality of layers without constructing the rubble foundation all at once due to the condition of waves and tidal currents. It is also possible to construct by stacking the layers of the rubble foundation by placing asphalt mastic on the surface of each layer of the rubble foundation during the construction. Then, it is possible to prevent the rubble foundation constructed with small stones from being washed away by the tidal current, and it is possible to deal with the situation of the construction site where only small stones can be used. In addition to the above configuration, when the seabed is rock, there is no need to excavate the rock to build a rubble foundation, level the unevenness of the construction ground evenly, or scrape off the part with insufficient strength. The portion where the asphalt mastic is placed can be constructed by performing only the construction work. Therefore, it is possible to place a structure such as a caisson after constructing the prominent asphalt mastic on the bedrock so as to be flat, and to simplify the foundation construction. Furthermore, in the present invention, it is sufficient to use an asphalt plant without using a crane ship such as construction using an asphalt mat or a yard for manufacturing an asphalt mat, and to install equipment according to the construction scale. It is possible to use it to easily perform the asphalt mastic placing work.

[0013]

EXAMPLE A method for constructing a foundation for a marine structure according to the present invention will be described with reference to the illustrated example. The example shown in FIG. 1 shows a structure of an offshore structure 1 constructed by installing a caisson 3 on a rubble foundation 5, and similar to the case of constructing a conventional offshore structure, the seabed ground 2 is constructed. The rubble foundation 5 is constructed at a predetermined height above, and the caisson 3 is installed via the asphalt mastic layer 10 provided on the rubble foundation 5.
Further, the asphalt mastic constituting the asphalt mastic layer of the present invention is a mixture of sand and other filler materials in asphalt using a plant, which is heated to a high temperature to have fluidity. It is possible to use a material having fluidity larger than that of the asphalt mastic used when producing the asphalt mat of the above. And, when laying the asphalt mastic in water, even if it is rapidly cooled by water, it is possible to exert the asphalt fluidity in a good state, and the asphalt mastic between the stones of the target rubble foundation. In addition to that, use the one that has the property of forming a coating of asphalt mastic on the surface of the rubble foundation with a uniform thickness.

In the present invention, for example, as shown in FIGS. 2 to 4, a temporary work scaffold 20 constructed from land to sea is used, and asphalt mastic having high fluidity at high temperature is used in a bucket 15. It is possible to form the asphalt mastic layer 10 on the upper surface of the rubble foundation with a uniform thickness and a uniform flatness. The example shown in FIG. 2 shows a case where a small-scale offshore structure is constructed on a remote island or the like. The temporary work scaffold 20 is constructed by extending it from the land, and is constructed on the temporary work scaffold 20. Crane 21 etc. are arranged. Then, the work of dumping stones and the like of the rubble foundation using the crane 21 and the construction of asphalt mastic using the bucket 15 are performed, and the rubble foundation is constructed without using the crane ship. Configure the equipment to get.

As described above, when the temporary work scaffold 20 is used, if the temporary work scaffold is arranged on the open sea side of the rubble foundation, the temporary work scaffold can exert the action of protecting the rubble base from the waves of the open sea. As a result, even when relatively small stones are piled up to construct a rubble foundation, the discarded stones can be protected from the tidal current. Further, as shown in FIG. 2, after the rubble foundation is constructed to have a predetermined length, the surface portion of the rubble foundation is leveled substantially flat, and the asphalt mastic 1 using the bucket 15 suspended by the crane 21 is used.
It is possible to form the asphalt mastic layer substantially flat by casting 1 and utilizing the fluidity of the asphalt mastic. As described above, when the asphalt mastic is placed using the bucket, the lid member 16 of the bucket 15 is opened at a position close to the upper surface 6 as shown in FIG. Pour asphalt mastic 11.

