JPH0552366B2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention is applicable to civil engineering structures such as semi-underground structures such as boxes and excavated roads, hollow buried structures such as septic tanks and sewer pipes, or above-ground architectural structures. This article concerns a seismic reinforcement method for foundations for safe construction on relatively high sandy ground.

Conventional technology In general, sandy ground with a relatively high groundwater level, such as sand, gravel, reclaimed land, or drenched ground, is susceptible to liquefaction during an earthquake and may cause the ground to collapse. Due to the need to secure transportation routes,
When constructing a main trunk excavated road on such sandy ground, as shown in Fig. 12, for example, a reinforced concrete road 2 with a road width of 15 to 40 m and a depth of 5 to 10 m is required. Concrete roadbed 2
It is required that the thickness of a be approximately 1.5m and that it be seismically designed so that it protrudes considerably outward from the side wall.

However, this type of structure not only requires a large amount of reinforcing bars and concrete materials due to the large thickness of the subgrade and protrusion width, but also has problems such as a long construction period and high construction costs, and improvements are needed. It had been.

In order to meet this demand, as shown in Fig. 13, a liquid agent or cement 10 is mixed into the sandy soil below the road bed and solidified, and continuous walls 10 are installed on both sides of the road 2 as shown in Fig. 14. An improvement proposal was made by using a solidification method such as installing a

In addition, as shown in Fig. 15, there is a method of compacting the ground 1 below and on both sides of the road 2, and
As shown in the figure, there is a method of driving drainage piles 12 made of sand, gravel, etc.

Problems to be Solved by the Invention However, in the above-mentioned solidification method, for example, soil mortar small piles do not have tensile strength and are easily sheared by an earthquake, and the continuous wall 11 has problems in the center of the subgrade 2a. There are problems such as easy settlement, and the above compaction method has problems such as the construction area is wide and the construction work is large, the construction period is long, and the construction cost is high.Furthermore, the drainage pile method In this case, drainage is not carried out in areas where there is no difference in horizontal water head, and even if it is possible to prevent the road 2 from floating up, there are problems such as subsidence due to drainage.

Purpose of the Invention The present invention was made to solve the above-mentioned conventional problems, and its purpose is to create a foundation ground that not only can be constructed at low cost and in a short period of time, but also has a high reinforcement effect. The object of the present invention is to provide a seismic reinforcement method.

Means for Solving the Problems The method of seismically reinforcing foundation ground according to the present invention is to install small reinforcing piles with a friction material attached around a highly rigid core material under or on the side of a civil engineering structure or building structure. The reinforcing small piles are characterized by being driven in groups into the foundation ground, and the pile heads of the small reinforcing piles are separated from the structure.

In addition, the seismic reinforcement method of the second invention of the present application is to install drainage reinforcement small piles in which a drainage friction material for dissipating excess water pressure in the ground is fixed around a core material having high rigidity to a civil engineering structure or an architectural structure. It is characterized by being poured in groups into the foundation ground below or to the side of the object.

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

In Fig. 1, reference numeral 1 indicates sandy ground with a relatively high groundwater level WL, in which a dug road 2 made of reinforced concrete is constructed.

A large number of reinforcing small piles 3 are driven in groups at approximately equal intervals in the sandy ground 1 near the bottom and outside of the cut road 2. Thickness and number of reinforced small piles 3
According to the inventor's experiments as described later, the spacing etc. is nEA/As (kgf/cm ² ) [where n is the number of reinforcing small piles, E is Young's modulus, and A is the number of reinforcing small piles. The cross-sectional area, As, is the base area of the construction ground. It is understood that the substitution rate (A x n/As) x 100 is determined by the parameter of 7% is effective, and if it is less than that, there is a risk of subsidence and destruction of the structure. Even with the above, the effect remained unchanged and was found to be meaningless.

The reinforcing small pile 3 has a core material 3a as shown in FIG.
and a friction material 3b attached to its outer surface.

