JPS611717A - Ground improvement work by chemical stress - Google Patents

Abstract

PURPOSE:To improve the ground by a method in which hardener bodies are formed of an expansible adhesive hardening material under the ground, expanded, and hardened, and the ground is consolidated. CONSTITUTION:While injecting an expansible hardening grout into the ground 1, excavation is made in a continuous wall form to the bearing stratum 3, and a given number of precast parts 4 with projections are set into the grout before it begins to harden. Excavation is made to the bearing stratum 3 from the ground's surface 1, expansible concrete 5 is poured into the pit, and before the concrete 5 hardens, reinforcing steel materials 6 with collars are inserted into the concrete 5. A water-absorbable, expansible, and bonding hardener is mixed with the soil with stirring in the pit to form an expansible soil cement column 7.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention involves excavating, drilling, or drilling and agitating the ground to form wall-shaped or column-shaped underground members in a predetermined arrangement. It relates to a construction method that uses members to reinforce and strengthen the bearing capacity of the ground within a required range, while at the same time improving the ground itself.

[Conventional technology]

In recent years, various soft ground improvement methods have been developed and ground improvement is carried out using various methods. Alternatively, various methods have been implemented in which a wall-like foundation structural member is formed and external forces from the structure are directly transmitted and supported to the support layer.

In principle, various soft ground improvement methods apply compaction external forces such as preload, vibration, impact force, pressing force, and explosive force to the ground within the required improvement area to reduce the soil pore ratio.
Furthermore, in order to reduce the water content ratio of the soil in the improved area, two measures are taken independently or directly: promoting the discharge of pore water between soil particles. In addition, methods for forming underground members of the basic structure that reach the support layer include placing column-shaped or wall-shaped members from the ground to the support layer using methods such as digging, or by excavating, drilling, or drilling and stirring. Therefore, either a method of molding a columnar or wall-like member in one position is used.

In any of these methods, the purpose of construction is single and limited to either improving the ground or forming a member underground.

[Problems to be solved by the present invention]

In recent years, in view of the occurrence of disasters due to liquefaction of seawater sand layers during earthquakes, various specifications and standards require consideration to reduce various soil constants in foundation structure design for soil layers that are concerned about liquefaction during earthquakes. Therefore, even in foundation structures that use underground members that penetrate the water-retaining sand layer and reach the foundation, it is necessary to significantly strengthen the bending rigidity of the underground ladle, resulting in a significant increase in construction costs.

On the other hand, even in soft and viscous soil where there is no risk of liquefaction during an earthquake, it takes a long time to complete consolidation subsidence, and if the foundation structure is supported by underground members that reach the foundation,
The occurrence of a level difference between the bottom of a structure on a foundation and the ground due to subsidence of the ground beneath and around the foundation has caused various problems that are difficult to solve.

Therefore, in order to solve these problems, it is necessary to improve the ground by some method before constructing the foundation, and separately improve the ground to a level where there is no concern about liquefaction during an earthquake or long-term subsidence. It is necessary to implement improvement measures, and a construction method that simultaneously realizes the formation of underground members of the foundation structure and soil improvement has not been established.

These problems are the same in construction work to ensure the stability of slopes, embankments, etc. In order to strengthen the shear resistance of the soil layer, columnar members, etc. are installed orthogonal to or oblique to the assumed slip surface. There is a method of reinforcing the shear resistance of the soil layer using the shear resistance of the members, and on the other hand, reinforcing the shear resistance of the soil layer itself by injecting a binding hardening agent into the gaps between soil particles or constructing drainage poling holes. Although they are used in combination, a construction method that satisfies both effects simultaneously with a single construction method has not been established.

The construction method of the present invention solves these problems easily and economically by simply changing the bonding hardening material used to form the underground member to a material with expansion performance during the process of constructing the underground member. The aim is to provide an ideal ground improvement method that simultaneously satisfies both of the above-mentioned effects with a single method.

