JPS59429A - Foundation structure and its construction for building on soft ground - Google Patents

Abstract

PURPOSE:To prevent the liquefaction of soft ground by providing an improved ground in the surface layer of the inside of a continuous underground wall constructed to at least a depth deeper than the layer to be liquefied in the surrounding area of a building. CONSTITUTION:In the ground G consisting of a layer Ga to be liquefied, a layer Gb not to be liquefied, and a supporting layer Gc for a building, an underground continuous wall 1 is constructed to a depth deeper than the layer Ga at least in the surrounding area of a building 4, the ground is improved by arranging layers 2 surrounded by the walls 1 in mesh form 2a, for example, and the building 4 is supported by a foundation pile 3 reaching the layer Gc. Thereby, the deformation of sandy layer inside the wall 1 can be restricted and the shearing strength of the layer Ga can also be increased.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a foundation structure of a building on soft ground such as a sandy surface or a board, and a construction method thereof.

It is known that when sandy soil becomes liquefied during an earthquake, it causes significant damage to buildings and earth structures.

Therefore, in order to prevent the occurrence of liquefaction and reduce damage to facilities, soil improvement methods and foundation piles that reach strata prone to liquefaction have been developed. There are various methods such as those that improve the saturation level and those that lower the degree of saturation.

The present invention provides a building foundation structure and its construction method that are effective when constructing a high-rise building in a place prone to liquefaction, such as a landfill, where there is no risk of liquefaction but there is a soft cohesive soil layer. The purpose is to

The feature of the present invention is to construct a continuous underground wall to the point where it is easy to liquefy, improve the surface layer of the ground surrounded by this underground wall, and install foundation piles on this improved ground.

The basic structure of the present invention will be explained based on the drawings.

In FIG. 1, the layer of the ground G is divided from the surface into a liquefaction layer Ga such as a sand layer, a ground layer Gb with no risk of liquefaction, and a building support layer GO located at the deepest layer.

First, a continuous underground wall 1 is constructed at a construction site. This involves constructing a continuous underground wall (overlap pile) by excavating at least the liquefaction layer Ga with an earth auger or other excavator (Figure 2), and the remaining piles driven in place are CIP. Any of piles, MIP piles, and PIP piles may be used.

Next, the surface layer 2 of the ground surrounded by this continuous underground wall 1 is improved by arranging piles 2a in a mesh shape, for example.

This ground improvement method involves excavating with an earth auger, cementing,
Compact this ground by injecting quicklime or by applying other appropriate means.

Therefore, foundation piles 3 are driven into predetermined positions of the surface layer 2 of the soil-improved flood basin, as shown in the second diagram, until they reach the support layer Gc. Of course, this foundation pile 3 may be either a ready-made pile or a pile cast in place by injecting mortar.

The building 4 is supported by the foundation piles 3.

Therefore, even if the continuous underground wall 1 and the surrounding sand layer Ga liquefy, the deformation of the sand layer within this underground wall will be restrained.
Since the increase in excess pore water pressure is suppressed and the underground wall itself has a water-blocking effect, liquefaction of the sand layer within the underground wall is prevented. Furthermore, the shear strength of the liquefied layer Ga is increased by the piles 2a in the surface layer 2 where the ground has been improved.

As explained above and in point 7, according to the present invention, even if the liquefied layer liquefies during an earthquake, the continuous underground wall suppresses the rise in pore water pressure from the surrounding ground and reduces horizontal stress. Continuous underground walls can reduce the effects of flat stress. For this reason, the foundation piles only need to be of the minimum strength necessary to support the building, and there is less need to consider liquefaction.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a sectional view;
FIG. 2 is a plan view. ■・Continuous underground wall, 2. Improved ground (surface layer), 2a... Pile, 3... Foundation pile, 4... Building, Ga... Liquefaction layer 0 or more Patent applicant Co., Ltd. Hasegawa Construction Agent
Patent Attorney Matsu 1) 3 - Patent Attorney Matsu 1) Kazuko Patent Attorney Susumu Kodaira Figure 1

Claims (2)

[Claims] (1) Foundation piles that support the building, a continuous underground wall built around the building that is at least susceptible to liquefaction, and improved ground provided on the inner surface layer of this continuous underground wall. Foundation structure of a building on soft ground composed of 0 (2) Build underground walls at least to the point where they are susceptible to liquefaction,
A construction method for the foundation structure of a building on soft ground, characterized by improving the ground at the inner surface layer of this underground wall, and then constructing foundation piles on this improved ground.