JP7325701B2 - Vacuum Consolidation Method, Vacuum Consolidation Dredging Method, Vacuum Consolidation Test System, Vertical Drain Driving Machine, and Airtight Loading Box - Google Patents

Description

The present invention is a rapid vacuum consolidation method that uses the newly confirmed fine bubble effect to improve the ground, and a vacuum consolidation dredging method for seabed soil, etc., in which rapid vacuum consolidation and dredging are performed in a series of steps. It also relates to a vacuum consolidation test system, a vertical drain material placement machine used in each construction method, and an airtight loading box, which are used in the implementation plan of the construction method. The present invention also relates to sterilization of sludge ground and the like, decomposition of organic matter, and purification of soil by combined effect with the already known fine bubble effect.

When constructing a heavy structure on soft cohesive ground, it is common to improve ground settlement, deformation, and strength in advance. As a countermeasure method for this, there is a preload method. In this construction method, an embankment load equal to or greater than that of the structure is applied on the ground in advance to cause consolidation settlement and increase the strength of the ground, and then the embankment load is removed to construct the structure. is. Normally, the preloading method uses a vertical drain method to shorten the consolidation drainage distance and promote consolidation.

The vacuum consolidation method started around 1949 when Kjellman of Sweden proposed an atmospheric pressure loading method using atmospheric pressure instead of embankment load. Currently, the vacuum pump is used exclusively for exhaust, and the system has evolved into a steam-water separation tank system that separates exhaust and waste water. The vacuum consolidation method has an excellent feature that the embankment loading method does not have. Feature 1 does not require the process of carrying in embankment materials, embankment construction, and embankment removal. Characteristic 2 is a stable deformation in which the outer ground is pulled inward as the ground subsidence and contraction of the improvement area progresses. Therefore, it can be easily applied to soft ground where loading embankment is not possible. On the other hand, the vacuum loading pressure (difference between atmospheric pressure and vacuum pressure) in the vacuum consolidation method has a theoretical limit of 101.3 kPa. The most important issue in the vacuum consolidation method is to keep the fluid pressure in the drain as low and stable as possible. The current decompression performance is -70 to -80 kPa under an airtight sheet.

There is a vacuum consolidation dredging method as a construction method that utilizes the vacuum pressure of the seabed ground. This is a construction method that combines vacuum consolidation and dredging. In this construction method, a steel box-shaped device called an airtight loading box is used to ensure the airtightness of the ground, consolidate loading, and act as a bucket for dredging. The structure of the airtight loading box is a box-shaped structure with an opening at the bottom, and a thin tank for horizontal drainage is installed on the inner ceiling surface, and directly below it is divided by a box partition with a drain function to form multiple compartments. A water-permeable cover is provided on the upper surface of the compartment, and an air-water separation airtight tank and a tower are attached to the central portion of the outer upper surface of the box. (See Patent Document 1) (See Patent Document 2) (See Patent Document 3) (See Patent Document 6)

The work process of the vacuum consolidation dredging method is divided into the installation process of setting the airtight loading box on the seabed, the consolidation process, the dredging process, and the transportation process of the dredged soil. The dredging process is the process of lifting the filling soil held by the box from the seabed and pushing it out of the box. This lifting corresponds to loading of the dredged soil, and pushing out the filling soil corresponds to loading and unloading of the dredged soil.

When the box is set on the seabed, airtightness is ensured. Then, the seabed soil is packed in the airtight loading box. In the consolidation process, the seabed soil is made strong enough to be dredged by the box with an opening at the bottom. That is, consolidation is promoted so that the moisture content of the seabed cohesive soil to be dredged is below the liquid limit, and the vacuum pressure difference (vacuum suction) between the upper and lower surfaces of the filling soil is used in the dredging process. At this time, it is meaningless if only the upper surface of the filling soil is lifted and the rest falls down. Therefore, the filling soil must be strong enough not to separate and fall under its own weight. As a result of verification by model experiments, the integral condition of this filling soil is the strength obtained by consolidating the water content ratio of the filling soil below the liquid limit.
This realizes a construction method in which consolidation and dredging are performed as a series of processes using an airtight loading box with an opening at the bottom. This method is also used for maintenance dredging of the channel. Therefore, further shortening of the consolidation time is a subject.

In 2019, in the effective use of vacuum pressure, a high vacuum consolidation system was invented in which the pressure reduction under the airtight sheet approaches -100 kPa. Conventional reduced pressure is -70 to -80 kPa. If the reduced pressure is stably maintained at 98 kPa, the reduced pressure is improved by 25% to 40%. The power of this high-vacuum consolidation system is that the pore water can be boiled by reducing the pressure until the current temperature of the pore water in the clay ground reaches the boiling point. Once the pore water is boiled, the consolidation settlement of the clay ground proceeds rapidly by maintaining the highest vacuum pressure in the range that does not cause boiling. (Refer to Patent Document 5 for a high-vacuum consolidation system.) Hereinafter, the phenomenon in which consolidation subsidence rapidly progresses due to boiling under reduced pressure is referred to as vacuum boiling consolidation. Since the high-vacuum consolidation system is an extremely important system, the system functions and characteristics will be described below.

As we all know, water evaporates without boiling. In particular, water vapor is actively generated in a vacuum. When water turns into gas (steam), its volume increases dramatically. The generation of water vapor therefore acts as a very large pressurization counter to the vacuum pressure of the reduced pressure. Conventional vacuum consolidation systems overlook this effect of water vapor pressure. Therefore, the pressure reduction of the conventional vacuum consolidation system is limited to about 70 to 80 kPa. A solution to this water vapor pressure is to incorporate a cold trap in the vacuum path of the vacuum consolidation system.

The vacuum-related equipment of the high-vacuum consolidation system that enables vacuum boiling consolidation is installed in the order of a high-vacuum pressure storage tank and a cold trap between the steam-water separation vacuum tank and the vacuum pump. The role of the cold trap is to maximize the function of the vacuum pump by collecting water vapor generated in the vacuum path as frost (ice) with the cold trap. This high vacuum consolidation system is also incorporated into the consolidation process of the vacuum consolidation dredging method, such as the seabed. In this construction method, it is necessary to consolidate in the shortest possible time to the strength that can be dredged with an airtight loading box with an opening at the bottom. At this time, vacuum (reduced pressure) boiling consolidation is effective.