[Means for solving problems]

The gist of the construction method of the present invention is to form and place continuous or intermittent wall-like or columnar members in the ground within the required area using a bonded and hardened material that has expansion properties. [Effects of the invention method] When the invention method is implemented, The expansion force of the placed middle members exerts the same effect as the compaction external force in the soft ground improvement method described in lines 7 to 8 on page 8, and as a bonding hardening material, it removes pore water from the surrounding ground. If a material that absorbs and expands is used, it will be effective in promoting the drainage of pore water between soil particles in the soft ground improvement method, and it will also be possible to introduce the desired prestress into the formed hardened body by constraining the reinforcing material. It is also possible to improve the strength of the member, and the underground member formed in this way not only reinforces the shear strength of the ground, but also plays the role of directly transmitting the load of the structure on the underground member to the supporting ground. Become something.

[Examples of the invention method] Below are two examples of the invention method (Fig. 1 and 2).
(see figure) and specifically explain the construction method.

Example 1. (Due to the first cause) Excavation is carried out in a continuous wall form from the ground surface (1) to the support layer (3) while injecting the hardened expandable grout (2) as an excavation wall stabilizing liquid, and before the grout begins to harden, excavate in the form of a continuous wall. A required number of precast members (4) each having several stages of protrusions are installed to form a wall in the ground surrounding the required area. Next, a hole is drilled from the ground surface (1) to the support Jim (3), and expandable concrete (5) is poured into it. Before the solid concrete hardens, a reinforcing steel material (6 ) to form the required number of columns. Furthermore, the ground surface (
While drilling and stirring the ground from step 1), the water-absorbing and expanding bonded hardening material is mixed with the existing sandy soil to intermittently form expandable fill cement columns (7) that reach the support layer. In this way, the foundation structure is formed by compacting and improving the ground in the required range by the expansion force and water absorption during the hardening process of each sub-base member.

Example 2 (based on the second factor) From the ground surface <1) in a direction orthogonal or oblique to the assumed slip surface (2), ¥'! (3) Drill a slightly deeper hole,
While injecting expandable mortar (4) or water-absorbing expandable bond hardening material (5) into this hole, reinforcing steel (6) with several stages of local parts is inserted and installed, and the assumed sliding surface penetrates the cross-exit base. form a columnar member. The expansion and water absorption of this mortar or binder improves the shear resistance of the soil layer within the slope, and also introduces a desired chemical prestress into the formed columnar bodies, reinforcing the shear strength of the slope.

In addition, the C embodiment is based on the 6th Patent Publication of 1986-14, which was previously patented.
897'' and ``Japanese Patent Publication No. 58-45527''.

〔Effect of the invention〕

Example 1 of the present invention. In , the N value of the N-level penetration test shown in Figure 1 before implementation of the construction method of the present invention improved to a level (N≧18-28) where there was no concern of liquefaction during an earthquake two weeks after implementation of the present invention. .

Example 2 of the present invention. In this case, the shear strength of the slope was improved to a level where the slope remained stable even with the surface loading shown in (7) in Figure 2.

[Brief explanation of the drawing]

FIG. 1 shows Example 1 of the present invention. FIG. 2 is a plan view, a vertical cross-sectional view, and a soil columnar diagram, and FIG. 2 is an in-plane and cross-sectional explanatory view of Example λ of the present invention.

Claims (1)

[Claims] 1) Strengthen the bearing capacity of the ground by excavating, drilling or stirring the ground to form and arrange wall-shaped or column-shaped hardened bodies continuously or discontinuously in the ground. In this construction method, a cured body is formed using a bonded hardened material having a desired amount of expandability,
By the hardening expansion force of each hardened body, the ground around the hardened body in the required range and depth is pressurized to the required extent in multiple axial directions,
A construction method that statically compresses and improves consolidation of the ground. 2) In a construction method that strengthens the bearing capacity of the ground by forming and arranging wall-shaped or column-shaped hardened bodies in the ground in a continuous or discontinuous manner by excavating, drilling or stirring the ground, hardened bodies using a bonded hardened material having a desired amount of expansibility;
Before the expansible bonded hardening material begins to harden, a precast member or reinforcing material having several stages of flanges or protrusions is inserted into the expandable bonded hardening material to restrain or restrict expansion in one or two axial directions. Then, the expansion force in these directions is converted into the desired direction and efficiently exerted, and by this hardening expansion force of each hardened body, the ground around the hardened body in the required range and depth is transformed into the desired direction. A construction method that statically compresses and consolidates the ground by applying pressure to the required degree in the direction.