JP2568756Y2 - Device for reducing the water pressure of solid foundation - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid foundation used for construction, and more particularly to a device for reducing pumping pressure or buoyancy acting on a solid foundation.

[0002]

2. Description of the Related Art In recent years, many high-rise buildings have been built in each city due to the concentration of urban functions in the center of large cities and rising land prices. In order to make more effective use of urban land, the use of underground space must be promoted. Further, in the case of soft ground with a high groundwater level, solid foundations having a large area are often used as foundations for buildings in order to distribute the weight of the buildings as evenly as possible.
To install such a solid foundation, it must be excavated from 12 meters to 30 meters below ground or deeper.

[0003]

The superstructure of a building is designed according to the respective needs. Therefore, the weight of the building does not always work equally on the solid foundation. That is, it often happens that superstructures of different weights are placed simultaneously on the same solid foundation. And
When the superstructure is heavy, the load applied to the solid foundation is large, and when the superstructure is light, the load is small. Also, since the solid foundation is located deep underground, the pumping pressure or buoyancy due to the groundwater acts on such solid foundation in various sizes at high groundwater levels.

When a high pumping pressure acts on a solid foundation, the following problems may occur.

[0005] 1. When a light superstructure is partially mounted on a large solid foundation, if the buoyancy due to water pressure is greater than the load, the solid foundation may be lifted upward and separate from the soil. However, in some cases, where a heavy superstructure is placed, the buoyancy acting on the foundation is smaller than the load of the structure, and the solid foundation in this part does not rise,
Downward pressure acts on the soil. In such a case, a large moment acts on the solid foundation, which may eventually destroy the foundation slab of the solid foundation.

[0006] 2. As described above, for a solid foundation subjected to a high pumping pressure, the foundation is lifted at a place where the superstructure is light, and a heaving phenomenon occurs, and conversely, the foundation sinks at a place where the superstructure is heavy. Such uneven settlement can destroy the solid foundation and must be treated in some way.

[0007] 3. If the pumping pressure or pore water pressure is high,
Since a large upward load acts on the foundation beam and foundation slab of the solid foundation, more material is needed to determine the rigidity and strength of the foundation.

[0008] The treatment method when the pumping pressure or pore water pressure acting on the solid foundation is large, and the features and disadvantages of these methods are as follows.

1. Crushed underground tank load increase method mat foundation by underground water tank, the packed low strength concrete, cobbles, or sand, can be increased load of about 1.6~2.3t / m ² per meter thickness. However, since the height of the underground water tank is generally only 1.2 to 2.0 meters, this method cannot be completely applied to a very high pumping pressure. In addition, the construction of this method completely relies on man-made, the construction period is long, and environmental problems due to the construction are its disadvantages.

[0010] 2. Friction pile method A foundation pile is driven under a solid foundation, and lifting of the foundation is prevented by balancing the frictional force of the pile and the pumping pressure on the foundation. This method is relatively effective for sandy soil layers,
Not very effective on cohesive soil layers. The major drawbacks are the cost and length of construction and the need for pile loading tests.

3. Buoyancy prevention anchor method An earth anchor is installed at the bottom of the solid foundation to resist the pumping pressure to the foundation. This design is effective for bedrock,
It is still effective for sandy soil layers, but not very effective for clay layers. The buoyancy prevention anchor is very expensive, has a long construction period, it is difficult to adjust the pull-out resistance,
Durability is also a problem.

4. Structural Weight Increasing Method Thicken basement slabs and superstructure beams, columns, or slabs to increase the overall weight of the structure. Reinforced concrete has a unit weight of 2.4 tonnes / cubic meter, and adding 10 cm thick adds 240 kg / sq.m. In this method, the use of reinforcing bars is relatively increased, and construction costs are incurred. Further, there is a disadvantage that the depth of the excavation must be increased in order to maintain the planned space since the usable space is reduced.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is intended to reduce or control the pumping pressure acting on a solid foundation slab. A drainage layer provided between the drainage layer and a space for water passage, and a shielding layer provided between the drainage layer and the foundation slab to prevent concrete from entering the foundation slab, A filter layer that is provided between the drainage layer and the soil layer and that prevents soil from intruding from the soil layer, and that is provided between the filter layer and the drainage layer and that passes through the filter layer. A collecting pipe system for flowing water along a predetermined path, and a lower end thereof communicates with a flow path of water in the collecting pipe system, and an upper end thereof is located in a space above a water surface of a groundwater tank on the base slab. Overflow pipes that communicate with each other Are together to permit the flow of water to the upper end from the lower end, it is characterized in that is composed of a 礦物 barrage preventing device for preventing the flow of air from the top to the bottom.