The theoretical limit of ground improvement depth by the vacuum consolidation method is 10m. The vertical drain is filled with water, and the water can only be sucked up by the vacuum pump up to a depth of 10m from the water level. In order to boil the pore water in the clay soil, it is necessary to transfer high vacuum pressure directly to the cohesive soil. Therefore, a deep vacuum consolidation method was invented that greatly expands the 10m limit depth of ground improvement by the vacuum consolidation method by replacing the pore water of the cohesive ground that has accumulated in the vertical drain with air. (See Patent Document 4) (See Patent Document 5)

The principle of the vacuum boiling method lies in the newly confirmed fine bubble effect. The details of this are described in the paper titled "Next-generation vacuum boiling consolidation method, vacuum boiling consolidation method and blue carbon for a decarbonized society", which extensively considers based on experiments and further develops the vacuum boiling consolidation method. The description of the main part of this specification is the same as the content of the article. (See Non-Patent Document 1)

Patent No. 6582361 (PCT/JP2017/010246) PCT/JP2018/014036 PCT/JP2018/019707 Patent application 2019-213667 PCT/JP2020/036153 PCT/JP2020/036152

Non-Patent Document 1: Masayoshi Kondo et al. / Next Generation Vacuum Consolidation Method "Vacuum Boiling Consolidation Method" and Blue Carbon for Decarbonized Society / 14th Environmental Geotechnical Symposium Presentation Papers / Japanese Geotechnical Society September 2021

At present, the vacuum boiling consolidation method is extremely effective for ground (soil) and ground for which it is not. For example, effective results have not been obtained for sludge ground containing a lot of humus. These measures have not yet been established. In addition to the atmospheric pressure, water pressure is added to the seabed ground. The decompression boiling phenomenon in this case is not clear. The fundamental problem is that the principle and mechanism of rapid consolidation in the vacuum boiling consolidation method have not been elucidated. For this reason, the characteristics of this construction method have not been fully utilized.

A high-vacuum consolidation system disclosed in Patent Document 5 has been established as a high-vacuum consolidation system. The high-vacuum consolidation system used in the present invention integrates the high-vacuum storage tank and the cold trap of the existing system, and has the same basic function as the system. These systems are systems in which the vacuum due to decompression approaches 100 kPa as much as possible. This system can reliably reduce the pressure of pore water such as closed clay ground to the saturation vapor pressure at which the current temperature is the boiling point, and boil the pore water. However, the evaluation of Patent Document 5 states that even if the high vacuum consolidation system is applied to the vacuum boiling consolidation method for submarine ground with a large water depth, it is difficult to boil the pore water of clay. The reason is that in addition to the atmospheric pressure, water pressure corresponding to the water depth is generated in the cohesive ground. (Although Patent Document 5 describes excessive pore water pressure, it is a mistake in describing the water pressure corresponding to the depth of water.) For this reason, a vacuum consolidation method using a high vacuum pressure that does not exceed the limit vacuum pressure at which the current temperature of the pore water becomes the boiling point is used. is said to be good. In other words, the vacuum boiling consolidation method is not effective in seabed soil.

In the following description, the clay ground will be used as a representative example. The vacuum boiling consolidation method utilizes the characteristic that if the necessary boiling time can be secured, the consolidation promoting effect will continue even after boiling is stopped. The relationship between this boiling time and the consolidation promotion effect cannot be verified without a vacuum consolidation tester. Conventionally, such devices do not exist. Patent document 5 verifies with a vacuum consolidation test device. However, it is due to an imperfect vacuum consolidation test device in the early stages of development. Therefore, the verification itself is not sufficient. The result obtained in the vacuum consolidation test of Patent Document 5 is that "the vacuum boiling consolidation method has ground (soil) that is extremely effective and the ground that is not. The consolidation promotion effect continues even if it is stopped.”

Task 1 is the development of a reliable vacuum consolidation test apparatus. Subject 2 is to clarify the mechanism of the vacuum boiling consolidation method by conducting vacuum boiling consolidation tests with various clay samples. What is the difference between effective and non-effective soil? Is there a workaround for this or not? It is considered that there is no effect on the seabed ground, but is it true? It is a verification experiment such as. Subject 3 is the review and examination of the existing vacuum boiling consolidation method, the vacuum consolidation dredging method incorporating this method, and the equipment and devices related to these methods, based on the principle and mechanism of the vacuum boiling consolidation method.

Task 1 is the development of a reliable vacuum consolidation tester and vacuum consolidation test system. The vacuum consolidation test system consists of a vacuum consolidation tester and a high vacuum consolidation system. The high-vacuum consolidation system already has a proven track record as a countermeasure against water vapor. The problem is to keep the vacuum consolidation tester airtight. There are two points to be held. Between the bottom plate and the consolidation ring of the vacuum consolidation tester, and between the consolidation ring and the pressure plate. In particular, since the pressure plate and the compression ring move relative to each other, it is extremely difficult to maintain airtightness. A common method is to cut a groove on the outer peripheral surface of the side surface of the pressure plate and embed about half of the O-ring. If the vacuum consolidation tester is fitted with an O-ring in a state where air is barely sucked into the container during vacuum, the circumferential friction with the consolidation ring will be excessive. Due to the influence of friction, this tester has lower accuracy than the true value because the amount of subsidence in the measured value is lower than the true value. A vacuum pressure close to 100 kPa strongly attracts the O-ring. If even a small part of the O-ring is displaced from the groove, the pressure plate cannot sink at all. For this reason, early vacuum consolidation testers are imperfect testers.

According to claim 3 of the present invention, the countermeasure between the compression ring and the pressure plate is a cap system made of a soft and highly elastic material. Grease the inner surface of this cap and fit it snugly over the compaction ring and pressure plate. This is the temporary sealing. At the time of the vacuum consolidation test, this cap is sucked and adhered by vacuum pressure to maintain airtightness. The advantage of this is that it does not create peripheral friction of the compaction ring like an O-ring. However, the upper limit of the difference between the inner diameter of the compression ring and the outer diameter of the compression plate was set to less than 0.2 mm in order to prevent the cap from being sucked into the gap between the pressure plate and the compression ring due to the vacuum pressure. On the other hand, the lower limit is made 0.1 mm or more in order to avoid circumferential friction between the pressure plate and the compaction ring due to the extremely narrow gap. Also, the integration of the compression ring and the guide ring avoids joints that cause vacuum leaks. However, as long as this countermeasure is taken, they do not have to be physically integrated. A vacuum consolidation test system according to claim 3 of the present invention is obtained by connecting the vacuum consolidation tester of the present invention to a device of a high vacuum pressure system.

Using the improved vacuum consolidation test system of the present invention, a comparative experiment with a weight load consolidation test was carried out. The clay sample is a sludge sample containing kaolinite, smectite and humus (organic compounds) as the main clay minerals. The temperature of the clay sample is about 15°C. The saturated vapor pressure of the interstitial water of the clay sample with this boiling point is 1.7 kPa (gauge pressure: 99.6 kPa). Therefore, the reduced pressure during boiling was -99.6 kPa, and the reduced pressure during consolidation after boiling was -96.0 kPa. Moreover, the applied load amount of the weight loading consolidation test was set to 98.1 kPa. The boiling time was extended while observing the test results, and the test was repeated. Compared to the consolidation rate of the weight loading consolidation test curve, the consolidation rate of the boiling vacuum consolidation test curve is about the same or even slower. Under a high vacuum (-96.0 kPa) where boiling does not occur, consolidation proceeds rapidly.

It was confirmed experimentally that the acceleration effect of consolidation settlement by vacuum boiling consolidation differs greatly depending on the type of clay. The boiling time of the clay sample, the main clay mineral of which is kaolinite, was only 1 to 2 minutes, and a remarkable effect was obtained. Smectite was effective at boiling times of 5 to 10 minutes. And, the longer the boiling time, the greater the effect. The humus-rich sludge has a 50 minute boiling time, but a less stimulating effect. In Patent Document 5, the required boiling time for the vacuum consolidation method is said to be several tens of seconds to several minutes. This is the case for clay samples in which the major clay mineral is kaolinite.

