JP4996883B2 - Consolidation settlement method and loading equipment and work boat used for construction method. - Google Patents

Description

The present invention relates to a ground improvement technique for increasing the density of a soft viscous ground stably and rapidly by promoting consolidation.

Consolidation settlement of cohesive ground progresses with the construction of the facilities, and the consolidation increase load is applied to the ground and progresses. With consolidation settlement, the density of the ground increases and the strength increases. Conventionally, soft ground countermeasures for harbor facilities have mainly been shear fracture of the foundation ground during the construction of the facility and consolidation settlement after the facility has been used. These ground improvement methods mainly consisted of the sand drain method and sand compaction pile method, which are a type of vertical drain method. The vertical drain method is a method of installing a drain in the vertical direction in the ground, shortening the drainage distance, shortening the consolidation time, and promoting consolidation settlement by promoting consolidation settlement. On the other hand, the sand compaction pile method is a method in which a large number of compacted sand piles are created in the ground to increase the bearing capacity of the ground, prevent the foundation ground from being destroyed, and suppress the consolidation settlement.

If the embankment on soft ground is carried out continuously to the required height, the foundation ground will cause shear failure. Considering the stability against failure, stepwise while confirming the increase in strength of the ground in several degrees. Install to. For this reason, even if it is used together with the vertical drain method, the consolidation settlement method by loading requires a long period until the completion of the construction, and there is a disadvantage that it is not a rapid construction. The preloading method loads more than the load loaded by the facility construction, completes the target consolidation, and then removes the excess load. Consolidation has the problem of secondary consolidation, and even after the preloading method, consolidation settlement continues for a long time after the facility is used. Revetment, breakwater, etc. that can easily take countermeasures for settlement after operation can be used for soft ground by sand drain method and stepwise construction, but it is not easy and is fatal for facilities such as quay where continuation of settlement is not desirable. is there.
For this reason, the sand compaction pile method has been widely used for rapid construction, although the construction cost is significantly higher than the sand drain method.
However, in the previous Hyogoken-Nanbu Earthquake, the ground improved by the sand compaction pile method was destroyed by liquefaction and caused great damage to the quay. This indicates that there is a limit to the compaction of the sand compaction pile method. In addition, soft ground countermeasures must be accompanied by liquefaction countermeasures at the time of the earthquake based on the damage of the Hyogoken-Nanbu Earthquake.

One of the loading consolidation promotion methods is the vacuum consolidation method. This construction method is a construction method in which consolidation is promoted by applying the atmospheric pressure (practically 6 to 7 t / m ² ) by generating a negative pressure with the target improved ground surface sealed. The feature of this method is different from the embankment load in principle, and it is a mechanism that works as a three-dimensional consolidation load against the soil in the ground. Consolidation can be promoted under load. However, this vacuum consolidation method does not solve the secondary consolidation problem.

  There is a dynamic consolidation method as a method of promoting consolidation by vibration and impact. In this method, a huge hammer is repeatedly dropped from a high place on the surface of the target improved ground, and the ground is consolidated and strengthened by impact force and vibration applied to the ground. However, the dynamic consolidation method is a method that started from the compaction method of sandy soil, and is limited to viscous soil with less fine particles. In addition, the reverse effect can be considered for saturated clay. This is because large amplitude vibrations destroy the clay structure and inhibit consolidation.

Currently, from the viewpoint of global environmental conservation, efforts are being made to conserve construction resources to reduce environmental impact. The sand compaction pile method is a method that has a large environmental impact, such as using a large amount of high-quality sand and disposing of the raised soil of the original ground caused by pile driving. On the other hand, the loading consolidation settlement method combined with the vertical drain construction method is a construction method with a small environmental load, and an unprecedented rapid consolidation settlement method utilizing this advantage is required.

The present invention has been made in view of the above-mentioned problems. The load consolidation settlement method has been further developed from a new concept and has a low environmental impact, is economical, and does not risk liquefaction during an earthquake. The issue is how to achieve rapid consolidation settlement in a stable manner and how to solve the secondary consolidation problem. Further, since the present invention is basically a load consolidation settlement method, a vertical drain method and a vacuum consolidation method are used in combination as necessary.

