CN101831924B - Simulator for blocking groundwater seepage by underground structure - Google Patents

Abstract

A simulation device for underground structures blocking groundwater seepage in the technical field of construction engineering, comprising: a water tank, a model box, a baffle, a submerged aquifer, an aquifer, a confined aquifer, a displacement gauge and a water level observation tube, wherein: The water tank is connected to the model box, and several baffles are vertically arranged in the model box, and the unconfined aquifer, water-resisting layer and confined aquifer are laid horizontally in the model box from top to bottom, and the displacement gauge is installed vertically in the unconfined aquifer The surface of the water level observation tube is buried vertically in the confined aquifer of the model box and runs through the phreatic aquifer and the aquitard in turn. The invention can conveniently and effectively observe and study the three-dimensional seepage of groundwater and soil deformation at various moments in the soil with underground structures, and provide real, accurate and accurate information for design and construction by analyzing the test results of water head change and ground subsidence distribution. Effective parameters to ensure the efficiency and safety of urban underground engineering construction.

Description

Simulation device for blocking groundwater seepage by underground structures

technical field

The invention relates to a device in the technical field of building construction, in particular to a simulation device for blocking underground water seepage by underground structures.

Background technique

With large-scale urban construction, the number of underground structures has gradually increased. As a part of urban resources, underground space has been paid more and more attention, and various underground buildings such as basements, underground railways, and underground shopping malls have appeared in cities. At the same time, the development of the above-ground space has produced many underground structures such as underground diaphragm walls, caissons, and pile foundations. The presence of subsurface structures alters the geological environment, and some changes are permanent and difficult to recover. Underground structures hinder the flow of groundwater and cause land subsidence in varying degrees. When an underground structure is inserted into the aquifer, there is an obvious water level difference on both sides of the structure, which causes the groundwater level on the downstream side to decrease. If the lower water level on the downstream side lasts for a long time, it will cause continuous compression and deformation of the soil on the downstream side, resulting in large surface subsidence; adversely affect the environment. The influence of such underground structures on groundwater seepage and land subsidence can be observed and analyzed through indoor model tests. Most of the traditional seepage test devices are one-dimensional. Generally, they can only test the critical hydraulic gradient of the soil permeability coefficient test or the one-dimensional uniform seepage condition, and cannot better simulate the effect of underground structures on the three-dimensional seepage of groundwater and land subsidence in actual engineering. Influence.

After searching the existing technical documents, it is found that the Chinese patent document number CN 201265164A, published on July 1, 2009, records a "model test device for foundation pit engineering seepage damage", which consists of a model tank, water level control, water head It consists of four parts: measurement and deformation measurement. It can simulate the seepage field, stress field and deformation field of foundation pit engineering, reproduce the seepage damage of foundation pit engineering, and overcome the defect that the existing soil seepage damage test device can only reflect one-dimensional seepage. However, this device is limited to seepage damage in foundation pits with underground diaphragm walls, and cannot simulate the impact of underground structures on the surrounding environment and the ground subsidence caused by the existence of underground structures without damage, that is, it cannot simulate piles, subways, The impact of underground structures such as underground pipelines on groundwater seepage and land subsidence, especially the impact of underground structures on confined water seepage and the resulting land subsidence.

Contents of the invention

The present invention aims at the deficiencies of the above-mentioned existing test devices, and provides a simulation device for blocking groundwater seepage by underground structures, which can conveniently and effectively observe and study the three-dimensional seepage of groundwater and soil deformation at various moments in the soil where underground structures exist By analyzing the test results such as water head change and land subsidence distribution, it provides real, accurate and effective parameters for design and construction, so as to ensure the efficiency and safety of urban underground engineering construction.

The present invention is achieved through the following technical proposals, and the present invention comprises: water tank, model box, baffle plate, submerged aquifer, aquifer, pressurized aquifer, displacement gauge and water level observation tube, wherein: the water tank is connected with the model box, A number of baffles are vertically arranged in the model box, and the phreatic aquifer, water-resisting layer and confined aquifer are laid horizontally in the model box from top to bottom, and the displacement gauge is vertically installed on the surface of the phreatic aquifer, and the water level observation tube It is vertically buried in the confined aquifer of the model box and runs through the phreatic aquifer and the aquifer in turn.

