JP5213216B2 - Ground improvement method - Google Patents

Description

The present invention is an improvement method of the ground in the soil improvement technology in the construction field, and an object thereof is to improve the strength of the ground by supplying a grout material such as air cement milk or foam material from the ground part to the inside of the ground. And

In general, the safety and economic efficiency of underground work such as civil engineering, architectural foundation works, subways, and underground shopping streets are greatly affected by the quality of groundwater countermeasures.

Conventionally, as countermeasures for groundwater, there are known water-stopping works that prevent the inflow of groundwater with a shielding wall, or groundwater level lowering methods that lower the groundwater level by draining groundwater to the ground.

The inventors and applicants of the present application own the following patented invention.
Japanese Patent Laid-Open No. 2000-27170 (Patent No. 3243501) JP 2001-11846 (Patent No. 3280935)

The above-mentioned patented invention relates to a ground improvement method by lowering a groundwater level called a so-called superwell point method. The outline of the superwell point method is as follows. That is, it is a construction method in which forced drainage is performed while keeping the inside of the well in a vacuum by making the strainer part into a double pipe structure (special separate screen). Special separate screen structure The separate screen has a double structure consisting of an inner tube and a winding strainer. The groundwater flowing from the winding strainer is separated into air and water between the double pipes and flows into the well through the lower vent. Continuous vacuum drainage is made possible by applying a negative pressure to the inside of the double pipe by a vacuum pump.

This has the following effects. First, the vacuum effect is demonstrated at a large depth by the development of a special separate screen, and it can be propagated over a wide area and forcedly drained. Secondly, unlike the well point method, where the depth is limited to 6 to 7 m, forced drainage in a vacuum at a depth equivalent to that of the deep well has become possible. Thirdly, since the well effect is improved by the vacuum effect for deep wells having poor well efficiency due to gravity drainage and requiring a large number, the number of constructions can be reduced. Fourth, when the water level is lowered to the screen position by the vacuum deep well construction method, it is possible to eliminate the fact that air enters the well and the vacuum effect is lowered. Fifth, this construction method enables forced drainage due to the vacuum effect at large depths, and the pumping volume is 1.2 to several tens of times larger than the conventional construction method due to the geology, and the groundwater in a wider area can be quickly reduced. This is a deep vacuum drainage and consolidation dehydration method.

In the present invention, two or more wells are provided at a predetermined interval, and the ground improvement is further performed by carrying out the super well point method.

  The first of the present invention is a ground improvement method, and the first of the present invention is a step of extending a perforated pipe for supplying grout material from the ground surface to the ground in the ground improvement method. A super well where two or more wells are provided at predetermined intervals in the ground, and a process of covering the ground surface with an airtight sheet or a pavement made of concrete or asphalt or new sludge Air cement is pumped through a perforated pipe that extends from the ground surface to the ground by pumping groundwater near the ground by the point method and simultaneously depressurizing the surrounding area to make the ground almost vacuum. It consists of a step of supplying grout material such as milk or foaming material, and a step of returning underground water to the natural groundwater level.

  The second aspect of the present invention is a method of extending a perforated pipe (3a) for supplying fresh air or fresh water into the ground from the ground surface of the contaminated soil in the ground improvement method, By the process of laying an airtight sheet or concrete material or asphalt material on the surface of the ground, or by covering the ground with new airtight materials such as sludge, and the super well point method in which two or more wells are provided at predetermined intervals in the ground. Through the process of pumping groundwater in the vicinity of the ground and simultaneously reducing the pressure in the surrounding area of the ground to make the ground almost vacuum, and through the perforated piping of the grout material supply facility that extends from the ground surface to the ground It consists of a process of repeatedly supplying fresh air or fresh water, and a process of returning underground water to the natural groundwater level.

According to a third aspect of the present invention, in the ground improvement method according to the first invention, the operation of the super well point method in which two or more wells are provided at predetermined intervals is stopped, or the operation of the super well point method is performed. The airtight material laid on the ground surface is removed along with the stop of the air, and air is supplied by natural air supply due to a difference in pressure between the inside and outside of the ground and the ground surface.