The rapid consolidation settlement method of the present invention is a method that has been researched and developed on the basis of a hierarchical structure having a charge, which is a characteristic of clay.
In clay, fine clay particles are arranged in various arrangements to form peds (aggregates of structural units), and peds are also arranged in various arrangements to form a hierarchical structure of clay.
The gap between the clay particles is called the micropore, and the gap between the pads is called the macropore.
Since the clay particles that make up clay have a large specific surface area and are charged, physicochemical interactions are acting between the soil particles. This interaction has a great influence on the structure of clay, water retention of clay, and consolidation mechanism.
As for the consolidation phenomenon of clay, when compression pressure acts on clay, the compression pressure is first supported by the pore water pressure and excessive pore water pressure is generated. Excess pore water pressure creates a gradient of water pressure from the inside of the clay to the outside drainage layer, and macropore pore water is mainly discharged. At this time, the Ped is rearranged and compressed in a way that fills the macropores.
Then, the peds ensure effective stress between the peds that matches the compression pressure while expanding the contact surface between the peds. That is, an increase in strength commensurate with the increase in density appears. Consolidation is a phenomenon in which the compression time is delayed due to the drainage resistance of pore water and the deformation resistance of the skeleton structure of clay.
In order for consolidation to proceed, the outflow driving force of pore water must be superior to the water retention capacity of clay. There are basically two ways to promote consolidation. One is a method of increasing the outflow driving force, and the force causing the movement of pore water by this is generally a pressure gradient caused by loading. The preload method is representative of this.
However, the progress of consolidation becomes extremely slow when entering the secondary consolidation region where the deformation resistance element of the clay skeleton structure is large. The other is a new idea, which is a method of temporarily reducing the moisture retention of clay. A concrete method for reducing the moisture retention of clay can be realized by vibrating the ground. When the clay structure is destroyed, the moisture retention decreases and the shear force decreases. It is the sensitivity of clay. In the method of reducing the water retention force due to the disturbance of the clay structure, even if local consolidation promotion is expected, the adhesive force is greatly reduced, so the ground is plastically deformed by an increased load and the foundation ground is destroyed. Especially in the submarine ground where water is constantly supplied, the vibration that destroys the clay structure causes the water absorption and expansion of the clay.

The method for reducing the water retention capacity of the present invention is a decrease in the water retention capacity that facilitates rearrangement of the clay structure pads during consolidation without destroying the clay structure. In other words, it is a method for reducing the water retention capacity in which the change in the clay structure is limited to the direction of increasing density. This method acts on both the drainage resistance of pore water and the deformation resistance of the clay skeleton structure, so that consolidation is actively promoted even when entering the secondary consolidation region. When combined with the method for increasing the outflow driving force, the moisture retention reducing method of the present invention can promote rapid consolidation that cannot be obtained by itself. However, the water retention is reduced without destroying the clay structure. Since the method is a consolidation settlement accompanied by softening (decrease in strength) of clay, it is necessary to take measures against this because if the ground is loaded at once, there is a risk of shear failure of the foundation ground due to plastic deformation of the ground.

