Water bottom ground improvement device, water bottom ground improvement method

Abstract

To provide a water bottom ground improvement device capable of constructing with stable quality by grasping an amount of existing soil taken into a casing, an amount of manufactured modified soil, and quality of the manufactured modified soil on the spot at a site when the modified soil is manufactured.SOLUTION: A water bottom ground improvement device 5 comprises: a casing 21 capable of taking existing soil on a sea bottom into the inside thereof; a material feeding path 33 to feed a modifier into the casing 21; an agitation blade 23 to agitate and mix the existing soil taken into the casing 21 and the modifier and manufacture modified soil in the casing; and top end position measurement means 40 capable of measuring a top end position of the existing soil or the modified soil in the casing 21. The top end position measurement means 40 is constituted of both or either one of a non-contact ranging device 41 using an electromagnetic wave such as microwave and laser, and a penetration resistance measurement device 42 to measure cone penetration resistance.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a waterbed ground improvement device used for improving waterbed ground such as existing seabed ground made of clay soil, and a waterbed ground improvement method using the same. [Background technology]

[0002] FIG. 7 of Patent Document 1 discloses a subaqueous ground improvement device that can be used to improve subaqueous ground, including seabed ground.

[0003] The submarine ground improvement device disclosed in FIG. 7 of Patent Document 1 has a casing capable of taking in the existing seabed ground inside, a material supply pipe for feeding a modifier made of steelmaking slag or the like into the casing, and agitator blades for mixing the existing ground and modifier taken into the casing.

[0004] In seabed ground improvement using the seabed ground improvement device of Patent Document 1, the device is pressed into the seabed ground to take in the existing seabed ground (clay soil) into a casing, a predetermined amount of modifier is poured into the casing via a material supply line, and the existing ground and modifier inside the casing are stirred and mixed with a stirring blade to produce modified soil.

[0005] The modified soil produced in this way inside the underwater casing is then backfilled in the original location of the existing ground, for example, to replace the existing ground with the modified soil. By repeating this process of producing modified soil and backfilling in different locations on the seabed, the target ground is improved.

[0006] Patent Document 2 also describes a method of taking existing soil from the seabed into a casing, and then carrying out a mud-loosening process to loosen the taken-in soil with a stirring blade. Furthermore, as a measure for cases where the soil has a low moisture content, a method of adding water to the soil while loosening the soil is also described. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2017-190667 A (Fig. 7) [Patent Document 2] Patent Publication No. 2022-13447 Summary of the Invention [Problem to be solved by the invention]

[0008] When producing improved soil underwater using the above-mentioned underwater ground improvement equipment, the amount of existing seabed ground taken into the casing is important information for determining the amount of improvement material to be put into the casing. Also, the amount of improved soil produced by the underwater ground improvement equipment is important information for confirming the production volume.

[0009] Therefore, in the past, the amount of existing ground taken up was predicted in advance from the amount of casing injected into the seabed ground, and the amount of modifier to be added was determined in advance according to the predicted amount of take-up. Also, the production amount of modified soil was predicted from the predicted amount of existing ground taken up and the amount of modifier to be added that was determined based on that.

[0010] However, the actual amount of existing ground taken into the casing is not always uniform, even if the casing is repeatedly pumped into the same depth, and the amount of existing ground taken in usually varies from place to place. Therefore, in the past, the mixture ratio of the improvement material to the existing ground taken into the casing could vary greatly from place to place, which could cause the quality of the improved soil to vary from place to place. In addition, if the amount of existing ground taken in differs from the prediction, the predicted amount of improved soil produced by the underwater ground improvement device also differs from the actual amount produced, making it impossible to accurately grasp the amount of production.

[0011] In addition, in seabed ground improvement using the above-mentioned underwater ground improvement device, a thawing process is carried out to loosen the existing ground taken into the underwater casing with agitator blades, but if water is added to the ground at the same time as the thawing, there is a risk that the water and the ground will not be sufficiently mixed if the thawing is insufficient. Furthermore, when the existing ground and the modifier are mixed in the underwater casing by stirring and mixing with agitator blades to produce modified soil, if the mixing is insufficient, the modifier will not be sufficiently dispersed and there is a risk that the mixture will be unevenly mixed. Such insufficient thawing after water addition and uneven distribution of the modifier may lead to a decrease in the quality of the modified soil produced.

