JPH0160619B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for preventing ground failure that occurs in soft ground on a slope where unconsolidated soft ground is distributed in contact with solidified rock.

In general, the ground condition is on a slope where unconsolidated soft ground is distributed in contact with the consolidated bedrock.
Furthermore, if seepage water or groundwater flows down during rain or snow melting at the boundaries of the ground or in soft ground, and multi-scale subsurface water is formed, these boundaries can be used as failure surfaces to break the ground. There are many cases where disasters such as collapses and landslides occur.

When examining the locations where the above-mentioned ground failures and landslides occur, it is found that they frequently occur in sloped areas ranging from flat areas to mountainous areas, and are examples of cases where groundwater conditions are added to the above-mentioned ground conditions. is often recognized.

Therefore, conventional countermeasure construction methods to prevent the occurrence of ground collapse and landslides on soft ground on slopes include:
(b) Replacement method that replaces part of the soft ground layer;
Various countermeasure construction methods are used, such as (b), pile driving method, and (c), pile driving method and drainage boring to drain water horizontally. If the soil is more than 5 to 10 meters thick and distributed over a wide area, it is technically and economically difficult to directly construct it without performing some kind of ground preparation. In the pile driving method, the thicker the soft layer, the longer the piles are required. Therefore, it is necessary to construct a road for bringing large heavy machinery onto the slope, secure a foothold for construction machinery, or carry out temporary construction work. It is extremely difficult to construct. Even if it were possible to drive long piles, the soft soil that makes up the soft ground becomes muddy due to groundwater conditions and slips between the piles, reducing the deterrent effect of the driven piles. tend to be attenuated.

In addition, when ground improvement is used as a countermeasure, even if an attempt is made to improve soft soil, if the groundwater flowing through the sloped ground is obstructed, there is a risk that a dam will build up behind it, which may lead to a dangerous situation. become.

Furthermore, in order to effectively drain water from a groundwater aquifer with a multifaceted structure, a small number of holes limited to the horizontal direction will not necessarily drain water sufficiently; Drainage is difficult. In particular, a space is created after a hole is drilled by drainage boring, which is easily filled by earth pressure and inflowing earth and sand.Generally, perforated PVC pipes, etc. are inserted, but over a long period of time they gradually lose their ability to pass water. Therefore, it is inevitable that the drainage function will deteriorate.

However, the basis of measures to prevent the occurrence of ground failures and landslides on soft ground on slopes is to have effective underground drainage. The method is to replace the water-permeable material with a water-permeable material without disturbing the drainage hole at all, without creating a space to serve as a drainage hole by drilling holes, etc., and to carry out the construction on a flat surface to the necessary extent. It would be most desirable as a countermeasure against the above-mentioned ground failure and landslide if it were possible to form a drainage facility with a structure that is both expansive and interconnected vertically at the full depth reaching the bedrock layer.

This invention solves the drawbacks and problems of the conventional construction methods mentioned above.One, it is a disaster prevention construction method that prevents ground failure and landslides that occur on soft ground on slopes. The purpose of this method is to quickly restore the ground damaged by a disaster, and on sloped land where soft ground is distributed on solidified bedrock, it is carried out in a predetermined area centered on the boundary between the rock and soft ground. The first step is to install the pipe wedge, and the third step is to remove the groundwater that causes ground failure from the target ground in the soft ground where the pipe wedge is installed, and to remove the pore water that is dehydrated by the ground injection in the third step. A second step of injecting the water-permeable unsolidified composition into the ground to form a drainage network to form a drainage channel, and injecting the solidifying composition around the pipe wedge with the above-cast pipe wedge as the core. This method provides a construction method for preventing ground failure that occurs in soft ground on sloped land, which is obtained by sequentially carrying out three steps, including the third step, which focuses on improving and strengthening the area around the pipe wedge. .

Hereinafter, the construction method according to the present invention will be described in detail with reference to the accompanying drawings.

First, in the first step according to the present invention, when unconsolidated soft ground 2 is distributed on solidified rock 1 on a slope from a flat land to a mountainous area as shown in FIG. In order to integrate the two parts by suturing them together, a pipe wedge 3 as shown in FIGS. 2 and 3 is installed only in a required predetermined area.

In general, in soft ground on a slope as shown in Figure 1, there are many cases where groundwater flows mainly along the interface between rock mass 1 and soft ground 2, and the a-a' line or the b-b' line This is the failure surface or expected ground failure surface.

In the conventional technology, long piles had to be driven to the depth required by the design using a large construction machine, but with the construction method of the present invention, a small boring machine with a self-propelled function is used. The rod 4 is attached to the pipe wedge 3, which can be easily moved to the installation point of the pipe wedge 3 and is made of a material whose stability has been tested in advance in advance and has the necessary strength. This makes it possible to set the depth to . In this case, the length of the pipe wedge 3 shall be the length of the range where ground failure is likely to occur, or the length including the range where ground failure has already occurred and the range predicted in the future.
To connect the rod 4 to the
This is done by fitting the fixing pin 5 fixed to the upper end connection part 3a of the pipe wedge 3 into the engagement groove 4a formed in the lower end connection part of the rod 4.

A drilling bit 6 is fixed to the tip of the pipe wedge 3, and reinforcing reinforcing bars 7 are appropriately incorporated inside.

Next, in the second step that is carried out following the first step, water permeates into the boundary between the rock mass 1 and the soft ground 2 or a predetermined area around where the pipe wedge 3 is installed to exclude groundwater flowing through the soft ground 2. A plurality of plate-shaped water-permeable structures 8 formed in a substantially vertical direction are formed by injecting into the ground using an injection liquid made of an unsolidified composition.