In the vacuum boiling consolidation method, in order to obtain a sufficient consolidation promotion effect, the boiling time tends to be longer in the order of kaolinite, smectite, and sludge containing a large amount of humus. Comparing the cation exchange capacities CEC (meq/100 g) of these, kaolinite is 2-10, smectite is 60-100, and humus is 150-300. Comparing the experimental boiling time with respect to the boiling time of kaolinite, smectite is 10 to 30 times longer and sludge is 30 to 75 times longer. Samples with smectite as the main clay mineral appear to be slightly short of the required boiling time. It seems that the sludge containing a lot of humus had a very short boiling time. This suggests that the boiling time of the vacuum boiling consolidation method is closely related to the cation exchange capacity of the soil.

Clay particles (clay minerals) of saturated clay are tabular, negatively charged on the surface and positively charged at the ends, and the negative charge is predominant. Water molecules are adsorbed on the surface of the clay particles, and more cations are electrostatically attracted to form a diffuse ion layer (electric double layer). The structure of clay is a hierarchical structure in which clay particles form peds (crumbs), and the peds form the clay skeleton and gaps (macropores). Here, the clay particles, the adsorbed water layer, and the diffused ion layer surrounding them maintain electrical equilibrium and are stable, and the contact surfaces of pets also maintain electrical equilibrium and the clay structure is stable. That is, an attractive force acts between the negatively charged clay particles and the cations to stabilize them. It is thought that the diffused ion layer on the pet's contact surface is stable in the covalent state of the corresponding clay particles.

When the interstitial water of clay boils, countless fine bubbles are generated. These bubbles are presumed to be negatively charged fine bubbles. This is because the clay voids are not wide enough for normal millibubbles to occur. The fine bubbles adsorb cations in the diffusion ion layer and greatly disturb the electrical balance. That is, the corresponding clay particles on the pet's contact surface are held together by electrical attraction through the covalent diffusion ion layer and are stable. Negatively charged fine bubbles are adsorbed to the cations in this diffused ion layer to temporarily lose their electrical attraction. Consolidation subsidence advances the rearrangement of the peds in the direction of reducing the gap, but the function of the fine bubbles at this time is to temporarily reduce the viscous resistance in the rearrangement of the peds, thereby promoting rapid consolidation. is considered to be This is the mechanism of the vacuum boiling consolidation method. The vacuum boiling consolidation mechanism of humus is considered to be similar to that of clay minerals, except that the amount of negative charge is much larger than that of clay minerals. Patent document 5 could not specify that the bubbles generated in the interstitial water due to boiling are fine bubbles, and could not clarify the mechanism of the vacuum boiling consolidation method.

Fine bubbles refer to bubbles having a diameter of 100 μm or less. Fine bubbles are characterized by being negatively charged. Fine bubbles are classified into two types. Bubbles with a diameter of 100 µm or less and 1 µm or more are classified as microbubbles, and bubbles with a diameter of 1 µm or less are classified as ultrafine bubbles, each of which has its own characteristics. Ordinary bubbles with a diameter of 100 microns or more are visible, and when they occur in water, they immediately rise to the surface and burst on the water surface. The microbubbles float slowly while shrinking. As the dissolution progresses, it shrinks and disappears. Microbubbles become cloudy and can be visually observed. Ultra fine bubbles do not disappear for a long time. The finer the thing, the longer the life. The ultra-fine bubbles are colorless and transparent, so they cannot be seen with the naked eye. However, when irradiated with green laser light, the trajectory of scattered light due to Brownian motion can be confirmed linearly.

Fine bubbles produce effects from various actions. Surface activity is a common function of microbubbles and ultrafine bubbles. Fine bubbles have a negatively charged surface in water, attracting positively charged objects and repelling negatively charged objects. As an action unique to microbubbles, as the gas dissolves, the bubbles shrink and self-collapse. Due to the impact action at this time, the adhering substances are peeled off, and there is a cleaning effect. In addition, free radicals generated by the energy generated by this impact are said to have sterilizing and disinfecting effects. As a phenomenon peculiar to ultra-fine bubbles, there is Brownian motion and long-term stability in water. In addition, there is a long-term stable gas storage action in water. Owing to this action, gas encapsulation of ozone has a strong effect of cleaning, sterilizing, and decomposing organic matter. In addition, it has a physiologically active effect of promoting plant growth. The rapid consolidation promoting effect of the fine bubbles is an effect confirmed by the present invention, and is due to the surface active action of the fine bubbles.

Considering the vacuum consolidation test results described above, it is recognized that the precise setting of the boiling time for the vacuum boiling consolidation method is extremely important. The boiling time of the clay sample whose main clay mineral is kaolinite is 1 to 2 minutes, which is almost appropriate. Kaolinite has a cation exchange capacity CEC (meq/100 g) of 2-10. Here, it should be noted that CEC has a wide range depending on the content of the main clay minerals. The CEC of smectite is 60-100. The boiling time of smectite is 5 to 10 minutes, and judging from the CEC, it is speculated that if the boiling time is greatly extended, a better effect can be obtained. In other words, although the exact boiling time cannot be predicted by CEC alone, it provides a rough indication of the boiling time. In order to accurately set the effective boiling time of the vacuum boiling consolidation method, it is essential to verify it with a highly accurate vacuum consolidation test. In practice, a plurality of boiling times are set and verified by a vacuum consolidation test. In this case, the CEC of the soil is a measure of the effective boiling time, and a small number of vacuum consolidation tests can determine the effective boiling time.

In addition to the atmospheric pressure, water pressure equivalent to the atmospheric pressure is added to the seabed ground at a depth of 10 m. The boiling phenomenon of the vacuum boiling consolidation method when such a large water pressure is applied is not clear. Therefore, the following verification experiment of boiling under reduced pressure was performed.
A transparent pipe with a height of 11.0 m and sealing lids at the top and bottom are prepared and placed vertically. The pipe is filled with water to a height of 10.5m and sealed leaving a 0.5m height space at the top. Then, the upper end was evacuated with a vacuum pump and observed. The water temperature is 17.5° C. and its saturated vapor pressure is 2.0 kPa. The reduced pressure is -99.8 kPa (absolute pressure: 1.5 kPa), which is slightly higher than the saturated vapor pressure. It was visually confirmed that millibubbles of 0.1 mm to 0.2 mm were actively generated near the water level of 1.0 m (upper layer), grew into centibubbles as the water level rose, and burst at the water surface. The transparency was visually confirmed between the water level of 8.0 m and 10.5 m (lower layer). Next, a green laser beam was irradiated and the trajectory of scattered light due to Brownian motion was confirmed linearly. However, since scattered light also occurs in impurities, it cannot be said unconditionally that the generation of ultra-fine bubbles has been confirmed. What is noteworthy about this experiment is that, with the passage of time, a phenomenon was observed in which countless millibubbles stuck to the entire inner surface of the observation pipe. Normally, the internal pressure of a millibubble is 1 atm. However, at a water depth of 10 m, an internal pressure of 2 atmospheres is required. This phenomenon was presumed to be caused by the formation of fine bubbles, which coalesced to grow into high internal pressure millibubbles.