[0012] In view of the above-mentioned problems, the object of the present invention is to provide a submerged ground improvement device and a submerged ground improvement method that can perform work with stable quality by grasping the amount of existing ground taken into the casing, the amount of modified soil produced, and the quality of the modified soil produced on-site when the modified soil is produced. [Means for solving the problem]

[0013] The above-mentioned object can be achieved by a submerged ground improvement device having a casing capable of taking in existing ground at the bottom of the water, a material supply line for supplying a modifying material toward the inside of the casing, a stirring blade for stirring and mixing the existing ground taken into the inside of the casing with the modifying material to produce modified soil within the casing, and a top position measuring means for measuring the top position of the existing ground taken into the casing or the modified soil produced within the casing.

[0014] In the above-mentioned waterbed ground improvement device, the top end position measuring means is composed of a penetration resistance measuring device that measures a cone penetration resistance value and / or a non-contact distance measuring device that utilizes electromagnetic waves.

[0015] In addition, in the case where the top end position measuring means is configured to include the penetration resistance measuring device for measuring the cone penetration resistance value, the penetration resistance measuring device has a cone that is penetrated into the existing ground or the modified soil in the casing, a sensor provided on the cone for measuring the penetration resistance value of the cone, and a cone rod that has the cone at its lower end and is capable of being raised and lowered.

[0016] In addition, in the above-mentioned waterbed ground improvement device, the penetration resistance measuring device for measuring the cone penetration resistance value further has a recording means for recording the value of the cone penetration resistance for each penetration depth of the cone.

[0017] The above object is also achieved by a submerged ground improvement method including the steps of: pressing a casing into the submerged ground to take in the existing ground at the submerged ground into the casing; a conventional ground measurement step of measuring the top position of the existing ground taken in the casing using a top position measurement means; a sludge deflocculation step of loosening the existing ground taken in the casing; a step of introducing a modifier into the casing in accordance with an amount of soil taken in based on the measurement values ​​in the conventional ground measurement step; a step of supplying the modifier into the casing via a material supply path; a step of stirring and mixing the existing ground and the modifier taken in the casing to produce modified soil within the casing; and an improved soil measurement step of measuring the top position of the modified soil produced in the casing using the top position measurement means.

[0018] The above object can also be achieved by a method for improving ground at the bottom of the water, which includes the steps of: pressing a casing into the ground at the bottom of the water to take the existing ground in the water bottom into the casing and / or after a mud-loosening step of loosening the existing ground taken into the casing, measuring the top position of the existing ground using a penetration resistance measuring device that measures cone penetration resistance value or a non-contact ranging device that uses electromagnetic waves; penetrating a cone of the penetration resistance measuring device into the existing ground to measure the position where the cone penetration resistance value begins to increase; and measuring the cone penetration resistance value for each penetration depth of the cone of the penetration resistance measuring device.

[0019] The above object is also achieved by a method for improving ground at the bottom of the water, comprising the steps of: pressing a casing into the ground to take in the existing ground at the bottom of the water into the casing; supplying a modifier into the casing through a material supply line; stirring and mixing the existing ground and the modifier taken into the casing to produce modified soil within the casing; measuring the top position of the modified soil using a penetration resistance measuring device that measures cone penetration resistance or a non-contact distance measuring device that uses electromagnetic waves; penetrating the cone of the penetration resistance measuring device into the modified soil to measure the position where the cone penetration resistance value begins to increase; and measuring the cone penetration resistance value for each penetration depth of the cone of the penetration resistance measuring device.

[0020] In addition, in the above-mentioned subsurface ground improvement method, when the cone penetration resistance value of the modified soil produced in the casing is measured, the measured cone penetration resistance value is compared with a predetermined standard value, and if the measured cone penetration resistance value does not satisfy the standard value, the modified soil in the casing is further stirred and mixed.

[0021] Furthermore, in the above-mentioned submerged ground improvement method, when the cone penetration resistance value of the modified soil produced in the casing is measured, the measured cone penetration resistance value is compared with a predetermined standard value, and if the measured cone penetration resistance value does not satisfy the standard value, further modifying material is supplied into the casing and the modified soil in the casing is further stirred and mixed. Effect of the Invention

[0022] By measuring the top position (height) of the existing ground taken into the casing, the volume of the existing ground taken into the casing can be determined, and based on that, the amount of existing ground taken in can be grasped almost accurately every time. As a result, it becomes possible to add the improvement material in an amount that corresponds to the actual amount of existing ground taken in, and it is possible to produce improved soil with consistent quality. In addition, by measuring the top position (height) of the reformed soil produced inside the casing, the volume of the reformed soil produced can be determined, making it possible to grasp the production volume of the reformed soil almost accurately every time. As a result, it becomes possible to grasp the production volume accurately.

