JP4607485B2 - Expanded caisson foundation structure and seismic reinforcement structure for existing caisson foundation - Google Patents

Description

  The present invention relates to a caisson foundation and ground improvement in the construction field, and a combination of both.

  In recent years, the caisson used as the foundation has improved the seismic standards for structures and the road bridge specifications have been revised. According to this new road bridge specification (see, for example, Non-Patent Document 1), the design load at the time of the earthquake was significantly increased compared to the old design specification.

  As a result, the new caisson foundation is larger than the old design, and the size of the frame is larger, the amount of excavated soil is increased, and a significant increase in construction costs is inevitable.

  In addition, for the existing caisson foundations, applying the seismic load of the new road bridge specifications to the caisson foundations designed according to the old design specifications resulted in insufficient proof strength, requiring seismic reinforcement.

  In the new caisson foundation, the cross-sectional area of the structure 11 as shown in FIG. 24 (b) is shown in FIG. 24 (b), in accordance with the new road bridge specifications, in contrast to FIG. 24 (a) showing the caisson foundation designed by the old design specifications. Is made larger or, as shown in FIG. 24C, a design is made to increase the set depth of the structure 11.

  As a method of reinforcing the existing caisson foundation, as shown in FIG. 25, a foundation pile 15 is separately added in the vicinity of the existing caisson 11, and the additional pile 15 and the foundation of the existing caisson 11 are connected by concrete 14 to both. There is an example of a construction method that can reduce the load burden on the existing caisson foundation and withstand the seismic load of the new road bridge specifications on both the existing caisson foundation and the additional pile.

On the other hand, there are techniques that use ground improvement methods in combination with caisson construction (see, for example, Patent Documents 1 to 4), but these are positioned as auxiliary construction methods for constructing caisson works, such as those that improve the accuracy of caisson installation There is no disclosure of a method for actively using the caisson to improve the strength of the foundation.
JP 05-009940 A Japanese Patent Laid-Open No. 10-306439 JP 2000-087361 A JP 2001-342637 A Road Bridge Specification / Explanation, March 2002, Japan Road Association

  Conventionally, the new caisson foundation is designed based on the new road bridge specifications, but as mentioned above, it involves a significant increase in construction costs. The problem is to reduce this increase in construction cost by some method.

  In the existing caisson foundation, there are practically few means for reinforcing the existing caisson foundation. In recent years, the method of winding the outer periphery of a structure with a steel plate, the method of adhering reinforcing fibers, the method of applying prestress with a PC cable, etc. are the structures where the target property exists in the ground called caisson In practice, it is practically impossible due to the fact that most of them are large objects.

  In addition, there are methods to improve the concrete properties of the structure itself, and to drill the structure vertically in order to increase the amount of reinforcement and insert a reinforcing bar. Even if it exists, it is not realistic because it causes a problem that a state below the design performance is generated for a long period of time, and there are many cases where the existing structure does not have a cross-sectional margin for performing reinforcement.

  In such a situation, as described in the conventional example shown in FIG. 25, as a method for reinforcing the existing caisson foundation, a foundation pile 15 is separately added in the vicinity of the existing caisson 11, and the additional pile 15 and the existing caisson 15 are installed. A construction method for improving the earthquake resistance by connecting the caisson 11 and integrating the two is being implemented.

  However, with this reinforcing method, there is a high possibility that the burden will be large both in terms of construction cost and construction period. Furthermore, there are some properties that cannot be constructed depending on the installation conditions of the foundation. Therefore, finding a technique that makes it possible to reinforce the caisson foundation with a stable material at low cost has become an issue.

  Against this backdrop, we have invented an expanded caisson method that increases the apparent diameter of the caisson by improving the ground around the caisson itself. According to the present invention, it is possible to provide an economically enlarged diameter caisson foundation structure that satisfies the current road bridge specifications and has excellent workability in both a newly installed caisson foundation and an existing caisson foundation, and an earthquake resistant reinforcement structure for an existing caisson foundation. With the goal.