Boiling is a phenomenon in which the phase transition from liquid to gas occurs violently not only from the surface of the liquid but also from the inside. Evaporation inside the liquid generates minute bubbles. At this time, the vapor pressure inside the bubble exceeds the external pressure. The boiling point is the temperature at which the saturated vapor pressure of a liquid equals the external pressure. And the temperature of a boiling liquid is approximately equal to its boiling point.
By the way, the verification experiment of boiling under reduced pressure is organized as follows. Numerous millibubbles were generated in the upper layer and soon surfaced, growing into centibubbles and bursting on the water surface. Normal boiling. Microbubbles were generated in the intermediate layer. This bubble rises slowly. Ultra-fine bubbles were generated in the lower layer. This bubble hardly floats due to Brownian motion. The intermediate and lower layers are also boiling because they are vaporization inside the liquid. However, it seems to be different from normal boiling. Fine fine bubbles have a much higher internal pressure than normal millibubbles. For example, the internal pressure of a bubble with a diameter of 100 nm is calculated to be a high pressure of approximately 30 atmospheres. In other words, fine bubbles are generated even with a large external pressure that cannot be generated by being crushed by millibubbles. Therefore, it is distinguished from ordinary boiling. For the sake of convenience, the normal boiling of millibubbles is referred to as violent boiling, and the boiling of fine bubbles is referred to as quiet boiling.

The vacuum consolidation method of claim 1 of the present invention is equivalent to the necessary fine bubbles set based on the cation exchange capacity of cohesive soil and the vacuum consolidation test based on the principle and mechanism of the vacuum boiling consolidation method. The effective boiling time to generate volume is incorporated separately into the vacuum consolidation process. The vacuum consolidation method of claim 1 temporarily eliminates the electrical attraction between the peds that form the skeleton of the clay by the fine bubble effect, and simultaneously improves the water permeability of the clay to perform rapid vacuum consolidation. This is a vacuum consolidation method that shortens the consolidation time of clay ground and increases consolidation settlement.
Incorporating the effective boiling time in a separate frame means that in the vacuum consolidation process, the effective boiling time and the consolidation progress time can be clearly divided and managed. Conventionally, there was no technique or means for specifically setting the boiling time under reduced pressure. For this reason, there was no environment for quantitative construction management.

The purpose of the vacuum boiling consolidation method is diverse. A ground improvement method that aims to increase the strength of the ground by rapid consolidation settlement of the fine bubble effect. A water depth maintenance method for routes, etc. that aims at ground subsidence by rapid consolidation subsidence with fine bubble effect. A soil remediation method for the ground (soil) with a fine bubble effect. Or it is a composite construction method of these. The boiling time and consolidation time differ depending on the purpose.
Therefore, the vacuum consolidation method of claim 1 of the present invention is intended as a composite method, and is intended to shorten the consolidation time of clay ground and increase the consolidation settlement, improve the ground, or sterilize and remove harmful ions together with the consolidation drainage. It is a vacuum consolidation method characterized by soil remediation.

The pore water in deep cohesive soil or deep seabed cohesive soil is in a high water pressure state. In such a case, boiling under reduced pressure can generate only fine bubbles by utilizing the difference in the high vacuum pressure of normal millibubbles and fine bubbles. Ordinary millibubbles generate a large amount of water vapor when boiling. In maintaining a high vacuum, water vapor is a nuisance. On the other hand, the generation of water vapor from microbubbles by boiling is very small, and ultra-fine bubbles are hardly generated. Therefore, this high vacuum consolidation system can greatly reduce the defrosting step of the cold trap, allowing the system to operate continuously for long periods of time.
Therefore, the vacuum consolidation method for cohesive soil under high water pressure according to claim 2 of the present invention does not cause a violent boiling caused by normal millibubbles when the high vacuum pressure is set by reducing the pressure, but only fine bubbles are generated. Bring to a gentle boil. Evaporation due to boiling is suppressed as much as possible to maintain a stable high vacuum pressure, and the fine bubble effect temporarily eliminates the electrical attraction between the pods that form the skeleton of the clay, and improves the permeability of the clay. A vacuum consolidation method characterized by ground improvement that aims to shorten the consolidation time of clay ground and increase consolidation settlement by performing rapid vacuum consolidation, or sterilization and soil purification that removes harmful ions together with consolidation drainage. is.

By the way, Patent Document 5 regarding seabed ground states that it is better to implement a vacuum consolidation method using a high vacuum pressure that does not exceed the limit vacuum pressure at which the current temperature of pore water becomes the boiling point. Here, the difference of claim 2 of the present invention will be described. The intent of US Pat. No. 5,900,000 is to create as high a vacuum pressure as possible without boiling, since it is difficult to boil. The behavior of the vacuum boiling consolidation phenomenon, in which boiling is sufficiently secured, is sluggish during boiling. However, when boiling is stopped, consolidation settlement progresses rapidly. Patent document 5 is based on the idea that if the boiling is slow, the boiling time is wasteful, so that this time is excluded and only the loading pressure due to the vacuum pressure is expected. In contrast, the idea of the present invention is to generate only fine bubbles by quiet boiling of fine bubbles instead of normal violent boiling. Then, we expect both the fine bubble effect and the loading pressure due to the vacuum pressure. For example, let the temperature of the clay ground be about 17.5°C. The saturated vapor pressure of normal interstitial water with this boiling point is 2.0 kPa (gauge pressure: 99.3 kPa). However, the actual boiling point of pore water in the ground has a wider width (2.0±αkPa) under various conditions than ordinary water. Boiling under reduced pressure in the present invention is a high vacuum pressure at which only fine bubbles are generated. In this case, it is necessary to make a clear difference. For example, the high vacuum pressure in the above example is 10.0 kPa (gauge pressure: 91.3 kPa), which is significantly different from 2.0 kPa. The saturated vapor pressure with 10.0 kPa as the normal boiling point of millibubbles is about 46°C. However, fine bubbles are surely generated even at 17.5°C under 10.0 kPa. The present invention takes advantage of this phenomenon.

As described above, the high vacuum pressure set by claim 2 of the present invention and patent document 5 is fundamentally different in whether bubbles generated by boiling are millibubbles or fine bubbles. There is also a clear difference in the degree of difficulty in maintaining an actual high vacuum pressure. For example, it is extremely easy to reduce the pressure from 100 kPa to 99 kPa. Then, the pressure is reduced from 11.0 kPa to 10.0 kPa. Reduce pressure from 3.0 kPa to 2.0 kPa. Although it is the same reduced pressure of 1.0 kPa, the latter is much more difficult under such a high vacuum pressure. In addition, referring to the results of the vacuum consolidation test, the amount of subsidence after one hour consolidation of claim 2 of the present invention and patent document 5 will be compared. Now, it is assumed that the vacuum gauge pressure is -91 kPa in the present invention and -98 kPa in Patent Document 5. The loading pressure due to vacuum pressure is 91 kPa and 98 kPa, respectively, which is about 8% less than the present invention. This loading pressure is proportional to the amount of consolidation settlement. However, in practice, the present invention adds a fine bubble effect. This effect corresponds to approximately double the amount of subsidence. When this is added, the present invention is about 86% larger.