The inner side of the model box is provided with a slot, and the baffle is movably arranged in the slot.

The phreatic aquifer is silt or sandy soil with a thickness of 0.2-0.4m.

The water-repelling layer is clay with a thickness of 0.2-0.4m.

The confined aquifer is sandy soil with a thickness of 0.2-0.4m.

The water level observation tube includes: a tube body, a float and a sealing filter cloth, wherein: the tube body is a transparent tube with both ends transparent, and a scale is marked on the tube wall; the floater is movable inside the tube body and floats on the liquid surface ; The sealing filter cloth is fixedly arranged at the lower end of the pipe body.

The displacement meter is used to measure soil deformation caused by water level changes.

Compared with the prior art, the present invention can simulate the influence of the existence of underground structures on groundwater seepage and land subsidence, reproduce its complex seepage field, stress field and deformation field, and overcome that the existing soil seepage model test can only simulate There are defects of one-dimensional seepage and damage in the underground diaphragm wall. By adjusting the filling height, the impact of the existence of the underground diaphragm wall on the seepage of groundwater during the excavation of the foundation pit can be simulated, and the formation deformation and surface settlement changes in the upstream and downstream caused by it can be simulated. By adjusting the insertion depth of the baffle, the influence of the depth of the enclosure structure inserted into the confined aquifer in the foundation pit project on the seepage of the confined water and the distribution of the ground subsidence caused by it can be simulated. By replacing different forms of baffles, the influence of different forms of underground structures on groundwater seepage and land subsidence can be simulated. It is suitable for the verification of the influence of underground structures on groundwater seepage and land subsidence, can provide experience and suggested parameters for design and construction, and is also suitable for teaching and scientific research in geotechnical engineering and hydraulic engineering.

Description of drawings

Fig. 1 is the schematic diagram of the model test device of the influence of underground structures on groundwater seepage and land subsidence;

Fig. 2 is the schematic diagram of the surface subsidence observation device in the confined water seepage model test;

Fig. 3 is the schematic diagram of the water level observation device in the confined water seepage model test;

Fig. 4 is the distribution diagram of the confined water level at different times on the longitudinal axis in the confined water seepage model test;

Fig. 5 is a diagram showing the distribution of land surface settlement at different times on the longitudinal axis in the confined water seepage test.

Detailed ways

Below in conjunction with accompanying drawing, the embodiment of the present invention is described in detail: present embodiment is carried out under the premise of technical scheme of the present invention, has provided detailed embodiment and test process, but protection scope of the present invention is not limited to following Example.

As shown in Fig. 1, Fig. 2 and Fig. 3, the present embodiment includes: water tank 1, model box 2, baffle plate 3, submerged aquifer 4, aquifer 5, confined aquifer 6, water level observation pipe 7 and displacement 8, wherein: the water tank 1 is connected with the model box 2, a number of baffles 3 are vertically arranged in the model box 2, and the submerged aquifer 4, the water-resisting layer 5 and the confined aquifer 6 are horizontally laid on the model box from top to bottom. Inside the box 2 , the displacement gauge 8 is arranged on the upper surface of the phreatic aquifer 4 , and the water level observation tube 7 is buried vertically in the pressurized aquifer 6 inside the model box 2 , and runs through the phreatic aquifer 4 and the aquifer 5 .

The water tank 1 is connected with the model box 2 through a hose 12, and the water level in the water tank 1 can be kept at a fixed value.

The mold box 2 is provided with a card slot 9, and the baffle plate 3 is movably arranged in the card slot 9;

Both sides of the model box 2 are respectively provided with a water inlet 10 and a drainage hole 11, the water inlet 10 is connected to the water tank 1 through a hose 12, the drainage hole 11 is connected to the drainage channel by the hose 12, and the inlet Water holes 10 and drainage holes 11 are provided with filter cloths to avoid water penetration and take away fine particles in the soil.

The model box 2 is provided with three horizontal steel supports to prevent the larger lateral deformation of the model box 2 under the action of water and soil pressure.

A glass sheet 13 is arranged at the lower part of the displacement meter 8 , wherein the glass sheet 13 is placed between the end of the displacement meter 8 and the upper surface of the submerged aquifer 4 .

