CN108532648A - The foundation model experimental rig and test method of vacuum pre-pressed joint heating - Google Patents

Abstract

The invention discloses the foundation model experimental rigs and test method of a kind of heating of vacuum pre-pressed joint, experimental rig includes that bucket is heated made of hot water circuit instrument, piston and metal, when use, weak soil is filled to the built-in vertical foundation model in inner cavity on the inside of heating bucket, using water as energy storage and heat transfer medium, water is passed through in the toroidal cavity around heating bucket, foundation model is heated, it can make foundation model thermally equivalent, and the bucket wall area for heating bucket is big, therefore heating source area is big, to can realize basic mode type over the ground it is comprehensive, lasting, be evenly heated.The foundation model experimental rig and test method of vacuum pre-pressed joint heating of the present invention are tested for piling prepressing, the foundation experiment under vacuum preloading experiment, positive/negative-pressure experiment, the piling prepressing experiment of coupling temperature, the negative pressure of vacuum experiment of coupling temperature, the positive/negative-pressure experiment of coupling temperature and different drainage conditions provides a kind of new approaches.

Description

Foundation model test device and test method for vacuum preloading combined with heating

technical field

The invention belongs to the technical field of foundation treatment, and in particular relates to a foundation model test device and a test method for vacuum preloading combined with heating.

Background technique

Deep soft soil layers are widely distributed in the coastal and inland river and lake areas of my country. The outstanding characteristics of soft soil are high water content, high compressibility, poor water permeability and low natural strength. As a negative pressure drainage consolidation method, the vacuum preloading method is considered to be the best method for strengthening soft clay foundations because of its simple equipment, convenient operation, large reinforcement area, less energy consumption, good reinforcement effect, and no environmental pollution. one of the effective methods. The vacuum preloading method refers to setting bagged sand wells or plastic drainage boards as drainage channels in soft clay, and using the method of vacuuming to form a local negative pressure source in the soil, and discharge the pore water in the soil. It is a foundation reinforcement method that reduces the pore water pressure in the soil, thereby increasing the effective stress of the soil to compact the soil layer. Since it was put forward in 1952, key technologies such as sealing technology, vacuuming technology, gas-water separation technology, and vertical drainage channels of the vacuum preloading method have been greatly developed.

Although the vacuum preloading method has many advantages, it has the problems of long construction period and large post-construction settlement when dealing with ultra-soft soil with poor permeability. In order to solve this problem, scholars at home and abroad have recently proposed the technology of vacuum negative pressure combined heating. For example, Ye Guanbao and An Xin proposed a temperature-increasing vacuum preloading idea. The core idea is to vaporize and extract pore water in the soil through high temperature (above 62°C), thereby accelerating the consolidation process of the soft foundation; Lin Wei'an et al. The idea of vacuum preloading combined with thermal drainage is also proposed, that is, the circulating hot water in the U-shaped pipe is used to heat the soft soil of the foundation and supplemented by vacuum preloading. The above research is still in the conceived stage, and the research and development of test equipment and experimental research on vacuum preloading combined heating have not been carried out.

Contents of the invention

The technical problem to be solved by the present invention is to provide a vacuum preloading combined heating system capable of heating the foundation model in an all-round, continuous and uniform manner and simultaneously applying vacuum negative pressure and simulated load positive pressure. Foundation model test device and test method.