In the vacuum boiling consolidation method, the required boiling time for this method is long except for clay samples whose main clay mineral is kaolinite. Therefore, if the necessary amount of fine bubbles cannot be secured only by short-time boiling under reduced pressure, it is advisable to use fine-bubble water produced by a fine-bubble generator to make up for the shortage of the amount of fine bubbles. Therefore, according to the vacuum consolidation method of claim 4 of the present invention, the amount of fine bubbles is replenished by incorporating the step of supplying fine bubble water into the vacuum consolidation step. In the case of sludge ground, etc., it is rational to use not only ground improvement but also soil remediation. Therefore, according to claim 4, by replenishing the amount of fine bubbles, it is possible to surely shorten the consolidation time of a wide variety of clay soils and increase the consolidation settlement. It is a vacuum consolidation method characterized by soil remediation. In this construction method, not only the amount of fine bubbles to be replenished is a problem, but also the characteristics of microbubbles and ultrafine bubbles are used properly. As a result, it was sufficiently effective for sludge ground containing a lot of humus.

The fine bubble water supply device and machine are different from land and seabed. The vacuum consolidation method, which is used in combination with the vertical drain method on land, uses a vertical drain material driving machine. The vertical drain placing machine adds the function of supplying ultra-fine bubbled water with extremely long life to the function of placing drain material. The vertical drain placing machine of claim 5 of the present invention is provided with a nozzle device for injecting ultra-fine bubbled water at a tip end of a mandrel holding a drain material at a high pressure in a horizontal direction and downward. Equipped with an ultra-fine bubble water supply function that injects ultra-fine bubble water at high pressure into the ground in the required direction at the same time as material is placed, or injects only ultra-fine bubble water into the ground at high pressure without placing a drain material. .
The reason why the fine bubble water to be supplied is ultra-fine bubble water is that it has a very long life. This is necessary because there is a time lag of about one to two months between the vertical drain placement process and the vacuum consolidation process. Microbubbles, on the other hand, do not have a very long life. In addition, the first stage of supply of ultra-fine bubble water to the ground is horizontal, downward high-pressure injection. Especially the horizontal direction is important.

In the vacuum consolidation method using the vertical drain method together, when replenishing the deficit of the amount of fine bubbles with ultra-fine bubble water, the most important thing is to utilize the fine bubble effect evenly. For this reason, in the vacuum consolidation method of claim 6 of the present invention, the ultra-fine bubble water supply position with respect to the plane position of the ground of the vertical drain is the same position as the vertical drain, and if necessary, it is surrounded by the vertical drain position. In the center position, the working process is a process that combines drain placement and ultra-fine bubble water supply, then a diffusion process that takes the brown diffusion time of ultra-fine bubbles, and then shifts to a vacuum consolidation process. As a result, the ground distribution of the ultra-fine bubbles is evened out, and the ultra-fine bubble effect is evenly utilized. The Brownian diffusion time is the second step to evenly supply ultra-fine bubbled water to the ground.

Patent Document 5 states that the vacuum boiling consolidation method is ineffective because interstitial water is in a state of high water pressure in the seabed ground, but this is incorrect. In the vacuum boiling consolidation method, what is required is negatively charged fine bubbles. Further, since the boiling point of fine bubbles is much lower than that of millibubbles, verification experiments have revealed that the seafloor ground does not present any problems in the environment in which fine bubbles are generated.

The vacuum consolidation method applied to floating mud ground such as seabed, sludge ground, and soft ground uses an airtight loading box with an opening at the bottom. The amount of fine bubbles necessary for the sludge ground is insufficient only by boiling under reduced pressure. Therefore, according to the vacuum consolidation method of claim 7 of the present invention, perforated pipes functioning as countless nozzles for jetting fine bubble water at high pressure are stretched around the bottom of the airtight loading box. In the vacuum consolidation method of claim 7, fine bubble water is injected at high pressure in the step of supplying fine bubble water parallel to the step of installing this airtight loading box on soft ground, etc., and the required amount of fine water is applied to the soft ground. The bubbles are uniformly mixed, and the fine bubble effect shortens the consolidation time of soft ground and increases the consolidation settlement. In the sludge ground, it is characterized by sterilization, decomposition of organic matter, and soil purification. In addition, it is premised that fine bubble water spreads over soft ground such as sludge by high-pressure injection. Otherwise, use ultra-fine bubble water and require the process of Brownian diffusion. Further, when the major purpose is soil remediation, ultra-fine bubble water containing ozone is considered as fine bubbles to be replenished.

Conventionally, the vacuum consolidation method for submarine ground or the like, or the airtight loading box used for the vacuum consolidation dredging method has been equipped on a dedicated work ship. If the airtight loading box becomes gigantic, the dedicated work boat will be gigantic. That will drive up public works costs for port and coastal water projects. Therefore, the huge airtight loading box used in the construction method of the present invention is a self-submersible airtight loading box without using a dedicated work boat, thereby reducing the construction cost. There are two types of this airtight loading box according to the type of floating body, and two types for standard depth and high depth.

In the airtight box according to claim 8 of the present invention, a rigid floating body is attached to almost the entire upper surface of the box, and the lifting and lowering of the box is performed by exchanging air and water in the inner space of the floating body by a diving operation device. Do it freely. In addition, a horizontal telescopic beam with spuds, which has a plurality of hydraulic cylinders with vertical telescopic spuds fixed to the tip, is attached to the outer edge of the upper surface of the box in two directions, and the horizontal movement of the box on the seabed in the front, back, left, and right directions. Movement is freely performed by the above-mentioned diving operation device and the horizontal movement operation device of the horizontal telescopic beam. The use of a submersible operation device during horizontal movement is used to float the box above the sea floor. It is a self-submersible airtight loading box characterized by freely performing diving and horizontal movement on the seabed with these operating devices.

In the airtight box according to claim 9 of the present invention, a flexible closed floating body is attached to almost the entire upper surface of the box, and the lifting and lowering of the box is performed by injecting and discharging compressed air into and out of the internal space of the floating body using a diving operation device. This can be done freely by increasing or decreasing the volume of the floating body. Others are the same as those of claim 8. The difference from the rigid floating body is that the floating body operates faster and the maintenance cost is a little higher.

In the self-submersible airtight loading box of the present invention, a box tower is installed at the center of the upper surface of the box. The purpose of the box tower is to identify the position using the navigation system while the tower head is in the sea when the box body is submerged. In addition, there are two types of boxes, depending on whether or not they are equipped with operation-related equipment and devices at the top of the box tower.

The airtight loading box according to claim 10 of the present invention is an airtight loading box for standard depths of less than 20 m. The box is a self-submersible airtight loading system that is characterized by a structure in which a box tower equipped with equipment and devices related to its operation is attached to the center of the upper surface of the box, and the operation equipment of the box is a complete structure. It is a box body.