The following is a brief technical principle of the present invention made as described above. 1. Formation of pumping pressure When excavating ground with a high groundwater level and installing a box-shaped hollow substructure, the pumping pressure acting on the bottom of the foundation, i.e., buoyancy, will be maintained over a long period of time even if the ground is cohesive soil. Gradually increases, eventually reaching the hydrostatic pressure of the ground. The value at this time becomes maximum and is expressed by the following equation. Pw = γw · Hw Here, γw is the unit volume weight of water, and Hw is the distance from the groundwater table to the bottom of the foundation or the pressure head.

2. Principle of pumping pressure reduction A stable and highly permeable drainage layer under the solid foundation foundation slab, i.e., a "pumping pressure reduction structure of solid foundation" is installed, and the continuous underground wall is impermeable layer or low-permeable soil. Layer (k
= 10 ^-6 to 10 ^-8 cm / sec). This continuous underground wall has a sufficient penetration depth and the groundwater may penetrate from the soil or other gaps to the bottom of the solid foundation, but it will take a considerable time for the groundwater pressure to be balanced with the surrounding groundwater pressure. It takes. Also, if the amount of permeation is smaller than the designed drainage, the water pressure acting on the bottom of the foundation does not continuously rise and is kept at a certain pressure or becomes zero. And then
The goal is to reduce or control buoyancy.

The permeation rates of water flowing through several soil layers having different permeability coefficients are as follows. k = 10 ⁻⁵ cm / sec v = 315.5 cm / year k = 10 ⁻⁶ cm / sec v = 31.6 cm / year k = 10 ⁻⁷ cm / sec v = 3.16 cm / year k = 10 ⁻⁸ cm / sec v = 0.3cm / year

That is, the groundwater in the ground is blocked to some extent by the continuous underground wall, but penetrates below the foundation from the gap in the soil or other gaps to become the pumping pressure, and its value is equal to the surrounding groundwater pressure. It takes one to ten years for the balance to be achieved.

3. The pumping pressure reduction method at the bottom of the foundation differs depending on the ground, but the following method is usually adopted.

A. In the case of a clay layer or a layered low-permeability layer, various permeability characteristics of the ground are usually used. First, a continuous ground wall is constructed to completely enclose the foundation. Next, the ground is excavated while pumping groundwater. That is, due to the construction, there is a difference in water level between the excavated surface inside the continuous ground wall and the groundwater level outside (see FIGS. 7 and 8). Groundwater seeps into the excavated surface due to this water level difference. When the ground permeability is low, the rate of rise of the water level inside the continuous ground wall is extremely slow because the permeation rate of groundwater is low and the permeability is small.
If the daily pumping volume is higher than the water that permeates the excavation surface, the water level on the excavation surface should not rise. If an impermeable base slab is constructed on the excavated surface, water infiltration will be cut off, but after a long time, water infiltration will gradually increase the pumping pressure below the base slab, and the surrounding groundwater The change continues until pressure is balanced. Such a high pumping pressure is disadvantageous for the foundation slab. Utilizing poor water permeability in the ground, a permeable layer (including a filter layer, a mesh polymer grid for drainage, and an impermeable PVC sheet) is created under the foundation slab, and water is collected in a groundwater tank by a drainage pipe system. , The water is pumped up to the drain on the ground and disposed of. If the drainage capacity of the foundation slab is much larger than the ground penetration, no pumping pressure will be generated for the foundation slab.

B. In the case of bedrock or hard soil layer In the same way as the principle shown in A of the previous paragraph, if the imperviousness of the bedrock or hard soil layer is used to remove almost all of the groundwater that has infiltrated below the solid foundation, No water pressure or buoyancy is generated. The exclusion method is the same as the principle shown in A, and a drainage layer having good water permeability (including a filter layer, a mesh polymer grid for drainage, and an impermeable PVC sheet) is provided under the foundation.

