Large-size drainage consolidation test device and test method for ultra-soft soil containing drainage unit

Abstract

The invention discloses a large-size drainage consolidation test device and method for an ultra-soft soil drainage unit. The device is composed of a consolidation container, a drainage unit, a pressurization system, a test system and the like. During testing, an ultra-soft soil sample is placed in a container with a vertical drainage belt and a pore water pressure sensor, the pore water pressure sensor and a displacement meter are connected with an acquisition instrument, static load is applied through a pressurization system, and data of excess pore water pressure and time, displacement and time and displacement and time are acquired. According to the testing device and the testing method, the automation degree is high, the testing method for the composite consolidation coefficient and the horizontal permeability coefficient is achieved, and a theoretical basis can be provided for drainage consolidation and reinforcement design of a drainage-containing unit of an ultra-soft soil foundation.

Description

Technical Field

[0001] The present invention relates to the technical field of geotechnical engineering geotechnical testing, and more specifically, to a large-scale drainage consolidation testing device and a testing method containing drainage units in super-soft soil drainage consolidation. Background Art

[0002] As land resources become increasingly scarce, the number of land reclamation projects at home and abroad is increasing. Every year, my country produces a large amount of super-soft soil in waterways, rivers, lakes, etc., which has high natural water content, poor water permeability, high compressibility, low strength, and is in a state from soft plastic to fluid plastic. Using these super-soft soils as materials for land reclamation solves the problem of the disposal of super-soft soils and has huge environmental, social and economic benefits.

[0003] One of the most commonly used foundation treatment methods for ultra-soft soil sites is preloading drainage consolidation. The preloading method refers to the process in which after a load is applied to a saturated soft soil foundation, the pore water is slowly discharged, the pore volume is reduced, and the foundation undergoes consolidation deformation. At the same time, as the excess hydrostatic pressure gradually dissipates, the effective stress gradually increases, and the strength of the foundation soil gradually increases. After reaching the predetermined standard, the foundation soil is unloaded to compact, settle, and consolidate. The conventional preloading method calculates the consolidation degree of the entire soil layer based on the vertical consolidation coefficient and the radial consolidation coefficient.

[0004] The Standard for Geotechnical Test Methods (GB T50123) provides a one-dimensional consolidation test method, but the soil sample is small and has no drainage unit. The water is not actually drained from the sample during the test. This is inconsistent with the actual construction process of preloading (or vacuum) drainage consolidation in the project, resulting in the post-construction moisture content, void ratio, consolidation coefficient, etc., which cannot truly guide construction. On the other hand, the displacement in the Standard is manually recorded, and the degree of automation is not high. Summary of the invention

[0006] An object of the present invention is to solve at least the above problems and to provide at least the advantages which will be described hereinafter.

[0007] The technical solution adopted by the present invention to solve this technical problem is: a large-scale drainage consolidation test device for supersoft soil containing drainage units, comprising: A consolidation container, which is used to hold super-soft soil samples; A drainage unit, comprising: an upper permeable plate, a lower permeable plate, a vertical drainage belt and a drainage port, wherein the upper permeable plate and the lower permeable plate are respectively installed on the top and the bottom of the consolidation container, the drainage port is arranged at the bottom of the consolidation container, and the vertical drainage belt is arranged on the wall surface of the consolidation container and inside the consolidation container; A pressurization system for applying static loads to super-soft soil specimens; The test system comprises: a pore water pressure sensor, a displacement meter, a drainage measurement container and a collection instrument; the collection instrument is connected with the pore water pressure sensor and the displacement meter; the pore water pressure sensor is used to measure the excess pore water pressure of the super soft soil sample; the displacement meter is used to measure the settlement of the super soft soil sample; the drainage measurement container has a scale and is used to measure the drainage.

[0008] As a further solution of the present invention, the consolidation container is a hollow cylindrical structure.

[0009] As a further solution of the present invention, the vertical drainage belt is a plastic drainage board, and the length of the vertical drainage belt is the initial height of the super soft soil sample. As a further solution of the present invention, the vertical drainage belts are arranged symmetrically in the consolidation container with the vertical center axis of the container as a reference.

[0010] As a further solution of the present invention, the pressurizing system includes a pressurizing frame, a pressure sensor and a pressurizing cover plate; the pressurizing cover plate is arranged above the upper permeable plate, a pressure sensor is arranged between the pressurizing cover plate and the pressurizing frame, and the pressure sensor is connected to the collector.