The present invention satisfies the following requirements in order to stably secure a rapid consolidation promotion under a consolidation increase load.
The first requirement is that during consolidation, the clay structure of the target ground must be temporarily reduced without temporarily destroying the clay structure of the target ground. At this time, it is necessary to minimize the softening of the clay. The solution to this first requirement is to maintain a uniform constant load (consolidation increase load in the normal loading method) and repeated load uniformly in a plane as long as the target ground does not cause ground failure. Add.
As a result, a wave of excess pore water pressure, which is obtained by repeatedly adding excess pore water pressure to a constant excess pore water pressure as a base, is generated in the target ground.
The generation of the excessive pore water pressure wave is carried out by using the loading device for repeatedly applying a loading load to the constant loading load of the present invention. The loading device includes a pressure plate that uniformly transmits a loading load to the target ground in a planar manner and a repeated loading load generator. The generating device is a generating mechanism based on the rotational force of the eccentric weight. Here, the loading device has a weight that does not generate vibration due to an oscillating force and a pressure area that is large enough to obtain a uniform loading state, that is, a width that is approximately the same as the depth of the target ground. It has a pressurized area and is used in contact with the ground surface. For this reason, the loading device repeatedly applies a load, not a vibration load, to the target ground. In addition, it is preferable to use a loading device having functions of repeatedly increasing / decreasing the loading load and adjusting the cycle by making the rotation radius and rotation angular velocity of the eccentric weight of the generator variable.
The second requirement is to positively prevent the shear failure of the foundation ground and ensure a rapid consolidation promotion. In other words, it creates a state in which the target ground does not cause ground failure due to a larger excess pore water pressure. The solution to the second requirement is to confine plastic deformation of the ground by surrounding the surface ground directly loaded with the target ground with a structure. Specifically, the structure is a pressure box having a restraint wall attached to the outer periphery of the bottom of the pressure plate of the first requirement. As a result, the outer peripheral ground of the pressurizing box serves as a pressing load for preventing the shear failure of the foundation ground.
The third requirement ensures easy preloading of unloading. In general, the preload material is earth and sand and rock mass, and the unloading work is large and requires a long construction period. The solution to this third requirement is the use of atmospheric pressure and water pressure. The vacuum consolidation method is the same as the conventional loading method in terms of consolidation time, but is characterized by the use of atmospheric pressure that makes loading easy. The loading and unloading work of the vacuum consolidation method is incorporated into the rapid consolidation method by the wave of excess pore water pressure of the present invention. In this method, the pressure ground is used, the surface ground is hermetically sealed, and the target ground is negative pressure. That is, the atmospheric pressure is loaded using the vacuum consolidation method together.

The effect of the first solution is to generate a wave of excessive pore water pressure uniformly in the target ground without destroying the clay structure and realize rapid consolidation settlement. The consolidation settlement method by the wave of excess pore water pressure of the present invention is a method based on a completely new idea. Here, the wave of excess pore water pressure within a range that does not destroy the clay structure is the minimum necessary softening that facilitates rearrangement of the pad of the clay structure so that the clay moves in the compression direction.
FIG. 1 is an example of a comparison of time-consolidation strain amount curves of a standard consolidation test and a micro-vibration consolidation test. The micro-vibration consolidation tester is a standard consolidation tester incorporating a piston vibrator type vibration device. A copper circular perforated plate having a drainage function is attached to the lower end of the consolidation ring for setting the test sample. The micro-vibration consolidation load (repeated load) is due to repeated impact of the circular perforated plate. In addition, the consolidation test sample is in a one-dimensional consolidation state in which plastic deformation is constrained in the same manner as the standard consolidation test apparatus. The micro vibration consolidation test method conforms to the standard consolidation test. The consolidation test sample is an undisturbed clay, load stage = 5, consolidation load P5 = 157 KN / m ² , and minute vibration consolidation load P = 3 KN / m ² . The consolidation increase load in this test is P5 / 2 = 78.5 KN / m ² , and the minute vibration consolidation load is 3.8% of this consolidation increase load. What is important here is that the state of the micro-consolidation test sample in FIG. 1 is a one-dimensional consolidation state in which the consolidation load is larger than the vibration consolidation load. And no shear strain occurs. Therefore, the clay structure is not destroyed. In other words, a constant consolidation increase load is replaced by a constant excess pore water pressure, and a micro-vibration consolidation load is repeatedly replaced by an excess pore water pressure. In other words, the clay structure of the test sample is not destroyed, and a wave of excess pore water pressure is generated in the test sample. The micro-vibration of the micro-vibration consolidation test of FIG. 1 is carried out for 1 minute after 24 hours of compaction of load stage = 4, P4 = 78.5 KN / m ² , and the next load stage = 5, P5 = 157 KN / This was carried out at m ² for 30 minutes.
Although the micro-vibration consolidation load of FIG. 1 is only 3.8% of the consolidation increase load, it shows a significant consolidation promotion. For example, in the micro-vibration consolidation test, the consolidation strain amount ε _f = 2.72% in 24 hours (1,440 minutes) of the standard consolidation test is reached in 7.6 minutes. The effect of this consolidation promotion is to increase the consolidation increase load by a factor of about 2 unless a micro-vibration consolidation load is used. This is a tremendous effect as consolidation consolidation. This is due to the fact that secondary consolidation is taken in and consolidation is progressing. The density of cohesive soil increases due to consolidation, and excess pore water pressure replaces effective stress. If the micro-vibration compaction load is stopped, the moisture retention power recovers with time, the adhesive strength increases greatly with increasing density, and the secondary compaction stops. It is a solution to the secondary consolidation problem.