  According to the first aspect of the present invention, in the newly installed caisson foundation, a ground wall is provided on the ground surrounding the caisson itself so as to surround the caisson with a certain distance from the caisson, and the entire ground surrounded by the caisson and the ground wall By creating an improved body using the ground improvement method, and fixing the underground wall and improved body and caisson foundation together, the diameter of the caisson is kept small, and the caisson, the underground wall and the entire improved body The diameter expansion caisson that generates the diameter expansion effect of the caisson foundation reduces the construction cost of the new caisson.

  The invention of claim 2 is the newly installed caisson foundation, the ground surrounding the caisson itself is provided with a ground wall so as to surround the caisson with a certain distance from the caisson, and the entire ground surrounded by the caisson and the ground wall An improved body is created by the ground improvement method, the underground wall and the improved body and the caisson foundation are fixed, and the head of the underground wall and the head of the caisson are connected by a concrete member to further strengthen the unity. The diameter-enlarged caisson reliably generates the caisson foundation diameter-enlargement effect. The caisson main body has a small diameter, and the construction cost of the new caisson is reduced.

  The invention of claim 3 applies the invention of claim 1 to the seismic reinforcement structure of the existing caisson foundation, and the underground wall surrounding the caisson with a certain distance from the caisson around the ground surrounding the existing caisson foundation The entire ground surrounded by the caisson and the underground wall is constructed by the ground improvement method, and the underground wall and the improved body and the caisson foundation are fixed and integrated, so that the existing caisson foundation can be integrated. It is characterized by seismic reinforcement of the existing caisson foundation by generating a diameter expansion effect.

  The invention of claim 4 applies the invention of claim 2 to the seismic reinforcement structure of the existing caisson foundation, and the underground wall surrounding the caisson with a certain distance from the caisson on the ground surrounding the existing caisson foundation The ground is surrounded by the caisson and the underground wall, the improved body is created by the ground improvement method, the ground wall and the improved body and the caisson foundation are fixed and integrated, and the top of the underground wall and the caisson By connecting them together with a concrete member, the caisson foundation is expanded more securely, and the existing caisson foundation is seismically strengthened.

  According to the present invention, by improving the ground by a commonly used jet stirring method, the caisson itself designed for caisson alone is made smaller in diameter for the new caisson foundation, and as a result, Economic design is possible. For existing caisson foundations, the difference between the old design and the new design standard can be sufficiently reinforced by ground improvement, and the effect of increasing the strength of underground structures at low cost without impeding the operation of the caisson foundation Play.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  The embodiment of the present invention aims at the caisson diameter expansion effect by ground improvement or the like, and this is the same in the case of the new caisson and the existing caisson. That is, there is a caisson itself, and the improvement of the surrounding ground and the like afterwards is the same for the new caisson and the existing caisson, and the embodiment does not change. Therefore, the following description of the embodiment will be made without dividing the new caisson and the existing caisson. Hereinafter, embodiments will be described in detail with reference to the drawings. In the following description, the newly installed caisson itself and the existing caisson foundation are collectively referred to as a caisson body.

  FIG. 1 is a cross-sectional view showing a structure according to a first embodiment of the present invention, FIG. 1B is a cross-sectional view taken along line XX in FIG. 1A, and FIG. 2 is the ground according to the first embodiment. It is sectional drawing which shows the high-pressure jet stirring state for improvement.

  In the first embodiment, as shown in FIGS. 1A and 1B, the caisson main body 11 has a circular cross section, and the caisson main body 11 is driven to the support layer (predetermined position) 8 at the tip 11b. The pier (structure) 10 is supported by the head 11a. In the ground 7 around the caisson main body 11, a cylindrical steel sheet pile wall (underground wall) 12a is driven to a predetermined depth described later. Next, the ground between the caisson body 11 and the steel sheet pile wall 12 is improved by high-pressure jet stirring or the like, the solidified layer 13 is provided, the caisson main body 11, the steel sheet pile wall 12 a and the solidified layer 13 are integrated, and the entire diameter is expanded. The caisson 16 is assumed.

