JP7795585B1 - Dredged soil transportation method - Google Patents

Abstract

[Problem] To provide a method for transporting dredged soil efficiently. [Solution] This dredged soil transportation method involves first setting up temporary storage areas A and B at the bottom of the dam lake (3), which is exposed above water when the water level of the dam lake is low and submerged below water when the water level is high. The soil dredged from the bottom of the dam lake (3) is dumped into temporary storage areas A and B for temporary storage, and when the water level is low and the bottom of the dam lake (3) is exposed above water, the soil accumulated in temporary storage areas A and B is transported out of the lake. [Selected Figure] Figure 2

Description

The present invention relates to a method for efficiently transporting dredged soil generated when dredging sediment deposited at the bottom of a dam lake.

Dams are subject to mud, sediment, and other debris (hereinafter referred to as "sediment") flowing into them from upstream rivers. This deposit of sediment at the bottom of the dam lake, particularly near the dam body, poses a risk of impairing the dam's functionality, so dredging of the deposited sediment is carried out periodically.

Dredging of this sediment is mainly carried out during the non-flood season, from October to July of the following year. For example, the excavated sediment is landed on the exposed lake bottom when the water level drops using a dredger's grab bucket, and then transported from that location to an exit port before being removed from the dam lake.

A known method for transporting the unloaded dredged soil to the discharge port is to transfer the soil to a vehicle such as a dump truck at the unloading site, and then have the vehicle travel over the bottom of the dam lake exposed by the drop in water level to transport it out the discharge port.

Japanese Patent Application Laid-Open No. 2008-106497

However, with the conventional technology described above, as shown in Figure 5, the water level of the dam lake fluctuates significantly throughout the year, and as the water level drops, the areas where the lake bottom is exposed also change. This makes it difficult to land the dredged soil in the same place throughout the dredging work period and transport it by dump truck.

Furthermore, when the discharge point can only be located at a distant location upstream due to reasons such as the steep slope of the dam lake bank, transporting the soil using vehicles such as dump trucks takes time, and due to the aforementioned changes in water level, the soil and sand that are brought ashore cannot be temporarily stored, so dredging work has to be stopped while it is being transported.

Furthermore, while dredging of sediment has traditionally been carried out during the non-flood season from October to June of the following year, it would be desirable to be able to carry out dredging work during the flood season (July to September) in order to improve operational efficiency.

In light of these conventional problems, the present invention was made with the aim of providing a method for transporting dredged soil that can efficiently transport dredged soil without limiting the duration of dredging work.

The invention described in claim 1, which aims to solve the above-mentioned problems of the prior art, is characterized by a method for transporting dredged soil produced when dredging soil from the bottom of a dam lake, out of the dam lake. A temporary storage area is first established at the bottom of the dam lake, which is exposed above water when the water level of the dam lake is low and submerged below water when the water level is high. When the water level of the dam lake is high and the bottom of the dam lake is submerged, the dredged soil is dumped into the temporary storage area from above water. The dredged soil produced by dredging the bottom of the dam lake is dumped into the temporary storage area and temporarily stored there. When the water level is low and the bottom of the dam lake is exposed above water, the dredged soil accumulated in the temporary storage area is transported out of the lake.

The invention described in claim 2 is characterized in that, in a method for transporting dredged soil produced when dredging soil from the bottom of a dam lake, the dredged soil is transported out of the dam lake by: first, temporary storage areas are established in advance at the bottom of the dam lake at multiple depths that are exposed above water when the water level of the dam lake is low and submerged below water when the water level is high; the dredged soil produced by dredging the bottom of the dam lake is dumped into the temporary storage areas for temporary storage; and when the water level is low and the bottom of the dam lake is exposed above water, the dredged soil accumulated in the temporary storage areas is transported out of the lake.

The invention described in claim 3 is characterized in that, in addition to the configuration of claim 1 or 2, the temporary storage area is equipped with an outflow prevention wall at least on the downstream side.

By incorporating the configuration described in claim 1, the dredged soil transporting method of the present invention allows dredging operations to be carried out even during flood seasons and other periods when the water level is high, eliminating the need to stop dredging operations and enabling the efficient transport of soil accumulated in dam lakes.

Furthermore, by adopting the configuration described in claim 2 of the present invention, dredged soil can be transported in each season when the water level differs.

Furthermore, by incorporating the configuration described in claim 3, the present invention can reliably prevent the outflow of soil and sand accumulated in the temporary storage area.