According to a fourth aspect of the present invention, in the ground improvement method according to the first aspect, in the alternate layer ground of the viscous soil layer and the sand layer, the pore water pressure of the sand layer below the viscous soil layer is set at a predetermined interval between two or more wells. By applying a stress load to the viscous soil layer and depressurizing it, the viscous soil is consolidated and dehydrated by suctioning and depressurizing each other by a super well point method provided open.

In the ground improvement method according to the fifth and first inventions of the present invention, in the alternate layer ground of the viscous soil layer and the sand layer, two or more wells are provided at predetermined intervals in the sand layer below the viscous soil layer. By sucking and depressurizing each other by the Superwell Point method, a vacuum is created to evaporate and dehydrate the moisture in the viscous soil layer.

According to a sixth aspect of the present invention, in the ground improvement method according to the first aspect, in the alternate layer ground of the viscous soil layer and the sand layer, two or more sand layers below the viscous soil layer are provided at a predetermined interval. By suctioning and reducing pressure by super well point construction method, the existing structure foundation and the lower ground of the ground structure installed on the unevenly subsurface surface are drilled with a curved boring machine, and the structure foundation ( 7) A structure in which the perforated piping is installed in the horizontal direction with the left and right side installed in the shape of the ground, and the ground is improved by injecting grout material from the perforated piping into the ground. It is intended to lift things up.

According to a seventh aspect of the present invention, in the ground improvement method according to the first invention, the sand layer is sucked into the ground by a super well point method in which two or more wells are provided at predetermined intervals. After reducing the water level in the ground by reducing the pressure, the dynamic consolidation method is performed.

The eighth aspect of the present invention is a ground improvement method according to the first aspect of the present invention, in the operation of a super well point method in which two or more wells are provided at predetermined intervals in the ground of a sand layer. Among the wells, a water-tightening action is generated in the ground by alternately repeating the relationship of giving a pumping action to one well and giving a suction action to the other well every predetermined time.

Since the present invention is configured as described above, the following effects can be obtained. In other words, various vacuum effects occur when pumping and compacting dewatering at a large vacuum depth Pv≈−0.085Mp. Using this effect, early consolidation dehydration is possible, and new ground improvement can be achieved by using the features in a complex manner. According to the first and second aspects, the water level can be partially lowered greatly by sucking each other by two or more superwell point methods due to the vacuum effect. Moreover, it can be loaded by increasing the stress load by lowering the lifting pressure of the lower part of the clay soil instead of the method of pressurizing with the embankment as a ground improvement of the clay soil. And the underground vaporizes and moisture evaporates and dries. In addition, when the stalks in the soil come off, a vacuum state is generated except for the soil particles. Therefore, what is desired to be injected can be easily and uniformly put in order to return to atmospheric pressure. It is effective for water-stopping effect, ground improvement and soil purification method. Moreover, in Claim 2, it has the effect which can purify | clean the contaminated soil efficiently.

According to the fifth aspect of the present invention, the residual subsidence amount of the viscous soil can be subsidized even under the existing structure by sucking each other by the two or more superwell point methods.

According to the sixth aspect, the uneven settlement of the generated structure can be corrected by lifting it with a permanent grout material.

In claim 7, the combination of two or more superwell point methods and dynamic consolidation methods can lower the water level to deeper locations, create unsaturated ground, and propagate impacts to deeper locations. Ground improvement became possible.

According to the eighth aspect of the present invention, the water grounding effect of the sand ground can be expected by the swing cleaning effect of the super well point method. In addition, the super well cleaning effect can strengthen the ground by removing clay and colloids from the loose sand ground.

The present invention is configured as described above, and the best mode for carrying out the invention is as follows. As the best mode for carrying out the present invention, an airtight material is covered on the ground surface, and two wells with high pumping efficiency are excavated as a means for pumping groundwater, and the superwell point method is used. A case where a perforated pipe is buried between two wells will be described with reference to the drawings.

