CN109629547B - System and method for measuring hydrodynamic characteristic parameters of large-burial-depth soil - Google Patents
System and method for measuring hydrodynamic characteristic parameters of large-burial-depth soil Download PDFInfo
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- CN109629547B CN109629547B CN201910025648.7A CN201910025648A CN109629547B CN 109629547 B CN109629547 B CN 109629547B CN 201910025648 A CN201910025648 A CN 201910025648A CN 109629547 B CN109629547 B CN 109629547B
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
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- E02D1/00—Investigation of foundation soil in situ
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Abstract
The invention relates to a system and a method for measuring hydrodynamic characteristic parameters of soil with large burial depth, comprising the following steps: the outer layer box body with automatic constant pressure pressurization facility that comprises by rigid material sets up the sample room that at least one lateral wall comprises elastic material in the outer layer box body, and the sample room bottom is fixed in the bottom of outer layer box body to be equipped with the sample mouth that can pack the soil sample, be equipped with sealed lid on the sample mouth, sealed cover the inlet port that sets up and be connected with aqueous vapor pressurization facility, the sample room top is equipped with the gas outlet pipe, the sample room top is in the suspended state that can reciprocate, the top and the bottom of soil sample in the sample room set up the permeable stone respectively. The invention utilizes the outer water tank to simulate the state of large burial depth of a soil sample in natural environment, measures various soil parameters of the saturated state and the dry state of the soil sample in the simulated state, and finally obtains various physical parameters and hydrodynamic characteristic parameters thereof in the large burial depth state.
Description
Technical Field
The invention relates to a system and a method for measuring hydrodynamic characteristic parameters of soil with large burial depth, in particular to a soil hydrological measuring instrument and a method, which are used for measuring physical characteristic parameters and hydrodynamic parameters of soil.
Background
In the technical field of soil hydrology, soil sampling is often required to perform related researches such as soil hydrologic process. For example, soil physical parameters and their hydrodynamic parameters are important grounds for studying soil hydrologic processes. In order to obtain physical parameters of soil and hydrodynamic characteristic parameters thereof, the soil is generally obtained by sampling undisturbed soil and measuring in a laboratory. Soil is composed of solid soil particles, water between voids, and a multiphase medium composed of voids, and due to the different characteristics of soil constituent materials, general soil expands during an increase in water content and contracts during a decrease in water content. However, for the soil with larger burial depth, the soil pressure applied to the soil is correspondingly increased due to the increase of the depth, so that the structure adjustment in the water transmission process of the soil is limited, and the water transmission and other soil water characteristics of the soil are adversely affected. Therefore, in order to ensure the accuracy of the measured physical parameters of the soil and the hydrodynamic characteristics thereof, it is necessary to ensure that the sampled soil sample can still be maintained in a state at a corresponding depth position during the soil measurement.
The existing method for measuring the permeability coefficient and the water diffusion coefficient of the soil with large burial depth cannot effectively perform pressurization treatment on the soil sample in time, so that the soil sample is restored to a state when the soil sample is buried with large burial depth, and further the measured accuracy of the permeability coefficient, the water diffusion coefficient and the like is reduced.
Disclosure of Invention
In order to overcome the problems in the prior art, the invention provides a system and a method for measuring hydrodynamic characteristic parameters of soil with large burial depth. The system and the method utilize the double-layer water tank to simulate the soil environment with large underground burial depth, and measure the physical parameters and hydrodynamic characteristic parameters of the soil.
The purpose of the invention is realized in the following way: a system for measuring hydrodynamic characteristics of soil with large burial depth, comprising: the outer layer box body with automatic constant pressure pressurization facility that comprises rigid material, outer layer box in set up the sample room that at least one lateral wall comprises elastic material, sample room bottom fix in the bottom of outer layer box to be equipped with the sample mouth that can pack into soil sample, the sample mouth on be equipped with sealed lid, sealed cover and set up the inlet port of being connected with aqueous vapor pressurization facility, sample room top be equipped with the gas outlet pipe, sample room top be in the suspended state that can float from top to bottom, sample room indoor soil sample's top and bottom set up the permeable stone respectively.