The loading device of the present invention reproduces the state of the micro-vibration consolidation testing device at an actual site. However, it is very difficult to reproduce complete one-dimensional consolidation as in the consolidation test described above. Accordingly, in the present invention, a constant load and a repeated load are applied to the target ground within a range in which the foundation ground is not destroyed. The loading device of the present invention does not vibrate itself when loaded, and is always in contact with the target ground, eliminating the impact load. In addition, since the wave size of the excess pore water pressure is such that the foundation ground does not break, there will be no shear slip in the target ground leading to the foundation ground breaking. Therefore, only the excess pore water pressure is propagated in the target ground. Such a state is a state in which the moisture retention is reduced, which is limited to the direction of increase in density of the clay structure, and the softening of the clay is the minimum necessary state. Thereby, the rapid consolidation proceeds stably .
The consolidation method based on the wave of excess pore water pressure of the present invention has an optimum value that maximizes the effect while achieving both stability of the ground and consolidation promotion. Consolidation progresses faster when the excess pore water pressure is larger, but the ground becomes unstable and the risk of ground failure increases accordingly.
The preload method has a stability limit to increase the excess pore water pressure due to loading. Therefore, when the total sum of excess pore water pressure within the stability range of the ground is fixed, there exists a combination of the optimum ratio of constant excess pore water pressure and repeated excess pore water pressure. Repeated excess pore water pressure is zero and everything is constant excess pore water pressure, which is the same as the conventional loading method. Repeated excess pore water pressure has a surprising effect on consolidation promotion, and the greater this, the greater the consolidation promotion effect. Now, a part of the constant excess pore water pressure is gradually and repeatedly replaced with the excess pore water pressure. However, repeated excess pore water pressure is accompanied by softening of the clay. There is a risk of ground failure at a certain excess pore pressure rate. The limit value at this time is the optimum ratio value of the excess pore water pressure.
The consolidation method of the present invention is the reason why the minimum softening is required to facilitate rearrangement of the clay-structured pads. In addition, the wave period of excess pore water pressure has a significant effect on consolidation promotion. The optimum period for the ground is generally effective for short periods, but there are differences depending on the type of clay and the ground condition.
The consolidation settlement method of the present invention is based on the charge and hierarchical structure characteristics of the clay, and the optimum load ratio and constant load ratio that best suits the stability and consolidation of the ground, and the cycle of the repeated load is the optimum cycle. These combined loadings are applied to the target ground, and the wave of the optimal excess pore water pressure is generated in the target ground to maximize the effect of rapid consolidation settlement.

The effect of the second solution is to widen the range of excess pore water pressure that does not cause ground failure in the target ground. As a specific effect, the target ground inside the pressurizing box is in a one-dimensional consolidated state, like the test sample in the consolidation ring of the consolidation test. The structural function of the pressurizing box corresponds to that obtained by removing the bottom plate of the micro-vibration consolidation test apparatus, integrating the loading plate and the consolidation ring, and repeatedly applying a loading load to the loading plate. Therefore, the target ground below the bottom surface of the pressurizing box can be regarded as the foundation ground. It is good if this foundation ground does not withstand the excessive pore water pressure wave and cause ground destruction. The outer peripheral ground of the pressurizing box serves as a pressing load for preventing shear fracture of the foundation ground. Therefore, the necessary pressing load can be ensured by the height of the restraining wall of the pressurizing box. In addition, the pressurization box sinks due to the consolidation settlement. Thereby, the position of the foundation ground is also lowered, and the holding load of the outer peripheral ground is relatively increased. Therefore, it is reasonable to gradually increase the excess pore water pressure wave as a small one.