The water level observation tube 7 includes: a tube body, a float 14 and a sealing filter cloth 15, wherein: the tube body is a transparent plexiglass tube with an inner diameter of 20-30mm, and a scale is provided on the tube wall; the float 14 is movable It is arranged inside the pipe body; the sealing filter cloth 15 is outsourced and fixed on the nozzle test water level at the lower end of the pipe body, which is the scale on the pipe body corresponding to the top of the float 14 minus the length of the float floating above the liquid surface.

The sealing filter cloth 15 is a 200-mesh stainless steel filter cloth with a pore size of 0.075 mm.

Described float 14 is made of hollow plastic pipe, and both ends are closed, and built-in plastic foam is to increase buoyancy.

As shown in Figure 2, described phreatic aquifer 4 is the sandy soil layer that thickness is 0.3m, and its component and content are silt 10%, fine sand 85%, medium sand 5%, and soil particle specific gravity is 2.463, The void ratio was 0.705.

The water-resistant layer 5 is a clay layer with a thickness of 0.3m, a dry density of 1.486, and a specific gravity of soil particles of 2.701.

The confined aquifer 6 is a sand layer with a thickness of 0.3m, and its components and contents are 10% silt, 85% fine sand, 5% medium sand, the specific gravity of soil particles is 2.463, and the void ratio is 0.689.

This embodiment includes the simulation of the groundwater seepage test performed by the device in the following manner:

(1) Spread the soil in layers and sprinkle water for maintenance.

Spread the test soil evenly in the model box 2 layer by layer, each layer is 50mm thick, ensure that the soil layers are on the same level, and sprinkle water for maintenance.

(2) Insert the baffle 3 into the slot 9 .

When laying soil to the lower position of the baffle plate 3, the baffle plate 3 should be inserted in the draw-in groove 9. Adhesive water-stop foam at the joint between the card slot 9 and the baffle 3, and glue the inner wall of the baffle 3 and the model box 2 with water-sealing tape along the joint between the card slot 9 and the baffle 3 to ensure that the baffle 3 It is closely connected with the model box 2 to prevent water from leaking along the joint between the draw-in groove 9 and the baffle plate 3 .

(3) Water level observation pipe 7 is buried vertically.

When the soil is spread to the position of the water level observation point, the water level observation pipe 7 should be buried vertically, and a float 14 should be put into the pipe to observe the test water level. The vicinity of the pipe mouth should be filled with medium coarse sand to prevent fine soil particles from entering the pipe.

(4) Install the displacement meter 8 .

After the whole soil laying process is completed, place a glass sheet 13 at the position of the designed settlement observation point, and install a displacement meter 8 on the support. The data obtained by the displacement meter 8 is processed into a real surface settlement value by a stress-strain conversion instrument.

(5) Water injection and pressurization.

After adjusting the position of the water tank 1 to the position corresponding to the initial water head required for the test, open the water inlet valve 16 to inject water and pressurize the soil in the model box 2 to saturate the aquifer until the water levels in the aquifer are all required for the test Close the water inlet valve 16 during the upstream water level. During the water injection process, the test water level can be observed at any time by the float 14 in the water level observation tube 7 .

(6) Self-weight consolidation.

Keep the test water level in each water level observation tube 7 as the upstream water level, and wait for the soil layer to consolidate under the action of its own weight. When the data of the displacement meter 8 at each settlement observation point in the model box 2 no longer changes, it means that the self-weight consolidation has been basically completed.

(7) Seepage test.

Keep the upstream water level constant, set the outlet of the drain hose 12 to the downstream water level required for the test, and open the water inlet valve 16 and the drain valve 17 at the same time to conduct the seepage test. During the test, the water level and surface settlement should be observed in real time to obtain the changes of the confined water seepage field and soil deformation field at different times under a certain water head difference, and analyze the influence of underground structures on the confined water seepage and the surface deformation caused by it. The distribution and change of settlement.

