CN210982151U - Road foundation soil unsaturated permeability coefficient measuring system - Google Patents
Road foundation soil unsaturated permeability coefficient measuring system Download PDFInfo
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- CN210982151U CN210982151U CN201921324626.2U CN201921324626U CN210982151U CN 210982151 U CN210982151 U CN 210982151U CN 201921324626 U CN201921324626 U CN 201921324626U CN 210982151 U CN210982151 U CN 210982151U
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Abstract
The utility model relates to a road engineering field especially relates to a road bed soil unsaturated permeability coefficient measurement system. The utility model provides a roadbed soil unsaturated permeability coefficient measuring system, which comprises a sample accommodating device and a water supply device, wherein the sample accommodating device comprises a sample accommodating part, a temperature measuring device and a matrix suction measuring device are also arranged in a sample accommodating cavity, the system also comprises a top cover for covering an upper opening of the sample accommodating part, and the top cover is detachably connected with the sample accommodating part; the sample accommodating piece further comprises an air guide channel, a water inlet channel and a water drainage channel. The utility model provides a road bed soil unsaturated permeability coefficient measurement system and measurement method that corresponds thereof has characteristics such as function integration, simple operation, control are accurate, can gather dynamic data in real time at experimental overall process to check through inside and improve measurement accuracy by a wide margin, realize the automatic measurement to unsaturated permeability coefficient under the change of soil sample moisture content.
Description
Technical Field
The utility model relates to a road engineering field especially relates to a road bed soil unsaturated permeability coefficient measurement system and relevant measuring method thereof.
Background
In road engineering, groundwater permeates into an upper soil matrix under the capillary action of pores among soil particles, and rising of the groundwater and infiltration of precipitation and migration of film water cause fluctuation of water content in the soil matrix and reduction of dry density of a soil body, often cause the problems of roadbed strength attenuation, deformation instability, freeze thawing, slurry turning and the like, and harm the safety, stability, long-term effect and durability of traffic infrastructure. The permeability coefficient is an important index for representing the resistance of roadbed soil to moisture migration and maintaining strength and stability, and a corresponding test method has been proposed for measuring the permeability coefficient of a saturated soil sample in the highway geotechnical test regulation. Currently, relevant scholars and scientific research institutions have developed corresponding measuring devices for unsaturated permeability coefficients of roadbed soil, but the existing test method and device have the following key problems to be solved urgently: (1) the initial state of the soil sample, such as water content, compactness, porosity and the like, is difficult to accurately control in the sample preparation process; (2) the soil sample has small size and is greatly influenced by the variability of soil body and the scale shrinkage effect; (3) the structure is complex, the operation is complicated, test data are observed and recorded through naked eyes, and the accuracy of a test result depends on the proficiency of an operator; (4) the water content and the permeability coefficient of the soil sample at a specific moment can only be obtained, and the change rule of the permeability coefficient along with the water content or the saturation in the whole test process cannot be obtained.
SUMMERY OF THE UTILITY MODEL
In view of the above-mentioned shortcomings of the prior art, the present invention is directed to a roadbed soil unsaturated permeability coefficient measuring system and a related measuring method thereof, which are used for solving the problems in the prior art.
In order to achieve the above and other related objects, an aspect of the present invention provides a roadbed soil unsaturated permeability coefficient measuring system, including a sample accommodating device and a water supply device, where the sample accommodating device includes a sample accommodating part, the sample accommodating part includes a sample accommodating cavity with an upper opening, a porous buffer layer is disposed at the bottom of the sample accommodating cavity, a temperature measuring device and a matrix suction measuring device are further disposed in the sample accommodating cavity, the system further includes a top cover for covering the upper opening of the sample accommodating part, and the top cover is detachably connected with the sample accommodating part;
the sample holds piece still includes air guide passageway, inhalant canal and drainage channel, water supply installation passes through inhalant canal and porous buffer layer intercommunication, porous buffer layer still passes through drainage channel and outside intercommunication, the top that the sample held the chamber is through air guide passageway and outside intercommunication.