The technical scheme adopted by the present invention to solve the above-mentioned technical problems is: a foundation model test device for vacuum preloading and combined heating, including a hot water cycler, a piston and a heating barrel made of metal, and an annular space is arranged around the heating barrel. cavity, the water inlet and outlet of the annular cavity communicate with the water outlet and water inlet of the hot water cycler respectively, and the inner side of the heating barrel is an inner cavity for filling soft soil, so The inner cavity is provided with a piezometer, an earth pressure cell, a vacuum measuring head and a temperature probe, the vacuum measuring head is connected with a vacuum gauge, and the side wall of the heating barrel is provided with wiring holes, so The upper end of the heating barrel is equipped with a cover plate, the piston includes a piston cylinder and a pressure plate arranged up and down, the piston cylinder is fixed in the middle of the pressure plate, and the outer dimension of the pressure plate is the same as that of the inner pressure plate. The outer dimensions of the cross section of the cavity are adapted, the piston barrel is installed on the cover plate, the upper part of the piston barrel protrudes from the cover plate, and the lower part of the piston barrel together with the The above-mentioned pressure plate is located in the inner cavity together, and the side wall of the described cover plate, the piston cylinder, the pressure plate and the heating barrel encloses a stacking positive pressure chamber, and the described cover plate is equipped with a A pneumatic joint connected to the positive pressure chamber. The piston cylinder and the pressure plate form a vacuum negative pressure chamber. The piston cylinder is plugged with a vacuum conduit, and the vacuum conduit extends into the vacuum chamber. The bottom of the negative pressure chamber, the vacuum conduit is connected with a gas-liquid separation device, the middle part of the pressure plate is provided with a drain hole communicating with the vacuum negative pressure chamber, and the inner cavity is provided with a The drainage mechanism corresponding to the position of the drainage hole described above.

When the vacuum preloading combined heating foundation model test device of the present invention is used, soft soil is filled into the inner cavity inside the heating barrel to establish a foundation model, water is used as the energy storage and heat transfer medium, and the water is passed into the surrounding of the heating barrel The foundation model is heated in the annular cavity, which can make the foundation model evenly heated, and the barrel wall area of the heating barrel is large, so the heat source area is large, so that the foundation model can be heated in an all-round, continuous and uniform manner. After the foundation model is established, ventilate into the surcharge positive pressure chamber to simulate the surcharge positive pressure. The positive pressure acts on the foundation model evenly through the pressure plate at the bottom of the piston cylinder. The soil settles and consolidates at the same time. The water discharged during the consolidation process It enters the vacuum negative pressure cabin through the drainage mechanism and the drainage hole on the pressure plate, and is drawn out of the vacuum negative pressure cabin by the gas-liquid separation device through the vacuum conduit.

Preferably, the positive pressure tank is sealed by a sealing mechanism, and the sealing mechanism includes a first sealing ring, a second sealing ring and an annular rubber sealing film, and the first sealing ring is installed on the Between the piston barrel and the cover plate, the outer ring of the rubber sealing film is pressed and fixed by the cover plate and the top end of the heating barrel, and the inner ring of the rubber sealing film is fixed by the The second sealing ring is pressed and fixed on the bottom end of the piston cylinder.

Preferably, a support cylinder is fixed on the cover plate, the upper part of the piston cylinder protrudes from the support cylinder, and a third sealing ring is installed between the piston cylinder and the support cylinder. The support cylinder prevents the piston from tilting, ensuring that the positive pressure can be applied evenly to the soil.

Preferably, an insulation layer is provided on the outside of the heating barrel. The setting of the insulation layer can reduce the heat loss of the water in the annular cavity and ensure the accuracy of the test results.

Preferably, the heating barrel includes an outer barrel, an inner barrel and a bottom plate, the outer barrel and the inner barrel are fixed on the bottom plate, the outer barrel is arranged outside the inner barrel, the The outer barrel, the inner barrel and the bottom plate surround the annular cavity, and the upper ends of the outer barrel and the inner barrel are equipped with an annular sealing plate, and the annular sealing plate seals the annular cavity, so A water inlet pipe and a water outlet pipe are respectively installed on the annular sealing plate, the water inlet pipe passes through the cover plate and communicates with the water outlet end of the hot water cycler through the first water pipe, and the water outlet pipe It passes through the cover plate and communicates with the water inlet end of the hot water cycle device through the second water pipe. The design of the above-mentioned heating barrel has a simple structure and is convenient for assembly. The water inlet pipe and the water outlet pipe can also play a certain positioning effect on the cover plate.

Further, a steel tie rod is installed between the cover plate and the bottom plate, the lower end of the steel tie rod is fixed on the bottom plate, and the upper end of the steel tie rod is screwed to the cover plate And press the cover plate by the nut. The steel tie rod can fix the cover plate to ensure that the cover plate remains still during the whole test process to ensure the smooth progress of the test.