4. The method of preventing clogging is described below.

A. Physical Clogging I) The use of the present invention is limited when the submerged soil particles under the foundation slab have a subsidence rate of more than three times the permeation rate of groundwater during the size test. II) The application of the filter layer follows FHWA guidelines. The range is as follows. The following properties are required for nonwoven materials. O ₉₅ ≦ 1.8D ₈₅ k (non-woven material) ≧ 10 k (±) O ₉₅ ≧ 2D ₁₅ where 0 ₉₅ = geometry of geotextile (expressed in mm), with 95% mesh Less than. D ₈₅ = the particle size corresponding to 85% of the percentage passage according to the particle size curve obtained from the particle size test. D ₁₅ = the particle size corresponding to 15% of the percentage passage according to the particle size curve obtained from the particle size test.

B. Nonreturn valve is attached to II) the water collecting pipe clogging I) not physically or chemical properties of the artificial drainage layer and ground water in the water collecting pipe line varies due to precipitate minerals, and collecting
No air can enter the water line system and the drainage polymer grid layer for drainage. This method prevents Ca ⁺⁺ or Si ⁺⁺ ions from binding to CO ₂ in the air, thereby preventing the formation of mineral precipitates.

By utilizing the above principle, the following advantages can be obtained.

1. The structural characteristics of the ground can be fully utilized.
That is, in general, when the pumping pressure acting on the foundation slab is too large, the force balancing method can be used. It can be said that the present invention fully utilized the structural characteristics of the ground and the principle of water penetration.

2. Construction time is short. In other words, the artificial filter layer, drainage layer, shielding layer, water overflow pipe, etc. are all materials made by scientific technology, and can be collected lightly and in a short time. In particular, the present invention can save a great deal of construction time for construction with a soft clay layer.

3. It is a highly reliable industrial product that can effectively control the gap between the filter layers, the drainage volume of the drainage layer, or the flow rate of the water collection pipe. Since the quality is more stable than natural materials, a highly reliable drainage layer can be created.

4. The pumping pressure can be controlled. The installation of the overflow pipe can control the pumping pressure acting below the foundation slab.

5. It is economical. Compared to other structures, it is more economical for the same purpose.

[0030]

Next, an embodiment of the present invention will be described with reference to FIGS.

1. Ground survey: When examining the foundation ground, in addition to general survey items, increase the on-site permeability test or indoor permeability test, examine the permeability coefficient of each soil layer under the foundation, and measure the groundwater level at the observation well. In addition, we investigate the water pressure distribution of each soil layer using various water pressure gauges, and draw a distribution diagram of the equivalent hydraulic conductivity.

2. Final settlement, differential settlement and slope analysis: Draw a load distribution diagram, adjust the distribution of loads according to the plastic settlement theory, calculate the final settlement, differential settlement and displacement gradient of each point of the foundation, Find the minimum differential settlement amount and the equilibrium point where the construction is most easily performed by redistributing the load when using the pumping pressure reduction structure of solid foundation.

3. Moment analysis of the entire structure: Draw a load distribution diagram, analyze the long-term stability of the entire structure, and reduce the moment so as not to affect the structure. Also,
The effect of the earthquake on the foundation is also analyzed.

4. Design of the depth of penetration of the continuous underground wall: The continuous underground wall is impermeable, and the design of the depth of the underground shall simultaneously satisfy the following conditions. A. The amount of permeation should be less than 1.0 m ³ / hr. B. The vertical penetration rate V _up is such that the smallest particles of soil under the solid foundation are lower than the settlement rate V _{down in} water. This design is installed in a poorly permeable, viscous soil layer and has low penetration, so eliminating it has little effect on the surrounding hydraulic gradient. In addition, since the amount of water to be treated is small, it can be easily drained with a pump.

5. Installation of the artificial filter layer (21): The ground is excavated to the design depth, and a filter layer (21) having a water permeability of 100 times or more the ground is laid. At this time, using the coefficient of permeability ^{k = 10 0 ~10 3 cm /} sec in the nonwoven, the minimum clearance is impervious only particles of D ₁₅ particle size less than the soil in contact. Here, D ₁₅ is a particle size corresponding to 15% of the percentage passed by the particle size curve obtained from the particle size test. The artificial filter layer has the following advantages. A. Construction is convenient. By installing the filter layer, the ground is covered with non-woven fabric, and the disturbance to the soil due to the construction is reduced, which is convenient for the subsequent construction. B. The drainage function of the drainage layer (22) can be secured. Soil particles in the ground are prevented from entering the drainage layer (22) thereon,
It is possible to prevent the drainage function of the drainage layer from decreasing. C. The reliability of pumping pressure reduction is improved. When the gap and the thickness of the filter layer selected reasonably (i.e., which satisfies the condition of D _15), in addition to effectively control the vertical penetration amount, the thickness of the filter layer itself increases the horizontal permeation rate of water And local clogging does not affect the overall drainage function.