FIG. 1 is a flowchart showing a ground liquefaction prevention method according to this embodiment. In the same figure, in the soil improvement work of cohesive soil in this embodiment, as a step (1): preparatory work, a impermeable wall is constructed so as to surround the target ground. Step (2): A plurality of wells (super well points) are installed. Process (3): Supply equipment for grout material 9 such as air cement milk or foam material is installed on the ground and in the ground. Step (4): Covering the ground surface with an airtight material. Step (5): The groundwater pumping and air bubbles in the ground are degassed by the super well point method installed in the step (2). Step (6): The grout material 9 is vacuum infiltrated into the ground by supplying it through a perforated pipe of a liquid material supply facility such as air cement milk or foamed material in the step (3). Then, the liquid material uniformly penetrates into the ground. Step (7): All or part of the airtight material covered in the step (4) is removed. Step (8): The supply equipment installed in the step (3) is removed. Step (9): Condensate groundwater to the natural water level. Step (10): The two wells installed in the step (2) are removed. Step (11): The impermeable wall constructed in the step (1) is removed.

In the above embodiment, depending on the structure of the target ground, the structure existing on the ground, the state of the ground surface, etc., the steps (1) and (4) and the steps (7) and (11 corresponding to these, respectively. ) May be omitted. Hereinafter, each of the above steps will be described in detail, and then the state change in the ground will be described.

“Step (1): Construction of the impermeable wall 5 As shown in FIG. 2, first, the ground 1 b of the alternate layer ground 1 composed of the sand layers 1 ₁ and 1 ₃ and the viscous soil layer 1 ₂ to be improved is surrounded. In addition, the water-impervious wall 5 is constructed and constructed from the ground with steel sheet piles, etc. to the required depth, and the height of the top of the impermeable wall 5 is constructed so as to protrude from the ground surface 1a. It is assumed that water shielding is ensured between members such as steel sheet piles constituting 5.

“Step (2): Installation of Well 2 (Superwell Point)” Next, a plurality (two in the illustrated example) of wells 2 (superwells) are formed inside the water shielding wall 5 constructed in the above step (1). Point).

Here, as shown in FIG. 8, the well 2 (super well point) includes a casing 2a, an airtight lid 2b, a strainer 2c, an earth and sand pit 2d, a pumping pump 2e, a drainage pump 2f, a vacuum pump 2g, pipes 2h and 2i, In addition, a large-capacity and high-head type pumping system that has a water collecting function into the well 2 and a pumping function to the outside of the well 2 with the independent vacuum pump 2g and the pumping pump 2e, with the water tank 2j as a main component. Yes, and proposed by the present applicant (see Patent Document 1). Here, FIG. 8 shows a state in which the groundwater surface 1c is lowered, and arrows in the drawing indicate the flow directions of the groundwater and air. In FIG. 2, the ground equipment shown in FIG. 8 is omitted.

“Step (3): Installation of Grout Material Supply Facility 3” Next, as shown in FIG. 2, a necessary number of perforated pipes 3 a are bored inside the impermeable wall 3 d constructed in (1) above. The perforated drilling method is installed, and pipes 3b and 3b and a valve 3c are installed at the upper end of the perforated pipe 3a to constitute a supply equipment 3 that functions as a grout material introduction path from the ground. Note that the valve 3c is closed at the installation stage of the grout material supply equipment 3 such as air cement milk or foam material. Here, the arrows indicate the flow direction of the grout material 9 from the ground surface 1a to the ground 1b. The grout material supply facility 3 in FIG. 3 is a ground from one well to the other of the two wells installed across the ground structure 8 installed in the existing foundation structure 7. A perforated pipe 3a is embedded in the lateral direction from the surface 1a to the ground 1b by using a drilling method such as a boring work and passing under the existing structures 7 and 8. The supply equipment 3 can also be used for supplying fresh air or fresh water.

“Step (4): Covering with Airtight Material 6” Subsequently, the ground surface 1a of the underground 1b, which is the object of liquefaction prevention, is surrounded by the water-impervious wall 3d constructed in the step (1). The grout material 9 from the ground part is covered by covering the material 6 and treating the ends of the gas-tight material and the openings formed by the perforated pipe 3a and the well 2 so that the gas-tight material can be held. Is limited to one system of the supply equipment 3 installed in the above (3). As the airtight material 6, an airtight sheet, paving with asphalt material or concrete material, new sludge that does not emit bad odor, and the like can be used. The grout material 9 includes air cement milk or foam material.

By going through the above steps (1) to (3), the target underground 1b is constructed as a region where the side and upper part are sealed in a certain range.