In some embodiments of the present invention, the porous buffer layer comprises a permeable stone layer and a filter paper layer, and the filter paper layer covers the surface of the permeable stone layer.
In some embodiments of the present invention, the side wall of the sample holder is provided with a detection device accommodating cavity, and the temperature measuring device and the matrix suction measuring device are located in the detection device accommodating cavity.
In some embodiments of the present invention, the detection device receiving cavity runs through the side wall of the sample receiving member, and the temperature measuring device and the matrix suction measuring device are closely attached to the detection device receiving cavity.
The utility model discloses in some embodiments, including three or more matrix suction measuring device, matrix suction measuring device holds the extending direction in chamber at the sample and staggers evenly distributed, and is preferred, holds the extending direction in chamber at the sample, and the interval between the matrix suction measuring device is 5 ~ 10 cm.
The utility model discloses in some embodiments, can dismantle through the mounting between top cap and the sample holds and be connected, the preferred dead lever that extending direction and sample hold an extending direction unanimity that holds of mounting, the one end and the sample of dead lever hold a fixed connection, and the other end can be dismantled with the top cap and be connected, more preferably threaded connection.
In some embodiments of the present invention, a flow control device is disposed on the water inlet channel and/or the water outlet channel.
In some embodiments of the present invention, the sample accommodating chamber has a height of 20-40 cm and a volume of 1570cm3～12560cm3The permeability coefficient of the permeable stone layer is more than or equal to 10-3cm/s, and the permeability coefficient of the filter paper layer is more than or equal to 10-3cm/s, the sample holding cavity is preferably cylindrical, and the diameter of the cylindrical section is 10-20 cm.
In some embodiments of the present invention, the apparatus further comprises a data acquisition device in signal connection with the temperature measurement device and the matrix suction measurement device.
The utility model discloses another aspect provides a road bed soil unsaturated permeability coefficient measuring method, uses road bed soil unsaturated permeability coefficient measurement system, include:
A) filling a sample in the sample accommodating cavity;
B) introducing a water body into the sample accommodating cavity through the water inlet channel;
C) acquiring temperature parameters and substrate suction parameters of a sample;
D) acquiring the volume water content of the sample according to the matrix suction parameter provided in the step C), and acquiring the amount of seepage water of the sample according to the variation of the volume water content;
E) obtaining the permeation speed of the sample according to the permeation water amount of the sample provided in the step D);
F) acquiring a pressure water head of the sample according to the matrix suction parameters provided in the step C);
G) acquiring the hydraulic slope of the sample according to the pressure water head provided in the step F);
H) and obtaining the unsaturated permeability coefficient of the roadbed soil according to the permeability speed of the sample provided by the step E) and the hydraulic gradient of the sample provided by the step G).
In some embodiments of the present invention, in step a), in the sample accommodating chamber, the height of the sample is 20-40 cm, the diameter is 10-20 cm, and the size of the sample matches with the sample accommodating chamber;
in some embodiments of the invention, in step C), the monitoring is performed until the reading of the substrate suction measuring device on the uppermost layer is stable.
Drawings
Fig. 1 shows the overall structure of the present invention.
Fig. 2 shows a schematic structural diagram of the sample accommodating device of the present invention.
Fig. 3 shows a schematic view of sample loading in example 1 of the present invention.
Fig. 4 is a schematic diagram showing the experimental results of embodiment 1 of the present invention.
Description of the element reference numerals
1 sample accommodating device
11 sample holder
111 sample holding cavity
112 porous buffer layer
1121 layer of water permeable stone
1122 filter paper layer
113 detection device accommodating cavity
114 air guide channel
115 water inlet channel
116 drainage channel
117 flow control device
12 temperature measuring device
13 matrix suction measuring device
14 Top cover
15 fixing piece
2 Water supply device
21 liquid level height measuring device
22 water body conveying device
3 data acquisition device
4 pressure bar
Detailed Description
In order to make the objects, technical solutions and advantageous technical effects of the present invention clearer, the present invention is further described in detail with reference to the following embodiments. It should be understood that the embodiments described in this specification are only for the purpose of explaining the present invention, and are not intended to limit the present invention.