Further, the automatic constant pressure pressurization facility comprises a water pressure sensor arranged in the outer water tank, the top of the outer water tank is connected with a booster water pump controlled by the water pressure sensor, and the bottom of the outer water tank is provided with a pressure relief valve controlled by the water pressure sensor.
Further, an observation facility is arranged on the outer water tank.
Further, a deformation sensor is arranged on the side wall of the sample chamber.
Further, the deformation sensor comprises a circumferential deformation sensor and an axial deformation sensor.
Further, a weighing sensor and a dryness sensor are arranged in the sample chamber.
Further, the water-gas pressurizing facility comprises a siphon pipe with a water filling valve and a flowmeter, and a high-level water storage tank connected with the siphon pipe, wherein the height of the bottom of the high-level water storage tank exceeds the height of the top of the sample chamber.
Furthermore, the top and the bottom of the sample chamber are respectively provided with a water dispersing facility.
Further, the water inlet of the sample chamber is connected with a heating air blower, and the water outlet pipe is connected with an air pump.
The method for measuring the hydrodynamic characteristic parameters of the soil with large burial depth by using the system comprises the following steps:
step 1, obtaining a soil sample: obtaining a soil sample in a field of a research area, and measuring the depth, weight, temperature and humidity of the soil sample in situ;
step 2, filling a soil sample: loading a soil sample into the sample chamber from the bottom of the sample chamber, and tightly covering the sealing cover, wherein the circumferential deformation sensor and the axial deformation sensor of the side wall of the sample chamber are set to be zero, and the weight of the sample is checked through the weighing sensor;
step 3, pressurizing: calculating the pressure of the soil sample in situ according to the environment of obtaining the soil sample in the field, starting the pressurizing facility to inject water into the outer water tank and achieving the calculated pressure so as to simulate the pressure of the soil sample in situ, and recording the deformation of the side wall of the sample chamber, including the circumferential deformation and the axial deformation;
step 4, water injection: opening a water injection valve, injecting water to the soil sample until the water flow of the water outlet pipe flows out, at the moment, saturating the soil sample, closing the water injection valve, and recording the saturated circumferential deformation and axial deformation of the soil sample, and the saturated weight and water injection of the soil sample;
step 5, drying: starting a heating air blower and an air pump, evaporating water in the soil sample by utilizing the heat of the hot air, observing a dryness sensor until the soil sample is completely dried, and gradually reducing the water pressure in an outer water tank according to the dryness of the soil sample while feeding the hot air; after the soil sample is dried, the deformation of the side wall of the sample chamber is recorded, the weight of the soil sample is recorded, and other physical parameters and hydrodynamic characteristic parameters of the soil under the condition of large burial depth are calculated through the numerical values measured in the saturated state and the dry state.
The invention has the beneficial effects that: the invention utilizes the outer water tank to simulate the state of large burial depth of a soil sample in natural environment, measures various soil parameters of the saturated state and the dry state of the soil sample in the simulated state, and finally obtains various physical parameters and hydrodynamic characteristic parameters thereof in the large burial depth state. The system has simple structure, can realize complete automatic measurement, greatly reduces manual intervention and improves measurement accuracy.
Drawings
The invention is further described below with reference to the drawings and examples.
FIG. 1 is a schematic diagram of a system according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a system with an automatic constant pressure pressurization facility according to a second embodiment of the present invention;
FIG. 3 is a schematic view of a deformation sensor of a sidewall of a sample chamber according to a fifth embodiment of the invention;
FIG. 4 is a schematic view of a water vapor pressurization facility according to a seventh embodiment of the present invention;
FIG. 5 is a schematic view of a sample cell diffusion and collection apparatus according to an embodiment of the present invention;
FIG. 6 is a schematic view showing a structure of a sample chamber with a heating means according to a ninth embodiment of the present invention;
fig. 7 is a flow chart of a method according to an embodiment of the invention.