The core material 3a is made of a metal material such as a PC bar, a reinforcing bar, an aluminum alloy bar, a reinforcing bar cage, or a non-metallic material such as a synthetic resin, which has high rigidity against tension, compression, bending, buckling, etc. , Young's modulus E≧
Any material with a diameter of 10 ⁴ kgf/cm ² may be used, and a diameter of about 5 to 100 mm is preferable.

The friction material 3b is a granular material such as coarse sand with a diameter of about 5 to 20 mm, and is firmly adhered to the outer surface of the core material 3a with a synthetic resin adhesive such as an epoxy adhesive. , which allows for frictional engagement with the surrounding sand. This frictional force with the sand is larger than the internal frictional force of the sand. still,
The outer surface of the core material 3a is textured or has many rod shapes.
The friction material 3b may be formed by forming or fixing a small protrusion such as a plate shape.

Referring again to FIG. 1, the reinforcing small piles 3 may be inserted slightly (for example, about 10 cm) into the support layer 4 below the sandy ground 1, or may be hardened, or simply placed on the surface of the support layer 4. The support layer 4 may be placed in a floating state, or may be placed in a floating state with some distance from the surface of the support layer 4.

On the other hand, the pile heads of the reinforcing small piles 3 are not fixed to the lower surface of the roadbed 2a of the excavated road 2, but are kept apart therefrom. Incidentally, a gravel mat may be laid on the lower surface of the roadbed 2a, and the pile heads may be freely inserted into this.

Since this embodiment is configured as described above,
For example, even if shear force τ is generated in the ground 1 due to an earthquake as shown in Fig. 3A, and shear deformation occurs as shown in Fig. 3B, the reinforcing small piles 3 that behave in the same manner are Since it has high tensile rigidity, a material force T is generated inside the reinforcing small pile 3 due to the above deformation, and as a reaction force, the sandy soil around the reinforcing small pile 3 has a force T as shown in Fig. 3C. It is understood that a restraining force T' is generated to compact the ground 1.

Furthermore, as shown in Fig. 4A, when a compressive force P due to the load of the excavated road 2 etc. acts on the ground 1, a compressive stress R is also generated on the reinforcing small piles 3, but the reinforcing small piles 3 have a considerably high compression stress. Since it exhibits rigidity, a restraining force R' as shown in Fig. 4B is generated in the sandy soil around the reinforcing small piles 3 as a reaction force, and the ground 1 resists the compressive force P.
This can be understood as suppressing the subsidence of

FIG. 5 shows an embodiment of the second invention of the present application, in which the ground 1 below and outside the cut road 2 is
A large number of drainage reinforcing small piles 5 having a diameter of about 20 to 30 cm are driven in groups almost evenly.

As shown in FIG. 6, the drainage reinforcing small pile 5 includes a core material 5a and a drainage friction material 5b fixed to the outer periphery of the core material 5a.
It consists of The core material 5a has substantially the same rigidity and outer diameter as the core material 3a of the above-mentioned embodiment, and its outer periphery has been subjected to surface processing and treatment to enhance the fixing effect of the drainage friction material 5b.

Further, the drainage friction material 5b is, for example, made of rubble, gravel, etc. hardened with cement, and has a large number of communicating voids and can frictionally engage with the surrounding sand. Any material may be used as long as it can be reliably fixed to the surface.

Again in FIG. 5, the lower end of the drainage reinforcing small pile 5 may or may not be hardened to the support layer 4.
Further, the pile head is freely inserted into a gravel mat 6 laid on the ground surface and the outer periphery of the excavated road 2. The gravel mat 6 is made of, for example, gravel or porous concrete, and has a thickness of about 50 to 100 cm.

Therefore, in this embodiment, when an earthquake occurs, the reinforcing small piles 3 behave in the same way as the reinforcing small piles 3 explained in FIGS. Excess pore water generated in the ground 1 can also be absorbed and raised, and drained through the gravel mat 6. However, the drainage reinforcing small pile 5 of the present invention is merely intended to dissipate excess pore water pressure around the pile, and is not actively expected to have a drainage effect that causes ground subsidence.