As shown in FIG. 3, the work of placing the asphalt mastic 1 using a bucket is performed as follows.
As shown in FIG. 4, the asphalt mastic layer 10 having a predetermined thickness can be formed on the upper surface 6 by repeatedly performing the operation at predetermined intervals. At the same time, asphalt mastic with high fluidity enters between the stones, and the stones on the upper surface 6 are fixed to each other, so even in the sea area where the tidal current is relatively fast, the stones of the rubble foundation are washed away by the tidal current. The condition of the rubble foundation can be maintained in good condition until the caisson is installed. As described above, the rubble stone foundation formed by casting asphalt mastic on the upper surface is in a state in which no large unevenness is formed due to the fluidity of the asphalt mastic. Even if there is some unevenness on the surface of the asphalt mastic layer, when a heavy caisson is installed, the pressure of the caisson causes the asphalt mastic layer to fall between the flat surface of the lower surface of the caisson and the unevenness of the upper surface. In this state, no void is formed and the lower surface of the caisson is completely filled. Therefore, the asphalt mastic layer uniformly contacts the lower surface of the caisson, and the frictional state between the caisson and the rubble foundation can be maintained well.

As shown in FIG. 2, in addition to the case where a temporary work scaffold is used to construct an offshore structure, a crane ship is used to construct a rubble foundation as in the conventional construction method for constructing an offshore structure. Construction and asphalt mastic layer placement operations can also be performed. In addition, a short temporary work scaffold will be constructed from the land to construct a short section on the land side of the offshore structure, and then a crane will be installed using the constructed offshore structure to construct a rubble foundation and asphalt. It is also possible to carry out the work of placing the mastic layer. In other words, when using the construction method as described above, the construction of the rubble foundation is divided into short sections according to the size of the caisson,
It is possible to use a method of constructing a coating with an asphalt mastic layer and placing caisson one by one on the rubble foundation to extend the offshore structure. And if the extended offshore structure is used as a scaffolding for construction, all the other work can be done from land simply by transporting and installing the caisson on the sea, without using many large ships. It will be possible to construct offshore structures.

In addition to the construction method shown in FIG. 2, in the present invention, it is also possible to construct a rubble stone foundation in a sea area where the tidal current is very fast, by using a stone having a relatively small diameter. For example, in the example shown in FIG. 5, the lower part of the rubble foundation is assumed as one layer, and after the lower rubble layer 8 is constructed at a predetermined height,
Asphalt mastic is poured on the surface of the lower rubble layer 8 to build a protective asphalt layer 12, and small stones are fixed to each other through the asphalt mastic in a state where the asphalt mastic is allowed to enter between the stones to face the rough waves and tidal currents. I will let you. Then, by choosing the quiet time of the next wave, the upper rubble layer 9 is constructed, and the surface of the upper rubble layer 9 is also laid by asphalt mastic as shown in FIG. The coating of. In addition, in the sea area where the waves are rough or the tidal current is fast, the slope protection layer 13 is applied to the side surface of the rubble foundation with a predetermined thickness,
Allows a rubble foundation constructed of small stones to be protected from tidal currents. Furthermore, before the caisson is constructed or at any time, asphalt mastic is poured on the upper surface of the rubble foundation 5 to construct an asphalt mastic layer 10 having a predetermined thickness, and the caisson 3 is installed as shown in FIG. This will enable the construction of offshore structures.

In the offshore structure constructed as shown in FIG. 7, it is not necessary to construct the rubble foundation at once,
It is possible to use construction methods such as dividing the layers of the rubble foundation during the quiet time or period of the waves. And in the rubble foundation that is constructed by dividing it into multiple layers, multiple layers are stacked while the surface of the thin layer is covered with asphalt mastic, so the rubble foundation is stable against tidal currents and waves. Can be maintained. In addition,
When constructing the offshore structure of FIG. 7, the slope protection layer 1
No. 3 needs to be constructed so that asphalt mastic can be inserted between the stones, and only the stones on the slope of the rubble foundation need to be protected. Only the asphalt mastic layer with a certain thickness is constructed on the upper surface of the rubble foundation. Since the support portion is provided with a substantially uniform flatness, it is not necessary to use the asphalt mastic in a very large amount. In addition, as described above, even when constructing the offshore structure shown in FIG. 7, by shortening the section for constructing temporary work scaffolds, etc., by using the construction method of sequentially extending the offshore structure from the land. It is also possible to carry out the construction without using a ship.

Each of the embodiments of the present invention as described above is shown as an example of constructing a rubble foundation when the seabed for constructing a structure is sandy soil or mud, etc. ,
Even if the seabed is rock, it can be dealt with only by constructing an asphalt mastic layer. For example, in FIG.
As shown in, when the seabed is rock 2a, the excavation portion 2c is formed by cutting the protrusion 2d or excavating a portion having a small supporting strength with respect to the ground for constructing a structure such as a caisson.
Construct. Then, rubble stones or the like are put into the excavated portion 2c having a weak strength to construct a substantially flat ground, and the protrusion 2d is leveled to make the caisson 3
Asphalt mastic layer 10 corresponding to the building part of
Construct.