[0023] In addition, in the present invention, the top end position measuring means can be composed of, for example, a penetration resistance measuring device that measures a cone penetration resistance value, or a non-contact distance measuring device that uses electromagnetic waves. Non-contact distance measuring devices that use electromagnetic waves such as microwaves and lasers have a short measurement time and can grasp the top position almost in real time, improving work efficiency. The penetration resistance measuring device for measuring cone penetration resistance has an electric cone whose penetration resistance does not react to water, so by penetrating the cone and finding the position where the resistance starts to rise, the top height of the ground can be accurately determined. Note that slight unevenness on the top of the existing ground taken into the casing does not result in a large error in the amount of existing ground taken in overall. Furthermore, when producing modified soil, if the top of the soil is very uneven (convex and concave), there is a risk that the top position cannot be measured correctly using a non-contact distance measuring device that uses electromagnetic waves, but by examining the position where the cone penetration resistance value begins to rise, it is possible to grasp the top position of the modified soil excluding the uneven part. That is, in the uneven part (uneven surface part) at the top of the modified soil inside the casing, the cone penetration resistance value shows a relatively low value, and the cone penetration resistance value rises once the uneven part is exceeded, so by examining the position where the cone penetration resistance value begins to rise, it is possible to grasp the top position of the modified soil excluding the uneven part. Therefore, by providing at least one of a penetration resistance measuring device that measures cone penetration resistance value and a non-contact distance measuring device that uses electromagnetic waves, and preferably both, and by selectively using cone penetration resistance value measurement and electromagnetic wave measurement depending on the situation, it becomes possible to quickly measure the top end position and improve work efficiency.

[0024] In addition, after the existing ground has been introduced into the casing or after the existing ground inside the casing has been deflocculated, the cone of a penetration resistance measuring device can be inserted into the existing ground and the position where the cone penetration resistance value begins to increase can be measured, thereby measuring the top position (height) of the existing ground inside the casing.

[0025] In addition, by recording the cone penetration resistance value for each penetration depth of the cone, when adding water to the ground at the same time as thawing, it is possible to check the variation in cone penetration resistance value for each depth and confirm whether thawing after water addition is sufficient. If the water and ground are sufficiently mixed, the cone penetration resistance value will show a uniform depth distribution close to the mud water pressure, but if there is insufficient thawing, the water and ground will be partially separated, resulting in significant variation in the depth distribution of the cone penetration resistance value. If it is determined that thawing is insufficient, thawing can be resumed immediately.

[0026] In addition, after producing the modified soil in the casing, the cone of the penetration resistance measuring device is inserted into the modified soil to measure the position where the cone's penetration resistance value starts to increase, thereby measuring the top position (height) of the modified soil in the casing. In addition, by measuring the cone penetration resistance value for each penetration depth and investigating the depth at which the cone penetration resistance value is specifically high, it is possible to find the depth in the modified soil where mixing is insufficient (the target depth where remixing is required). As a result, by performing remixing only at that target depth (since there is no need to remix the entire depth), it becomes possible to efficiently mix the modified material that was insufficiently mixed and unevenly into the entire existing ground, thereby improving the quality of the modified soil produced. Furthermore, since any problems with the modified soil (areas that have not been mixed properly) can be detected before the modified soil is discharged from the casing, mixing can be quickly resumed and re-mixing carried out to the target depth, allowing for a speedy recovery and construction with stable quality.

[0027] In addition, by performing re-mixing only when necessary, work efficiency during the production of modified soil is improved.