[0011] As a further solution of the present invention, the pore water pressure sensor adopts an optical fiber pore water pressure sensor.

[0012] As a further solution of the present invention, the displacement meter is a displacement sensor.

[0013] The present invention also provides a test method using the large-scale drainage consolidation test device containing drainage units for supersoft soil, which is characterized by comprising the following steps: S1. Debug the test device and load the super-soft soil sample; S2. The super-soft soil samples are loaded in stages through a pressurizing system, and data are collected. The relationship between the excess pore water pressure, displacement, and drainage volume and time is recorded through a data acquisition instrument. After the test is completed, the curves are analyzed to obtain the porosity ratio, compression coefficient, compression modulus, compression index, and degree of consolidation after drainage consolidation stabilization under different loads, and then the composite consolidation coefficient with drainage unit, horizontal consolidation coefficient and vertical consolidation coefficient, horizontal and vertical permeability coefficients are obtained.

[0014] As a further solution of the present invention, before loading the supersoft soil sample into S1, the supersoft soil sample needs to be left to stand for 24 hours, the supersoft soil sample and the vertical drainage belt are placed, the upper permeable plate is placed so that it is in full contact with the top surface of the soil sample, and then the pressure cover is covered.

[0015] As a further solution of the present invention, in said S2, when applying the load, ensure that the load is vertical, loads the center position of the pressure cover plate, and is perpendicular to the pressure cover plate, and loads in stages until the test is completed.

[0016] The present invention includes at least the following beneficial effects: The present invention provides a large-scale drainage consolidation test device and method for ultra-soft soil containing drainage units. By arranging permeable plates above and below the ultra-soft soil sample, arranging drainage belts on the sides and inside, and connecting them with the permeable plates, a complete drainage channel is formed, which can drain water in time and achieve rapid drainage and consolidation. By arranging pore water pressure sensors, displacement meters, and drainage volume measurement containers, the pore water pressure, settlement, and drainage volume can be automatically recorded in real time. The test device and test method of the present invention have a high degree of automation and can provide design parameters and theoretical basis for the drainage consolidation reinforcement design of ultra-soft soil foundations by preloading.

[0017] Other advantages, objectives and features of the present invention will be embodied in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of the test device of the present invention; Figure 2 The displacement-time relationship curve of the presence or absence of the vertical drainage unit under a certain load described in the present invention; Figure 3 It is a curve showing the relationship between the degree of consolidation and time of a vertical drainage unit under a certain load as described in the present invention; Figure 4 It is a curve showing the relationship between the consolidation coefficient and time of a vertical drainage unit under a certain load as described in the present invention.

[0019] Among them, 1-base, 2-drainage outlet, 3-lower permeable plate, 4-column, 5-consolidation container, 6-supersoft soil sample, 7-vertical drainage belt, 8-upper permeable plate, 9-pressure cover plate, 10-pressure sensor, 11-pressure frame, 12-displacement meter, 13-pore water pressure sensor, 14-collector, 15-discharge measurement container. DETAILED DESCRIPTION

[0020] The present invention is described in detail and completely below in conjunction with the accompanying drawings. A person of ordinary skill in the art will be able to implement the present invention based on these descriptions. Before describing the present invention in conjunction with the accompanying drawings, it should be particularly pointed out that the technical solutions and technical features provided in each part of the present invention, including the following description, can be combined with each other without conflict.

[0021] In addition, the embodiments of the present invention involved in the following description are generally only a part of the embodiments of the present invention, rather than all the embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0022] The present invention is further described in detail below in conjunction with the accompanying drawings and implementations, and its specific implementation process is as follows: like Figure 1 As shown, the present invention provides a large-scale drainage consolidation test device for supersoft soil containing a drainage unit, comprising: A consolidation container 5, which is used to contain an ultra-soft soil sample 6, and the consolidation container 5 is installed on the base 1; The drainage unit includes: an upper permeable plate 8, a lower permeable plate 3, a vertical drainage belt 7 and a drainage port 2. The upper permeable plate 8 and the lower permeable plate 3 are respectively installed on the top and bottom of the consolidation container 5, the drainage port 2 is arranged at the bottom of the consolidation container 5, and the vertical drainage belt 7 is arranged on the wall surface of the consolidation container 5 and inside the consolidation container 5. The function of the drainage unit is to increase the drainage channel, discharge water faster through the drainage channel, and accelerate the consolidation of the soil sample.