The airtight loading box according to claim 11 of the present invention is an airtight loading box for high depth. The equipment and devices related to the operation of the box are mounted on the operation ship, and the role of the box tower is to specify the position of the box and attach power cables, signal cables, and various pipes for the operation of the operation-related devices. It is a self-submersible airtight loading box characterized by reducing the weight of the box tower by using it as a floating body and increasing the stability as a floating body by lowering the position of the center of gravity of the box.

The vacuum boiling consolidation method for sedimentary sludge ground such as the seabed lacks a large amount of necessary fine bubbles only by boiling under reduced pressure. Therefore, the shortage of fine bubble water was solved by incorporating the fine bubble water supply process into the vacuum consolidation process, realizing rapid consolidation and soil remediation. In the vacuum consolidation dredging method of claim 12 of the present invention, an airtight loading box with a bottom opening is used. In order to dredge soft ground with an airtight loading box with a bottom opening, it is necessary to increase the strength of the dredging soft ground. In other words, when the airtight loading box is lifted from the seabed, it must be strong enough so that the mass of dredged soil inside the box sucked by the vacuum pressure will not break and fall due to its own weight. For this reason, the construction method incorporates the fine bubble supply step of the vacuum consolidation method into the steps of the construction method. This construction method uses the fine bubble effect to rapidly vacuum consolidate soft ground, etc., to a strength that enables dredging in an airtight loading box with the bottom opening, in an extremely short period of time. Furthermore, it is a vacuum consolidation dredging method characterized by sterilizing the sludge ground, decomposing organic matter, and refining the soil by the fine bubble effect.

The rapid consolidation promotion effect of the vacuum boiling consolidation method was clarified by the mechanism caused by negatively charged fine bubbles generated in the interstitial water by boiling under reduced pressure. The boiling time was incorporated separately into the vacuum consolidation process. As a result, the fine bubble effect was sufficiently exhibited, and the ground improvement method for shortening the consolidation time of clay soil and increasing consolidation settlement was realized. The rapid consolidation acceleration effect of this construction method is the new fine bubble effect discovered in the present invention.

The fine bubble effect has the effect of sterilizing and cleaning the soil by removing harmful ions together with the consolidation wastewater. The vacuum boiling consolidation method was effective as a composite method of ground improvement method and soil remediation method.

In the vacuum boiling consolidation method, if the necessary amount of fine bubbles cannot be secured by boiling under reduced pressure for a short period of time, the fine bubble water supply process produced by the fine bubble generator is incorporated into the vacuum consolidation process to reduce the amount of fine bubbles. replenish the minutes. At this time, by selectively using fine bubbles to be replenished according to the characteristics of microbubbles and ultra-fine bubbles, the amount and content of fine bubbles can be satisfied, resulting in the effect of becoming a composite construction method of soil improvement and soil remediation for a wide variety of clay ground. brought

Conventionally, the vacuum consolidation method for submarine ground or the like, or the airtight loading box used for the vacuum consolidation dredging method has been equipped on a dedicated work ship. If the airtight loading box becomes huge, the dedicated work boat will become huge, and the construction cost will be huge. That will drive up public works costs for port and coastal water projects. Therefore, the huge airtight loading box used in the construction method of the present invention is a self-submersible airtight loading box without using a dedicated work boat. This has had the effect of reducing project costs.

Explanatory diagram showing an example of a high vacuum consolidation system used in the construction method of the present invention Elevation and horizontal section of vertical drain material for deep depth Explanatory drawing showing an example of the vacuum consolidation test system of the present invention 1 is a vertical sectional view of a vertical drain driving machine of the present invention; FIG. Construction explanatory drawing of the same vertical drain driving machine Plan view of the position of the same vertical drain and the supply position of ultra-fine bubble water A vertical cross-sectional view of a standard rigid floating body type airtight loading box of the present invention. same plan view A vertical cross-sectional view of a standard flexible floating body type airtight loading box of the present invention. FIG. 2 is a vertical cross-sectional view of a rigid floating body type airtight loading box for high depth of the present invention. Explanatory drawing of underwater movement of the standard rigid floating body type airtight loading box of the present invention Explanatory drawing of the horizontal movement of the airtight loading box on the seabed

An embodiment of the present invention will be described below with reference to FIGS. 1 to 12. FIG.

FIG. 1 is an explanatory diagram showing an example of a high-vacuum consolidation system used in the construction method of the present invention. The path of the system is divided into a vacuum path 2A leading to a vacuum pump 1A and a pressure path 2B leading to a compressor 1D. The high vacuum consolidation system used in the construction method of the present invention is partially different from conventional systems. A vacuum path 2A of a conventional system passes through a vertical drain 12 and a steam separation tank 10, and then branches into a plurality of branches to connect a high vacuum storage tank 1C, a cold trap 1B, and a vacuum pump 1A in series. The vacuum paths 2A of these serial vacuum devices are connected to form a network. In contrast, the high-vacuum consolidation system used in the method of the present invention integrates the high-vacuum storage tank 1C and the cold trap 1B. The position of the vacuum path 2A of the cold trap 1B can be switched between before and after the high-vacuum storage tank 1C by means of a valve. This is because the function of the cold trap 1B in operation deteriorates over time, and it is convenient to switch over because it requires a defrosting process. In FIG. 1, number 11 is an airtight sheet that seals the ground. Further, the vacuum path 2A in FIG. 1 is an example of two rows after branching.

FIG. 2 is an elevation view and a horizontal section view of an existing vertical drain for deep depth applications. The depth to which the conventional vacuum consolidation method can be directly applied is up to 10m. The vertical drain material for high depth is intended to replace the interstitial water in the clay ground that has accumulated in the vertical drain with air in order to break through the limit depth of 10 m. The vacuum consolidation method of the present invention is applied to the vertical drain material for deep depth shown in FIG. 2 and the high vacuum consolidation system shown in FIG. In FIG. 2, the number 12 is a vertical drain material for deep depth, 12A is a drain core material, 12B is a filter cloth, 12C is a drain upper cap, and 12D is a drain lower cap.

The outline of the implementation of the vacuum consolidation method of the present invention using the deep-depth vertical drain material 12 is that if the internal space of the deep-depth vertical drain 12 is filled with interstitial water and the consolidation speed decreases and the interstitial water remains A compressor 1D blows compressed air pressure from the tip (lower portion) of the vertical drain member 12 to move interstitial water integrally through the top portion of the vertical drain member 12 to the steam separation tank 10. With the interstitial water in the internal space of the vertical drain member 12 replaced with air, the process proceeds to the vacuum consolidation step of the present invention. In the deep vacuum consolidation method, interstitial water remains in the vertical drain material 12 over time. Then, the pore water replacement process with air and the vacuum consolidation process form a cycle. Interstitial water in deep ground has a high water pressure, but the vacuum consolidation method of the present invention generates fine bubbles without generating normal millibubbles, so the consolidation promotion effect is sufficiently exhibited.