(a) is a plan view showing the preparatory work state in the dredged soil transportation method of the present invention, (b) is a plan view showing the work state when the water level is at its lowest, and (c) is a plan view showing the work state when the water level has risen to the middle level. FIG. 10 is a vertical cross-sectional view showing the dredging operation and the transportation of dredged soil when the water level is low. (d) is a plan view showing the working condition when the water level is high, (e) is a plan view showing the working condition when the water level has dropped to a medium level, and (f) is a plan view showing the working condition when the water level has dropped to a low level. FIG. 2 is a vertical cross-sectional view showing the state of dredging work when the water level is high. 1 is a graph showing an example of fluctuations in the water level of a dam lake.

Next, an embodiment of the dredged soil transport method according to the present invention will be described based on the example shown in Figures 1 to 5. In the figures, reference numeral 1 denotes a dam.

As shown in Figures 1 and 2, the downstream side of the dam lake is blocked by the dam body 2, and the water depth downstream near the dam body 2 is deep. As shown in Figure 5, the water depth changes depending on the season and the dam's discharge, and when the water level is low, the bottom of the dam lake upstream 3 is exposed.

Note that reference number 3 indicates the exposed bottom of the dam lake, and reference number 4 in the figure indicates the outer edge of the dam lake. For convenience, the area where the dam lake bottom 3 is submerged is indicated by diagonal lines, and reference number 5 indicates the water surface.

At this dam 1, sediment (hereinafter referred to as sediment) accumulated at the bottom 3 of the dam lake is dredged, and the sediment (hereinafter referred to as dredged sediment) produced during dredging is transported out of the dam lake through an outlet 4a located upstream.

The dredged soil 6 is transported out of the dam lake by dredging the dam lake bottom 3 and dumping the resulting dredged soil 6 into temporary storage areas A and B, which have been set up in advance at designated locations, and then, when the water level 5 drops and the dam lake bottom 3 is exposed above water, the dredged soil 6 accumulated in temporary storage areas A and B is transported to the transport outlet 4a using a dump truck 7 or the like and removed from the lake.

Specific methods for transporting dredged soil are described in detail below.

First, as shown in Figure 1(a), a pier 8 is assembled in a designated location during a period when the water level is low due to the release of water from the dam 1 (for example, from September to October), and this pier 8 is used to assemble transportation means such as a dredger 9 and soil transporter 10, as well as a temporary storage area A downstream.

The specified location is the location where the dam lake bottom 3 is exposed when the water level of the dam lake is at its lowest and is submerged below the water surface 5 when the water level is high, and is preferably near the boundary with the water surface when the water level of the dam lake is at its lowest.

As shown in Figure 1(a), temporary storage area A is equipped with an outflow prevention body 11 that is U-shaped in plan view and has wall sections 11b, 11b on both sides of an outflow prevention wall 11a located downstream, allowing dredged soil 6 to be temporarily stored within the outflow prevention body 11.

The outflow prevention wall 11a and wall sections 11b, 11b are constructed, for example, from a continuous sheet pile wall formed by engaging the sides of multiple steel sheet piles driven into the dam lake bottom 3, and are designed to hold back the dredged soil 6 and prevent it from outflowing downstream.

Furthermore, it is preferable that the height of the outflow prevention body 11 be such that its upper end is sufficiently submerged below the water surface 5 when the water level rises, and that it does not interfere with the operation of the dredger 9 or soil transport vessel 10.

The configuration of the outflow prevention body 11 is not limited to the above-mentioned embodiment, and it is sufficient if it is equipped with an outflow prevention wall 11a at least on the downstream side.

Furthermore, the configuration of temporary storage areas A and B is not limited to those using the above-mentioned outflow prevention body 11. For example, they may be those in which a recess for dumping soil is created by excavating the bottom 3 of the dam lake, which is exposed when the water level of the dam lake is at its lowest and submerged below the water surface 5 when the water level is at its highest, or they may utilize the topography of the dam lake.

The dredger 9 may be one that excavates the bottom of the dam lake 3 using a grab bucket delivered from a crane installed on a barge, or a pump-type dredging device may be used.

The means of transportation is not limited to the soil transport barge 10; for example, the soil may be pumped from the dredger 9 to temporary storage areas A and B through a pressure pipe.

Next, once the dredger 9, soil transporter 10, and other transportation means, as well as the downstream temporary storage area A, are ready, the dredger 9 begins dredging the dam lake bottom 3 near the embankment 2, as shown in Figures 1(b) and 2, and the transportation of dredged soil 6 to the temporary storage area A begins.