In the first embodiment, the distance r ′ between the caisson body 11 and the steel sheet pile wall 12a and the driving depth d of the steel sheet pile wall 12a are shown in FIG. 3 when the diameter of the caisson body is 2r and the depth is h. as such, the depth d is diameter 2 (r + r '), the depth d to h is the diameter 2r, and a caisson which is considered, the stability is calculated by the current specifications for highway bridges, interval Determine the dimensions of r 'and driving depth d.

  In the first embodiment, when the caisson body 11 is expanded in diameter, first, as shown in FIG. 2, the steel sheet piles having a depth d are concentrically arranged around the caisson body 11 at the interval r ′ described above. To cast. Next, a predetermined chemical solution or a solidifying material is injected or stirred and mixed between the caisson main body 11 and the steel sheet pile wall 12a placed by the chemical solution injector 20 and solidified.

  At this time, in the ground improvement body of the first embodiment, as shown in FIG. 4, the ground improvement body retains the necessary ground improvement strength that the ground improvement body does not compressively break against the maximum ground reaction force generated during the earthquake in the expanded caisson 16. This is confirmed, and the diameter-enlarged caisson 16 of the first embodiment is completed.

  The new caisson foundation and the existing caisson can be designed particularly advantageous in the following cases. As in the example shown in FIG. 5, (a) when the good support layer 8 is in a relatively shallow position, (b) the hard rock layer 9 exists at the lower part of the support layer 8 and is supported at the upper part of the support layer 8. If this is desired, if the diameter-enlarged caisson 16 shown in FIG. 5 (c) of the first embodiment is created, ground improvement with excellent seismic reinforcement can be performed easily and at low cost.

  6 is a cross-sectional view showing a ground improvement body and a concrete placement state according to the second embodiment of the present invention, FIG. 6B is a cross-sectional view taken along line XX in FIG. 6A, and FIG. Is a cross-sectional view taken along line YY in FIG. 6A, FIG. 7 is a cross-sectional view showing a high pressure jet stirring state for ground improvement of the second embodiment, and FIG. 8 is a ground excavation state of the second embodiment. FIG. 9 is a sectional view of concrete connecting the caisson body of the second embodiment and a cylindrical steel sheet pile wall.

  In the second embodiment, as shown in FIGS. 6A, 6 </ b> B, and 6 </ b> C, the caisson body 11 has a circular cross section, and the tip 11 b of the caisson body 11 has a support layer (predetermined position) 8. The pier (structure) 10 is supported at the head 11a. A cylindrical steel sheet pile wall (underground wall) 12a is driven into the ground 7 around the caisson body 11 to a predetermined depth. Next, between the caisson main body 11 and the steel sheet pile wall 12a, the ground is improved by high-pressure jet stirring or the like, the solidified layer 13 is provided, and the caisson main body 11, the steel sheet pile wall 12a and the solidified layer 13 are integrated. Furthermore, concrete 14 for connecting the caisson main body 11 and the steel sheet pile wall 12a is placed on the solidified layer 13 so as to be integrated with each other.

  In the second embodiment, when the diameter of the caisson body 11 is expanded, first, as shown in FIG. 7, a steel having a depth d at the interval r ′ described in the first embodiment around the caisson body 11. The sheet pile wall 12a is driven concentrically. Next, a predetermined chemical solution or a solidifying material is injected or stirred and mixed between the caisson main body 11 and the steel sheet pile wall 12a placed by the chemical solution injector 20 and solidified.

  Next, in order to place concrete 14 that connects the caisson main body 11 and the steel sheet pile wall 12a, the ground is excavated as shown in FIG. As shown in FIG. 10, the concrete 14 to be placed has a reinforcing bar T fixed to the cross section of the head 11a of the caisson main body 11, and a fixing reinforcing bar T is welded to the head of the cylindrical steel sheet pile wall 12a. At this point, the reinforcing bar T is disposed between the two, and the concrete 14 is filled in this portion, so that the integrity of the caisson main body 11 and the expanded diameter portion is made stronger.