Detailed Description
Embodiment one:
the embodiment is a system for measuring hydrodynamic characteristic parameters of soil with large burial depth, as shown in fig. 1. The embodiment comprises the following steps: the outer layer box 2 with automatic constant pressure pressurization facility 1 that comprises rigid material, outer layer box in set up at least one lateral wall 301 and constitute by elastic material's sample room 3, sample room bottom 302 fix in outer layer box's bottom to be equipped with the sample mouth that can pack into soil sample, the sample mouth on be equipped with sealed lid 303, sealed cover on set up the inlet that is connected with aqueous vapor pressurization facility 4, sample room top 304 be equipped with out the trachea 5, sample room top be in the suspended state that can float from top to bottom, sample room indoor soil sample 6's top and bottom set up permeable stone 305, 306 respectively.
The basic idea of this embodiment is: the outer water tank is used for simulating the pressure in soil, so that the pressure is generated on a soil sample in the sample chamber, the pressure applied to the soil in the soil layer is from multiple directions, namely from the periphery and the top, only the bottom is used for generating the pressure on the lower soil layer, so that the pressure can be ignored, the whole sample chamber is placed at the bottom of the outer water tank, the water pressure is generated on the sample chamber from the upper part and the periphery, and the actual pressed state of the soil sample in practice can be well simulated.
It can be seen that the outer tank must be constructed of a rigid material and must have a certain strength to resist a certain water pressure, and steel or other metallic materials may be used. For convenient observation, an observation window can be arranged on the outer water tank, or a pinhole camera and other facilities are used for observing the expansion and contraction conditions of the sample chamber.
In order to generate the pressure required by the experiment in the outer water tank, an automatic constant pressure pressurizing device is arranged in the embodiment. The automatic constant pressure pressurizing device mainly uses external water pressure to generate constant pressure in the outer water tank. The automatic constant pressure pressurizing means may take various forms, such as constant pressure generated by using a stable water level in the high-level water tank, or automatic control by using a water pump and water pressure in the outer water tank of the automatic control system, etc. The outer water tank can be in various shapes such as cubes, cylinders, balls and the like, but is used as a low-pressure container, and the cylinders are the most realistic design for convenient manufacture.
The sample chamber is a key element of the present embodiment, and is a facility for mainly performing experiments. In order to measure various parameters of the soil sample in a saturated state and a dry state, various sensors are arranged in the sample chamber, and the soil sample is observed and measured.
A plurality of sample chambers can be arranged in one outer water tank, so that a plurality of soil samples can be observed at the same time, and the working efficiency is improved.
For measuring the expansion of the soil sample, the side walls of the sample chamber described in this embodiment are made of a flexible material with elasticity, the ends and the bottom of the sample chamber also being made of a rigid material, so that the sample chamber can be deformed in two dimensions, i.e. in the axial direction and in the outer circumferential direction (circumferential direction). It should be noted here that the shape of the sample chamber is a cylinder, because the shape of the soil sample is a cylinder because the sampling is a borehole sampling, and the shape of the sample chamber is also a cylinder in order to adapt to the shape of the soil sample.
The lower end of the sample chamber is fixed at the bottom of the outer water tank, and the side wall of the sample chamber is made of elastic flexible materials, so that the top of the sample chamber is in a suspension state and can stretch up and down along with the expansion of the soil sample, and meanwhile, the diameter of the soil sample is increased (excircle Zhou Pengzhang) when the soil sample expands due to the elastic materials, and the side wall of the sample chamber is also increased.
In order to load the soil sample into the sample chamber, a sample port is formed in the bottom of the sample chamber. The sample port is tightly sealed by a sealing cover, and the sealing cover is required to have a plurality of sealing measures because of bearing larger pressure, and meanwhile, the sealing cover is fastened by adopting a standard sealing method of a pressure container.