The effect of the third solution is comprehensive rapid consolidation. Incorporates the atmospheric pressure that is easy to unload, which is the feature of the vacuum consolidation method, in order to shorten the compaction time due to the wave of excess pore water pressure, which is the feature of the consolidation method of the present invention. A method of making the ground surface of the target ground hermetically sealed is the use of the pressure box. The pressurizing box is vibrated on the target ground surface, and it is easy to ensure a sealed state of the ground surface. Completion of comprehensive rapid consolidation method. Since the atmospheric pressure loading of the vacuum consolidation method works as a three-dimensional consolidation load, the holding load for preventing the shear failure of the foundation ground may exclude this atmospheric pressure loading.
In addition, the vacuum consolidation method has the advantage that water pressure corresponding to the water depth can be taken in the case of submarine ground. The above-mentioned comprehensive rapid consolidation method of the present invention is an amazing rapid consolidation method, and therefore has a wide range of applications as well as improvement of soft ground. For example, deepening due to seabed subsidence that does not depend on dredging in securing the water depth of the channel. For example, improvement of bottom sediment by covering sand without dredging at river ports.

用している。図２（ａ）のＡ１，Ａ２地盤が改良対象地盤で，Ａ１地盤が加圧函体１で塑性変形が拘束されている地盤，Ａ２，Ｂ２地盤が基礎地盤である。Ｃは水中である。地盤中の点線で示した曲線は，基礎地盤が載荷重に耐えかねて地盤破壊する時の一般的なせん断滑り面１４を示したものである。この時，加圧函体１の外周のＢ１地盤が基礎地盤の破壊を防止する押さえ荷重の役目をする。対象載荷重は水圧（Ｈωγω）の載荷重によるせん断滑りである。図２（ｂ）はこの時の各々の載荷重を図化したものである。ここでの一定載荷重は大気圧と水圧の和（Ｕｓ＋Ｈωγω）である。ただし，水圧は地表面の載荷圧であるから載荷の面積に応じて深部の応力は低減している。本発明の圧密工法は，前記一定載荷重と繰り返し載荷重が組み合わされる。この時，載荷重の組み合わせ割合を最適割合，繰り返し載荷重の周期を最適周期とする。このよ

波動となるように設定して対象地盤全体に伝播させるのが好適である。FIG. 2 is a diagram for explaining a mechanism which is the best mode for carrying out the comprehensive rapid consolidation settlement method of the present invention on the seabed ground. Here, FIG. 2A is a longitudinal sectional view of an embodiment of a comprehensive rapid consolidation method in which the vertical drain method and the vacuum consolidation method are used in combination with the method of the present invention. However, the diagram of equipment, etc. in the known construction method in the figure is the minimum necessary. FIG. 2 (b) is a relationship diagram between each load x and depth y of a constant load and a repetitive load that are the waves of excess pore water pressure of the target ground.
FIG. 2A shows a state in which the loading device structure Y that repeatedly applies a loading load to the constant loading load of the present invention is installed on the seabed ground at a water depth Hω . The loading device structure Y is composed of a pressurizing box 1, a repetitive load generating device 2, and a pressurizing tower 3, and is structurally integrated. The pressurizing box 1 is composed of a pressurizing plate 1-1 and a constraining wall 1-2. Here, the vacuum pump 7 is operated, and the entire target ground is set to a negative pressure (−Us) through the inside of the pressurizing box 1 and through the vertical drain 10. Further, the load generator 2 is operated repeatedly. 2A, the pressure plate 1-1 of the pressurization box 1 has a vertical load of atmospheric pressure (Us), water pressure (Hωγω), and a load.

I use it. The A1, A2 ground in FIG. 2A is the ground to be improved, the A1 ground is the ground in which plastic deformation is constrained by the pressure box 1, and the A2, B2 ground is the basic ground. C is underwater. A curve indicated by a dotted line in the ground indicates a general shear sliding surface 14 when the foundation ground fails to withstand the load and the ground breaks down. At this time, the B1 ground on the outer periphery of the pressurizing box 1 serves as a holding load for preventing the foundation ground from being destroyed. The target load is a shear slip due to a load of water pressure (Hωγω). FIG. 2 (b) illustrates the respective loading loads at this time. The constant load here is the sum of atmospheric pressure and water pressure (Us + Hωγω). However, since the water pressure is the loading pressure on the ground surface, the stress in the deep part is reduced according to the loading area. In the consolidation method of the present invention, the constant load and the repeated load are combined. At this time, the combination ratio of the loading load is the optimum ratio, and the cycle of repeated loading is the optimum period. This

It is preferable to set it to be a wave and propagate it to the entire target ground.

Hereinafter, an embodiment in which the seabed ground is improved by offshore construction by the consolidation settlement method of the present invention will be described with reference to FIGS.