As shown in FIG. 10, when the seabed ground can be constructed relatively flat, the asphalt mastic layer 10 should have as few irregularities as possible before the asphalt mastic is applied to a predetermined thickness. Can be built by. Further, as shown in FIG. 8 in the previous term, in the state where the seabed ground is inclined to one side, in response to the inclination,
One side is thick and the other side is thin.
The asphalt mastic is cast so that the supporting surface of is almost flat. Furthermore, as shown in Fig. 8 in the previous term, in the case of the construction method in which the bedrock that constitutes the seabed is used as it is as a support base for the structure, stones etc. are registered for the part where the ground inclination angle is relatively large. By doing so, the surface portion can be flattened substantially flat, and then the asphalt mastic can be cast to a predetermined thickness. Therefore, by constructing an asphalt mastic layer as described above, it is possible to easily construct a support foundation for a structure by using the ground rock as it is without constructing a rubble foundation on the seabed. can do.

In addition to the above-mentioned structure, in the present invention, a construction method in which the bedrock on the seabed is used as it is and a construction method for constructing a rubble foundation are constructed in combination according to the situation of the seabed ground, and the like. The asphalt mastic can be cast after the upper surface of the support base of the structure is formed to be substantially flat. By constructing the surface of the asphalt mastic layer to be cast on the support base so as to have a substantially uniform flatness, the caisson or the like can be easily constructed. Also, when using the method of the present invention, after the support base is configured to be substantially flat,
When the asphalt mastic is cast, the asphalt mastic enters the gaps of stones and fills the recesses, so it exerts the effect of integrating the support base such as caisson and the like, and supports the structure. It can be done in good condition. Furthermore, when the support base is rock, it is possible to reduce the construction cost of the offshore structure by using the construction method that uses the support strength of the rock as it is, and to directly support the asphalt mastic on the support base. By driving the structure, it becomes possible to increase the friction coefficient for supporting the caisson or the like and stably support the structure.

[0023]

EFFECT OF THE INVENTION The foundation construction method for offshore structures of the present invention is
Since it is constructed as described above, after the rubble foundation is constructed by leveling the top surface evenly, an asphalt mastic layer is poured onto the upper surface to form an asphalt mastic layer with little unevenness. By placing a caisson on the layer, it is possible to set a large friction coefficient between the caisson and the rubble foundation. Further, asphalt mastic flowing on the rubble foundation as described above, due to the fluidity in the state of being heated to a high temperature, in addition to the state where large unevenness does not occur, due to the pressing action when placing the caisson, Since it is formed to be flat naturally, the asphalt mastic layer uniformly applied to the lower surface of the caisson can be brought into contact with the caisson to exert its function as a friction increasing member. Further, in the present invention, in a sea area where the tidal current is fast, a rubble foundation is constructed by laminating relatively small-diameter stones, the surface of which is covered with asphalt mastic, and the stones are fixed to each other by asphalt mastics and the stones Can be prevented from being washed away. And
It is possible to construct a rubble foundation that is loaded with relatively small stones, and it is possible to easily construct a marine structure even at a construction site where large stones cannot be obtained.

Further, according to the present invention, in the sea area where the tidal current is fast, it is possible to construct all the rubble foundations at a time depending on the condition of the waves and the tidal current.
When constructing a rubble foundation in a state of being divided into a plurality of layers, asphalt mastic can be cast on the surface of each gravel foundation layer to build up the layers of the rubble foundation. Then, it is possible to prevent the rubble foundation constructed with small stones from being washed away by the tidal current, and it is possible to deal with the situation of the construction site where only small stones can be used. Furthermore, in the present invention, it is sufficient to use an asphalt plant without using a crane ship such as construction using an asphalt mat or a yard for manufacturing an asphalt mat, and to install equipment according to the construction scale. It is possible to use it to easily perform the asphalt mastic placing work.

In addition to the effects of the present invention as described above, in the present invention, when the seabed is rock, the rock is used as it is as a support base for the structure without constructing a rubble foundation. The asphalt mastic layer can be applied to a predetermined thickness. When the construction method as described above is used, the strength of the bedrock can be used as it is, the construction cost of the supporting base of the structure can be reduced, and the construction can be easily performed. .