[0028] In addition, by adding additional modifier only when necessary and performing further mixing, the work efficiency during the production of modified soil can be improved, and the quality of the modified soil produced can be improved. [Brief description of the drawings]

[0029] [Figure 1] FIG. 1A is a side view showing a work vessel (ground improvement vessel) equipped with the underwater ground improvement device of the present invention, and FIG. 1B is an enlarged side view showing the seabed ground improvement process using the underwater ground improvement device. [Diagram 2] 1 is a perspective view (enlarged side view) showing a waterbed ground improvement device according to the present invention. [Diagram 3] FIG. 1 is a schematic diagram showing a general configuration of a penetration resistance measuring device that constitutes a top end position measuring means. [Figure 4] 10 is a schematic diagram showing how the top end position is measured by a non-contact distance measuring device constituting the top end position measuring means. FIG. [Diagram 5] FIG. 1 is a schematic diagram showing how cone penetration resistance is measured by a penetration resistance measuring device that constitutes a top end position measuring means. [Figure 6] 1 is a graph showing a specific example of a cone penetration resistance distribution measured by a penetration resistance measuring device. [Figure 7] 1 is a graph showing a specific example of a cone penetration resistance distribution measured by a penetration resistance measuring device. [Figure 8] FIG. 1 is a process diagram showing an example of seabed ground improvement using a waterbed ground improvement device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] The waterbed ground improvement device according to the present invention is mounted on a work ship 1 (ground improvement ship) as shown in Fig. 1(a). The work ship 1 has a leader 3 erected on the bow side and a waterbed ground improvement device 5 installed along the leader 3 so as to be able to move up and down freely.

[0031] As shown in FIG. 1(b), the underwater ground improvement device 5 can be used in ground improvement work, for example, to produce improved soil by stirring and mixing the existing seabed ground (clay soil) and an improvement material in situ to replace the existing seabed ground with the improved soil.

[0032] The configuration of the waterbed ground improvement device 5 will be described below with reference to Figs. In addition, specific examples of the "bottom" in this application include the bottom of the ocean, the bottom of a river, and the bottom of a lake. In the following explanation of the present invention, the bottom of the ocean will be given as an example of the bottom of the ocean.

[0033] (Underwater soil improvement device) As shown in FIG. 1, the waterbed ground improvement device 5 is provided so as to be able to move up and down along the leader 3. Also, as shown in FIGS. 1 and 2, A casing 21 capable of incorporating the existing seabed soil (clay soil) inside; A mixing blade 23 for mixing the existing ground and the modifying material taken into the casing 21; an auger motor 7 that drives the stirring blade 23 via a rod; A support tube 31 which is an outer tube of the multi-wall tube 30 and supports the casing 21; A material supply passage 33 which is an inner pipe of the multiple pipes 30 and supplies a modifier into the casing 21; The crest position measuring means 40 is composed of a non-contact distance measuring device 41 that uses electromagnetic waves and a penetration resistance measuring device 42 that measures the cone penetration resistance value.

[0034] The casing 21 is a box-shaped container-like component (rectangular casing) that is generally rectangular in plan view, and is configured so that the opening at the bottom can be opened and closed. A support tube 31, which is an outer tube of the multiple tubes 30, is connected to the center of the top end of the casing 21. The casing 21 can be raised and lowered by raising and lowering the support tube 31.

[0035] An openable grab 27 is provided at the tip (lower end) of the casing 21. The combination of the casing 21 and the grab 27 can be said to constitute one casing as a whole. When the grab 27 is opened, the bottom of the casing 21 opens, and when the grab 27 is closed, the bottom of the casing 21 closes and is sealed. The grab 27 not only serves as a means for taking in the existing ground on the seabed into the casing 21, but also serves as a lid for opening and closing the bottom of the casing 21 (a lid for sealing the bottom of the casing 21).

[0036] The grab 27 has, for example, a hydraulic cylinder as a means for opening and closing the grab. When the grab 27 is in an open state, the bottom of the casing 21 is open. Then, through a series of operations when the grab 27 is closed from the open state, the existing ground on the seabed can be taken into the inside of the grab 27 and the casing 21. When the grab 27 is closed, the bottom of the casing 21 is closed and the casing 21 is sealed. When the grab 27 is closed after the existing ground is taken into the casing 21, the casing 21 is sealed and the existing ground is trapped inside the casing 21.

[0037] The material supply passage 33, which is the inner pipe of the multiple pipes 30, has a modifying agent outlet 34 above (directly above) the agitating blade 23, and functions as a flow path for feeding the modifying agent toward the agitating blade 23 inside the casing 21. The outlet 34 at the lower end of the material supply passage 33 is provided to face the agitating blade 23 at a predetermined distance. The outlet 34 of the material supply passage 33 is located in the center inside the casing 21. A material inlet 35 for feeding the modifying agent into the material supply passage is provided above the material supply passage 33.