は，台船４の中心部に切り欠き空間６を設け，この切り欠き空間の外周鉛直上空に伸びる前記ガイドタワー５を固定し，構造的に一体型のものである。該作業船は，載荷装置構造体Ｙの加圧タワー３を浮構造体Ｚの台船４の切り欠き空間６とガイドタワー５に組み入れて，加圧函体１を台船４の底面に装備し，且つ加圧函体１は台船４の下の水中を昇降する機能を備え，且つ加圧函体１を海底地盤に据付けた密閉状態において，加圧函体１の内部圧を減圧，加圧する機能を備えた作業船である。図３において，加圧函体１の細部構造は，１−１は加圧板，１−２は拘束壁，１−３は剛性フィルター，１−４は負圧時の水平帯状集水空間である。また，７は真空ポンプ，８はコンプレッサー，９は加圧函体１の内部の圧気滞留層，１０は鉛直ドレーン，１１は水平ドレーンのサンドマットである。圧気滞留層９は載荷装置構造体Ｙの浮力として使われる。FIG. 3 is a longitudinal sectional view of the construction of the vertical drain 10 and the sand mat 11 at the previous stage and the work ship used for the construction method before the start of the operation in the case of the comprehensive rapid consolidation settlement method of the present invention on the seabed ground. It is.
The main structure of the working ship used in the method of the present invention is composed of Theissen 4 and the guide tower 5 constituting the front Symbol loading device structure Y and floating structure Z. Loading device structure

Is provided with a notch space 6 at the center of the carriage 4 and fixed with the guide tower 5 extending vertically above the outer periphery of the notch space. The work ship incorporates the pressure tower 3 of the loading device structure Y into the notch space 6 and the guide tower 5 of the carrier 4 of the floating structure Z and equips the bottom of the carrier 4 with the pressure box 1. In addition, the pressurizing box 1 has a function of moving up and down in the water under the carriage 4 and, in a sealed state where the pressurizing box 1 is installed on the seabed ground, the internal pressure of the pressurizing box 1 is reduced. It is a work ship with a function to pressurize. In FIG. 3, the detailed structure of the pressurizing box 1 is that 1-1 is a pressurizing plate, 1-2 is a constraining wall, 1-3 is a rigid filter, and 1-4 is a horizontal belt-like water collecting space at negative pressure. . Further, 7 is a vacuum pump, 8 is a compressor, 9 is a pressurized air retaining layer inside the pressurizing box 1, 10 is a vertical drain, and 11 is a sand mat of a horizontal drain. The pressurized air retention layer 9 is used as the buoyancy of the loading device structure Y.

FIG. 4 is a horizontal sectional view of the work boat of the present invention at the position of the X1-X1 line of FIG.

FIG. 5 is a longitudinal cross-sectional view of the pressurized ship 1 of the work ship, in which the pressurized air retention layer 9 is removed and the loading device structure Y is lowered to a predetermined position on the target seabed ground and installed. Placing the restraining wall 1-2 of the pressurizing box 1 is performed by operating the load generating device 2 repeatedly.

FIG. 6 is a horizontal sectional view of the work boat of the present invention at the position of line X2-X2 in FIG.

FIG. 7 is a longitudinal sectional view showing a state in which consolidation is rapidly progressing by using the vacuum consolidation method described in FIG. The vacuum pump 7 is operated, and the entire target ground is set to a negative pressure through the inside of the pressurizing box 1 and through the vertical drain 10. Furthermore, the load generator 2 is operated repeatedly, and the wave of the optimal excess pore water pressure is generated in the entire target ground.
The pore water is discharged from the target ground through the vertical drain 10, the sand mat 11, the rigid filter 1-3, the horizontal belt-shaped water collection space 1-4, and the vacuum pump 7.
The power cable and drain pipe of the vacuum pump 7 are preferably wired and piped inside the support pipe of the pressurizing tower 3.

FIG. 8 is a longitudinal cross-sectional view showing a situation in which the predetermined consolidation settlement is completed and the loading device structure Y is pulled out from the ground and lifted. Now, pressurized air is sent to the inside of the pressurizing box 1 of the work ship by a compressor 8 to form a pressurized air retention layer 9 and increase buoyancy.
The constraining wall 1-2 is repeatedly attached to the ground by repeatedly operating the load generator 2 and cutting the edge. Then, the pressurizing box 1 of the loading device structure Y is mounted on the bottom surface of the carriage 4 of the floating structure Z. Necessary ground improvement is carried out by carrying out the work cycles shown in FIGS. 3, 5, 7 and 8 on the work boat. Further, it is preferable that the compressor 8 is piped inside the column pipe of the pressurizing tower 3.