The top of the sample chamber is also rigid, and when a soil sample is placed in the sample chamber, the soil sample arches the top of the sample chamber. The diameter of the top of the sample chamber should be larger than the diameter of the soil sample in order to leave room for the soil sample to expand. When the soil sample is placed in the sample chamber, the flexible side walls of the sample chamber are not wrapped around the sample, or are loosely wrapped around the soil sample, as the outer water tank is not yet pressurized. The resilient side wall is now in a relatively stationary state without external pressure.
When the soil sample is expanded, the expansion is in principle in all directions, but in the actual measurement, the expansion in any direction can be simplified to the axial extension of the cylinder and the circumferential extension of the outer circumference, which is actually the increase of the soil sample in all radial directions, so that the expansion of the whole soil sample in all directions can be measured by using the deformation sensors in both directions.
The deformation sensing has various schemes, namely, the deformation sensing can be directly measured by adopting a graduated scale mode, and also can adopt a resistance chip deformation sensor or a semiconductor deformation sensor and other modes.
In order to measure the expansion of the soil sample in the saturated state (saturation expansion under the condition of external pressure), the soil sample must be in the saturated state, and in this embodiment, a water inlet is arranged at the bottom of the sample chamber, and a water outlet pipe is arranged at the top. The water inlet is introduced with a certain pressure of water-air mixture, so that the water is gradually carried out in the soil sample and gradually permeates until water flow occurs in the water outlet pipe, and the soil sample is in a saturated state.
The water-air pressurizing device is used for generating certain pressure on the water mixed with air, and the water-air pressurizing device can be used for injecting the water into the soil sample from the bottom in various modes, such as a siphon pipe mode for introducing the water in the water storage tank with a certain height into the sample chamber, or a constant-pressure water pump or peristaltic pump mode for injecting the water into the soil sample.
Because the water inlet and the water outlet are both punctiform bodies, the water flow can generate diffusion or aggregation effect when penetrating and separating out soil samples so as to adapt to the punctiform body states of the water inlet and the water outlet, diffusion facilities can be arranged at the water inlet, and aggregation facilities can be arranged at the water outlet.
After measuring various parameters of the saturated soil sample, measuring various parameters of the completely dried soil sample, and connecting a heating air blower to a water inlet of the sample chamber so as to send hot air into the sample chamber and bake the soil sample, and connecting a heating air blower to a water outlet pipe so as to generate negative pressure in the sample chamber, so that the hot air for baking the soil sample can smoothly leave the sample chamber. At this time, the soil sample can be regarded as a ventilation plate, the heating air blower and the air pump promote the power that the hot air flows in the soil sample formed in the sample inner chamber, the hot air can pass through the gaps of the soil, the soil sample is baked, the moisture in the soil is gradually separated from the soil and flows away along with the hot air, and finally the whole soil sample is baked. In the baking process, the water pressure in the outer water tank also plays a role in extruding water in the soil sample, so that the drying process of the soil sample can be accelerated, and the actual soil drying process can be simulated.
In order to detect the weight change of the soil sample in saturated as well as dry state, a load cell may be provided in the sample chamber. The discharge pressure and other weights in the system, the load cell can accurately measure the weight of the soil sample in saturated and dry conditions.
To know the dryness of the soil sample, a dryness sensor may be provided in the sample chamber. And the drying process is controlled by the dryness sensor, so that automatic detection is realized.
In order to keep the integrity of the soil sample and avoid loose deformation in the saturation process, permeable stones can be arranged at the top and the bottom of the soil sample, and as the outer side of the sample chamber is made of elastic materials, after the soil sample is placed in the sample chamber, the side wall of the sample chamber is slightly elongated, and the soil sample is clamped by the permeable stones from top to bottom by utilizing the pressure generated by the elasticity of the side wall of the sample chamber. The outside of the sample chamber cannot be excessively stretched to generate larger pressure, so that the soil sample is prevented from being clamped and deformed.