6. Installation of specific drainage layer (22): The artificial drainage layer (22) is laid on the artificial filter layer (21). The purpose of this drainage layer is to create a gap where the water flows smoothly. Its water permeability must be greater than 1.0 cm / sec. (Generally 10~10 ⁰ cm / sec
Value). Also, a compressive strength of 5 to 10 times the design load is formed, and the load of the structure is transmitted to the ground below. The following two methods are used to install the drainage layer. A. Artificial drainage layer: An artificial grid is used. The material does not decay, the compressive strength satisfies the required conditions, and an artificial grid with good water permeability, high-density polyvinyl (HDPE), high-density PVC (HPVC), or high-density PE is used. . Its hydraulic conductivity is 10-1
0 ⁰ cm / sec, the horizontal water permeability Q 5.0l / m / m
greater than in. B. Natural drainage layer: The material with a large natural gap is filled on the artificial filter layer. Crushed stone or medium fine sand is used as the material, and its thickness is 5.0 l / m / min.
Greater conditions should be satisfied. That is, the thickness of the natural drainage layer is determined by the gap and penetration amount of crushed stone or medium fine sand, and generally takes a value of 10 cm to 30 cm.

7. Installation of Moyogi water collecting pipe (23): the entire Moyogi water collecting pipe (23) on the artificial filter layer (21), is placed between the artificial drainage layer (22) or vertically thereon,
As a drainage pipe system. Collection that constitutes collection pipe system
The porosity of the water tube is greater than 3.0%, and the outside is wrapped with a nonwoven fabric similar to the artificial filter layer. The diameter of the collection tube is between 1.0 inch and 2.0 inches, depending on the daily penetration. Also, in order to avoid all clogging, it is necessary to take a safety factor of 100 times or more of the total permeation amount.

8. Installation of artificial shielding layer: Artificial shielding layer (2
4) is made of PVC material and has complete waterproofness. This layer is installed mainly so that the concrete of the foundation slab does not enter the artificial drainage layer.

9. Installation of overtopping pipe (15): Since the upper portion of overtopping tube and connects with the atmosphere, the magnitude of lift water pressure determined by the height of the pipe, the value of the lift hydraulic table by:
Is done .

Pw = γw × Δh Here, Pw = pumping pressure of the base slab, t / m ² γw = unit weight of water, and 1.0 t / m ³ Δh = exit of the overflow pipe from the bottom of the base slab Height to

Accordingly, when the outlet of the overflow pipe (15) is higher than the maximum water level of the basement water tank and lower than the surrounding groundwater level, water flows into the groundwater tank and, if balanced, the pumping pressure of the base slab is adjusted. The head is the height from the bottom of the foundation slab to the outlet of the overflow. By appropriately adjusting the height of the overflow pipe (115), the magnitude of the pumping pressure below the base slab (11) can be controlled, and the pumping pressure received by the base slab can be reduced. As shown in FIG. 3, when the outlet (35) of the overflow pipe is higher than the surrounding groundwater level, the pumping pressure received by the foundation slab is the hydrostatic pressure from the groundwater level to the bottom thereof. That is, as shown in FIG. 4, the pumping pressure from the groundwater level (30) to the foundation slab is equal to the water pressure of the foundation slab thickness (112).

10. Installation of a drainage system for the underground water tank: An underwater pump (13) is installed in the underground water tank, and the water flowing into the underground water tank is discharged to a drainage ditch outside the building by controlling an automatic water level measurement switch. In order to ensure the reliability of this drainage system, it is necessary to prepare two sets of facilities, main and spare.

11. Installation of a horizontal overflow pipe (19) in the groundwater tank (119): Generally, a sewage tank is built in a solid foundation groundwater tank, and the sewage is discharged to an external drain by a pump.
A horizontal overflow pipe (19) is installed between the sewage tank and a groundwater tank for collecting permeated water. The location of this overflow pipe is slightly higher than the maximum water level of the groundwater tank that collects infiltration water. If the submersible pump (13) of the above-mentioned drainage system fails and the water level of the underground water tank collecting permeated water becomes higher than the design value (18),
The extra water can be drained using a horizontal overflow pipe attached to this side.