[0038] The modifier fed from the material feed port 35 passes through the material supply path 33, is discharged from the discharge port 34 protruding into the casing 21, and is fed into the casing 21. The modifier fed into the casing 21 is distributed by the stirring blades 23 so as to be evenly distributed over the entire existing ground taken into the casing 21.

[0039] 1(a), the auger motor 7 is connected to the leader 3 so as to be able to rise and fall freely, and its upper end is connected to the wire rope 4. By operating the wire rope 4 in the up and down direction, the entire waterbed ground improvement device 5 including the auger motor 7 rises and falls along the leader 3. The rotational power output from the auger motor 7 is transmitted to a rod (not shown) installed in parallel with the multiple pipes 30, and is further transmitted to the mixing blade 23 via a gear box or the like.

[0040] The agitator 23 is provided rotatably and vertically movable within the casing 21. The agitator 23 mainly plays a role in agitating and mixing the existing seabed ground taken into the casing 21 by the grab 27 and the modifier charged into the casing 21. The agitator 23 also plays a role in loosening (loosening) the existing ground taken into the casing 21 before the above-mentioned agitation and mixing is performed.

[0041] The top position measuring means 40 has the role of measuring the top position of the existing ground taken into the casing 21 or the improved soil produced within the casing, as well as measuring the cone penetration resistance value of the existing ground or the improved soil.

[0042] Also, a camera 6 is provided inside the casing 21 for monitoring the state of taking in the existing ground into the casing 21, the state of production and discharge of the reformed soil inside the casing 21, etc. By checking the video from this camera 6, it is possible to grasp, for example, the presence or absence of water inside the casing 21 when the existing ground is taken into the casing 21 (the presence or absence of water exceeding the top of the taken-in existing ground), etc.

[0043] The configuration of the crest position measuring means 40 provided in the water-bed ground improvement device 5 will be specifically described below with reference to Figs.

[0044] (Means for measuring top position) In this embodiment, the top position measuring means 40 equipped in the waterbed ground improvement device 5 is composed of a non-contact distance measuring device 41 that uses electromagnetic waves and a penetration resistance measuring device 42 that measures the cone penetration resistance value.

[0045] In this embodiment, the waterbed ground improvement device 5 is equipped with both a non-contact ranging device 41 that uses electromagnetic waves and a penetration resistance measuring device 42 that measures the cone penetration resistance value as the top end position measuring means 40, but it is also possible to adopt a form in which only one of the devices is equipped as the top end position measuring means 40.

[0046] The non-contact distance measuring device 41 using electromagnetic waves is composed of a known non-contact distance measuring device such as a known microwave level meter or a laser distance measuring device. A microwave level meter measures the round-trip time it takes for a microwave (electromagnetic wave) emitted from the level meter body to be reflected by the object to be measured and return to the level meter, thereby deriving the distance to the object to be measured. A laser distance measuring device measures the round-trip time it takes for a laser (electromagnetic wave) emitted from the distance measuring device body to be reflected by the object to be measured and return to the distance measuring device, thereby deriving the distance to the object to be measured.

[0047] As shown in FIG. 3, the penetration resistance measuring device 42 includes: An electric cone 51 that penetrates the existing ground or the modified soil in the casing 21; A cone rod 52 having an electric cone 51 at its tip and capable of ascending and descending; A forward / reverse rotating underwater motor 53 for raising and lowering the cone rod 52; A control device such as a computer for electronically controlling the underwater motor 53; The device has a memory, data storage, etc., which is a means for recording the value of the cone penetration resistance for each penetration depth of the electric cone 51.

[0048] The cone rod 52 is provided so that it can move up and down so that the electric cone 51 at its tip can reach the lower end of the casing or its vicinity. A connecting part 54 is provided at the base end of the cone rod 52 to connect the cone rod 52 to a chain 55. The electric cone 51 at the tip of the cone rod 52 is provided with a sensor for measuring the penetration resistance of the cone.

[0049] When the underwater motor 53 rotates forward and backward, the rotational power is transmitted to the connecting part 54 via the chain 55 and pulley 56, and the cone rod 52 moves up and down. The rotational speed of the underwater motor 53 is controlled by a control device such as a computer.

[0050] 4, the non-contact distance measuring device 41 using electromagnetic waves can be used to measure the top position of the existing ground taken into the casing 21. In addition, the non-contact distance measuring device 41 using electromagnetic waves can be used to measure the top position of the improved soil produced in the casing 21.