Embodiment two:
this embodiment is a modification of the first embodiment, and is a refinement of the first embodiment with respect to the automatic constant pressure pressurizing facility. The automatic constant pressure pressurization facility according to this embodiment includes a water pressure sensor 101 disposed in an outer water tank, a booster pump 102 controlled by the water pressure sensor is connected to the top of the outer water tank, and a pressure release valve 103 controlled by the water pressure sensor is disposed at the bottom of the outer water tank, as shown in fig. 2.
This embodiment has a relatively simple control procedure: the booster water pump delivers water into the outer water tank, and when the water pressure in the outer water tank reaches a preset value, the booster water pump stops delivering water into the outer water tank. When the water pressure in the outer water tank is overlarge, the pressure relief valve is opened to relieve pressure, and when the pressure in the outer water tank is insufficient, the booster pump is opened to boost pressure. Because of the need of high-precision constant pressure control, a singlechip can be matched with a variable-frequency water pump to maintain high-precision constant pressure.
The control process can be realized by using pressure sensors or by using simple logic circuits, and a singlechip and other complex control systems can be used for realizing accurate control.
The pressure sensor may be a conventional pressure gauge or pressure transmitter. Some pressure gauges have electrical parameter outputs, and can automatically change pressure into electrical parameter outputs, and the electrical parameters through the outputs can control the starting and stopping of the electrical appliance. Such a pressure gauge may be applied to the present embodiment. And a pressure transmitter which is special for outputting electric parameters can be directly used for controlling electric appliances.
The booster pump can use general water pump, and the relief valve can use general solenoid valve.
Embodiment III:
this embodiment is a modification of the above embodiment and is a refinement of the above embodiment with respect to the outer tank. The outer water tank of this embodiment is provided with an observation facility.
The observation facility in this embodiment may be an observation window or an electronic device such as a pinhole camera mounted inside the outer tank.
Embodiment four:
this embodiment is a modification of the above embodiment, and is a refinement of the above embodiment with respect to the side walls of the sample chamber. The side wall of the sample chamber in this embodiment is provided with a deformation sensor.
The side wall of the sample chamber is made of elastic material and can expand and contract along with the expansion and contraction of the soil sample. Expansion and contraction of the soil sample is an important soil parameter and thus requires accurate measurement. The strain sensor may be of various forms.
In order to measure the integral deformation of the sample, two sensors can be used for measuring the deformation of the side wall of the sample chamber respectively, namely, the deformation of the outer circumference of the soil sample and the deformation of the height of the soil sample are measured, and of course, one sensor can be used for measuring the deformation of two modes together.
Fifth embodiment:
this embodiment is a modification of the above embodiment, and is a refinement of the above embodiment with respect to the deformation sensor. The deformation sensor according to the present embodiment includes a circumferential deformation sensor 3011 and an axial deformation sensor 3012, as shown in fig. 3.
The expansion or contraction of the outer circumference is mainly represented by the increase or decrease of the diameter of the soil sample, and if the soil sample is not in the sample chamber, the diameter thereof can be directly measured by a ruler, which is very convenient, but since the soil sample is in the sample chamber, the diameter is not very convenient to measure, but the outer circumference of the soil sample can be very conveniently measured by using the deformation sensor, namely, the change of the outer circumference of the cylinder of the soil sample can be measured, as indicated by the expansion and contraction direction of arrow a in fig. 3.
Likewise, the change in height of the soil sample cylinder can be measured using a deformation sensor, as indicated by the telescoping direction of arrow B in fig. 3.
Example six:
this embodiment is a modification of the above embodiment and is a refinement of the above embodiment with respect to the sample chamber. The sample chamber in this embodiment is provided with a weighing sensor and a dryness sensor.
The weight of the soil sample is a very important parameter, and other parameters can be calculated from the weight parameter, so it is very important to measure the weight of the soil sample in various states. When the soil sample is taken out of the soil layer and then is to be weighed, the weight of the soil sample is to be monitored in the whole measuring process, so that a weighing sensor is arranged in the sample chamber, the weight of the soil sample is monitored, and data are output at any time. The weighing sensor can use a high-precision strain sensor and is matched with a precise measuring circuit, so that high-precision weighing can be realized.