Please refer to fig. 1 to 4. It should be understood that the structure, ratio, size and the like shown in the drawings attached to the present specification are only used for matching with the content disclosed in the specification, so as to be known and read by those skilled in the art, and are not used for limiting the limit conditions that the present invention can be implemented, so that the present invention has no technical essential meaning, and any structure modification, ratio relationship change or size adjustment should still fall within the scope that the technical content disclosed in the present invention can cover without affecting the function that the present invention can produce and the purpose that the present invention can achieve. Meanwhile, the terms such as "upper", "lower", "left", "right", "middle" and "one" used in the present specification are for convenience of description, and are not intended to limit the scope of the present invention, and changes or adjustments of the relative relationship thereof may be made without substantial technical changes, and the present invention is also regarded as the scope of the present invention.
The utility model discloses a first aspect provides a road bed soil unsaturated permeability coefficient measurement system, as shown in fig. 1-2, road bed soil unsaturated permeability coefficient measurement system can include sample accommodate device 1 and water supply installation 2, sample accommodate device 1 includes sample accommodate piece 11, sample accommodate piece 11 includes sample hold chamber 111 that the upper shed is opened, the bottom in sample hold chamber 111 is equipped with porous buffer layer 112, still be equipped with temperature measuring device 12 and matrix suction measuring device 13 in sample hold chamber 111, still include and be used for covering top cap 14 that the upper shed is opened on sample accommodate piece 11, can dismantle between top cap 14 and the sample accommodate piece 11 and be connected; the sample accommodating member 11 further includes an air guide passage 114, a water inlet passage 115, and a water discharge passage 116, the water supply device is communicated with the porous buffer layer 112 through the water inlet passage 115, the porous buffer layer 112 is further communicated with the outside through the water discharge passage 116, and the top of the sample accommodating chamber 111 is communicated with the outside through the air guide passage 114. The roadbed soil unsaturated permeability coefficient measuring system can be used for measuring the roadbed soil unsaturated permeability coefficient, when the roadbed soil unsaturated permeability coefficient measuring system is used, a sample can be filled in a sample accommodating cavity, then a water body in the water supply device 2 is introduced into the sample accommodating cavity through a water inlet channel, the temperature parameter and the matrix suction parameter of the sample can be obtained through the temperature measuring device 12 and the matrix suction measuring device 13, the change of the parameters relative to time is monitored, the volume water content of the sample, the permeability speed of the sample, the pressure head of the sample and the hydraulic gradient of the sample can be further obtained respectively according to the provided matrix suction parameter and the matrix suction parameter, and the roadbed soil unsaturated permeability coefficient can be further obtained according to the permeability speed of the sample and the hydraulic gradient of the sample.
The utility model provides an among the unsaturated permeability coefficient measurement system of roadbed soil, porous buffer layer 112 is used for transporting water evenly to the sample bottom generally, and porous buffer layer 112 has certain osmotic coefficient usually, and it can be with sample bottom fully contact, and the contact surface is level and smooth relatively usually to guarantee that sample bottom can not take place excessive deformation on the whole. The utility model discloses a specific embodiment, porous buffer layer 112 can include permeable stone layer 1121 and filter paper layer 1122, filter paper layer 1122 can cover in permeable stone layer 1121 surface, and the bottom and the filter paper layer 1122 contact of sample, and the thickness on permeable stone layer can be 1 ~ 1.5cm, and the osmotic coefficient on permeable stone layer is more than or equal to 10-3cm/s, and the permeability coefficient of the filter paper layer is more than or equal to 10-3cm/s。
The utility model provides an among the unsaturated permeability coefficient measurement system of roadbed soil, can include a plurality of matrix suction measuring device 13 usually, preferably can include more than three, more than four, more than five or more matrix suction measuring device 13, matrix suction measuring device 13 holds the extending direction of chamber 111 at the sample and staggers evenly distributed to can monitor the parameter variation of each part of sample fully. In a specific embodiment of the present invention, the temperature measuring device 12 and the substrate suction measuring device 13 are both located on the side wall of the sample accommodating chamber 111, the number of the substrate suction measuring devices 13 is five or more, and the interval between the substrate suction measuring devices 13 is 5 to 10cm in the extending direction of the sample accommodating chamber 111 (i.e., the height direction of the sample accommodating device 1).