[Brief description of drawings]

FIG. 1 is an explanatory view of a marine structure constructed by the method of the present invention.

FIG. 2 is an explanatory diagram of a work for constructing an asphalt mastic on a rubble foundation.

FIG. 3 is an explanatory diagram showing a state in which asphalt mastic is made to flow down from a bucket.

FIG. 4 is an explanatory view of the action of constructing an asphalt mastic layer on the upper surface of a rubble foundation.

FIG. 5 is an explanatory diagram of a construction in which a rubble foundation is divided into a plurality of layers for construction.

6 is a cross-sectional view of a rubble foundation constructed by the method of FIG.

FIG. 7 is an explanatory view showing a state in which a caisson is placed on the rubble foundation of FIG.

FIG. 8 is a method for constructing an offshore structure in which an asphalt mastic layer is constructed on rock and caisson or the like is placed.

FIG. 9 is an explanatory view of a marine structure constructed using a conventional asphalt mat.

FIG. 10 is an explanatory diagram of a conventional example of constructing a marine structure on rock. It is explanatory drawing of the offshore structure using the conventional asphalt mat.

[Explanation of symbols]

1 offshore structure, 3 caisson, 4 asphalt mat, 5 rubble foundation, 10 asphalt mastic layer, 11 asphalt mastic,
15 buckets, 20 temporary work scaffolds.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takaki Waki 1-29-4 Tsurugamine, Asahi-ku, Yokohama-shi, Kanagawa Prefecture (72) Inventor Mitsuru Nonoda 2-chome, Tamagawa, Ota-ku, Tokyo 11 No. 20 Japan Road Co., Ltd. (72) Inventor Mitsuhiro Sato 3-13-1, Kyobashi, Chuo-ku, Tokyo Yuraku Building Taisei Rotec Co., Ltd. (72) Inventor Katsuo Matsuzaki 2-10 Akasaka, Minato-ku, Tokyo No. 9 Sea of Japan Construction Co., Ltd.

Claims (4)

[Claims] 1. A rubble foundation for a marine structure such as a breakwater constructed by constructing a rubble foundation at a predetermined height on the seabed ground and placing a caisson or the like on the rubble foundation via a friction member. The asphalt mastic that has been made to flow by heating is poured onto the upper surface of the asphalt mastic to form an asphalt mastic layer having a substantially uniform thickness by utilizing the fluidity of the asphalt mastic. A method for constructing a foundation for a marine structure, wherein a structure such as a caisson can be positioned on the asphalt mastic layer. 2. A rubble foundation in a marine structure such as a breakwater constructed by constructing a rubble foundation at a predetermined height above the seabed ground and placing a caisson or the like on the rubble foundation via a friction member. The asphalt mastic which is made to have fluidity by being heated is poured onto the upper surface of the asphalt mastic to form an asphalt mastic layer having a substantially uniform thickness and a substantially uniform thickness by utilizing the fluidity of the asphalt mastic. Along with it, an asphalt mastic is also cast on the slope part of the rubble foundation to form a slope protection layer, and a structure such as a caisson can be positioned on the asphalt mastic layer. Foundation construction method. 3. A rubble foundation for a sea structure such as a breakwater constructed by constructing a rubble foundation at a predetermined height above the seabed ground and placing a caisson or the like on the rubble foundation via a friction member. Is constructed by dividing it into multiple layers, and the construction of coating the asphalt mastic with fluidity by heating the upper surface of one layer of the rubble foundation, each time the rubble foundation layer is constructed. , The asphalt mastic is repeatedly cast to build a rubble foundation with a predetermined height, and after building the rubble foundation, the asphalt mastic is cast on the top surface of the rubble foundation to make it substantially uniform. The foundation of a marine structure characterized by forming an asphalt mastic layer having a thickness and a substantially uniform flatness, and enabling a structure such as a caisson to be positioned on the asphalt mastic layer. Built method. 4. When the seabed for constructing the offshore structure is rock, work is performed to correct the unevenness or slope of the rock, and work to remove the insufficient strength of the rock is performed. Foundation construction method for offshore structures, characterized in that an asphalt mastic layer whose top surface has a substantially uniform flatness is formed on the bedrock, and structures such as caisson can be positioned on the asphalt mastic layer. .