An embodiment of water quality treatment without dredging in rivers and harbors utilizing the consolidation settlement method of the present invention and bottom sediment improvement by sand covering will be described with reference to FIG.
Countermeasures for contaminated bottom sediments in river ports are broadly divided into excavation removal and in situ treatment. Sand-capping is in-situ processing, and there are solidification processing. In-situ processing is considered when excavation processing is difficult, such as along piers and along revetments. However, since in-situ processing reduces the river volume with sand-capping material, solidified material, etc., it is limited to cases where there is room in the river volume. In addition, the solidification method is advantageous for the environment although the construction cost for countermeasures is significantly higher than that of the sand-capping method.

FIG. 9 is a longitudinal sectional view showing a situation in which a sand mat 11 is laid at the bottom quality improvement target position and a work ship used for the rapid consolidation settlement method of the present invention is installed on the bottom of the water. In FIG. 9, E is the land, G is the revetment, and 12 is the water purification tank. Moreover, since the contaminated ground is a surface layer, the vertical drain 10 is not used. With the loading device structure Y of the working ship of the present invention, the wave of the optimum excess pore water pressure is generated in the entire target contaminated ground, and consolidation is promoted. The discharge path of pore water (contaminated elution water) in the target contaminated ground is as follows: sand mat 11, rigid filter 1-3, horizontal strip water collection space 1-4, vacuum pump 7, drain pipe inside the column of pressurizing tower 3 And collected in the water purification tank 12.
Water is treated in the water septic tank 12 and discharged with water quality that satisfies the environmental standard value. When the necessary consolidation settlement of the target contaminated ground is completed, the loading device structure Y of the work ship is lifted, and good quality sand is covered on the sand mat 11. If there is a flow, cover the sand with a crushed stone.
The features of bottom sediment improvement utilizing the consolidation settlement method of the present invention are as follows. (1) Since the thickness of the sand cover is secured by rapid consolidation settlement, it is not constrained by the restriction of the river volume. (2) Since it is shielded by the pressurizing box 1 of the loading device structure Y at the time of construction, there is no fear of contamination diffusion. (3) There is no fear of contaminated elution water after bottom sediment improvement. (4) In the case of along the revetment, the ground will be improved by increasing the density, and the stability of the revetment will be improved. (5) The water quality treatment plus sand-capping method of the present invention is environmentally friendly, and the construction cost for countermeasures is significantly lower than that of other methods of excavation and removal and in-situ solidification treatment.

An embodiment in which the old seabed ground in a landfill is improved by land construction by the comprehensive rapid consolidation settlement method of the present invention will be described with reference to FIG.
FIG. 10 is a longitudinal sectional view showing a situation in which the vertical drain 10 and the sand mat 11 are constructed on the target ground, and the loading device structure Y of the present invention is installed. The loading device structure Y includes a pressurizing box 1 and a repeated load generator 2. There is no pressurized tower 3 because it is used on land. In FIG. 10, D and E are landfills, F and G are old submarine grounds, and the consolidation target grounds are F and H grounds. In the loading device structure Y of the present invention, when the wave of the optimum excess pore water pressure is generated in the entire target ground, consolidation is promoted.
The constant load of the target ground is the load of the earth covering thickness and the atmospheric pressure (Us). The repeated loading is as described in FIG.
In FIG. 10, 13 is a hook used when lifting and moving the loading device structure Y. When moving the loading device structure Y, four traveling vehicles having a lift function are used. The features of the comprehensive rapid consolidation settlement method of the present invention are basically the same as those on land and sea.