The dryness sensor can use two electrodes respectively arranged at the top end and the bottom end of the sample, and measure the resistance between the two electrodes, namely the resistance at the upper end and the lower end of the soil sample, and the dryness of the soil or the moisture content in the soil sample can be judged through the change of the resistance. The measuring mode can adopt a high-precision resistance measuring instrument or use a signal generator to act as a power supply, and meanwhile, high-precision voltage and current meters are used for measuring to obtain a high-precision resistance value, and the moisture content in the soil sample is obtained through analysis of the resistance value.
Embodiment seven:
this embodiment is a modification of the above embodiment, and is a refinement of the above embodiment with respect to the water vapor pressurization facility. The water-gas pressurizing device in this embodiment comprises a siphon tube 403 with a water filling valve 401 and a flowmeter 402, and a high-level water storage tank 404 connected with the siphon tube, wherein the bottom of the high-level water storage tank exceeds the top of the sample chamber, as shown in fig. 4.
This embodiment takes a simple way of filling the soil sample with water from the bottom by gravity. Because the bottom of the high-level water storage tank is higher than the top of the sample chamber, the injected water can keep stable pressure from the bottom to the top of the soil sample by utilizing the siphon effect, and the whole soil sample is uniformly filled.
The siphon is also provided with a flowmeter for recording the water quantity entering the soil sample and controlling the water injection quantity through a water injection valve.
Example eight:
this embodiment is a modification of the above embodiment and is a refinement of the above embodiment with respect to the sample chamber. The top and bottom of the sample chamber in this embodiment are provided with collection means 307 and diffusion means 308, respectively, as shown in fig. 5.
The diffusion device in this embodiment is to make the water flowing out of the siphon tube enter the permeable stone uniformly, and the aggregation setting is just opposite to the diffusion device in action, and the water flowing out of the permeable stone is aggregated and flows out through the water outlet.
The collecting device and the diffusing device can have various forms, the embodiment adopts flaring and necking similar to a horn shape, and the structure is quite simple and the cost is low.
Example nine:
this embodiment is a modification of the above embodiment, and is a refinement of the above embodiment with respect to the outer tank. The water inlet 3031 of the sample chamber in this embodiment is connected to a heating blower 3032, and the water outlet pipe is connected to an air pump 3033, as shown in fig. 6.
The heater blower may be an air pump with an electric heater. Air pumps with electric heaters should also be provided with automatic control systems to allow control of the heating temperature and hot air flow. The temperature of the heated air is typically maintained below 60 degrees.
Example ten:
the embodiment is a method for measuring hydrodynamic characteristic parameters of soil with large burial depth by using the system described in the embodiment. The basic idea of the method is as follows:
the method comprises the steps of pressurizing an outer water tank, simulating the pressure of soil around a soil layer with a certain depth and the pressure of the top, injecting water into a soil sample from the bottom under the state with the pressure, measuring various parameters, heating and blowing air, starting an air pump, completely drying the soil sample under the condition of keeping the pressure, measuring various parameters of the sample again, and obtaining the saturated and dried soil parameters of deep soil.
The method comprises the following specific steps:
step 1, obtaining a soil sample: soil samples were taken in the field of the study area and measured for depth, weight, temperature, humidity in situ.
The field soil sampling generally uses a rotary sampling mode, the sample is a cylinder, the sampling depth and the soil sample outline dimension record are recorded immediately after sampling, and then weighing, temperature measurement, humidity measurement and other measurements are carried out. And then the soil sample is stored in a closed mode, and is opened when the soil sample is to be measured.
Step 2, filling a soil sample: soil samples are loaded into the sample chamber from the bottom of the sample chamber, the sealing cover is tightly covered, at the moment, the circumferential deformation sensor and the axial deformation sensor of the side wall of the sample chamber are set to zero, and the weight of the samples is checked through the weighing sensor. The encapsulated soil sample was opened in the laboratory.