[0023] A pressurizing system for applying a static load to the super-soft soil specimen 6; The test system includes: a pore water pressure sensor 1310, a displacement meter 12, a drainage measurement container 15 and a collector 14; the collector 14 is connected to the pore water pressure sensor 1310 and the displacement meter 12; the pore water pressure sensor 1310 is used to measure the excess pore water pressure of the super soft soil sample 6; the displacement meter 12 is located on the upper side of the pressure cover plate 9 and is used to measure the settlement of the super soft soil sample 6; the drainage measurement container 15 has a scale and is used to measure the drainage.

[0024] The technical solution may further include the following technical details to better achieve the technical effect: the consolidation container 5 is a hollow cylindrical structure, and in this embodiment the consolidation container 5 is a steel cylinder.

[0025] The technical solution may also include the following technical details to better achieve the technical effect: the vertical drainage belt 7 is a plastic drainage board, the length of the vertical drainage belt 7 is the initial height of the super soft soil sample 6, and the width and thickness are determined according to the well diameter ratio. The technical solution may also include the following technical details to better achieve the technical effect: when the vertical drainage belt 7 is arranged in the consolidation container 5, it is symmetrically arranged with the vertical center axis of the container as a reference.

[0026] The technical solution may also include the following technical details to better achieve the technical effect: the pressurizing system includes a pressurizing frame 11, a pressure sensor 10 and a pressurizing cover plate 9; the pressurizing cover plate 9 is arranged above the upper permeable plate 8, a pressure sensor 10 is arranged between the pressurizing cover plate 9 and the pressurizing frame 11, the pressure sensor 10 is connected to the collector 14, the pressurizing frame 11 is arranged on the column 4, and pressure is applied to the pressurizing cover plate 9 through the pressurizing frame 11, and the applied pressure is detected by the pressure sensor 10. Among them, the pressurizing system can adopt screw rod type, hydraulic type and pneumatic type loading devices, which are mainly used to apply static loads to super soft soil samples 6. The collector 14 is used to collect data collected by the pore water pressure sensor 1310, the displacement meter 12, and the pressure sensor 10.

[0027] The technical solution may also include the following technical details to better achieve the technical effect: the pore water pressure sensor 1310 uses an optical fiber pore water pressure sensor 1310 or other pressure sensor 10 to measure the relationship between excess pore water pressure and time.

[0028] The present technical solution may further include the following technical details to better achieve the technical effect: the displacement meter 12 is a displacement sensor used to measure the relationship between settlement and time.

[0029] The present invention also provides a method for using a large-scale drainage consolidation test device containing drainage units for supersoft soil, comprising the following steps: S1. Debugging the test device and loading the super-soft soil sample 6. Debugging the test device specifically includes debugging the pore water pressure sensor 1310, the displacement meter 12, and the pressure sensor 10 to ensure that they are connected to the collector 14 normally.

[0030] S2. The super-soft soil sample 6 is loaded in stages by a pressurizing system, and data is collected. The relationship between the excess pore water pressure, displacement and drainage volume and time is recorded by a data collector 14. After the test is completed, the curve is analyzed to obtain the porosity ratio, compression coefficient, compression modulus, compression index and degree of consolidation after drainage consolidation stabilization under different loads, and then the composite consolidation coefficient with drainage unit, the horizontal consolidation coefficient and the vertical consolidation coefficient, and the horizontal and vertical permeability coefficients are obtained.

[0031] The technical solution may also include the following technical details to better achieve the technical effect: before loading the super-soft soil sample 6 into S1, the super-soft soil sample 6 needs to be left to stand for 24 hours, the super-soft soil sample 6 and the vertical drainage belt 7 are placed, the upper permeable plate 8 is placed so that it is in complete contact with the top surface of the soil sample, and then the pressure cover plate 9 is covered.

[0032] This technical solution may also include the following technical details to better achieve the technical effect: in said S2, when applying the load, ensure that the load is vertical, load the center of the pressure cover plate 9, and be perpendicular to the pressure cover plate 9, and load in stages until the end of the test. After the test is completed, the curve is analyzed to obtain the porosity ratio (obtain the porosity ratio of the soil under the condition of preloading (or vacuum) drainage), compression coefficient, compression modulus, compression index, and consolidation degree after drainage consolidation stabilization under different loads, and then obtain the composite consolidation coefficient with drainage unit, horizontal consolidation coefficient and vertical consolidation coefficient, horizontal and vertical permeability coefficient, etc.