“Process (5): Groundwater pumping, air bubble deaeration” Here, the well 2 installed in the above (2) is made to function by using the superwell point method, so that the groundwater existing in the underground 1b is well 2 The groundwater collected in the well 2 is pumped up and drained to the ground, and the groundwater surface 1c is lowered to the required groundwater level. At this time, the state of the underground 1b is that groundwater existing in the underground 1b in the region higher than the groundwater surface 1c is removed and the grout material 9 existing in the underground 1b is also escaped and excluded. However, although the soil particles constituting the underground 1b exist, a very high vacuum state (hereinafter referred to as “substantially vacuum”) is formed. In FIG. 8, the state of the fall of the groundwater surface 1c used as a natural groundwater level is shown.

“Process (6): Supply of grout material 9 such as air cement milk or foaming material” Next, grout material 9 such as air cement milk or foaming material is provided from the ground by the supply equipment 3 installed in the above step (3). Is supplied to the underground 1b using the pressure difference by opening the valve 3c via the pipes 3b and 3b and the perforated pipe 3a. However, before moving to this step of supplying the grout material 9 to the underground 1b, the functions of pumping and draining the well 2 and degassing are stopped. Here, since the underground 1b is almost in a vacuum state as described above, the underground 1b is uniformly filled at a very high diffusion rate. Further, when supplying fresh air or fresh water instead of the grout material 9, the above-described supply equipment 3 is also used.

“Step (7): Removal of Airtight Material 6” Next, the airtight material 6 covered in the step (4) is removed. At this time, since the atmospheric pressure in the vicinity of the ground surface 1a of the underground 1b is close to the atmospheric pressure by the step (3), there is no difference in the internal and external pressure between the underground 1b and the ground, and it can be easily removed.

“Process (8): Removal of grout material supply facility 3” Subsequently, the grout material supply facility 3 is removed and the pipe mine is refilled.

"Step (9): Condensate" Here, the groundwater pumped up in the above step (5) is condensed using the well 2 to the groundwater surface 1c at the natural groundwater level. In this process, for the construction properties where the water head difference between the groundwater surface 1c after pumping the groundwater and the groundwater surface 1c in the natural state is small, the process may proceed to the next step (10) without returning the groundwater taken from the well 2. What is necessary is just to determine by construction scale.

“Step (11): Removal of Well 2 (Super Well Point)” Next, the well 2 is removed and the well mine is refilled.

“Process (12): Removal of impermeable wall 5”
Finally, the impermeable wall 5 is removed and a series of processes is completed. Here, when it is necessary to repeat the improvement measures of the ground 1 periodically, without removing the perforated pipe 3a, the well 2 and the water shielding wall 5 of the supply facility 3, the man-hour for the next construction can be reduced. Just leave it behind.

Next, an embodiment under an environment different from the steps (1) to (10) will be described. However, the part which overlaps with the said process is abbreviate | omitted and only a changed part is demonstrated.

As shown in FIG. 3, when the ground surface 1a is made of concrete or asphalt and the airtight material 6 is paved, the structure foundation 7 and a large oil tank or lime are added to the underground 1b to be further improved. Each example of the case where the ground structure 8 such as a tank is constructed, and further, the case where the underground 1b to be improved is extensive will be described.

In such an example, the steps (1), (4), (7), and (11) can be omitted, and in the step (1) for the reason of targeting a wide range of underground 1b. Without constructing the impermeable wall 5, it becomes possible to cope by lowering the groundwater surface 1c over the surrounding area of the target underground 1b, and the removal of the impermeable wall 5 described in the step (11) is unnecessary. It becomes. In addition, an airtight material 6 is applied to the ground surface 1a. As the material, vinyl sheet, waterproof tent, paving with cement, asphalt, etc., fresh sludge that does not emit bad odor, etc. are easy to aim and procure. It shall be used according to Moreover, even if the airtight material 6 is not constructed, the ground structure is such that a highly airtight impermeable layer is widely formed in the upper region of the underground 1b for the purpose of ground improvement. In this case, this impermeable layer can be an alternative material for the airtight material 6 (not shown).