Since the diameter and height of the soil sample are generally determined, the diameter and height of the sample chamber are also generally determined. Since the side walls of the sample chamber are made of an elastic material, the dimensions of the sample chamber can be determined as follows: the height of the sample chamber should be slightly smaller than the soil sample, so that when the soil sample is loaded into the sample chamber, the side wall of the sample chamber is slightly elongated, and the upper end and the lower end of the sample chamber clamp the soil sample; the diameter of the sample chamber is slightly larger than that of the soil sample, and after the soil sample is filled into the sample chamber, the middle part slightly contracts and is close to the soil sample due to the extension of the side wall of the sample chamber, so that the soil sample is wrapped. At this time, the deformation sensor may be changed, and for accurate measurement, the deformation sensor may be cleared as the measurement origin.
After the soil sample is loaded into the sample chamber, the load cell is also calibrated. After the soil sample package is opened, precise weight measurement is performed first, the weighing origin is used, and after the soil sample package is filled into the sample chamber, the weighing sensor is calibrated, and the output value of the weighing sensor is consistent with the precise measurement result.
Step 3, pressurizing: calculating the pressure of the soil sample in situ according to the environment of obtaining the soil sample in the field, starting the pressurizing facility to inject water into the outer water tank and achieving the calculated pressure so as to simulate the pressure of the soil sample in situ, and recording the deformation of the side wall of the sample chamber, including the circumferential deformation and the axial deformation.
After the soil sample is loaded into the sample chamber and sealed, pressurization is first performed. The pressure applied to the soil sample in the subsurface is calculated according to the depth of the soil sample before pressurization, and the outer water tank is pressurized according to the calculated pressure. It should be noted that the outer water tank should be empty and no water should be present before the soil sample is loaded into the sample chamber, so as to avoid interfering with the loading of the soil sample into the sample chamber.
Step 4, water injection: and (3) opening a water injection valve, injecting water to the soil sample until the water flow of the water outlet pipe flows out, at the moment, saturating the soil sample, closing the water injection valve, and recording the saturated circumferential deformation and axial deformation of the soil sample, and the saturated weight and water injection amount of the soil sample.
When the outer water tank reaches the due pressure, the water injection valve is opened to inject water to the soil sample, the circumferential deformation and the axial deformation are observed in the water injection process, meanwhile, the weight change of the soil sample and the water injection flow are observed, and the data can be automatically recorded by the automatic recorder. When the water outlet pipe is used for discharging water, the soil sample is saturated, water injection is not needed any more, and the water injection valve is closed.
Step 5, drying: starting a heating air blower and an air pump, evaporating water in the soil sample by utilizing the heat of the hot air, observing a dryness sensor until the soil sample is completely dried, and gradually reducing the water pressure in an outer water tank according to the dryness of the soil sample while feeding the hot air; after the soil sample is dried, the deformation of the side wall of the sample chamber is recorded, the weight of the soil sample is recorded, and other physical parameters and hydrodynamic characteristic parameters of the soil under the condition of large burial depth are calculated through the numerical values measured in the saturated state and the dry state.
After each parameter of the saturated state of the soil sample is recorded, the water inlet is cut into the heating air blower, the water outlet pipe is switched to the air extracting pump, and the heating air blower and the air extracting pump are started, so that the soil sample chamber can be regarded as a ventilation plate, and air can pass through a gap of the soil. Under the combined action of the heating air blower and the air pump, hot air flows through the sample chamber from bottom to top, so that the soil sample in the sample chamber is heated, the moisture in the soil sample is gradually evaporated, and finally the soil sample is completely dried. The drying process may be performed by observing the data output by the dryness sensor. The dryness is usually detected by using a resistance measurement mode, and the dryness is judged according to resistance values measured at the upper end and the lower end of the soil sample.
Deformation of the sample chamber, as well as weight change, was recorded continuously during and after the soil sample was dried. Since the soil is contracted during the drying process, the pressure around the soil of the sample is also reduced, and thus the pressure of the outer tank is adjusted down according to the calculation to simulate the variation of the pressure reduction.