Preferably, the drainage mechanism is a vertical drainage plate or a sand well.

Utilize above-mentioned test device to carry out the foundation model test method of vacuum preloading combined heating, comprise the following steps:

(1) Prepare homogeneous soil, measure the total mass, water content and liquid-plastic limit of the soil, calculate the water content according to the three-phase ratio index of the soil, control the water content of the soil at its liquid limit, and add to the heating barrel The inner cavity is filled with soft soil layer by layer. The thickness of each layer of soft soil is 15-25cm. After each layer of soft soil is filled, it is pre-pressed. Set up a drainage mechanism, and respectively bury the piezometer, earth pressure cell, vacuum measuring head and temperature probe at the predetermined positions, and at the same time connect the wires of the piezometer, earth pressure cell, vacuum measuring head and temperature probe from the heating barrel through the wiring hole The inside is connected to the outside of the heating barrel; after all the soil is filled, the soil is preloaded with a pressure of 3-7kPa. When the settlement of the soil is less than 1mm in 24 hours, the preload is completed and the foundation model is established;

(2) Install the piston, place the pressure plate on the soil, install the cover plate, and connect the water inlet and the water outlet of the annular cavity with the water outlet and the water inlet of the hot water cycler respectively;

(3) Turn on the hot water circulator, set the outlet water temperature of the hot water circulator, and when the outlet water temperature reaches the requirement, pass the hot water into the annular cavity through the hot water circulator, and the corresponding test can be carried out.

Preferably, the tests include a heap preload test, a vacuum preload test, a positive and negative pressure test, a coupled temperature heap preload test, a coupled temperature vacuum negative pressure test, and a coupled temperature positive and negative pressure test.

Preferably, in step (1), after the preloading is completed, a drainage sand cushion is laid on the upper surface of the soil to conduct tests under different drainage conditions.

Compared with the prior art, the present invention has the following advantages: when the vacuum preloading combined heating foundation model test device and test method disclosed in the present invention are used, soft soil is filled into the inner cavity inside the heating barrel to establish a foundation model, Water is used as the energy storage and heat transfer medium, and the water is passed into the annular cavity around the heating barrel to heat the foundation model, which can make the foundation model evenly heated, and the wall area of the heating barrel is large, so the heat source area is large, Thus, omnidirectional, continuous and uniform heating of the foundation model can be realized. The foundation model test device and test method of the vacuum preloading combined heating of the present invention are surcharge preload test, vacuum preload test, positive and negative pressure test, surcharge preload test of coupled temperature, vacuum negative pressure test of coupled temperature, coupled The temperature positive and negative pressure test and the foundation test under different drainage conditions provide a new way of thinking.

Description of drawings

Fig. 1 is a schematic diagram of the structural connection of the foundation model test device of vacuum preloading combined with heating in the embodiment.