The utility model provides an among the unsaturated permeability coefficient measurement system of roadbed soil, can be equipped with detection device in the sample holds piece 11 and hold chamber 113, temperature measuring device 12 and matrix suction measuring device 13 can be located detection device and hold chamber 113. The positions and the number of the detecting means accommodating chambers 113 generally correspond to the positions where the temperature measuring means 12 and the substrate suction measuring means 13 are required to be disposed. One or more measuring devices may be provided in the same detecting device accommodating chamber 113. In a specific embodiment of the present invention, the detection device accommodating cavity 113 runs through the side wall of the sample accommodating member 11, and the temperature measuring device 12 and the substrate suction measuring device 13 are closely attached to the detection device accommodating cavity 113, so that the installation and use of the measuring device can be facilitated. In another embodiment of the present invention, the detection device receiving cavity 113 includes a first device receiving cavity for receiving the temperature measuring device 12 and a second device receiving cavity for receiving the substrate suction measuring device 13.
The utility model provides an among the unsaturated permeability coefficient measurement system of roadbed soil, top cap 14 and sample hold and can dismantle through mounting 15 between the piece 11 and be connected, the mounting can be located the sample generally and hold outside the chamber 111. In a specific embodiment of the present invention, the fixing member 15 is a fixing rod whose extending direction is the same as the extending direction of the sample holder 11, one end of the fixing member is connected to the sample holder 11 (the sample holder 11 may preferably include a base, and one end of the fixing member 15 may be fixedly connected to the base), and the other end of the fixing member is detachably connected to the top cover 14, and more preferably connected to a screw, for example, a thread may be disposed on a side wall of the fixing rod, and an outer diameter of the top cover 14 is generally larger than an outer diameter of an outer side wall of the sample holder 11, so that a screw hole matched with the thread may be disposed at a corresponding position of. In another embodiment of the present invention, a plurality of fixing members 15 may be included, the plurality of fixing members 15 being evenly circumferentially distributed around the sample holder 11.
The utility model provides an among the unsaturated permeability coefficient measurement system of roadbed soil, sample holds a 11 can include the base, can be equipped with open specimen cylinder holding tank on the base, the diameter of the cross section of specimen cylinder holding tank cooperatees with the external diameter that the sample holds a 11 usually, thereby can stretch into the specimen cylinder holding tank with the bottom that the sample holds a 11, and realize the inseparable suit of the outer wall that the sample holds a 11 and specimen cylinder holding tank inner wall, still further be equipped with porous buffer layer holding tank in the specimen cylinder holding tank, the diameter of the cross section of porous buffer layer holding tank cooperatees with the internal diameter that the sample holds a 11 usually, thereby can cooperate with the inner space that the sample holds a 11, both form columniform sample jointly and hold the chamber. In a specific embodiment of the present invention, the height of the sample accommodating cavity 111 can be 20-40 cm, and the volume can be 1570cm3～12560cm3The sample accommodating cavity 111 is preferably cylindrical, and the diameter of the cylindrical section can be 10-20 cm.
The utility model provides an among the unsaturated permeability coefficient measurement system of roadbed soil, be equipped with flow control device 117 on inhalant canal 115 and/or the drainage channel 116 to can be when needs the switching or adjust the flow of water in the passageway, flow control device can be valve etc. usually. In a particular embodiment of the invention, the water inlet channel and the water discharge channel may be located in the base.
The utility model provides an among the unsaturated permeability coefficient measurement system of roadbed soil, among the water supply installation 2, the level of water is higher than the sample on the whole and holds the piece to can introduce the sample with the water through gravity and hold the chamber. The water supply device 2 may be generally provided with a liquid level height measuring device 21, so as to collect the variation of the water body in the water supply device 2, and the liquid level height measuring device 21 may be a liquid level meter or the like. The water supply 2 may also be in fluid communication with a water delivery device 22, such that the amount of water in the water supply 2 may be replenished by the water delivery device 22, which water delivery device 22 may be a water pump or the like.