FIG. 3 is an explanatory diagram showing an example of the vacuum consolidation test system of the present invention. 20B is a pressure plate; 20C is a gasket; 20D is a flexible rubber cap; 20E is a polar stone; 20F is a bottom plate of a container; A vacuum consolidation test system is composed of a vacuum consolidation tester 20 and a vacuum consolidation system. What is particularly important in the vacuum consolidation tester 20 is the airtightness between the relatively moving consolidation ring 20A and pressure plate 20B. A countermeasure for this is the cap 20D system, which is made of a flexible and highly elastic material. The inner surface of the cap 20D is greased to fit snugly over the compaction ring 20A and pressure plate 20B. This is the temporary sealing. At the time of the vacuum consolidation test, this cap 20D is sucked and adhered by vacuum pressure to maintain airtightness.

FIG. 4 is a vertical sectional view of the vertical drain driving machine of the present invention. In the figure, 40 is a vertical drain driving machine, 41 is a mandrel leader, 42 is a mandrel, 43 is an operator room, 44 is a vertical drain material for standard depth, 44A is a reel for drain material, and 45 is a storage of ultra-fine bubble water. A tank, 45A is a hose reel, 45B is a bubble water hose, and 45C is a bubble water flow meter. The main body of the vertical drain driving machine 40 is basically the same as the conventional one. The major difference lies in the equipment and functions for supplying ultra-fine bubble water to the ground.
The apparatus and functions of the driving machine 40 are such that a mandrel 42 holding a drain material 44 is provided with a nozzle apparatus for horizontally and downwardly injecting ultra-fine bubble water at a high pressure. When the drain material 44 is placed, at the same time, ultra-fine bubbled water is jetted at a high pressure in a required direction. Alternatively, only ultra-fine bubbled water is jetted at high pressure without placing the drain material 44 .

FIG. 5 is an explanatory view of construction of the vertical drain driving machine. In the figure, 44 is a vertical drain material, 46 is a mixing area of ultra-fine bubbled water, and 49 is an improvement zone ground. (A) of FIG. 5 is a diagram of a situation in which the drain driving machine 40 is placed at a predetermined position, and (B) and (C) of FIG. In parallel, the work situation diagram of high-pressure injection of ultra-fine bubble water is also shown, and (D) is a work situation diagram of pulling out the mandrel 42 after completing the placement of the drain material 44 and the high-pressure injection of ultra-fine bubble water.

FIG. 6 is a plan view of the position of the vertical drain member and the supply position of the ultra-fine bubbled water. In the figure, 47 is the position where the drain material is placed and the high-pressure injection of the ultra-fine bubbled water is performed simultaneously, and 48 is the position where only the high-pressure injection of the ultra-fine bubbled water is performed. In the vacuum consolidation method, when replenishing the shortage of fine bubbles with ultra-fine bubble water, the most important thing is to utilize the fine bubble effect evenly. FIG. 6 shows the first stage of supplying ultra-fine bubble water to the ground evenly. The second stage is a state in which the ultra-fine bubbles diffuse Brownian evenly over the entire improved area ground 49 due to Brownian motion.
FIG. 6 shows the case where the supply of ultra-fine bubbled water is completed in one time. When the supply continues for a long period of time, a normal vertical drain is installed for supply at the position 48 where only the high-pressure injection of ultra-fine bubble water is performed, and the ultra-fine bubble water is sent via a horizontal drain pipe. Connect to pumping equipment. Then, when necessary, a necessary amount of ultra-fine bubble water is supplied to the ground. A normal vertical drain is the vertical drain 12 for deep depth shown in FIG.

Conventionally, the vacuum consolidation method for submarine ground or the like, or the airtight loading box used for the vacuum consolidation dredging method has been equipped on a dedicated work ship. The huge airtight loading box used in the construction method of the present invention is a self-submersible airtight loading box that can freely dive and move horizontally on the seabed without depending on a dedicated work boat. There are two types of this airtight loading box depending on the type of floating body, and there are two types for standard depth and high depth.

FIG. 7 is a vertical sectional view of the airtight loading box of rigid floating body type for standard depth of the present invention, and FIG. 8 is a plan view of the same. In the figure, 50 is a tower-type airtight loading box for standard depth, 51 is an airtight loading box for standard depth, 52 is a box tower for standard depth, 53A is a rigid floating body, 53B is a flexible floating body, and 54 is a horizontal body with spuds. A telescopic beam, 54A horizontal telescopic beam, 54B a vertical telescopic spud, 55 equipment and devices related to the operation of the box, 71 the sea surface, 72 the sea floor, and 73 the seabed ground. FIG. 7(A) shows a situation where the tower-type airtight loading box 50 is floating on the sea surface 71, and (B) shows a situation where it is installed on the sea floor 72. FIG.
The lifting and lowering of the box 50 is performed by exchanging air and water in the inner space of the rigid floating body 53A by a diving operation device. In addition, a plurality of spud-equipped horizontal telescopic beams 54 with vertical telescopic spuds 4B fixed to their tips are attached to the two outer edge portions of the upper surface of the box 50, and the horizontal movement of the box 50 on the seabed in the front, rear, left, and right directions is prevented. The diving operation device and the horizontal movement operation device of the horizontally telescopic beam 54A are used to freely perform the operation. The submersible control device is used for horizontal movement on the seafloor because
This is to allow the box 50 to float above the seabed from the state where it is installed on the seabed.

FIG. 9 is a vertical sectional view of the airtight loading box of the flexible floating body type of the present invention. In the figure, 53B is a flexible floating body. The lifting and lowering of the box 50 is freely performed by increasing and decreasing the volume of the floating body by injecting compressed air into and out of the internal space of the flexible floating body 53B for standard depth using a diving operation device. Others are the same as the rigid floating body 53A.

FIG. 10 is a vertical cross-sectional view of a rigid floating body type airtight loading box for high depth. In the figure, 60 is a tower-type airtight loading box for high depths, 61 is an airtight loading box for high depths, and 62 is a box tower for high depths.
The equipment and devices 55 related to the operation of the box 60 are mounted on the operation ship of the airtight loading box 61, and the role of the box tower 62 for deep depths is to display the position of the box 60 and to operate the operation-related devices. The power cable, signal cable, and various pipes are attached to the tower to reduce the weight of the tower.

FIG. 11 is an explanatory diagram of underwater movement of a rigid floating body type tower-type hermetic loading box for standard depth. (A) of FIG. 11 shows the state in which the airtight loading box 50 is floating on the sea surface 71, and (B) shows the tower-type airtight loading box 50 installed on the sea floor 72, and the seabed ground by the vacuum consolidation method. (C) is a situation in which the airtight loading box 50 is floating up to the sea floor 72.

FIG. 12 is an explanatory view of horizontal movement on the seabed of a rigid floating body type airtight loading box for standard depth. (A) of FIG. 12 is a plan view of the airtight loading box 50 of (C) of FIG. The vertically telescopic spuds 54B of the horizontally telescopic beams 54 with spuds are in a state of being stuck in and fixed to the seabed ground 73 . Similarly, (B) shows a situation in which the airtight loading box 50 is moved horizontally by extending the horizontally telescopic beam 54A.

