CN107870128A - A mud-sealed vacuum preloaded indoor test model - Google Patents

Abstract

The present invention relates to a kind of mudding formula vacuum preloading laboratory test model, including drain bar, glass molds molding box, unidirectional bowknot, wired hose, wired hose branch pipe, wired hose supervisor and experiment soil sample, experiment soil sample is placed in glass molds molding box, drain bar is inserted with soil sample is tested, plastic draining board is connected with being connected with the unidirectional bowknot of wired hose, wired hose is connected by threeway with wired hose branch pipe, and wired hose branch pipe is connected with wired hose supervisor；Characterized in that, the geotextiles under one layer of laying above experiment soil sample, the Muddy Bottoms clay of hydraulic reclamation is equipped with lower geotextiles, geotextiles are equipped with the surface of the Muddy Bottoms clay of hydraulic reclamation；Wired hose supervisor is placed in above geotextiles.

Description

A mud-sealed vacuum preloaded indoor test model

technical field

The invention relates to a mud-sealed vacuum preloading chamber test model.

Background technique

In recent years, with the rapid development of my country's economy, the tension of land use in coastal areas has become increasingly prominent. Under such circumstances, cities have set off an upsurge of land reclamation. The foundation formed by land reclamation is mainly clay-based deep dredging fill. Most of the coastal cities in my country have a large amount of muddy soil, and land reclamation mostly uses dredging supersoft soil. The clay content of particle size less than 0.005mm is between 30% and 50%, and generally has the characteristics of high water content, large void ratio, low strength, high compressibility, low permeability and rheology, so this super soft Soil cannot meet the basic conditions required for engineering construction, and the consolidation of ultra-soft soil under its own weight will take several years or even longer to complete. In order to make the ultra-soft soil foundation have a certain strength in a short time to meet the needs of engineering construction, Professor Kjellman of Sweden first proposed the vacuum preloading method.

In order to study the mechanical engineering properties of soft soil under vacuum preloading conditions and to explore new construction techniques, it is often necessary to carry out indoor model tests, so as to provide a reliable guarantee for engineering practice. At present, many experts use indoor model tests to focus on the research of vacuum preloading with sand cushion, vacuum preload without sand cushion, gas injection pressurization, air pressure splitting and other working conditions. Lei Huayang et al. (2016) used indoor model tests to evaluate the effect of foundation reinforcement for these combinations of working conditions. Wei Bo and He Huaijian (2003) conducted indoor model tests on the effect of combined vacuum-surcharge preloading treatment on soft foundations. Yan Shuxiang et al. (2011) used indoor model tests to study the pore pressure change of soil, surface settlement, vacuum degree and conventional construction technology during the vacuum preloading process.

And the construction process of traditional vacuum preloading is mainly divided into 9 construction steps. First, the drainage of the site; if there is water on the site, it needs to be drained; second, the laying of woven fabrics is mainly to ensure the safety of the construction and to isolate the mud; third, the laying of non-woven geotextiles to ensure sufficient mud isolation ; Fourth, insert the plastic drainage board; Fifth, the plastic drainage board is connected to the branch pipe, and the branch pipe is connected to the main pipe; Sixth, lay 2 layers of polyvinyl chloride or polyethylene vacuum film; Seventh, uniformly arrange the membrane device in the area And connected with the water and gas separation tank. The eighth, loading, monitoring; the ninth, unloading, detection.

In the traditional construction process, this step of laying the vacuum film is indispensable and a key part of the entire construction process. The integrity of the vacuum membrane directly affects the evaluation of the detection effect and the acceptance of the project. For example, the vacuum membrane leaks, resulting in the failure of the vacuum pressure to reach 80kPa, which affects the acceptance period.

Considering that the winter construction is different from the summer construction, the water evaporates less, and there is water on the membrane, the site may be frozen, making settlement monitoring difficult, etc. In addition, the frozen hard shell often has engineering characteristics such as low permeability coefficient and self-sealing , the use of vacuum film is a waste.

In summary, the current vacuum preloading chamber model test method has the following problems:

1. It is impossible to achieve energy-saving, environmentally friendly, efficient and fast construction techniques. During the construction process of vacuum preloading, the vacuum membrane often leaks air, which requires a lot of manpower and material resources. During the production process, a large amount of plastic needs to be produced. After the construction, the vacuum membrane cannot be reused, which is not harmonious with the environment.

2. Failure to comprehensively consider the soft soil engineering characteristics of the dredged muddy clay. Dredged fill silt soft soil has low permeability, so few experts use this engineering characteristic to study engineering problems.