Detailed ways

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

The base model test device of the vacuum preloading combined heating of the embodiment, as shown in Figure 1, comprises a hot water circulator 1, a piston and a heating barrel 2 made of metal, the outer side of the heating barrel 2 is provided with an insulating layer 3, and the heating barrel 2 is provided with an annular cavity 21, the water inlet and outlet of the annular cavity 21 are respectively connected with the water outlet and water inlet of the hot water cycler 1, and the inner side of the heating barrel 2 is an inner cavity for filling soft soil 22. A piezometer 71, an earth pressure cell 72, a vacuum measuring head 73 and a temperature probe 74 are arranged in the inner chamber 22, and a vacuum gauge (not shown in the figure) is connected to the vacuum measuring head 73. The side wall of the heating barrel 2 There is a wiring hole 23 on the top, and a cover plate 24 is installed on the upper end of the heating barrel 2. The piston includes a piston cylinder 41 and a pressure plate 42 arranged up and down. The piston cylinder 41 is fixed in the middle of the pressure plate 42. The external dimensions of the cross section of the piston barrel 41 are installed on the cover plate 24, the top of the piston barrel 41 protrudes from the cover plate 24, the bottom of the piston barrel 41 is located in the inner cavity 22 together with the pressure plate 42, and the cover plate 24 , the piston barrel 41, the pressure plate 42 and the side wall of the heating barrel 2 enclose a positive pressure cabin 43 for loading, and the cover plate 24 is equipped with a pneumatic joint 44 communicating with the positive pressure cabin 43 for loading, and the piston cylinder 41 and the pressure plate 42 form a positive pressure cabin 43. Vacuum negative pressure cabin 45, plug in piston cylinder 41 is provided with vacuumizing conduit 46, and vacuumizing conduit 46 stretches into the bottom of vacuum negative pressure cabin 45, and vacuumizing conduit 46 links to each other with a gas-liquid separation device (not shown in the figure), The gas-liquid separation device adopts the prior art. The middle part of the pressure plate 42 is provided with a drainage hole 47 communicating with the vacuum negative pressure cabin 45. A drainage mechanism corresponding to the position of the drainage hole 47 is provided in the inner cavity 22. In this embodiment, the drainage mechanism For vertically arranged plastics drainage board 48.

In this embodiment, the positive pressure cabin 43 is sealed by a sealing mechanism, the sealing mechanism includes a first sealing ring 51, a second sealing ring 52 and an annular rubber sealing film 53, the first sealing ring 51 is installed between the piston barrel 41 and Between the cover plates 24, the outer ring of the rubber sealing film 53 is pressed and fixed by the top of the cover plate 24 and the heating barrel 2, and the inner ring of the rubber sealing film 53 is pressed and fixed on the bottom end of the piston barrel 41 by the second sealing ring 52 ; The support cylinder 25 is fixed on the cover plate 24, the upper part of the piston cylinder 41 protrudes from the support cylinder 25, and the third sealing ring 54 is installed between the piston cylinder 41 and the support cylinder 25.

In this embodiment, the heating barrel 2 includes an outer barrel 26, an inner barrel 27 and a bottom plate 28, the outer barrel 26 and the inner barrel 27 are fixed on the bottom plate 28, the outer barrel 26 is arranged on the outside of the inner barrel 27, the outer barrel 26, the inner barrel 27 and the bottom plate 28 Surrounded by an annular cavity 21, an annular sealing plate 29 is installed on the upper ends of the outer barrel 26 and the inner barrel 27, and the annular sealing plate 29 seals the annular cavity 21, and the water inlet pipe 13 and the water outlet pipe 14 are respectively installed on the annular sealing plate 29. The water pipe 13 passes through the cover plate 24 and communicates with the water outlet end of the hot water cycler 1 through the first water pipe 11, and the water outlet pipe 14 passes through the cover plate 24 and communicates with the water inlet end of the hot water cycler 1 through the second water pipe 12; Steel pull rod is installed between plate 24 and base plate 28, and the lower end of steel pull rod is fixed on the base plate 28, and the upper end of steel pull rod is screwed with cover plate 24 and compresses cover plate 24 by nut.

Utilize above-mentioned test device to carry out the foundation model test method of vacuum preloading combined heating, comprise the following steps:

(1) Prepare homogeneous soil, measure the total mass, water content and liquid-plastic limit of the soil, calculate the amount of water mixed according to the three-phase ratio index of the soil, control the water content of the soil at its liquid limit, and send to the heating barrel 2 The inner cavity 22 is filled with soft soil in layers, and the thickness of each layer of soft soil is 20cm. After each layer of soft soil is filled, it is pre-pressed. Set up a drainage mechanism, and respectively bury the piezometer 71, earth pressure cell 72, vacuum probe 73 and temperature probe 74 at predetermined positions, and at the same time connect the piezometer 71, earth pressure cell 72, vacuum probe 73 and temperature probe 74 The wire is connected from the inside of the heating barrel 2 to the outside of the heating barrel 2 through the wiring hole 23; after all the soil is filled, pre-press the soil with a pressure of 3-7kPa, and when the settlement of the soil is less than 1mm in 24 hours, After the preloading is completed, the foundation model 6 is established;