[0051] As shown in Fig. 5, the penetration resistance measuring device 42 can be used to penetrate an electric cone 51 into the existing ground taken into the casing 21 or into the modified soil produced in the casing 21, and measure the position where the penetration resistance value of the electric cone 51 starts to increase. Also, as exemplified in Fig. 6 and Fig. 7, the penetration resistance measuring device 42 can be used to measure the cone penetration resistance value for each penetration depth of the electric cone 51 when measuring the cone penetration resistance value of the existing ground or modified soil.

[0052] In addition, although the penetration resistance measuring device 42 is primarily used to measure the cone penetration resistance value, it can also be used to measure the top position (height) of the existing ground taken into the casing 21 or the improved soil produced within the casing 21.

[0053] In addition, when measuring the top position of the existing ground taken into the casing 21 or the improved soil produced within the casing 21, either a non-contact distance measuring device 41 that uses electromagnetic waves or a penetration resistance measuring device 42 that measures cone penetration resistance may be used. The non-contact distance measuring device 41 that uses electromagnetic waves such as microwaves and lasers has a short measurement time and can grasp the top end position almost in real time, improving work efficiency. The penetration resistance measuring device 42, which measures the cone penetration resistance value, has an electric cone 51 whose penetration resistance does not react to seawater (including fresh water), so by penetrating the electric cone 51 and examining the position where the resistance begins to rise, the top height of the existing ground can be correctly determined. Note that slight unevenness on the top of the existing ground taken into the casing does not result in a large error in the amount of existing ground taken in overall. Furthermore, during the production of modified soil, even if the top end of the modified soil is significantly uneven (convex and concave) after production, it is possible to grasp the top end position of the modified soil excluding the uneven portion by examining the position where the cone penetration resistance value begins to increase using the penetration resistance measuring device 42. That is, in the uneven portion (uneven surface layer portion) of the top end of the modified soil inside the casing, the cone penetration resistance shows a relatively low value, and the cone penetration resistance increases once the uneven portion is exceeded, so it is possible to grasp the top end position of the modified soil excluding the uneven portion by examining the position where the cone penetration resistance value begins to increase. Therefore, by using either cone penetration resistance measurement or electromagnetic wave measurement depending on the situation, it is possible to quickly measure the top position and improve work efficiency.

[0054] (Example of seabed ground improvement using underwater ground improvement equipment) Next, a specific example of seabed ground improvement work using the above-mentioned waterbed ground improvement device 5 will be described mainly with reference to Fig. 8. Note that steps a to h described below correspond to Fig. 8(a) to (h).

[0055] Process a The tip of the underwater ground improvement device, i.e., the grab 27 at the tip of the casing 21, is pressed in an open state against the top of the seabed ground (conventional ground) to be improved.

[0056] Process b Next, the casing 21 is pressed into the seabed to the target depth, and the existing ground, which is made of clay, is taken into the casing 21. Once the existing ground has been taken into the casing 21, the grab 27 at the end of the casing is closed. This seals the casing 21, and the existing ground taken into the casing 21 is isolated from the seawater and existing ground around the casing.

[0057] Process c Next, the agitator blade 23 in the casing 21 is lowered, and the existing ground taken into the casing 21 is loosened by the rotation and elevation of the agitator blade 23. This loosens the hard existing ground in the casing 21, making it possible to uniformly mix the existing ground and the modifier in the subsequent step (step f). If the moisture content of the existing ground to be taken into the casing 21 is low and there is a risk that the modifier cannot be mixed in sufficiently uniformly by just loosening the ground, water may be added to the existing ground at the same time as the mud deflocculation process. This can improve the uniformity of the mixture of the modifier. The method of adding water may be to take in seawater into the casing 21 at the same time as injecting the casing 21 into the seabed and to perform sludge deflocculation, or to attach a water distribution pipe to the supply path 33 of the modifier and use a pump or the like to pump water toward the agitator blades 23 during the sludge deflocculation process.

[0058] Process d Next, the top position of the existing ground in the casing 21 is measured by a penetration resistance measuring device 42 that measures the cone penetration resistance. Specifically, a cone rod 52 equipped with an electric cone 51 at its tip is lowered to penetrate the existing ground in the casing 21, and the cone penetration resistance value is measured by a sensor attached to the cone to measure the top position (height) of the existing ground. The top position of the existing ground can be found by measuring the position where the cone penetration resistance starts to rise, as illustrated in FIG. 6. Then, if the top position of the existing ground taken into the casing 21 is known, the volume of the existing ground can be derived, and based on that, the amount of the existing ground taken in can be grasped almost accurately every time. Note that the measurement of the top position of the existing ground may be performed before the mixing and stirring in step c.