Next, a method for driving the drainage reinforcing small pile 5 will be explained.

First, as shown in FIG. 7A, the earth auger 8 is rotated within the casing 7 to excavate and discharge earth and sand, and the casing 7 is driven into the ground 1.

For example, if nEA/As=5000, the drilling diameter is 30
cm, and the driving distance between the centers of the piles is 1.5 to 2.0 m.

Next, the earth auger 8 is pulled out and the drainage friction material 5b is put into the casing 7 as shown in FIG. 7B. As shown in the figure, this drainage friction material 5b is made by mixing and twisting gravel or crushed stone, which has a uniform particle size by removing fine particles, and cement.

Next, as shown in Fig. 7C, the core material 5a is inserted by vibro or driving, then the casing 7 is pulled out as shown in Fig. 7D, and finally, the drainage reinforcing small pile is inserted as shown in Fig. 7E. Spread gravel 9 horizontally on top of 5. At this time, insert the pile head of the drainage reinforcement small pile 5 into the gravel 9 by about 20 cm. In this way, the porous drainage friction material 5b is formed around the core material 5a, and the gravel is fixed to the core material 5a by cement.

FIG. 8 is a graph showing the relationship between the aforementioned parameter nEA/As value and the rate of increase in the seismic shear strength of the ground, and it can be understood from this that the nEA/As value is a parameter of the seismic shear strength.

Figure 9 is a graph showing the shear stress ratio and the amount of vertical deformation during an earthquake, and the parameters
It can be seen that as nEA/As increases, deformation becomes more difficult.

FIGS. 10 and 11 are graphs showing seismic force and excess pore water pressure ratio, and it can be seen that even if the seismic force becomes large, the excess pore water pressure does not become so large.

Effects of the invention (1) As the small pile undergoes the same simple shear deformation as the ground due to shear strain during an earthquake, the surrounding sandy soil is compacted by the friction material, so the ground is reinforced and damped. It also has effects such as sand liquefaction resistance.

(2) It is easy to construct, has low material and construction costs, and has the advantage of shortening the construction period.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an embodiment of the first invention method of the present application, Fig. 2 A is a partially enlarged perspective view of a reinforcing small pile, and B
are its plan sectional views, Figures 3 A to C and Figure 4 A,
B is an explanatory diagram of the action of the reinforcing small pile, FIG. 5 is an explanatory diagram showing an embodiment of the second invention of the present application, A in FIG. 6 is a partially enlarged perspective view of the drainage reinforcing small pile, and B is a flat view thereof. Cross-sectional views, Figures 7A to 7E are explanatory diagrams showing the construction work of drainage reinforcement small piles, and Figure 8 is a parameter diagram.
A graph showing the relationship between the nEA/As value and the rate of increase in the seismic shear strength of the ground. Figure 9 is a graph showing the shear stress ratio and vertical deformation during an earthquake. Figures 10 and 11 are earthquake forces. 12 to 16 are graphs showing examples of conventional seismic construction. 1...Sandy ground, 2...Dug road, 3...Reinforcement small pile, 3a...Core material, 3b...Friction material, 4...Support layer, 5...Drainage reinforcement small pile, 5a...Core Material, 5b
...Drainage friction material, 6...Gravel pine.

Claims (1)

[Scope of Claims] 1. A method characterized by driving small reinforcing piles with a friction material attached around a core material having high rigidity into the foundation ground below or on the side of a civil engineering structure or a building structure. Earthquake reinforcement method for foundation ground. 2. The seismic reinforcement method for foundation ground according to claim 1, which comprises separating the pile heads of the small reinforcing piles from the structure. 3. Drive drainage reinforcing small piles with drainage friction material anchored around a highly rigid core material to dissipate excess water pressure in the ground into the foundation ground below or to the side of a civil engineering structure or building structure. A method for seismically reinforcing foundation ground, which is characterized by: 4. The seismic reinforcement method for foundation ground according to claim 3, characterized in that the pile heads of the reinforcing small piles are separated from the structure.