  The purpose of placing the concrete 14 is to improve the strength and integrity of the improved body between the caisson body 11 and the steel sheet pile wall 12a and both. The strength of the improved body described in the first embodiment is made stronger, and the reliability of the lateral resistance of the expanded caisson 16 is improved.

  From this point of view, when it is judged from the properties of the ground 7 that the effect of chemical injection cannot be exhibited as expected, or when higher strength improvement is required than the ground improvement, the concrete 14 is placed deeper. The ground 7 may be replaced.

  The calculation method of the distance r 'between the caisson body 11 and the steel sheet pile wall 12a and the driving depth d of the steel sheet pile wall 12a in the second embodiment is the same as the method shown in the first embodiment.

  FIG. 11 is a cross-sectional view showing a diameter-expanded state of the third embodiment of the present invention, and FIG. 11 (b) is a cross-sectional view taken along line XX in FIG. 11 (a).

  The said 3rd Embodiment shows that the cross section of the caisson main body 11 is applicable other than circular.

FIG. 11 is a view when the cross section of the caisson body 11 is rectangular (square or rectangular).

In the third embodiment, the distance b ′ between the caisson main body 11 and the steel sheet pile wall (underground wall) 12a and the driving depth d of the steel sheet pile wall 12a are as shown in FIG. when the side length b, and the depth was set to h, depth d and the side length b + 2b ', the depth d to h is a side length b, or a caisson was considered, current specifications for highway bridges The stability calculation is performed based on the above and the dimensions of the distance b ′ and the driving depth d are determined.

  The third embodiment is the same as the first embodiment except that the cross section is rectangular, and can be a diameter-expanded caisson 16 having the same effect. As shown in FIGS. 11 (a) and 11 (b), the caisson main body 11 is driven at the tip 11b to the support layer (predetermined position) 8, and supports the pier (structure) 10 at the head 11a. Since the caisson main body 11 is rectangular, when the caisson main body is expanded, first, as shown in FIG. 12, the depth d is set at the interval b ′ described above in the ground 7 around the caisson main body 11. The steel sheet pile wall 12a is driven concentrically. Next, a predetermined chemical solution or a solidifying material is injected or stirred and mixed between the caisson main body 11 and the steel sheet pile wall 12a placed by the chemical solution injector 20 and solidified. Since the above process is the same as that of the first embodiment, detailed description on the drawings is omitted.

  13 is a cross-sectional view showing a concrete addition state of the fourth embodiment of the present invention, FIG. 13B is a cross-sectional view taken along line XX in FIG. 13A, and FIG. 13C is FIG. It is sectional drawing which follows the YY line.

  The said 4th Embodiment shows that the cross section of the caisson main body 11 is applicable other than circular. FIG. 13 is a diagram when the cross section is rectangular (square or rectangular).

  The fourth embodiment is the same as the second embodiment except that the cross section is rectangular, and can be a diameter-expanded caisson 16 having the same effect.

  As shown in FIGS. 13A, 13B, and 13C, the caisson main body 11 has the tip 11b driven into the support layer (predetermined position) 8, and supports the pier (structure) 10 in the head 11a. . Since the caisson body 11 is rectangular, when the diameter of the caisson body 11 is increased, first, as shown in FIG. 12, b ′ described in the third embodiment in the ground 7 around the caisson body 11. A steel sheet pile wall (underground wall) 12a having a depth d is concentrically placed at intervals of. Next, a predetermined chemical solution or solidified material is injected or stirred and mixed between the caisson main body 11 and the cast steel sheet pile wall 12a by a chemical solution injector 20 to provide a solidified layer 13, and the caisson main body 11, the steel sheet pile wall 12a and the solidified layer are provided. 13 is integrated. Furthermore, concrete 14 for connecting the caisson main body 11 and the steel sheet pile wall 12a is placed at the upper part of the solidified layer 13 so as to be integrated with each other. Since the above process is the same as that of the second embodiment, detailed description on the drawings is omitted.