[0059] When measuring the cone penetration resistance value using the penetration resistance measuring device 42, the cone penetration resistance value may be measured at every predetermined cone penetration depth (for example, every 0.5 m) as illustrated in Fig. 6. This makes it possible to check whether the thawing performed in step c is sufficient.

[0060] In the specific example shown in Figure 8, a penetration resistance measuring device 42 that measures the cone penetration resistance value is used to measure the top position of the existing ground, but it is also possible to use a non-contact distance measuring device 41 such as a microwave level meter or a laser distance measuring device instead of or in addition to this.

[0061] Process e Next, with the bottom (grab 27) of the casing 21 still closed, an amount of modifier corresponding to the amount of existing ground taken into the casing (for example, 30% of the volume of the existing ground taken in) is poured into the casing 21 via the material supply line 33.

[0062] process f After the modifying material is poured into the casing 21, the agitating blades 23 inside the casing 21 are rotated and moved up and down inside the casing 21 to mix and stir the "existing ground taken into the casing 21" and the "modifying material poured into the casing 21." By mixing and stirring these inside the casing 21, "modified soil" is produced.

[0063] Process g Next, the electric cone 51 of the penetration resistance measuring device 42 is penetrated into the modified soil to measure the position where the cone's penetration resistance value starts to increase. Specifically, a cone rod with a cone at its tip is lowered to penetrate the modified soil in the casing, and the cone penetration resistance value is measured with a sensor attached to the cone, thereby investigating the position where the cone penetration resistance value starts to increase and confirming the top position (height) of the modified soil. If the top position of the modified soil produced in the casing 21 is known, the amount of modified soil produced in the casing 21 (i.e., the amount of modified soil replaced in step h) can be grasped each time.

[0064] When measuring the cone penetration resistance using a penetration resistance measuring device, the cone penetration resistance value may be measured for each penetration depth of the cone, as illustrated in FIG. 6. This makes it possible to find the depth where the mixing performed in step f is insufficient (the target depth where re-mixing is required). If such a target depth is found, as illustrated in FIG. 7, re-mixing can be performed only at that target depth (since there is no need to re-mix the entire depth), and the imbalanced improver due to insufficient mixing can be efficiently mixed into the entire existing ground, thereby improving the quality of the improved soil to be produced. It is desirable to measure the cone penetration resistance value again after re-mixing. Furthermore, since it is possible to detect any problems (areas where the soil is insufficiently mixed) in the modified soil before the produced modified soil is discharged from the casing 21, mixing can be quickly resumed in those areas and re-mixing can be carried out to the target depth, allowing for a speedy recovery.

[0065] In addition, when measuring the cone penetration resistance value in this process, the measured cone penetration resistance value is compared with a predetermined standard value, and if the measured resistance value does not satisfy the standard value, further modifying material may be supplied into the casing 21 and the modified soil in the casing 21 may be further stirred and mixed.

[0066] Process h Next, the bottom of the casing 21 (grab 27) is opened, the casing 21 is pulled out from the seabed, and the thoroughly mixed and stirred modified soil is discharged by dropping it from the casing 21, and the modified soil is backfilled in the original location (the location where the existing ground was taken in). Through the above procedure, the existing ground consisting of clay is replaced with the modified soil. When discharging the modified soil from the casing 21, if the modified soil does not fall well after the grab 27 is opened or if it is desired to forcibly discharge the modified soil, compressed air may be sent into the casing 21 as an auxiliary means. Also, the mixing blades 23 may be lowered without rotating to push the modified soil out of the casing 21.