The utility model provides an among the unsaturated permeability coefficient measurement system of roadbed soil, can also include data acquisition device 3, data acquisition device 3 can with temperature measuring device 12 and matrix suction measuring device 13 signal connection to be used for receiving the temperature data and the matrix suction data of the sample that temperature measuring device 12 and matrix suction measuring device 13 gathered and obtained. The data acquisition device 3 can also be in signal connection with the liquid level height measurement device 21, so as to be used for receiving the water body variation in the water supply device 2 acquired by the liquid level height measurement device 21. The data acquisition device 3 may also convert acquired data (for example, temperature data, matrix suction data, and the like) to calculate the unsaturated permeability coefficient of the roadbed soil of the obtained sample, and the data acquisition device 3 may specifically be a computer, a single chip, or the like.
The utility model provides an among the unsaturated permeability coefficient measurement system of roadbed soil, can also include display device, display device is usually with 3 signal connection of data acquisition device to can be used for showing the data of required output. The display device may specifically be a display or the like.
The utility model discloses the second aspect provides a method for measuring unsaturated permeability coefficient of roadbed soil, through the utility model discloses the unsaturated permeability coefficient of roadbed soil measurement system that the first aspect provided measures, include:
A) filling a sample in the sample accommodating cavity;
B) introducing a water body into the sample accommodating cavity through the water inlet channel;
C) acquiring temperature parameters and substrate suction parameters of a sample;
D) acquiring the volume water content of the sample according to the matrix suction parameter provided in the step C), and acquiring the amount of seepage water of the sample according to the variation of the volume water content;
E) obtaining the permeation speed of the sample according to the permeation water amount of the sample provided in the step D);
F) acquiring a pressure water head of the sample according to the matrix suction parameters provided in the step C);
G) obtaining hydraulic slope drop according to the pressure water head provided in the step F);
H) and obtaining the unsaturated permeability coefficient of the roadbed soil according to the permeation speed of the sample provided by the step E) and the hydraulic gradient provided by the step G).
The utility model provides a method for measuring unsaturated permeability coefficient of roadbed soil can include: the sample is filled in the sample accommodating cavity, the sample can be various types of soil samples and the like generally, the height of the obtained sample can be 20-40 cm, the diameter can be 10-20 cm, the size of the sample is matched with the sample accommodating cavity, and the sample accommodating cavity generally has certain compactness. The person skilled in the art can select an appropriate method for filling the sample accommodating chamber with the sample, and for example, a pressing rod or the like can be used.
The utility model provides a method for measuring unsaturated permeability coefficient of roadbed soil can include: and introducing the water body into the sample accommodating cavity through the water inlet channel. In the water supply device, the water body is higher in level than the sample accommodating member as a whole, so that the water body can be introduced into the sample accommodating chamber by gravity.
The utility model provides a method for measuring unsaturated permeability coefficient of roadbed soil can include: and acquiring the temperature parameter and the substrate suction parameter of the sample. The temperature parameter and the substrate suction parameter of the specimen can be monitored by the temperature measuring device 12 and the substrate suction measuring device 13. Generally, it is desirable to monitor at least the reading of the substrate suction measurement device at the uppermost layer for stability throughout the test.