  As shown in FIG. 10, the concrete 14 connecting the caisson main body 11 and the steel sheet pile wall 12a fixes the reinforcing bar T to the side surface of the head 11a of the caisson main body 11, and is attached to the head of the cylindrical steel sheet pile wall 12a. Reinforcing bar T or the like is attached by welding or the like, reinforcing bar T is disposed between the two, and concrete 14 is filled in this part, so that the integrity of caisson main body 11 and the enlarged diameter portion is made a stronger structure. .

  14 is a cross-sectional view showing a diameter-expanded state of the fifth embodiment of the present invention, FIG. 14B is a cross-sectional view taken along line XX in FIG. 14A, and FIG. 15 is the ground of the fifth embodiment. It is sectional drawing which shows the high-pressure jet stirring state for improvement.

  In the fifth embodiment, as shown in FIGS. 14A and 14B, in the ground 7 around the caisson main body 11, a soil cement wall (underground wall) is used instead of the cylindrical steel sheet pile wall 12a. 12b is formed in an annular shape. As shown in FIG. 15, the ground is improved between the caisson main body 11 and the soil cement wall 12b by high-pressure jet stirring or the like to provide a solidified layer 13, and the caisson main body 11 and the soil cement wall 12b and the solidified layer 13 are integrated. And the whole is made into an expanded caisson 16.

The annular soil cement wall 12b is formed by a columnar row underground continuous wall construction method or the like. As shown in the first embodiment, when the caisson body 11 has a diameter 2r and a depth h as shown in FIG. It is assumed that the diameter is 2 (r + r ') and the diameter is 2r from the depth d to h , and the caisson is assumed to be stable. The stability calculation is performed based on the current road bridge specifications, and the interval r' and the driving depth are Determine the dimension of d.

  The diameter-enlarged caisson of the fifth embodiment has the same effects as the first embodiment. In particular, in the fifth embodiment, since the underground wall is formed by the soil cement wall 12b instead of the steel sheet pile wall 12a, the diameter-expanded caisson 16 optimum for the work site can be further reduced depending on the ground conditions and the situation of the caisson main body 11. Can be constructed at a low cost.

  In addition, in this 5th Embodiment, although the soil cement wall was used as a column-column type underground continuous wall, you may form an annular underground wall using a cast-in-place pile wall, an existing pile wall, etc.

  16 is a cross-sectional view showing a diameter-enlarged caisson according to a sixth embodiment of the present invention, FIG. 16B is a cross-sectional view taken along line XX in FIG. 16A, and FIG. 16C is FIG. ) A cross-sectional view taken along line YY, FIG. 17 is a cross-sectional view showing the ground improvement high-pressure jet stirring state of the sixth embodiment, FIG. 18 is a cross-sectional view showing the ground excavation state of the sixth embodiment, FIG. 19 is a cross-sectional view of concrete connecting the caisson body of the sixth embodiment and a cylindrical soil cement wall.

  Since the shape and the like of the soil cement wall (underground wall) 12b of the sixth embodiment are the same as those of the fifth embodiment, the same reference numerals are assigned to the same components of the soil cement wall 12b, and detailed description thereof will not be given. Omitted. When the soil cement wall 12b is constructed, the ground between the caisson main body 11 is improved by high-pressure jet stirring or the like. As shown in FIG. 18, the ground improvement range leaves a portion where concrete 14 is to be placed later.

  Next, in order to place concrete 14 for connecting the caisson main body 11 and the soil cement wall 12b, the ground is excavated as shown in FIG. As shown in FIG. 20, the concrete 14 to be placed has a reinforcing bar T fixed on the cross section of the head part 11a of the caisson main body 11 and the head part of the soil cement wall 12b, and the reinforcing bar T is arranged between both. Concrete 14 is filled into the structure shown in FIG. 19, and the integrity of the caisson main body 11 and the enlarged diameter portion is made stronger.