(2) The piston is placed on the foundation model 6, the inner ring of the rubber sealing film 53 is enclosed within the bottom end of the piston cylinder 41, and then the second sealing ring 52 is installed, and the inner ring of the rubber sealing film 53 is sealed by the second sealing ring 52. Fix the bottom end of the piston barrel 41, then install the cover plate 24, press and fix the outer ring of the rubber sealing film 53 by the top of the cover plate 24 and the heating barrel 2, and install the first between the cover plate 24 and the piston barrel 41 Sealing ring 51, the third sealing ring 54 is installed between the support cylinder 25 and the piston cylinder 41, and finally the water inlet pipe 13 and the water outlet pipe 14 are respectively connected to the water outlet end and the water inlet end of the hot water cycler 1 to complete the foundation model test The installation of the device, the air tightness of the detection device, the specific method is: use the vacuum pump to draw air from the vacuum negative pressure cabin 45, observe the change of the vacuum gauge, if the reading of the vacuum gauge can be stable within half an hour, and the reading after stabilization is greater than 80kPa, Indicates that the airtightness of the foundation model is intact;

(3) Turn on the hot water circulator 1, set the outlet water temperature of the hot water circulator 1, and when the outlet water temperature reaches the requirement, pass hot water into the annular cavity 21 through the hot water circulator 1, and the corresponding test can be carried out , The tests include heap preload test, vacuum preload test, positive and negative pressure test, heap load preload test of coupling temperature, vacuum negative pressure test of coupling temperature, positive and negative pressure test of coupling temperature.

If it is necessary to carry out tests under different drainage conditions, other test steps are the same as those in the above-mentioned embodiments, except that in step (1), after the preloading is completed, a drainage sand cushion should be laid on the upper surface of the soil .

During the test, the sequence of adding (removing) pressure and raising (lowering) temperature is determined according to the stress path and temperature path, and the development process of vacuum negative pressure, temperature, pore pressure and settlement can be monitored through monitoring instruments.

Claims (10)

1. the foundation model experimental rig of vacuum pre-pressed joint heating, it is characterised in that including hot water circuit instrument, piston and metal Manufactured heating bucket is provided with toroidal cavity, the water intake end of the toroidal cavity and water outlet around the heating bucket It is connected to respectively with the water outlet of the hot water circuit instrument and water intake end, the inside of the heating bucket is for filling weak soil Inner cavity, the interior intracavitary are provided with pore pressure meter, soil pressure cell, vacuum probe and temp probe, connect on the vacuum probe It is connected to vacuum meter, cable hole is offered on the side wall of the heating bucket, the upper end of the heating bucket is equipped with cover board, described Piston include piston cylinder and pressing plate setting up and down, the piston cylinder is fixed on the middle part of the pressing plate, the pressure The appearance and size of plate is adapted with the appearance and size of the cross section of the inner cavity, and the piston cylinder is mounted on the cover board On, the top of the piston cylinder is stretched out from the cover board, and the lower part of the piston cylinder is together with the pressing plate position In the interior intracavitary, the cover board, piston cylinder, pressing plate and heats the side wall of bucket and surround the positive ballasting of preloading, the cover board On the pneumatic joint communicated with the positive ballasting of the preloading is installed, the piston cylinder surrounds negative pressure of vacuum with the pressing plate Cabin, the interior plug of the piston cylinder, which is equipped with, vacuumizes conduit, the bottom for vacuumizing conduit and stretching into the negative pressure of vacuum cabin, The conduit that vacuumizes is connected with a gas-liquid separation device, is offered in the middle part of the pressing plate and the negative pressure of vacuum cabin The osculum communicated, the interior intracavitary are provided with drainage mechanism corresponding with the draining hole site.