The permeable structure 8 drains groundwater flowing through the stratum boundary or soft ground 2, and
It will function as a drainage channel for the pore water that is dehydrated in the third step, which will be described later.

Here, the characteristics of the injection liquid made of the above-mentioned unsolidified composition are that it has viscosity while it diffuses into a predetermined area in a network shape during ground injection, and maintains the minimum required fluidity during injection. After the permeable structure 6, which is a net-like drainage system, is formed in the planned area, in order to prevent the fluid added material in the unsolidified composition from interfering with drainage, only the added material is kept as short as possible. This is to ensure that the drainage function of the injection material itself will not be impaired by leakage together with groundwater over time, and an additional material that does not cause pollution even if mixed into groundwater is selected. That is, as a result of various experiments, the unsolidified composition used in the present invention has a particle size distributed between 0.2 mm and 0.5 mm as the main component of the composition, and a weight percentage of 80 mm.
% or more, to which water and easily degradable polymer colloidal organic substances such as starch and cellulose are added as an auxiliary composition to provide the minimum fluidity required during injection. It is best to set the respective compounding ratios in terms of weight ratio: sand: auxiliary composition: water = 1: 0.002 to 0.004: 0.563 to 0.786.

Furthermore, in a third step performed following the second step, the pipe wedge 3 is installed and fixed in the first step, and the unsolidified composition is injected in the second step to form a net-like water permeable structure 8. After that, an injection liquid made of a solidifying composition is intensively injected around the pipe wedge 3 and the water-permeable structure 8 to form a reinforced structure 9.
is formed, and the soft ground in the area where the pipe wedge 3 is installed is improved and strengthened.By organically carrying out the three steps from the first step to the third step above, the final result is The bedrock 1 and the soft ground 2 are integrally sewn together to create a ground structure that is both strong and hydraulically stable.

Hereinafter, the three steps of the construction method according to the present invention from the first step to the third step will be explained in detail based on FIGS. 4A, 4B and 4C.

In the figure, Figure 4A shows the first step according to this invention, in which the pipe wedge 3 is installed so as to suture the bedrock 1 and the soft ground 2, and then in the second step, the pipe wedge 3 is installed. By injecting into the ground a predetermined area of the periphery using an injection liquid made of a water-permeable unsolidified composition, a plate-shaped water-permeable structure is formed in a substantially vertical direction. Then the fourth
As shown in Figure B, the solidified composition is intensively injected into the inside and outside of the pipe wedge 3 to improve and strengthen the soft ground in the area where the pipe wedge is installed, and then the area above the pipe wedge 3 is Rod 4 is separated and pulled out. FIG. 4C is an explanatory diagram showing the state in which ground drainage and the area around the pipe wedge have been improved and strengthened using the construction method according to the present invention.
The soft ground 2 is sutured to the bedrock 1 by the pipe wedge 3, and the surrounding area between the pipe wedge 3 and the ground drainage becomes a reinforced structure 9 reinforced with a solidifying composition. The peripheral part becomes a water permeable structure 8 made of a water permeable unsolidified composition,
Groundwater can be effectively drained.

As explained in detail above, according to the construction method of the present invention, it is possible to prevent ground collapse that occurs in soft ground on slopes in a short time and economically, and it is possible to prevent abnormalities such as during torrential rains or snow melting season. It can withstand uneven loads and concentrated loads due to the generation of pore water pressure or snow accumulation during the snowfall season, and can prevent ground collapse or quickly restore the ground that has been destroyed by a disaster.

[Brief explanation of drawings]

FIG. 1 shows an embodiment of the present invention, and is a sectional view showing an improved state of soft ground on a slope;
Fig. 2 is a perspective view showing a part of the pipe wedge used in this invention, Fig. 3 is a perspective view showing the connected state of Fig. 2, and Fig. 4 is a sectional view illustrating the process according to the invention. be. 1...Bedrock, 2...Soft ground, 3...Pipe wedge,
4...Rod, 5...Fixing pin, 6...Bit, 7...Reinforcing reinforcing bar, 8...Water permeable structure, 9...Reinforced structure.

Claims (1)

[Scope of Claims] 1. A first step of installing a pipe wedge in a predetermined range centered on the boundary between the rock mass and the soft ground on a slope where soft ground is distributed on solidified bedrock; A drainage network is created in the soft ground where the system is installed to remove groundwater that can cause ground failure out of the target ground, and to serve as a drainage channel for the pore water that will be dehydrated by the ground injection performed in the third step. The second step involves injecting the water-permeable unsolidified composition into the ground, and the solidifying composition is injected into the ground around the pipe wedge using the pipe wedge installed above as the core to concentrate the soil around the pipe wedge. A method for preventing ground failure occurring in soft ground on a slope, characterized in that the soft ground on the slope is improved and strengthened by a third step of improving and strengthening the soft ground. 2 In the second step of improving and strengthening the soft ground, the water-permeable unsolidified composition injected into the soft ground to form a drainage network has a particle diameter of 0.2 mm to 0.5 mm and a weight percentage of 80% or more. consisting of sand, an auxiliary composition consisting of an easily decomposable polymer colloidal organic substance such as starch or cellulose, and water for liquefying the sand and the auxiliary composition, and the sand, the auxiliary composition, and Water ratio by weight: 1:0.002~
A method for preventing ground failure occurring in soft ground on a slope as claimed in claim 1, characterized in that the ratio is set to 0.004 to 0.563 to 0.786.