1A Vacuum pump 1B Cold trap 1C High vacuum storage tank 1D Compressor 1E Submersible pump 10 Air-water separation tank 12 Vertical drain for deep depth (material)
20 Vacuum Consolidation Tester 20A Consolidation Ring 20B Pressure Plate 20C Gasket 20D Flexible Rubber Cap 40 Vertical Drain Placer 41 Mandrel Leader 42 Mandrel 44 Vertical Drain Material for Standard Depth 45 Storage Tank for Ultra-Fine Bubble Water 46 Ultra-Fine Bubble Water 50 standard depth airtight loading box 51 standard depth airtight loading box 52 standard depth tower 53A rigid float 53B flexible float 54 horizontal telescopic beam with spuds 60 high depth tower airtight loading box 61 Airtight loading box for high depth 62 Box tower for high depth

Claims (12)

In the vacuum consolidation method for boiling pore water such as cohesive soil under reduced pressure, in order to greatly disrupt the electrical equilibrium of the diffusion ion layer formed by the negative charges of clay minerals such as cohesive soil and humus and the cations attracted by the negative charges, The effective boiling time for generating the necessary amount of fine bubbles set based on the cation exchange capacity of the cohesive soil and the vacuum consolidation test is incorporated into the vacuum consolidation process in a separate frame, and the clay skeleton is formed by the fine bubble effect. By temporarily eliminating the electric attraction between the peds that form the A vacuum consolidation method characterized by improvement, sterilization, and soil remediation that removes harmful ions together with consolidation drainage. In the vacuum consolidation method of claim 1 in which interstitial water in a high water pressure state such as cohesive soil is boiled under reduced pressure, the high vacuum pressure due to the set reduced pressure does not cause violent boiling that usually causes millibubbles, but only fine bubbles are generated. By quiet boiling, the occurrence of evaporation due to boiling is suppressed as much as possible to maintain a stable high vacuum pressure, and the fine bubble effect temporarily eliminates the electrical attraction between the peds that form the skeleton of the clay. At the same time, by improving the water permeability of clay and performing rapid vacuum consolidation, it is possible to shorten the consolidation time of clay soil and increase the consolidation settlement. A vacuum consolidation method characterized by soil remediation. In the vacuum consolidation test system of claim 1, each test equipment is connected in series with a vacuum consolidation tester, a steam separation tank, a cold trap, and a vacuum pump, and the consolidation ring of the vacuum consolidation tester is integrated with the guide ring. A consolidation ring is used, and the difference between the inner diameter of the consolidation ring and the outer diameter of the pressure plate is in the range of 0.1 mm or more and less than 0.2 mm. A vacuum consolidation characterized by a mechanism in which a cap made of a flexible and highly elastic material is placed between the consolidation ring and the pressure plate, the cap is placed over the consolidation ring and the pressure plate, and the cap is sucked and adhered by vacuum pressure to maintain airtightness. system of exams. In the vacuum consolidation method of claim 1 under conditions where it is difficult to maintain a high vacuum that causes boiling under reduced pressure for a long time, if the necessary amount of fine bubbles cannot be secured only by boiling under reduced pressure for a short time, the amount of fine bubbles is insufficient. By incorporating the fine bubble water supply process into the vacuum consolidation process and replenishing the amount of fine bubbles, it is possible to shorten the consolidation time of various clay grounds and increase the consolidation settlement. A vacuum consolidation method characterized by soil remediation that removes ions, etc. by consolidation drainage. In the vertical drain material placing machine of the vacuum consolidation method according to claim 4, wherein the vertical drain method is also used, a nozzle device for spraying ultra-fine bubble water in the horizontal direction and downward at high pressure is provided at the tip of the mandrel that holds the drain material. Equipped with an ultra-fine bubble water supply function that injects ultra-fine bubble water at high pressure into the ground in the required direction at the same time as the drainage material is placed, or only ultra-fine bubble water is injected into the ground at high pressure. A vertical drain driving machine, characterized in that: In the vacuum consolidation method of claim 4, in which the vertical drain method is also used, the supply position of the ultra-fine bubble water with respect to the plane position of the ground of the vertical drain is the same position as the vertical drain, and if necessary, it is surrounded by the vertical drain position. In the central position, the work process is a process that combines drain placement and ultra-fine bubble water supply, then a diffusion process that takes the ultra-fine bubble Brownian diffusion time, and then shifts to a vacuum consolidation process. A vacuum consolidation method characterized by equalizing the ground distribution of ultra-fine bubbles and utilizing the ultra-fine bubble effect evenly. In the vacuum consolidation method of claim 4, which is applied to floating mud ground, sludge ground, and soft ground such as the seabed, fine bubble water is jetted at high pressure to the bottom part of the airtight loading box with a bottom opening used in the method. In the fine bubble water supply process, which is parallel to the process of installing this airtight loading box on soft ground, etc., by installing a perforated pipe that functions as a nozzle, fine bubble water is sprayed at high pressure. A seabed characterized by uniformly mixing a quantity of fine bubbles, shortening the consolidation time of soft ground and increasing consolidation settlement by the fine bubble effect, and sterilizing sludge ground, decomposing organic matter, and cleaning the soil. Etc. vacuum consolidation method. In the airtight loading box used in claim 7, a rigid floating body is attached to almost the entire upper surface of the box, and the lifting and lowering of the box is performed by exchanging air and water in the inner space of the floating body by a diving operation device. A plurality of horizontal telescoping beams with spuds are attached to the outer edges of the upper surface of the box in two directions, and the horizontal movement of the box on the seabed in the front, back, left, and right directions is possible. A self-submersible airtight loading box characterized by being freely operated by the above-mentioned diving operation device and the horizontal movement operation device of the horizontal telescopic beam, and by these operation devices, diving and horizontal movement on the seabed can be freely performed. In the airtight loading box used in claim 7, a flexible floating body is attached to almost the entire upper surface of the box, and the lifting and lowering of the box is performed by taking in and out compressed air from the internal space of the floating body with a diving operation device. The volume can be freely increased and decreased, and a plurality of horizontal telescopic beams with vertical telescopic spuds fixed to the tips are attached to the outer edges of the upper surface of the box in two directions, allowing the box to move forward, backward, left and right on the seabed. is freely moved horizontally by the diving operation device and the horizontal movement operation device of the horizontal telescopic beam, and by these operation devices, diving and seabed horizontal movement are freely performed. In the airtight loading box for standard depth used in claims 8 and 9, a box tower equipped with equipment and devices related to the operation of the box is attached to the center of the upper surface of the box, and the operating device of the box A self-submersible airtight loading box characterized by a complete structure. In the airtight loading box for high depth used in claim 10, the equipment and devices related to the operation of the box are mounted on the operation ship of the airtight loading box, and the role of the box tower is to display the position of the box. By attaching the power cable, signal cable, and various pipes for the operation of the operation-related equipment, the weight of the box tower is reduced, and by lowering the center of gravity of the box, the stability as a floating body is enhanced. A self-submersible airtight loading box characterized by In the vacuum consolidation dredging method for sludge ground and soft ground such as the seabed, the fine bubble supply process of the vacuum consolidation method of claim 7 is incorporated into the process, and the airtight loading box with the bottom opening is made to soft ground by the fine bubble effect. Rapid vacuum consolidation to dredging strength in an extremely short period of time. A vacuum consolidation dredging method characterized by:

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