JPS59161520A - Suppression of landslide - Google Patents

Abstract

PURPOSE:To effectively suppress the occurrence of landslide by providing a water infiltrating and injecting well through which collects ground water in near landslide portion and allows the ground water collected to flow down into the deep layer under the ground at given intervals. CONSTITUTION:Water infiltrating and injecting wells 1 of a diameter of 3-6m, passing through a landslide face S where landslide would occur, are provided at given intervals. Also, water-collecting pipes 3 are inserted into the wells 1 in the neighborhood of the landslide face S, and water-injecting pipes 5 are inserted into the wells 1 in rocked (d) or aquifer (e). Ground water responsible for landslide in the neighborhood of the landslide face S can thus be collected in the water-injecting section 4 and returned to the aquifer (e) or the rocked (d) through the water-injecting pipes 5.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a landslide suppression method implemented in a landslide area.

[Background of the invention and prior art]

The Japanese archipelago, which is located within the Pacific Ocean rice production area, has a complex geological structure, and Neogene M system and wide-area metamorphic rocks, which are prone to forming landslides, are widely distributed. Disasters caused by landslides, slope failures, and debris flows are caused not only by topographical factors but also by regional development, but based on past statistics, precipitation and snowmelt are the biggest triggers. Japan is located in this geographical, social, and climatic environment. Currently, there are approximately 70,000 locations that are at risk of such disasters.

Many of these occur due to heavy rains, long rains, or during the snowmelt season. This is because the occurrence of ground bells is in a t1M tangential relationship with groundwater, that is, the pressure of water in the soil (subsurface), and conversely, the treatment of groundwater controls the occurrence of ground bells. There is a lot of talk.

Horizontal polling, water collection wells, and drainage tunnels (combined with drainage polling) are used for the sole purpose of eliminating groundwater (lowering the groundwater level) as a method to prevent the occurrence of groundwater or to suppress its activity once it has occurred. ). Horizontal poling occurs at a horizontal angle of 0° to 15° from the ground surface, and the volume of each hole is small, so the possibility that this will encounter a water path is extremely small. Therefore, it is necessary to provide several holes, but the length of each hole is approximately 2031L to 60 m, and if the length is longer than this, the drilling error will increase. In addition, there is a risk that clogging may occur and the pipe may break due to the ground bell.It cannot be considered as a permanent problem; It will be done.

Water collection wells pose problems in how the groundwater collected here is drained. In other words, drain the bong and
Large-diameter long polling hole ``f'' on the tenas: When used as a drainage hole, it requires a hydraulic gradient that allows for natural drainage, and similar to horizontal boring, it is difficult to avoid due to multiple sliding movements of the ground surface. Multiple cuts may occur, making drainage impossible or connected.

Drainage tunnels must be dug from outside the ground for maintenance and security reasons. Therefore, the hole length becomes long, which is economically disadvantageous.

[Principle of the invention]

The soil structure of the landslide zone is composed of soil on the surface, a relatively permeable silt, and several alternating clay layers, with an inverted landslide layer (clay) in the geological changes below. Wang) There is a weathering, rock formations, and aquifers. The groundwater that influences the occurrence of ground bells originates from nearby areas. The water in this area is affected not only by seepage water from the ground surface, but also by the water level of upstream recharge sources (e.g. ponds, river water).

It depends on the amount of water. Therefore, in places where the water level is high, landslides are more likely to occur at times like this, both on the surface of the land and in the strata above it. The surface of the earth is weathered underground. The base itself does not allow water to pass through, but there are water channels (good permeability) such as joints and cracks that exist within the layer, so these parts The water level is often lower than the area near the surface or the ground surface. Therefore, in order to lower the water level on many sides of the landslide, it is sufficient to install a device that pumps water into the low-pressure area in the lower layer.

[Structure of the invention]

The method invented here was developed to improve the shortcomings of the conventional method by utilizing natural soil hydraulics for the reasons mentioned above.
In order to lower the groundwater level near the landslide surface (soil-rich clay) at intervals of i[ii3 N~6''% depth 1'0
71! ~8011E, a reinforced concrete water collection and injection well will be installed. A water collection/injection well has an upper water collection part and a lower water injection part in a single well, collects water from the upper well, uses the natural water head difference to collect groundwater in the water collection part, and uses the water injection part Water is injected into the ground from below to reduce pore water pressure near all surfaces. The size of the water injection part should be determined based on a preliminary investigation.
Knowing the natural water ji from near the bell surface, it is determined that this i can be injected. Depending on the ground condition, an effective method is to install a non-pullable poling hole above the ground level of the caisson and insert a water collection pipe, and install a water injection poling hole below the ground bell level. One possible method is to install a pipe and insert a water injection pipe.

〔Example〕

The drawing shows one embodiment, and first, a water collection/injection well 1 is provided that penetrates the expected landslide surface 8.

This water collection/injection well l has a diameter of about 3 m to 6 m. A plurality of water collecting vibes 3 inserted into the polling holes are installed near the ground bell surface 8 where the water level is most required to decrease, and this part is used as the water collecting part 2 to send the collected groundwater to the water injection part 4 below. . Note: As shown in the figure, the water capital 4 is located, for example, in the base @d that exists below the bell surface 8 or in the aquifer below it, and is also located in the water injection hole ( The groundwater collected by the pipe 5 is returned to the aquifer below.A large number of small holes are drilled in the water collection pipe 3 and the water injection pipe 5, so that the entire water collection or Water can now be injected.

In the figure, a indicates a layer with good permeability such as a sand layer, a layer with poor permeability such as a clay layer, and C indicates a weathered zone.

〔Effect of the invention〕

Collects groundwater near all nine surfaces, which is the main cause of ground bells,
By installing water collection and injection wells at predetermined intervals that allow the collected groundwater to flow down deep underground, it is possible to lower the groundwater level near the surface of the ground bell, effectively suppressing the ground water level, and especially for drainage. Because it does not require any equipment and is relatively easy to install,
Beni costs and maintenance costs are reduced compared to conventional construction methods.

[Brief explanation of the drawing]

The drawing is a longitudinal cross-sectional view C showing one embodiment of the present invention. 1...Water collection/injection well 2...Water collection section 3...Water collection vibe 4...Water injection section 5...Water injection vibe

Claims (3)

[Claims] (1) Water injection wells are installed at predetermined intervals in areas where ground bells are expected, and in order to lower the groundwater level near the ground level, water is pumped upward, and the collected groundwater is poured from below into the ground water. An underground control method that uses natural hydraulic gradients to inject water into the ground using the natural hydraulic gradient. (2) The method for suppressing soil and slip flooding according to claim 1, wherein the soft water injection wells are provided at intervals of 3 Cll to i's O*. (3) Claim 1 or fc is the method for suppressing the occurrence of underground potholes as set forth in Claim 2, in which a drainage poling hole is provided above the bell surface of the water collection/injection well, and a water injection poling hole is provided below.