However, since the existing structure foundation 7 and the ground structure 8 exist at the ground surface 1a position of the ground 1b of the alternate layer base 1 composed of the sand layers 1 ₁ and 1 ₃ and the viscous soil layer 1 ₂ to be improved, The structure of the supply equipment 3 in the step (3) is changed, and the lower layer ground of the structure foundation 7 is curved-bored instead of the perforated pipe 3a having the vertical arrangement as shown in FIG. By installing the perforated pipe 3a in the transverse direction in the form of passing, it becomes possible to supply the permanent grout 9 such as the effective foam material described in the step (6).

Other configurations are the same as those in the steps (2), (3), (5), (6), and (8) to (10).

From here, by adopting the superwell point construction method as the groundwater pumping process of the present embodiment, the explanation will be made more effectively, and the physical phenomenon occurring in the underground 1b that is the target of ground improvement will be clarified. This will be explained visually.

As shown in FIG. 4, in the steady state before the ground improvement work, the soil particles 4a as the main constituent material of the underground 1b, the groundwater 4b taking the form of free water, and the physicochemical (electrical) binding force There are adsorbed water 4c adsorbed on the soil particles 4a and air bubbles 4d interposed in the free water 4b.

Next, as shown in FIG. 5, in the step (5), the state of the underground 1 b after the pressure reducing action of the underground 1 b and the pumping and draining of the ground water 4 b is the state where the ground water 4 b is the free water 4 b. Therefore, since the water is collected in the well 2, only the soil particles 4a and the adsorbed water 4c exist. Here, the field pressure of the soil particles 4a and the adsorbed water 4c is almost in a vacuum 4e state. This improvement in the degree of vacuum makes a difference between the general well point method and the super well point method, and smoothly supplies the grout material 9 such as air cement milk or foam to the underground 1b described in the following paragraphs. Since it can be carried out and the supply amount of the grout material is maximized, it is a very effective means under conditions where the super well point method can be adopted.

Next, as shown in FIG. 6, in the step (6), the state in which the grout material is supplied to the underground 1b from the ground surface 1a is a region temporarily placed in the vacuum 4e state. Filled with supplied air.

Next, as shown in FIG. 7, in the step (9), the groundwater 4b is condensed in the ground 1b and the groundwater surface 1c is restored to the groundwater level in the steady state in a region filled with air. Since the free water 4b is submerged, the amount of air intervening in the groundwater 4b increases, so that the air content of the groundwater 4b increases. As a result, since the degree of unsaturation of the groundwater 4b, which is generally in an unsaturated state, further progresses, the water ratio is relatively reduced to suppress the increase in the water pressure of the pore water existing between the soil particles. The ground can be improved by avoiding the reduction of the frictional force.

9 and 10 show a gate-shaped structure 8 such as a crane that supports a horizontal girder 8 "with two right and left columns 8 ', and the foundation portion 7' that supports the structure is unequal. After the subsidence, two or more superwell point construction methods are used for vacuum dehydration, and after early dehydration, the permanent grout material 9 that allows foaming is formed by the curved perforated pipe 3 in FIG. By injecting below ′, the base can be lifted up so as to push it upward.

FIG. 11 shows a comparison of ground improvement work for loose sand ground. That is, when only the conventional dynamic consolidation method (FIG. 11 (b)) is used, the impact below the groundwater surface by the dynamic consolidation method is weak and the increase in strength is small. Therefore, in addition to the above-mentioned dynamic consolidation method, as shown in FIG. 11 (a), if two or more Superwell Point methods are used, the groundwater level is lowered by vacuum dehydration and early consolidation dehydration. makes it possible to convey the shock due to the dynamic consolidation method deeper deep, cohesive soil layer 1 ₂ may be dehydrated in vacuum effect.

FIG. 12 shows that in the case of two or more superwell point methods, a large amount of water (Q≈1 to 4.0 t / min) is fed into the ground, and then a high degree of vacuum (Pv = −0.1 to 0.1. Vacuum suction at 08MP). Water and suck in at the same time. By removing the fine particles of the sand particles, the particle matrix is prepared and the strength of the sand ground is increased (see FIG. 13). Note that the decrease in strength of the sand ground is due to the inclusion of a large amount of colloid and silt in the sand. Moreover, the effect of watertightness can be expected by the swing effect.