[0033] During the test, the super-soft soil sample 6 is placed in a container with a vertical drainage belt 7 and a pore water pressure sensor 1310, and the pore water pressure sensor 1310 and the displacement meter 12 are connected to the acquisition instrument 14. The static load is applied through the pressurization system to collect the data of excess pore water pressure and time, displacement and time, and drainage volume and time. When the pore water pressure-time or displacement-time curve is basically stable, the next level of load is applied to continue the test until the last level of load. According to the test, the variation law of excess pore water pressure and time, displacement and time under the condition of preloading (or vacuum) drainage is obtained, and then the consolidation parameters such as consolidation degree, composite consolidation coefficient, and permeability coefficient are obtained, and then the horizontal consolidation coefficient and horizontal permeability coefficient can be deduced. The test device and test method of the present invention have a high degree of automation, solve the test method of composite consolidation coefficient and horizontal permeability coefficient, and can provide a theoretical basis for the drainage consolidation reinforcement design of super-soft soil foundation containing drainage units.

[0034] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the embodiments shown and described herein.

Claims

1. A large-scale drainage consolidation test device for supersoft soil with drainage units, characterized in that: include: A consolidation container, which is used to hold super-soft soil samples; A drainage unit, comprising: an upper permeable plate, a lower permeable plate, a vertical drainage belt and a drainage port, wherein the upper permeable plate and the lower permeable plate are respectively installed on the top and the bottom of the consolidation container, the drainage port is arranged at the bottom of the consolidation container, and the vertical drainage belt is arranged on the wall surface of the consolidation container and inside the consolidation container; A pressurization system for applying static loads to super-soft soil specimens; The test system comprises: a pore water pressure sensor, a displacement meter, a drainage measurement container and a collection instrument; the collection instrument is connected with the pore water pressure sensor and the displacement meter; the pore water pressure sensor is used to measure the excess pore water pressure of the super soft soil sample; the displacement meter is used to measure the settlement of the super soft soil sample; the drainage measurement container has a scale and is used to measure the drainage.

2. The large-scale drainage consolidation test device for supersoft soil containing drainage units according to claim 1, characterized in that: The consolidation container is a hollow cylindrical structure.

3. The large-scale drainage consolidation test device for supersoft soil with drainage unit according to claim 1, characterized in that: The vertical drainage belt is a plastic drainage board, and the length of the vertical drainage belt is the initial height of the super soft soil sample.

4. The large-scale drainage consolidation test device for supersoft soil containing drainage units according to claim 1 or 3, characterized in that: When the vertical drainage belt is arranged in the consolidation container, it is arranged symmetrically with the vertical center axis of the container as the reference.

5. The large-scale drainage consolidation test device for supersoft soil containing drainage units according to claim 1, characterized in that: The pressurizing system includes a pressurizing frame, a pressure sensor and a pressurizing cover plate; the pressurizing cover plate is arranged above the upper permeable plate, a pressure sensor is arranged between the pressurizing cover plate and the pressurizing frame, and the pressure sensor is connected to the collector.

6. The large-scale drainage consolidation test device for supersoft soil with drainage units according to claim 1, characterized in that: The pore water pressure sensor adopts an optical fiber pore water pressure sensor.

7. The large-scale drainage consolidation test device for supersoft soil containing drainage units according to claim 1, characterized in that: The displacement meter is a displacement sensor.

8. A test method using the large-scale drainage consolidation test device for supersoft soil containing drainage units as claimed in any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Debug the test device and load the super-soft soil sample; S2, applying loads to the ultra-soft soil samples in stages through a pressurizing system, and collecting data, and recording the relationship between excess pore water pressure, displacement, and drainage and time through a data acquisition instrument; After the test is completed, the curve is analyzed to obtain the porosity, compression coefficient, compression modulus, compression index, and consolidation degree after drainage consolidation stabilization under different loads, and then the composite consolidation coefficient with drainage unit, horizontal consolidation coefficient and vertical consolidation coefficient, horizontal and vertical permeability coefficients are obtained.

9. The test method of the large-scale drainage consolidation test device for supersoft soil containing drainage units according to claim 8, characterized in that: Before loading the super-soft soil sample into S1, the super-soft soil sample needs to be left to stand for 24 hours, the super-soft soil sample and the vertical drainage belt are placed, the upper permeable plate is placed so that it is in full contact with the top surface of the soil sample, and then the pressure cover is covered.

10. The test method of the large-scale drainage consolidation test device for supersoft soil containing drainage units according to claim 3, characterized in that: In S2, when applying the load, ensure that the load is vertical, loads the center of the pressure cover plate, and is perpendicular to the pressure cover plate, and loads in stages until the test is completed.

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