Finally, it should be noted that the above is only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred arrangement, it should be understood by those skilled in the art that the technical solution of the present invention (such as the specific structure of the water tank, the specific linking manner of the sample chambers, the sequence of steps, etc.) may be modified or replaced equivalently without departing from the spirit and scope of the technical solution of the present invention.
Claims (6)
1. A system for measuring hydrodynamic characteristics of soil with large burial depth, comprising: the automatic constant pressure pressurizing device comprises an outer layer box body which is made of rigid materials and is provided with an automatic constant pressure pressurizing facility, at least one sample chamber which is made of elastic materials is arranged in the outer layer box body, the bottom of the sample chamber is fixed at the bottom of the outer layer box body and is provided with a sample port which can be filled with soil samples, a sealing cover is arranged on the sample port, a water inlet port which is connected with a water vapor pressurizing facility is arranged on the sealing cover, a water outlet pipe is arranged at the top of the sample chamber, the top of the sample chamber is in a suspended state which can float up and down, permeable stones are respectively arranged at the top and bottom of the soil samples in the sample chamber, the top of the outer layer box body is connected with a pressurizing water pump controlled by the water pressure sensor, the bottom of the outer layer box body is provided with a pressure relief valve controlled by the water pressure sensor, the side wall of the sample chamber is provided with a deformation sensor which comprises a circumferential deformation sensor and an axial deformation sensor, a weighing sensor and a dryness sensor are arranged in the sample chamber, the weighing sensor is in a suspended state which can float up and down, and the dryness sensors are respectively arranged at the top and the bottom of the sample are respectively arranged at two electrodes.
2. The system of claim 1, wherein the outer tank is provided with a viewing facility.
3. The system of claim 2, wherein the water pressurization facility comprises a siphon with a water filling valve and a flow meter, and a high level water storage tank connected to the siphon, the high level water storage tank having a bottom that exceeds the top of the sample chamber.
4. A system according to any one of claims 1-3, wherein the top and bottom of the sample chamber are provided with water distribution means, respectively.
5. The system of claim 4, wherein the water inlet of the sample chamber is connected to a heating blower and the water outlet is connected to a suction pump.
6. A method for measuring hydrodynamic characteristics of large-burial-depth soil using the system of claim 5, wherein the method comprises the steps of:
step 1, obtaining a soil sample: obtaining a soil sample in a field of a research area, and measuring the depth, weight, temperature and humidity of the soil sample in situ;
step 2, filling a soil sample: loading a soil sample into the sample chamber from the bottom of the sample chamber, and tightly covering the sealing cover, wherein the circumferential deformation sensor and the axial deformation sensor of the side wall of the sample chamber are set to be zero, and the weight of the sample is checked through the weighing sensor;
step 3, pressurizing: calculating the pressure of the soil sample in situ according to the environment of obtaining the soil sample in the field, starting the pressurizing facility to inject water into the outer water tank and achieving the calculated pressure so as to simulate the pressure of the soil sample in situ, and recording the deformation of the side wall of the sample chamber, including the circumferential deformation and the axial deformation;
step 4, water injection: opening a water injection valve, injecting water to the soil sample until the water flow of the water outlet pipe flows out, at the moment, saturating the soil sample, closing the water injection valve, and recording the saturated circumferential deformation and axial deformation of the soil sample, and the saturated weight and water injection of the soil sample;
step 5, drying: starting a heating air blower and an air pump, evaporating water in the soil sample by utilizing the heat of the hot air, observing a dryness sensor until the soil sample is completely dried, and gradually reducing the water pressure in an outer water tank according to the dryness of the soil sample while feeding the hot air; after the soil sample is dried, the deformation of the side wall of the sample chamber is recorded, the weight of the soil sample is recorded, and other physical parameters and hydrodynamic characteristic parameters of the soil under the condition of large burial depth are calculated through the numerical values measured in the saturated state and the dry state.
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