Figure 4 shows the variation of the confined water level at different times in the confined water seepage test obtained by applying the test system, in which the upstream water level is maintained at 640 mm. The baffle has an obvious blocking effect on the seepage of groundwater: the head of the confined water on the upstream side drops slowly, and the water level of the confined water on the downstream side drops quickly, and the confined water level at the observation points on both sides of the baffle has obvious Poor water level. When the test was carried out for 4 minutes, the pressurized water head at the observation point on the downstream side dropped from 640mm to 562mm, the pressurized water heads at the observation points on both sides of the baffle were 624mm and 602mm respectively, and the pressurized water head difference was 22mm. The water blocking effect is remarkable. When the test was carried out for 8 minutes, the pressurized water head at the observation point on the downstream side was 553mm, and the pressurized water head difference at the observation points on both sides of the baffle was 19mm. After 12 minutes of the test, the head of the pressurized water changes slowly and gradually tends to be stable. When the test was carried out for 16 minutes, the confined water head at the observation point on the downstream side was 540 mm, and the pressure water head difference at the observation points on both sides of the baffle was 20 mm.

Fig. 5 is the distribution diagram of land surface settlement at different times in the pressurized water infiltration test obtained by applying the test system, in which the upstream water level is maintained at 640mm. Due to the water retaining effect of the baffle, the head of the confined water on the upstream side changes little, causing small soil deformation, while the head of the confined water on the downstream side changes greatly, resulting in large land subsidence. When the test was carried out for 4 minutes, the maximum surface settlement on the downstream side was 0.142mm, and the difference between the surface settlement values at the observation points on both sides of the baffle was 0.04mm. When the test was carried out for 8 minutes, the maximum surface settlement on the downstream side was 0.164mm, and the difference between the settlement values at the observation points on both sides of the baffle was 0.045mm. When the test was carried out for 12 minutes, the maximum surface settlement on the downstream side was 0.168mm, and the settlement difference at the observation points on both sides of the baffle was 0.047mm. When the test was carried out for 16 minutes, the development of the surface settlement tended to be stable, the maximum surface settlement value on the downstream side was close to 0.2mm, and the difference between the surface settlement values at the observation points on both sides of the baffle was about 0.05mm.

By changing the initial water level of the water tank 1, the influence of underground structures on the seepage of confined water and land subsidence under the action of different water head differences can be obtained. By changing the depth at which the baffle plate 3 is inserted into the confined aquifer, the influence of the underground structure on the seepage of the confined water and ground subsidence under different buried depth conditions can be obtained. Change the width of the baffle 3, that is, the baffle only blocks part of the cross-section in the model box 2, so that the pressurized water can bypass the lower part and the side of the baffle and seep from the high water head area to the low water head area, and different Influence of underground structures on three-dimensional seepage of confined water and land subsidence in the form of water-resisting section. By replacing the test soils 4, 5, and 6 with sandy soil, the influence of underground structures on phreatic seepage and the distribution of ground subsidence can be obtained.

Claims (1)

1. the analogue means of a blocking groundwater seepage by underground structure; Comprise: model casing, displacement meter and water-level observation pipe; It is characterized in that: also comprise: water tank, baffle plate, phreatic aquifer, water barrier, artesian aquifer, water tank links to each other with model casing, vertically is provided with some baffle plates in the model casing; Phreatic aquifer, water barrier and artesian aquifer from top to bottom successively level be layed in the model casing; Displacement meter vertically is installed in the surface of phreatic aquifer, and the water-level observation pipe vertically is embedded in the artesian aquifer of model casing and runs through phreatic aquifer and water barrier successively, and the model casing inboard is provided with draw-in groove; Described baffle plate is movably set in the draw-in groove;

Described water-level observation pipe comprises: body, float and seal filter cloth, and wherein: body is the penetrating transparent tube in two ends, and tube wall is marked with scale; Float is movably set in body inside, swims on the liquid level; Seal filter cloth and be fixedly set in the lower end of body;

Described phreatic aquifer is that thickness is the sand layer of 0.3m, and its component and content are silt 10%, fine sand 85%, and medium sand 5%, specific gravity of soil particle are 2.463, void ratio is 0.705;

Described water barrier is that thickness is the argillic horizon of 0.3m, and dry density is 1.486, and specific gravity of soil particle is 2.701;

Described artesian aquifer is that thickness is the sand layer of 0.3m, and its component and content are silt 10%, fine sand 85%, and medium sand 5%, specific gravity of soil particle are 2.463, void ratio is 0.689.

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