In the figure, reference numeral 12 denotes a backhoe, which is used to load soil from the soil transport barge 10 into temporary storage area A or transfer soil from temporary storage areas A and B to the dump truck 7.

The dredged soil 6 transported to temporary storage area A contains a lot of moisture, making it difficult to transport by dump truck as is. Therefore, the dredged soil 6 is improved as needed by dehydration, aeration, addition of solidifying material, etc., and the improved dredged soil 6 is loaded onto a dump truck 7 or the like and transported toward the discharge point 4a.

Then, during periods when the water level at the location of Temporary Storage Area A is low, the above-mentioned dredging work, transporting soil and sand to Temporary Storage Area A, and transporting and conveying work to the discharge point 4a using dump trucks 7 or the like will be repeated.

Next, when the water level gradually rises (for example, from January to February), before the pier 8 is submerged, the transportation of dredged soil 6 by dump trucks 7 and other equipment is stopped, and heavy machinery such as backhoes 12 at temporary storage area A is evacuated to an area upstream where the dam lake bottom 3 is exposed.

In addition, in the area upstream where the dam lake bottom 3 is exposed, an outflow prevention structure 11 is installed, as shown in Figure 1(c), and a temporary storage area B is constructed upstream.

Meanwhile, dredging work by the dredger 9 continues even after transportation work by the dump trucks 7 and other vehicles has stopped, and the dredged soil 6 is transported by the soil transporter 10 to the downstream temporary storage area A, and the dredged soil 6 is dumped from the soil transporter 10 into the downstream temporary storage area A using the backhoe 12 mounted on the soil transporter 10.

When the water level rises further (for example, from March to April), approximately half of the dam lake bottom 3 is submerged, and the temporary storage area A downstream is submerged.

After the downstream temporary storage area A is submerged, dredging work continues using the dredger 9. As shown in Figure 4, the dredged soil 6 is transported to the downstream temporary storage area A by the soil transporter 10, and the dredged soil 6 is then dumped from the soil transporter 10 onto the downstream temporary storage area A from the water using a backhoe 12 mounted on the soil transporter 10.

At this time, an outflow prevention body 11 is installed in temporary storage area A, which prevents the dredged soil 6 dumped into the underwater temporary storage area A from flowing downstream, causing the dredged soil 6 to pile up in temporary storage area A and remain there temporarily.

Furthermore, during periods when the water level rises further (for example, from May to June), most of the dam lake bottom 3 is submerged, but dredging work continues using the dredger 9 during this time. As shown in Figures 3(d) and 4, dredged soil 6 is transported by a soil transporter 10 to temporary storage areas A and B set up at the dam lake bottom 3 on the downstream and upstream sides, which have different water depths. The dredged soil 6 is then dumped from the soil transporter 10 onto the downstream and upstream temporary storage areas A and B from the soil transporter 10 using a backhoe 12 mounted on the soil transporter 10.

At this time, outflow prevention bodies 11 are installed at the downstream and upstream temporary storage areas A and B, respectively, so the dredged soil 6 dumped into the underwater temporary storage areas A and B is prevented from flowing downstream, and the dredged soil 6 is piled up in the temporary storage areas A and B, where it is temporarily stored.

Furthermore, dredging work on the dam lake bottom 3 by the dredger 9 and dumping of dredged soil 6 into temporary storage areas A and B can continue as long as the capacity of each temporary storage area A and B is not exceeded.

Next, during the flood season (for example, July to September), the water level is rapidly lowered by releasing water from the dam as a flood prevention measure, so the water level in the dam lake gradually drops from the upstream side. As shown in Figure 3(e), first, temporary storage area B on the upstream side is exposed from the water, and as the water level drops further, exit 4a becomes passable.

The dredged soil 6 temporarily stored in the upstream temporary storage area B is then improved as necessary by dehydration, aeration, addition of solidifying material, etc., and the improved dredged soil 6 is loaded onto a dump truck 7 or similar and transported toward the discharge point 4a.

Furthermore, once the water level drops and the top of the downstream temporary storage area A and pier 8 are exposed from the water, heavy machinery such as a backhoe 12 is placed on the pier 8, as shown in Figure 3(f), and the dredged soil 6 temporarily stored in both temporary storage areas A and B is improved as necessary by dehydrating, aerating, adding solidifying material, etc., and the improved dredged soil 6 is loaded onto a dump truck 7 or similar, and transportation work toward the discharge point 4a is resumed.