The utility model provides a method for measuring unsaturated permeability coefficient of roadbed soil can include: and C), acquiring the volume water content of the sample according to the matrix suction parameters provided in the step C), and acquiring the permeation water volume of the sample according to the variation of the volume water content. For a specific sample, the matrix suction parameter and the volume water content of the sample usually have a fixed relation, and before measurement, the corresponding relation between the matrix suction and the volume water content on the soil-water characteristic curve can be obtained through a standard sample experiment. In a specific embodiment of the present invention, the method for obtaining the volumetric water content of the sample by calculating the substrate suction parameter specifically includes: and (3) calculating and obtaining the permeation water quantity Q/A of the sample according to the formula:
wherein △ w is the variation of the volume water content, L is the height (cm) of the sample, and h is the vertical distance (cm) from the layer to the bottom of the sample;
the utility model provides a method for measuring unsaturated permeability coefficient of roadbed soil can include: and D) obtaining the permeation speed of the sample according to the permeation water quantity of the sample provided in the step D). The utility model discloses a concrete embodiment, the method of the infiltration rate of obtaining the sample through the calculation of volume moisture content specifically can include: the permeation velocity v of the sample is obtained by calculation according to equation 2:
wherein Q is the amount of water permeated (L) in a soil sample at a certain layer in time t, and A is the cross-sectional area (cm) of the sample2) V is the permeation velocity (cm/s) and t is the time(s);
the utility model provides a method for measuring unsaturated permeability coefficient of roadbed soil can include: acquiring the pressure head of the sample according to the matrix suction parameters provided by the step C). In a specific embodiment of the present invention, the method for obtaining the pressure head of the sample by calculating the suction parameter of the matrix specifically includes: and calculating to obtain the pressure head of the sample according to the formula 4:
hp＝-uw/γw＝S/γw(formula 4)
In the formula, hpIs a pressure head (cm); s is substrate suction (kPa); u. ofwPore water pressure (kPa); gamma raywIs the gravity of water (N/cm)3) The water gravity is the density of the water.
The utility model provides a method for measuring unsaturated permeability coefficient of roadbed soil can include: obtaining hydraulic slope drop according to the pressure water head provided in the step F). In a specific embodiment of the present invention, the method for obtaining the hydraulic slope of the sample through the calculation of the pressure head may specifically include: calculating and obtaining the hydraulic gradient of the sample according to the formula 6:
J＝dH/dh＝dhp/dh +1 (formula 6)
Wherein J is hydraulic slope, H is total head (cm), HpIs the pressure head (cm).
The utility model provides a method for measuring unsaturated permeability coefficient of roadbed soil can include: and obtaining the unsaturated permeability coefficient of the roadbed soil according to the permeation speed of the sample provided by the step E) and the hydraulic gradient provided by the step G). In an embodiment of the present invention, the unsaturated permeability coefficient of the roadbed soil is calculated and obtained according to the formula 1
kJ (formula 1)
In the formula, k is a permeability coefficient (cm/s), v is a permeability speed (cm/s), and J is a hydraulic gradient.
The utility model provides a method for measuring unsaturated permeability coefficient of roadbed soil can also include: and C) acquiring the unsaturated permeability coefficient at the standard temperature according to the temperature parameter of the sample and the unsaturated permeability coefficient provided in the step H). In an embodiment of the present invention, the unsaturated permeability coefficient at the standard temperature is calculated and obtained according to equation 7
In the formula: k is a radical of20The unsaturated permeability coefficient (cm/s) at the standard temperature (20 ℃), η the kinetic viscosity coefficient (kPa · s) of water at the test temperature, η20Is the dynamic viscosity coefficient (kPa. s) of water at the standard temperature (20 ℃), η/η20Can consult the regulations on road soil engineering tests.
As above, the utility model provides a road bed soil unsaturated permeability coefficient measurement system and measurement method that corresponds thereof has characteristics such as function integration, simple operation, control are accurate, can gather dynamic data in experimental overall process in real time to check through inside and improve measurement accuracy by a wide margin, realize the automatic measurement to unsaturated permeability coefficient under the change of soil sample moisture content. The utility model discloses fully agree with actual engineering background, can provide necessary technical support for the evolution law prediction etc. of road disease under the engineering risk assessment, the moisture seepage flow effect of road bed filling under the humidity migration condition.
The following description of the embodiments of the present invention is provided for illustrative purposes, and other advantages and effects of the present invention will be readily apparent to those skilled in the art from the disclosure herein. The present invention can also be implemented or applied through other different specific embodiments, and various details in the present specification can be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.
Example 1
Adopt the utility model provides a road bed soil unsaturated permeability coefficient measuring device and test method measures the unsaturated permeability coefficient of the residual soil of Gannan granite to compare with the test result of matrix suction triaxial apparatus, matrix suction triaxial apparatus in this embodiment adopts 28-WF4005 type that Italy Controls company produced, and follows its operation regulation.