It is a time-consolidation distortion amount curve figure of a standard consolidation test and a micro vibration consolidation test. FIG. 2 (a) is a longitudinal sectional view of an embodiment of the present invention. FIG. 2 (a) is an explanatory view of a mechanism that is the best mode in the seabed ground of the comprehensive rapid consolidation settlement method of the present invention. FIG. 2B is a relationship diagram between the respective loading loads x and the depth y of the constant loading load and the repeated loading load. It is a longitudinal cross-sectional view before the work start of the work ship used for the construction method of this invention. It is a horizontal sectional view of the work ship of the present invention at the position of line X1-X1 in FIG. It is a longitudinal cross-sectional view in the condition which installed the loading apparatus structure Y of the working ship of this invention in the position of the predetermined submarine ground. It is a horizontal sectional view of the work ship of the present invention at the position of line X2-X2 in FIG. It is a longitudinal cross-sectional view which shows the condition where consolidation by the construction method of this invention is progressing rapidly. It is a longitudinal cross-sectional view which shows the condition of the completion | finish operation | work which draws out the loading apparatus structure Y from the ground after predetermined consolidation settlement is completed. In bottom quality improvement, it is a longitudinal cross-sectional view which shows the condition which installed the work ship of this invention in the water bottom of the object position. It is a longitudinal cross-sectional view which shows the condition which installed the loading apparatus structure Y of this invention in the predetermined position in land construction.

Y loading device structure, Z floating structure,
DESCRIPTION OF SYMBOLS 1 Pressurization box, 2 Repeat load generator, 3 Pressurization tower, 4 Cargo ship, 5 Guide tower, 7 Vacuum pump, 8 Compressor, 10 Vertical drain, 11 Sandmat,
A ( A1, A2 ) Improvement target ground, B1 foundation ground holding load,
C underwater,

Claims (4)

In the consolidation settlement method due to the loading of soft ground, a loading device composed of a pressure plate and a repeated load generation device is directly grounded to the surface of the target ground, and the pressure plate itself does not vibrate and has a constant vertical load. Consolidation settlement method that rapidly accelerates consolidation settlement by generating waves of excess pore water pressure by repeatedly applying excess pore water pressure to a constant excess pore water pressure by continuously loading repeated loading loads. 2. The consolidation settlement method according to claim 1, wherein a constraining wall that restrains plastic deformation of the ground is attached to the pressurizing plate, and a pressurizing box is placed on the surface of the target ground. The ground surface is sealed, and then the target ground in the sealed state is made negative to load atmospheric pressure and further water pressure to ensure a constant load and the repeated load is a load sufficiently smaller than the constant load. This is a consolidation settlement method that accelerates consolidation settlement rapidly, which suppresses the vibration of the pressurized box itself and generates waves of excess pore water pressure . 3. A work ship used in the consolidation settlement method according to claim 2, wherein the main structure of the work ship is a confined wall on the outer periphery of the bottom and a horizontal belt in the top edge space. It consists of a water collection space, a pressurization box with a rigid filter, a repetitive load generator, a loader structure in which a pressurization tower is integrated, and a floating structure in which a carriage and a guide tower are integrated. The carriage has a notch space at the center thereof, the guide tower is fixed to the outer periphery of the notch space, and the load device structure described above generates the repeated load on the upper surface of the center of the pressurizing box. The pressure tower equipped with a device is fixed, a pressure tower integrated with a pressure box is incorporated into the guide tower of the base boat, and the pressure box is equipped on the bottom surface of the base boat, And the pressurization box is the trolley A function of lowering the water, and the pressurized圧函body in a closed state in which installed in seabed, depressurize the interior pressure of the pressurized圧函body, work boats, characterized in that a function of pressurizing. 4. A bottom sediment improvement method for implementing bottom sediment improvement without dredging in a port or the like using the work ship according to claim 3, wherein the load ship structure of the work ship is repeatedly applied to a target seabed or river bed. To secure the airtight state inside the pressurization box by placing the restraining wall of the pressurization box in the soil, and then operate the vacuum pump to target the inside of the pressurization box and below the pressurization box A constant load is applied with negative pressure on the ground, and then the load generator is repeatedly actuated to generate waves of excess pore water pressure. The pore water, which is the contaminated solute water of the target contaminated ground due to the consolidation settlement that collects in the horizontal belt-like water collection space of the body, is collected in the water purification tank by pumping up, and then discharged after being treated with water that meets the environmental standard value The work vessel loading device structure was levitated on the surface and deepened by consolidation settlement. Sediment improved method, characterized in that by using a depth to cover the ground surface sand, stone or the like.

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