2. the foundation model experimental rig of vacuum pre-pressed joint heating according to claim 1, it is characterised in that described The positive ballasting of preloading is sealed by a sealing mechanism, and the sealing mechanism includes the rubber of the first sealing ring, the second sealing ring and annular Glue diaphragm seal, first sealing ring are mounted between the piston cylinder and the cover board, the rubber sealing film Outer ring be fixed by the top of the cover board and the heating bucket, the inner ring of the rubber sealing film is by described Second sealing ring is pressed abd fixed on the bottom end of the piston cylinder.

3. the foundation model experimental rig of vacuum pre-pressed joint heating according to claim 1, it is characterised in that described Be fixed with support tube on cover board, the top of the piston cylinder is stretched out from the support tube, the piston cylinder with it is described Third sealing ring is installed between support tube.

4. the foundation model experimental rig of vacuum pre-pressed joint heating according to claim 1, it is characterised in that described It is provided with insulating layer on the outside of heating bucket.

5. the foundation model experimental rig of vacuum pre-pressed joint heating according to claim 1, it is characterised in that described Heating bucket includes outer barrel, interior bucket and bottom plate, and the outer barrel and the interior bucket are fixed on the bottom plate, the outer barrel It is arranged in the outside of the interior bucket, the outer barrel, interior bucket and bottom plate surround the toroidal cavity, the outer barrel and institute The upper end for the interior bucket stated is equipped with annular seal plate, and the annular seal plate seals the toroidal cavity, the ring Oral siphon and outlet pipe are separately installed on shape sealing plate, the oral siphon passes through the cover board and through the first water pipe and institute The water outlet for the hot water circuit instrument stated is connected to, and the outlet pipe passes through the cover board and through the second water pipe and the hot water The water intake end of circulating instrument is connected to.

6. the foundation model experimental rig of vacuum pre-pressed joint heating according to claim 5, it is characterised in that described Reinforcing pull rod is installed, the lower end of the reinforcing pull rod is fixed on the bottom plate, described between cover board and the bottom plate The upper end of reinforcing pull rod is threadedly coupled with the cover board and by nut compressing cover board.

7. the foundation model experimental rig of vacuum pre-pressed joint heating according to claim 1, it is characterised in that described Drainage mechanism is vertically arranged drain bar or sand drain.

8. the foundation model for being carried out vacuum pre-pressed joint heating using the experimental rig described in any one of claim 1-7 is tested Method, which is characterized in that include the following steps：

(1) prepare uniform soil, the gross mass, water content and Atterberg Limit of the soil body are measured, according to three Phase Proportion index meters of the soil body Watering quantity is calculated, controls the water content of the soil body in its liquid limit, to the inner cavity placement in layers weak soil of heating bucket, every layer of weak soil thickness is 15 ~25cm, every layer of weak soil carries out precompressed after the completion of filling to it, during filling weak soil, in the center installing of the soil body filled Drainage mechanism, and pore pressure meter, soil pressure cell, vacuum probe and temp probe are buried respectively in precalculated position, at the same by pore pressure meter, The conducting wire of soil pressure cell, vacuum probe and temp probe is connected to out of heating bucket outside heating bucket through cable hole；The soil body all fills After the completion, precompressed is carried out to the soil body with the pressure of 3~7kPa, when the settling amount of the soil body for 24 hours is less than 1mm, precompressed terminates, ground Model is established and is completed；

(2) piston is installed, pressing plate is placed on the soil body, cover board is installed, and the water intake end of toroidal cavity and water outlet are distinguished It is connect with the water outlet of hot water circuit instrument and water intake end；

(3) hot water circuit instrument is opened, the leaving water temperature of setting hot water circuit instrument follows when leaving water temperature reaches requirement through hot water Ring instrument is passed through hot water to toroidal cavity, you can is tested accordingly.

9. test method according to claim 8, which is characterized in that the experiment includes piling prepressing experiment, vacuum Pre-compression test, positive/negative-pressure are tested, the piling prepressing experiment of coupling temperature, the negative pressure of vacuum experiment of coupling temperature, couple temperature Positive/negative-pressure is tested.

10. test method according to claim 8, which is characterized in that in step (1), after precompressed, in soil body upper table Face is laid with sand mat of subgrade, carries out the experiment under different drainage conditions.