  The diameter-enlarged caisson 16 of the sixth embodiment has the same effect as that of the second embodiment. In particular, in the sixth embodiment, since the underground wall is formed by the soil cement wall 12b instead of the steel sheet pile wall 12a, the diameter-expanded caisson 16 optimum for the work site is further reduced depending on the ground conditions and the situation of the caisson main body 11. Can be constructed at a low cost.

  FIG. 21 is a cross-sectional view showing a diameter-expanded state of the seventh embodiment of the present invention, and FIG. 21 (b) is a cross-sectional view taken along line XX in FIG. 21 (a).

  The said 7th Embodiment shows that the cross section of the caisson main body 11 in 5th Embodiment is applicable besides circular. As shown in FIG. 21, in the ground 7 around the caisson main body 11 having a rectangular cross section (square or rectangular), as shown in FIG. 12, the depth is the distance b ′ described in the third embodiment. The soil cement (underground wall) wall 12b of d is driven concentrically. Between the caisson body 11 and the soil cement wall 12b, the ground is improved by high-pressure jet stirring or the like, the solidified layer 13 is provided, and the caisson body 11 and the soil cement wall 12b and the solidified layer 13 are integrated to expand the entire diameter caisson. 16

  The diameter-enlarged caisson 16 of the seventh embodiment has the same effect as that of the third embodiment. In particular, in the seventh embodiment, since the underground wall is formed by the soil cement wall 12b instead of the steel sheet pile wall 12a, the diameter-expanded caisson 16 optimum for the work site can be further reduced depending on the ground conditions and the situation of the caisson main body 11. Can be constructed at a low cost.

  In the seventh embodiment, a soil cement wall is used as the columnar underground continuous wall. However, an annular underground wall may be formed using a cast-in-place pile wall or an existing pile wall.

  The distance b ′ between the caisson body 11 and the soil cement wall 12b and the driving depth d of the soil cement wall 12b in the seventh embodiment are the same as those described in the third embodiment, but in FIG. When the side length of 11 is b and the depth is h, it is assumed that the side length is b + 2b 'up to the depth d, and the caisson is considered as the side length b from the depth d to h. The stability calculation is performed based on the above, and the dimensions of the interval b ′ and the driving depth d are determined.

  22 is a cross-sectional view showing an expanded state of the eighth embodiment of the present invention, FIG. 22 (b) is a cross-sectional view taken along line XX in FIG. 22 (a), and FIG. 22 (c) is FIG. (A) It is sectional drawing which follows the YY line.

  The said 8th Embodiment shows that the cross section of the caisson main body 11 in 6th Embodiment is applicable besides circular. As shown in FIG. 22, in the ground 7 around the caisson body 11 having a rectangular cross section (square or rectangular), as shown in FIG. 12, the depth is the distance b ′ described in the third embodiment. The soil cement wall (underground wall) 12b of d is driven concentrically. As shown in FIG. 19, the caisson body 11 and the soil cement wall 12b are ground improved by high-pressure jet stirring or the like to provide a solidified layer 13, and the caisson body 11 and the soil cement wall 12b and the solidified layer 13 are integrated. Turn into.

  Next, the ground is excavated in order to place concrete 14 for connecting the caisson main body 11 and the soil cement wall 12b. As shown in FIG. 20, the concrete 14 to be placed has a reinforcing bar T fixed on the side surfaces of the head part 11a of the caisson main body 11 and the soil cement wall 12b, and the reinforcing bar T is disposed between the two. The concrete 14 is filled, and the integrity of the caisson main body 11 and the diameter-expanded portion is made to be a stronger structure.