Contents of the invention

The purpose of the present invention is to provide an indoor test model for researching the construction method of vacuum preloading in winter. The invention provides a vacuum preloading indoor model without a vacuum membrane in combination with the permeability characteristics of the silty dredging fill, self-sealing and environmental conditions for vacuum preloading construction in winter. To achieve the above object, the present invention takes the following technical solutions:

A mud-sealed vacuum preloading indoor test model, including a drainage board 1, a glass model box 2, a hand joint 3, a steel wire hose 4, a steel wire hose branch 7, a steel wire hose main pipe 9 and a test soil sample 10, the test The soil sample 10 is placed in the glass model box 2, and a drainage board 1 is inserted in the test soil sample. The plastic drainage board is connected with the hand joint 3 connected with the steel wire hose 4, and the steel wire hose 4 is connected to the steel wire hose through a tee The branch pipe 7 is connected, and the steel wire hose branch pipe 7 is connected with the steel wire hose main pipe 9; it is characterized in that a layer of lower geotextile 5 is laid on the top of the test soil sample, and the muddy clay 6 of blow filling is laid on the lower geotextile 5, An upper geotextile 8 is laid on the surface of the dredged muddy clay 6;

The present invention has the following advantages:

(1) the present invention builds an indoor test model without vacuum membrane, is used for researching the construction technology without vacuum membrane, utilizes the permeability and self-compacting property of dredging and filling muddy soft soil, does not adopt vacuum membrane in whole model test, The successful development of this kind of construction technology not only saves the part of the vacuum film, but also can achieve harmony with the environment.

(2) This kind of construction technology provides new ideas for scientific research, and solves engineering problems by utilizing the low permeability coefficient and self-compacting properties of dredged silt soft soil.

Description of drawings

Fig. 1 is a mud-sealed vacuum preloading chamber test model of the present invention and a layout diagram of the whole test system.

Explanation of symbols in the figure: 1 drainage board; 2 glass model box; 3 hand joint; 4 steel wire hose; 5 lower geotextile; Hose main pipe; 10 test soil samples

Detailed ways

The present invention will be described below in conjunction with the accompanying drawings and embodiments.

Referring to Fig. 1, the test system provided by the present invention including the mud-sealed vacuum preloading chamber test model comprises: add test soil sample 10 in glass model box 2, insert plastic drainage board 1 in soil sample, plastic drainage board It is connected with the hand joint 3 connected with the steel wire hose 4; a layer of lower non-woven geotextile is laid on the top of the test soil sample, and a 500mm thick blow-filled muddy clay 6 is laid on the lower geotextile 5, and the surface is laid The upper geotextile 8; the steel wire hose 4 is connected with the steel wire hose branch pipe 7 through a tee, the steel wire hose branch pipe 7 is connected with the steel wire hose main pipe 9, and the main pipe is placed on the upper geotextile 8; the steel wire hose main pipe 9 and the vacuum pump are respectively connected with the water-gas separation tank. The water-air separation tank is placed above the electronic scale to record the displacement of the test soil sample. A vacuum gauge is installed above the water-gas separation tank to record and monitor the vacuum pressure.

Experimental procedure embodiment:

(1) Connect the water-gas separation tank and other devices to check the airtightness of the device;

(2) put into the dredging fill test soil sample 10 of certain thickness in glass model box 2;

(3) Lay the lower geotextile 5;

(4) Insert the plastic drainage board 1 and connect with the hand joint 3;

(5) The plastic drainage plate 1 is connected to the steel wire hose 4 through the hand joint 3, the steel wire hose 4 is connected to the steel wire hose branch pipe 7 through a tee, and the branch pipe is connected to the main pipe;

(6) Lay the silty soft clay 6 of dredging filling with a thickness of 500mm, and ensure that the mud surface is smooth;

(7) Lay the upper geotextile 8, and inject water about 100mm away from the mud surface;

(8) open vacuum pump, carry out loading, observe the reading of the vacuum pressure of water-gas separation tank, if vacuum pressure is lower than 90kPa, will check the smoothness of the surface of 500 thick muddy soft clay;

(9) Turn off the vacuum pump, start unloading and testing.

Claims (1)

1. a kind of mudding formula vacuum preloading laboratory test model, including drain bar (1), glass molds molding box (2), hand-type joint (3), Wired hose (4), wired hose branch pipe (7), wired hose supervisor (9) and experiment soil sample (10), experiment soil sample (10) are placed in glass In glass model casing (2), drain bar (1), drain bar and the hand-type joint (3) for being connected with wired hose (4) are inserted with soil sample is tested It is connected, wired hose (4) is connected by threeway with wired hose branch pipe (7), and wired hose branch pipe (7) is responsible for wired hose (9) it is connected；Characterized in that, the geotextiles (5) under one layer of laying above experiment soil sample, lay above in lower geotextiles (5) There is the Muddy Bottoms clay (6) of hydraulic reclamation, upper geotextiles (8) are equipped with the surface of the Muddy Bottoms clay (6) of hydraulic reclamation；Wired hose master Pipe (9) is placed in above geotextiles (8).