[0067] Finally, the above-mentioned embodiment is an example of the present invention described in the claims, and the present invention is not necessarily limited to this embodiment. In addition, the application of the present invention is not limited to the improvement of seabed ground, but can also be used for the improvement of riverbeds and lakebeds. [Explanation of symbols]

[0068] 1. Work boat (ground improvement boat) 3. Leader 4. Wire Rope 5 Underwater soil improvement equipment 6. Camera 7 Auger motor 21 Casing 23 Stirring blade 27 Grab 30 multiple tubes 31 Support tube (outer tube) 33 Material supply path (inner pipe) 34 Outlet 35 Material input port 40 Top end position measurement means 41 Non-contact distance measuring device (top position measuring means) 42 Penetration resistance measuring device (top position measuring means) 51 Electric cone 52 Corn Rod 53 Underwater Motor 54 Connecting part 55 Chain 56 Pulley

Claims

1. A casing that can incorporate the existing ground at the bottom of the water into the inside, a material supply passage for supplying a modifier toward the inside of the casing; a mixing blade that mixes the existing ground and the modifying material taken inside the casing to produce modified soil inside the casing; A top position measuring means capable of measuring the top position of the conventional ground taken into the casing or the improved soil produced in the casing; A waterbed ground improvement device comprising:

2. The waterbed ground improvement device according to claim 1, characterized in that the top end position measuring means is composed of a penetration resistance measuring device that measures a cone penetration resistance value and / or a non-contact distance measuring device that uses electromagnetic waves.

3. In the case where the top end position measuring means includes the penetration resistance measuring device for measuring a cone penetration resistance value, The penetration resistance measuring device is A cone that penetrates the existing ground or the modified soil in the casing; A sensor provided on the cone for measuring a penetration resistance value of the cone; A cone rod having the cone at its lower end and capable of ascending and descending; The waterbed ground improvement device according to claim 2, further comprising:

4. The penetration resistance measuring device for measuring the cone penetration resistance value is A recording means for recording the value of the cone penetration resistance for each penetration depth of the cone, The waterbed ground improvement device according to claim 2 or 3, further comprising:

5. A method for improving a bottom ground using the bottom ground improvement device according to claim 1, A step of pressing a casing into the water bottom ground to capture the existing water bottom ground into the casing; A conventional ground measurement process for measuring the top position of the conventional ground taken into the casing by a top position measuring means; A mud-loosing process for loosening the native ground taken into the casing; A step of adding a modifying material according to an amount of intake based on the measurement value of the conventional ground measurement step; supplying the modifier into the casing through a material supply passage; A step of producing modified soil in the casing by stirring and mixing the existing ground and the modifying material taken into the casing; a modified soil measuring step of measuring a top end position of the modified soil produced in the casing by the top end position measuring means; A method for improving water bed ground, comprising:

6. A method for improving a bottom ground using the bottom ground improvement device according to claim 2, After a process of pressing a casing into the bottom ground to capture the existing ground at the bottom of the water into the casing and / or a mud-loosening process of loosening the existing ground captured in the casing, A step of measuring the top position of the conventional ground by a penetration resistance measuring device that measures cone penetration resistance or a non-contact distance measuring device that uses electromagnetic waves; A step of penetrating the cone of the penetration resistance measuring device into the conventional ground to measure the position where the cone penetration resistance value begins to increase; Measuring a cone penetration resistance value for each penetration depth of a cone of a penetration resistance measuring device; A method for improving water bed ground, comprising:

7. A method for improving a bottom ground using the bottom ground improvement device according to claim 2, A step of pressing a casing into the bottom ground to capture the existing ground at the bottom of the water into the casing; supplying a modifier into the casing through a material supply passage; A step of producing modified soil in the casing by stirring and mixing the existing ground and the modifying material taken into the casing; A step of measuring the top position of the modified soil by a penetration resistance measuring device that measures a cone penetration resistance value or a non-contact distance measuring device that uses electromagnetic waves; A step of penetrating a cone of the penetration resistance measuring device into the modified soil and measuring a position where the penetration resistance value of the cone begins to increase; Measuring a cone penetration resistance value for each penetration depth of the cone of the penetration resistance measuring device; A method for improving water bed ground, comprising:

8. When measuring the cone penetration resistance value of the modified soil produced in the casing, The measured value of the cone penetration resistance is compared with a predetermined reference value, If the measured value of the cone penetration resistance does not meet the standard value, the modified soil in the casing is further stirred and mixed. The method for improving a waterbed as claimed in claim 7.

9. When measuring the cone penetration resistance value of the modified soil produced in the casing, The measured value of the cone penetration resistance is compared with a predetermined reference value, If the measured value of the cone penetration resistance does not satisfy the reference value, the modifying material is further supplied into the casing and the modified soil in the casing is further stirred and mixed. The method for improving a waterbed as claimed in claim 7.

Images