At this time, the transportation of dredged soil 6 from the upstream and downstream temporary storage areas A and B can begin without waiting for dredging work by the dredger 9, since the dredged soil 6 has already been temporarily stored at temporary storage areas A and B.

On the other hand, dredging work by dredger 9 is carried out even during flood season, and as the transportation of dredged soil 6 from temporary storage areas A and B is resumed, the storage capacity of temporary storage areas A and B decreases, allowing newly dredged soil to be transported to temporary storage areas A and B, which now have excess capacity.

Furthermore, since flooding is expected during the flood season, it is desirable to install mooring facilities so that dredgers 9 and soil transport vessels 10 can be moored in the event of a flood.

After the desired amount of sediment accumulated at the bottom of the dam lake 3 has been dredged, the outflow prevention structures 11 and piers 8 that make up temporary storage areas A and B are removed, and if dredging work is to continue, the above-mentioned series of dredging work and sediment transportation work will be repeated throughout the year.

This method of transporting dredged soil involves first setting up temporary storage areas A and B at the bottom of the dam lake 3, which is exposed above water when the water level of the dam lake is low and submerged when the water level is high. The dredged soil 6 produced by dredging the bottom of the dam lake 3 is then dumped into temporary storage areas A and B for temporary storage. Dredging work, which was previously limited to periods when transportation work could be carried out using dump trucks 7, etc., can now be carried out at any time. This allows the same construction machinery to be used throughout the year, enabling seamless construction plans, improving work efficiency and increasing the amount of dredged soil per year.

In more detail, the amount of material transported by a dump truck 7, etc. typically depends on the number of dump trucks 7, etc. available per day and the number of days (number of operating days) that the lake bottom is exposed due to a drop in the water level. Therefore, dredging work by a dredger 9 is generally limited to the operating period of the dump trucks 7, etc., and cannot exceed the amount of material transported by a dump truck 7, etc.

In contrast, the dredged soil transportation method of the present invention temporarily stores dredged soil 6 in temporary storage areas A and B. This allows the dredger 9 to continue dredging the dam lake bottom 3 and transport soil to temporary storage areas A and B even when dump trucks 7 and other vehicles are not in operation, as long as the capacity of temporary storage areas A and B is not exceeded, allowing for a seamless construction plan throughout the year.

On the other hand, when it comes to transportation work using dump trucks 7, etc., the dredged soil 6 is already stored in temporary storage areas A and B before the water level rises. Therefore, once temporary storage areas A and B are exposed from the water, transportation work of the dredged soil 6 can begin without waiting for the current dredging work to end. This means that the number of operating days can be increased, a larger amount of dredged soil can be transported, and transportation work can be made more efficient.

In addition, with this method of transporting dredged soil, temporary storage areas A and B are set up at the bottom 3 of multiple dam lakes with different water depths, allowing soil transport work to resume sequentially from the upstream temporary storage areas A and B, making it possible to transport dredged soil more efficiently.

1 Dam 2 Dam body 3 Bottom of dam lake 4 Outer edge of dam lake 5 Water surface 6 Dredged soil 7 Dump truck 8 Pier 9 Dredger 10 Soil transporter 11 Outflow prevention body 12 Backhoe

Claims (3)

A method for transporting dredged soil produced when dredging soil from the bottom of a dam lake out of the dam lake, comprising:
A temporary storage area is set up in advance at the bottom of the dam lake, which is exposed above the water when the water level of the dam lake is low and is submerged below the water surface when the water level is high;
When the water level of the dam lake is high and the bottom of the dam lake is submerged, the dredged soil is poured into the temporary storage area from above the water, and the dredged soil produced by dredging the bottom of the dam lake is poured into the temporary storage area and temporarily stored there.
A method for transporting dredged soil, characterized in that the dredged soil accumulated in the temporary storage area is transported out of the lake when the water level is low and the bottom of the dam lake is exposed above water. A method for transporting dredged soil produced when dredging soil from the bottom of a dam lake out of the dam lake, comprising:
Temporary storage areas are installed in advance at the bottom of a plurality of dam lakes at different water depths, which are exposed above water when the water level of the dam lake is low and are submerged below water when the water level is high;
The dredged soil produced by dredging the bottom of the dam lake is poured into the temporary storage area and temporarily stored therein,
A method for transporting dredged soil, characterized in that the dredged soil accumulated in the temporary storage area is transported out of the lake when the water level is low and the bottom of the dam lake is exposed above water. 3. The method for transporting dredged soil according to claim 1, wherein the temporary storage area is provided with an outflow prevention wall at least on the downstream side.