JPH01239218A - Method for protecting structure constructed on sand base liable to be liquefied - Google Patents

Abstract

PURPOSE:To prevent a structure from sinking or floating up caused by liquefaction at the time of earthquake by forming a gravel layer on a sand base liable to be liquefied, and forming on the layer an underground base for a structure after a drain pipe is arranged in the layer. CONSTITUTION:A gravel layer 6 is formed on a sand base 12, and a base 14 is formed thereon, while drain pipes 22a-22c are provided and communicated with a rain water catch-basin 24 opened at the ground. A structure 10 composed of side walls 18, slabs 20 and the like on the base 14. It is thus possible to prevent the structure from sinking and floating up as excessive water from gaps is collected at the gravel layer and thereafter drained by the drain pipes.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for protecting structures built on sandy ground that is prone to liquefaction, and in particular to a method for preventing structures from sinking or rising.

(Conventional technology) When building structures are constructed on sandy ground, the sandy ground liquefies due to the rise in excess pore water pressure that occurs in the ground during an earthquake, causing damage in the past that caused these structures to sink or float. This often occurs during earthquakes.

Countermeasures against such problems include ground improvement, gravel drains, and groundwater level lowering methods, but these are not often adopted due to site constraints and long-term maintenance issues.

Therefore, as a method for solving such problems, there is a liquefaction prevention structure as disclosed in, for example, Japanese Patent Application Laid-Open No. 58-127823.

However, there are problems in specifically applying the structure disclosed in this publication to the protection of structures as described below.

(Problems to be Solved by the Invention) In other words, in the liquefaction prevention structure of the above-mentioned publication, gravel is placed around the outer periphery of the permeable concrete columns in the foundation ground that supports the structure.
A predetermined number of drain columns with permeable walls made of fine stone, slag, or other materials are installed to prevent excessive pore water pressure from rising. There were problems in that the construction was difficult and the construction costs were high.

Further, in a structure in which a drain column is provided below a structure, there is a problem in that the structure floats due to the pressure of water rising in the drain column when the ground becomes liquefied.

This invention was made in view of these conventional problems, and its purpose is to provide a structure on sandy ground that is prone to liquefaction, which is easy to construct and economical, and which prevents the sinking and floating of structures. The objective is to provide a protection method for structures constructed in the United States.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides a method for installing gravel that also serves as paving stones in the horizontal direction below the underground foundation of a structure constructed on sandy ground that is prone to liquefaction. At the same time as forming a layer, one or more drainage pipes were installed extending horizontally from this gravel layer through the underground foundation, and excess pore water generated in the sandy ground was collected by the gravel layer. After that, the water is drained onto the ground through the drain pipe.

(Function) According to the protection method with the above configuration, when seismic force acts on the sandy ground and pore water pressure increases, excess pore water is collected in the gravel layer and then buried in the underground foundation of the structure. Since water is quickly drained to the ground from horizontally extending drainage pipes, the rise in pore water pressure and liquefaction in the ground beneath the underground foundation is suppressed, effectively preventing the structure from sinking or rising.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the method for protecting a structure built on liquefied sandy ground according to the present invention.

The structure 10 shown in the figure is located on liquefiable sandy ground 12, and its foundation 14 is installed in the ground slightly dug below the ground surface.

The protection method is performed before constructing the structure 10, and first, a gravel layer 16 having a predetermined thickness is formed below the foundation 14 of the structure 10, which also serves as a paving stone top.

The gravel layer 16 uses gravel having a predetermined size, and is spread in a size corresponding to the area of the base 1i1114 to be constructed.

Once the gravel layer 16 is formed in this way, the foundation 14 is constructed above it, and the side walls 18 of the structure 10 are placed on the foundation 14.
The structure 10 is constructed by constructing the slab 20 and the like.

During construction of the foundation 14, one or more drain pipes 22a to 22C extending horizontally are installed inside the foundation 14.

In this embodiment, three hollow pipe-shaped drain pipes 22a-
One end of each of the drain pipes 22a to 22C is located in the gravel layer 16, and the other end opens to a rainwater drainage basin 24 provided on the ground.

Now, in the protection method configured as above, sand ground 1
When an earthquake force acts on the structure 10 and the pore water pressure increases, the excess pore water is collected in the gravel layer 16 and then the foundation 1 of the structure 10
Since water is quickly drained from the drain pipes 22a-c buried in the underground foundation 14 and extending horizontally to the drainage mass 24, an increase in pore water pressure and liquefaction in the ground below the underground foundation 14 are suppressed, and the structure 10 sinks. and floating are effectively prevented.

(Effects of the Invention) As explained in the embodiments above, according to the method for protecting structures built on sandy ground that easily liquefies, the method for protecting structures built on sandy ground that easily liquefies A gravel layer that also serves as a paving stone layer is formed in the horizontal direction below the underground foundation, and one or more drainage pipes are installed that extend horizontally from this gravel layer through the underground foundation, and Excess pore water generated in the sandy ground is collected in the gravel layer and then drained to the ground through the drainage pipe, so that liquefaction caused by increased pore water pressure in the ground under the underground foundation is alleviated and eliminated. , structures are prevented from sinking or rising.

In addition, the protection method forms a gravel layer that also serves as paving stones below the foundation of the structure, and a layer of gravel that extends almost horizontally from this gravel layer.
Since only one or more drainage pipes are installed, construction is easy and economical.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the method of the present invention. １０・・・・・・・・・・・・・・・・・・Structure 12・・・・・・・・・・・・・・・・・・Sand ground 14・・・・・・・・・・・・・・・・・・・・・・
Basics 16・・・・・・・・・・・・・・・・・・
Gravel layer 22 a-c・・・・・・・・・Drain pipe patent applicant Chubu Electric Power Co., Ltd.
Obayashi Co., Ltd. Kumiyo Attorney Patent Attorney - Ken Iro Kikushima Patent Attorney Matsu
Book Masari NI map

Claims (1)

[Claims] A gravel layer that also serves as paving stones is formed horizontally below the underground foundation of a structure built on sandy ground that is prone to liquefaction, and it extends horizontally from this gravel layer through the underground foundation. A sandy ground prone to liquefaction, characterized in that one or more drainage pipes are installed, excess pore water generated in the sandy ground is collected in the gravel layer, and then drained to the ground through the drainage pipe. A method of protection for structures built on top.