12. Installation of an automatic water level measurement switch in the underground water tank: A sensitive or buoyancy type water level converter (114) is installed in the solid foundation underground water tank, and if the water level is too high, the administrator is notified by an acoustic or light signal. The rising speed of the water level in this underground water tank is very slow, and its value varies depending on the scale, but the daily rising speed is about 0.01 to 1.0 cm / day. Since the daily permeation amount is 0.5 to 20.0 cubic meters / day, there is no problem of a rise in water level due to a failure of the submersible pump.

13. Installation of mineral clogging prevention device: Infiltration water in soil always contains Ca ⁺⁺ or Si ⁺⁺ ion,
Upon contact with CO ₂ in the air, CaCO ₃ and SiC
O ₃ is produced and precipitates. The device is fitted with a single non-return valve, which allows only gravity driven seepage water to flow from below to above, but prevents air from entering the drainage path.

[0046]

[Effect of the Invention] As is clear from the above description, the present invention
Water provided between the foundation slab and the soil layer below
Between drainage layer and foundation slab to secure space for
In the meantime, prevent concrete from entering the foundation slab
Since a shielding layer was provided, it was poured to form a basic slab
The ready-mixed concrete enters the drainage layer and drainage of the drainage layer
Does not impair. In addition, the drainage layer and the soil layer
Collecting water between the filter layer provided between and the drainage layer
A pipe system is provided to allow water passing through the filter layer to pass through
And the water in this collection pipe system
The lower end communicates with the flow path of the base, and the upper end is underground on the base slab.
Whether an overflow pipe communicating with the space above the surface of the water tank has been provided
If the groundwater level was high, it entered through the drainage layer
Groundwater is collected through a drainage pipe system,
Can be drained into a water tank. In addition, the water pipe
Allow water flow from the end to the top, and
Mineral clogging prevention device to prevent air flow to the end
Overburden clogged by minerals in groundwater
And the groundwater flow is not obstructed.
No. Therefore, the groundwater pressure applied to the bottom of the solid foundation
Buoyancy can be eliminated or adjusted.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the solid groundwater tank of the present invention and the pumping pressure reduction structure of the solid foundation slab.

FIG. 2 is a sectional view showing a pumping pressure reducing structure of the foundation of the present invention.

FIG. 3 is a view for explaining a case where the outlet (35) of the overflow pipe according to the present invention is higher than the external maximum groundwater level (30).

FIG. 4 is a view for explaining a case where the outlet (45) of the overflow pipe according to the present invention is lower than the minimum water collecting surface (17).

FIG. 5 is a diagram for explaining a state in which a solid foundation slab is subjected to a pumping pressure;

FIG. 6 is a diagram for explaining a state when another hydraulic action is applied from a solid foundation slab.

FIG. 7 is a diagram for explaining the relationship between the continuous underground wall and the groundwater pressure.

FIG. 8 is a diagram for explaining the effect of the continuous underground wall and the completed solid foundation on the groundwater pressure.

[Explanation of symbols]

13 Submersible pump 15 Overflow pipe pc 12 Unreinforced concrete 17 Water tank low water line 18 Water tank high water line 21 Artificial filter layer 22 Artificial drainage layer 23 Filtration water collecting pipe 24 Artificial shielding layer 51 Hydrostatic pressure line 61 Continuous underground wall 62 Water collecting pipe 63 Excavated surface of foundation 64 Basic groundwater pressure during excavation 65 Clay formation 66 Overflow pipe system 67 Water pressure line after drainage 68 Water pressure line before drainage 110 Soil layer under foundation 111 Solid bottom plate pumping pressure reduction structure 114 Water level converter 124 Water level indicator 125 Mineral clogging prevention device 661 Artificial drainage layer

Claims (1)

(57) [Scope of request for utility model registration] An object of the present invention is to reduce or control a pumping pressure acting on a foundation slab of a solid foundation, which is provided between the foundation slab and a soil layer below the foundation slab to secure a space for water to pass through. A drainage layer provided between the drainage layer and the soil layer, a shielding layer provided between the drainage layer and the foundation slab, and for preventing intrusion of concrete into the foundation slab; And a filter layer provided between the filter layer and the drainage layer to prevent soil from intruding therethrough, and a water collecting pipe system for flowing water passing through the filter layer to a predetermined path.
And a water overflow pipe whose lower end communicates with the flow path of water in this water collection pipe system and whose upper end communicates with a space above the water surface of the underground water tank on the foundation slab. Allows water flow to the top and prevents air flow from top to bottom
A device for reducing water pressure of a solid foundation, comprising a device for preventing clogging of minerals .