  Since the shape and the like of the soil cement wall 12b of the eighth embodiment are the same as those of the seventh embodiment, the detailed description with reference to the drawings for the same components is omitted, but the caisson body 11 and the soil cement wall 12b are connected. In order to place the concrete 14 to be ground, the ground improvement and ground excavation are performed while leaving a portion necessary for the subsequent concrete placement as shown in FIGS.

  The diameter-enlarged caisson of the eighth embodiment has the same effect as the fourth embodiment. In particular, in the eighth embodiment, since the underground wall is formed by the soil cement wall 12b instead of the steel sheet pile wall 12a, the diameter-expanded caisson 16 optimum for the work site is further reduced depending on the ground conditions and the situation of the caisson main body 11. Can be constructed at a low cost. In the eighth embodiment, the soil cement wall is used as the columnar underground continuous wall. However, an annular underground wall may be formed using a cast-in-place pile wall, an existing pile wall, or the like.

  In addition, according to each said embodiment, although the ground bridge pier on the ground was demonstrated as a diameter expansion method of the caisson foundation accompanied by ground improvement, and the seismic reinforcement structure of the existing caisson foundation, each said embodiment is described as a river crossing part etc. Of course, it can be applied to underwater bridge piers (underwater existing foundations). In this case, as shown in FIGS. 23 (a) and 23 (b), in the case of the steel sheet pile wall 12a, the depth below the riverbed is cut and removed. In addition, construction such as ground improvement and concrete placement will be below the riverbed. Further, according to each of the above embodiments, the basic shape of the caisson having a circular cross section or a rectangular cross section has been described, but it is needless to say that each of the above embodiments can be applied to a cross section other than a circular or rectangular shape such as an elliptical cross section.

(A) is sectional drawing which shows the structure of the diameter-enlarged caisson foundation by 1st Embodiment of this invention, (b) is sectional drawing which follows the XX line in the (a). It is sectional drawing which shows the high pressure jet stirring state of the said 1st Embodiment. It is explanatory drawing of the cross-sectional view of a false caisson used for stability calculation in the case of a circular cross-section caisson. It is explanatory drawing of the verification of the shear strength in a ground improvement body. In the new caisson foundation, the present invention is an advantageous example, (a) shows a conventional example when a good support layer is in a relatively shallow position, and (b) shows a hard rock layer below the support layer. And the conventional example in the case of wanting to support on the upper part of a support layer is shown, (c) is explanatory drawing which shows the case of the diameter expansion caisson of the said 1st Embodiment. (A) is sectional drawing which shows the structure of the diameter expansion caisson foundation by the said 2nd Embodiment of this invention, (b) is sectional drawing which follows the XX line in (a), (c) is the same (a). It is sectional drawing which follows a middle YY line. It is sectional drawing which shows the high pressure jet stirring state of the said 2nd Embodiment. It is sectional drawing which shows the excavation state of the ground of the said 2nd Embodiment. It is sectional drawing which shows the concrete expansion state of the said 2nd Embodiment. It is detail drawing of the connecting material of the concrete provided between a caisson and a steel sheet pile wall. (A) is sectional drawing which shows the structure of the diameter-expansion caisson foundation by 3rd Embodiment of this invention, (b) is sectional drawing which follows the XX line in the (a). It is explanatory drawing of the cross-sectional view of a false caisson used for stability calculation in the case of a rectangular cross-section caisson. (A) is sectional drawing which shows the structure of the diameter expansion caisson foundation by the said 4th Embodiment of this invention, (b) is sectional drawing which follows the XX line in the (a), (c) is the same (a). It is sectional drawing which follows a middle YY line. (A) is sectional drawing which shows the structure of the diameter expansion caisson foundation by the said 5th Embodiment of this invention, (b) is sectional drawing which follows the XX line in the (a). It is sectional drawing which shows the high pressure jet stirring state of the said 5th Embodiment. (A) is sectional drawing which shows the structure of the diameter expansion caisson foundation by the said 6th Embodiment of this invention, (b) is sectional drawing which follows the XX line in (a), (c) is the same (a). It is sectional drawing which follows a middle YY line. It is sectional drawing which shows the high pressure jet stirring state of the said 6th Embodiment. It is sectional drawing which shows the excavation state of the ground of the said 6th Embodiment. It is sectional drawing which shows the concrete expansion state of the said 6th Embodiment. It is a detailed view of a concrete connecting material provided between a caisson and a soil cement wall. (A) is sectional drawing which shows the structure of the diameter-enlarged caisson foundation by the said 7th Embodiment of this invention, (b) is sectional drawing which follows the XX line in said (a). (A) is sectional drawing which shows the structure of the diameter expansion caisson foundation by the said 8th Embodiment of this invention, (b) is sectional drawing which follows the XX line in the (a), (c) is the same (a). It is sectional drawing which follows a middle YY line. (A) is sectional drawing which shows the case where the structure of 1st Embodiment of this invention is applied to an underwater structure, (b) is the structure according to the said 2nd Embodiment of this invention applied to an underwater structure. It is sectional drawing which shows the case where it did. (A) is the shape of the caisson foundation according to the conventional design method, (b) is the shape of the caisson foundation when the support layer is not changed in the case of designing with the current road bridge specifications, and (c) is the length of the frame. It is explanatory drawing which shows typically the shape of the caisson foundation in the case of lengthening. It is explanatory drawing which shows the structure in the case of increasing the existing existing caisson foundation and performing earthquake-proof reinforcement by the pile method.