It is a flowchart which shows the ground improvement construction method of embodiment which concerns on this invention. It is sectional drawing which shows the structure by the well, the cutoff wall, vertical perforated piping, and an airtight sheet | seat in the ground improvement method of embodiment which concerns on this invention. It is sectional drawing which shows the structure by the well, the ground structure, curved perforated piping, and pavement in the ground improvement method of embodiment which concerns on this invention. It is a fragmentary sectional view which shows the relationship with the soil particle in the steady state of the ground improvement construction method of embodiment which concerns on this invention, free water, adsorbed water, and an air bubble. It is a fragmentary sectional view which shows the relationship with the soil particle and adsorbed water in the ground water (free water) and air bubble exclusion state of the ground improvement construction method of embodiment which concerns on this invention. It is a fragmentary sectional view which shows the relationship with the soil particle in the air supply state of the ground improvement construction method of embodiment which concerns on this invention, adsorbed water, and air. It is a fragmentary sectional view which shows the relationship between the soil particle in the condensate state of the ground improvement construction method of embodiment which concerns on this invention, free water, adsorbed water, and an air bubble. It is sectional drawing which shows the well (super well point construction method) utilized in the process of pumping up ground water in the ground improvement construction method of embodiment which concerns on this invention, and the pressure reduction process in the ground. It is the schematic which shows the lift up construction in which a structure inject | pours a permanent grout material into the foundation | foundation part of a portal crane according to this invention. FIG. 10 is an enlarged cross-sectional view of a part of FIG. 9. It is explanatory drawing of the conventional construction method in sandy ground improvement. It is explanatory drawing of the sandy ground improvement construction method by this invention. It is a schematic explanatory drawing of the present invention which adopted a swing washing system. It is a schematic explanatory drawing of the present invention which adopted a swing washing system with two or more wells (super well point method). It is an analysis figure which shows the particle size of the soil particle after the swing washing | cleaning of FIG.

1 …… Ground 1a …… Ground surface 1b …… Ground 1c …… Ground water surface 1 ₁ …… Sand layer 1 ₂ …… Viscous soil layer 1 ₃ …… Sand layer 2 below the viscous soil layer 2 …… Well (Super Well Point) ) 2a ... Casing 2b ... Airtight lid 2c ... Strainer 2d ... Earth and sand pit 2e ... Pumping pump 2f ... Drainage pump 2g ... Vacuum pump 2h, 2i ... Piping 2j ... Water tank 3 ... Air cement milk Or foam material grout supply equipment 3a ... perforated pipe 3b ... pipe 3c ... valve 4a ... soil particles 4b ... free water (groundwater) 4c ... adsorbed water 4d ... air or air bubbles 4e ... vacuum Part 5 …… Water-impervious wall 6 …… Airtight material 7 …… Structure foundation 8 …… Ground structure 8 ′ …… Stand 8 ”…… Horizontal girder 9 …… Grout material

Claims (2)

A water shielding wall (5) is constructed with steel sheet piles to the required depth so as to surround the underground (1b) of the ground (1), and within the water shielding wall (5), the water shielding wall (5) Covering the ground surface (1a) with an airtight sheet or pavement made of concrete or asphalt, or a new sludge airtight material (6), and a perforated pipe (3a) extending into the ground (1b) A step of supplying fresh air or fresh water from the ground surface (1a) of the ground (1) to the ground (1b) and two or more wells (2) in the ground (1b) at a predetermined interval By pumping groundwater from the well (2) using the Superwell Point method, and lowering the groundwater level to the required level, the unsaturated ground in the area surrounded by the impermeable wall is decompressed by pumping the groundwater. The process of vacuum dehydration by evaporating the moisture in the ground (1b) and dehydration through the perforated pipe (3a) extending from the ground surface (1a) to the ground (1b) Improved method of ground, characterized by comprising the step of returning the ground water in the ground (1b) to the sewage level.   Stop the operation of the super well point method with wells (2) provided at a predetermined interval, or stop the operation of the super well point method and remove the airtight material (6) covering the ground surface (1a). The ground improvement method according to claim 1, wherein air is supplied by natural air supply caused by a difference in pressure between the inside and outside of the ground (1b) and the ground surface (1a).

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