Explanation of symbols

7 Ground 8 Support layer 9 Hard rock layer 10 Pier pier body 11 New caisson caisson itself or existing caisson body (generally called caisson body)
11a New caisson itself or lower end of existing caisson housing 11b New caisson itself or upper end of existing caisson housing 12a Steel sheet pile wall (underground wall)
12b Soil cement wall (underground wall)
13 Ground improvement layer by high-pressure jet agitation 14 Concrete member 16 Expanded caisson 20 Chemical solution injector

Claims (4)

In caisson foundation structure of caisson foundation with ground improvement,
An annular underground wall is provided on the ground surrounding the caisson foundation so as to surround the caisson at a certain distance from the caisson, and the entire ground surrounded by the caisson and the underground wall is improved by improving the ground. And fixing the underground wall and the improved body and the caisson to integrate them ,
When the distance between the caisson and the underground wall is r ′, the depth of the underground wall is d, the diameter of the caisson is 2r, and the depth of the caisson is h, the depth of implantation of the underground wall It is assumed that the diameter is 2 (r + r ′) up to d and the caisson depth is 2r from the driving depth d of the underground wall to the depth h of the caisson. A diameter-enhanced caisson foundation structure characterized in that the size of the underground wall interval r ′ and the depth of the underground wall d is determined . The diameter-enlarged caisson foundation structure according to claim 1,
A diameter-enlarged caisson foundation structure characterized in that the head of the underground wall and the head of the caisson are connected by concrete. In the seismic reinforcement structure of the existing caisson foundation,
A ground wall is provided in the surrounding ground of the existing caisson foundation so as to surround the caisson with a certain distance from the caisson, and an improved body is improved by ground improvement for the entire ground surrounded by the caisson and the ground wall. Forming, fixing and integrating the underground wall and the improved body and the caisson foundation ,
When the distance between the caisson and the underground wall is r ′, the depth of the underground wall is d, the diameter of the caisson is 2r, and the depth of the caisson is h, the depth of implantation of the underground wall It is assumed that the diameter is 2 (r + r ′) up to d and the caisson depth is 2r from the driving depth d of the underground wall to the depth h of the caisson. A seismic reinforcement structure for an existing caisson foundation, characterized in that the dimension of the underground wall interval r ′ and the depth of d penetration of the underground wall is determined . A seismic reinforcement structure for an existing caisson foundation according to claim 3,
Seismic reinforcement structure for existing caisson foundation, wherein the head of the underground wall and the head of the caisson are connected by concrete

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