(1) The sample tube that adopts in this embodiment is 30cm high, the internal diameter is 10cm, a pedestal, the sleeve, depression bar etc. all form a complete set with it, base thickness is 2 ~ 3cm, be equipped with the sample tube holding tank of upper open mouth in the middle of the base, and closely suit with the outer wall of sample tube bottom, still further be equipped with porous buffer layer holding tank in the sample tube holding tank (highly being 1.5cm, the internal diameter is 10cm), its shape is unanimous with sample tube inner wall shape, both form columniform sample jointly and hold the chamber, still be equipped with inhalant canal and drainage channel in the base, communicate with each other with porous buffer layer holding tank respectively. The parts such as the sample cylinder, the base, the sleeve, the pressure lever, the top cover and the like are all made of stainless steel. The porous buffer layer holding tank (namely the bottom of the sample holding cavity) is provided with the permeable stone, the permeable stone is covered with filter paper with equal size, the filter paper is fully contacted with the sample, and the permeability coefficient of the permeable stone and the filter paper is2.5×10-3cm/s. The sample cylinder is provided with 5 substrate suction sensors and 1 temperature sensor, the substrate suction sensor is of HQTS type produced by Han Qin company, the distance between the access ports and the bottom of the sample cylinder is 5/10/15/20/25cm, the temperature sensor is of T10S-B type produced by Miao Xin company, and the distance between the access ports and the bottom of the sample cylinder is 15 cm.
(2) Weighing 4314.36g of soil sample, uniformly loading the soil sample into the sample cylinder in 12 layers, sequentially compacting the soil sample by a push rod, flattening a disc on the upper part of the push rod, matching the size of a round rod on the lower part with the inner diameters of the sample cylinder and the sleeve, tightly fitting and smoothly contacting the round rod and the inner walls of the sample cylinder and the sleeve, smoothly compacting the soil sample under the action of a press machine without resistance, and preventing soil particles from seeping out of gaps; the round rod is provided with scales, so that the compacted thickness of each layer of the soil sample can be conveniently controlled. After the sample in the sample cylinder is filled up, the sample containing cavity with the upper opening is covered by the top cover, the center of the top cover is provided with an air duct for communicating the sample with the atmosphere, the outer ring of the top cover is provided with a screw jack and a nut which are matched with a screw on the base, and the top cover is fastened on the sample cylinder.
(3) And (3) assembling the roadbed soil unsaturated permeability coefficient measuring device, introducing water into the porous buffer layer to drain air in the guide pipe and the permeable stone, starting and debugging a signal acquisition instrument and an operating system, connecting the temperature sensor and the matrix suction sensor into a sensor access port of the sample cylinder, and performing sealing and seepage prevention, wherein the sealing and seepage prevention of each part of the sample cylinder can perform seepage prevention work under mechanical action through a screw rod, a water-proof rubber ring, lubricating oil, vaseline, silicone grease and the like which are connected with the top cover and the base.
(4) Connect water supply installation and inlet channel, open inlet channel's valve and pipe wall drainage channel's valve, begin the penetration test, its level of water among the water supply installation is higher than the sample on the whole and holds the piece to can hold the chamber with the sample with the water introduction through gravity, through the change of signal acquisition appearance and operating system real-time recording temperature, matrix suction, water level in the test process.
(5) And after the reading of the uppermost substrate suction sensor is stable, the test is finished.
The processing method for processing the test data by the calculation method comprises the following steps:
(6) calculating the permeability coefficients of the sample at different saturation degrees according to Darcy's theorem (formula 1):
kJ (formula 1)
In the formula: k is the permeability coefficient (cm/s); v is the penetration speed (cm/s) and is calculated according to the formula 2-3; j is hydraulic slope and is calculated according to the formula 4-6.
Wherein Q is the amount of water (L) permeated by a soil sample at a certain layer in time t, and A is the cross-sectional area (cm) of the sample2) (ii) a v is the permeation velocity (cm/s); t is time(s).
And (3) acquiring the matrix suction change of the soil sample of each layer within the time t through a matrix suction sensor, obtaining the volume water content change of the soil sample of each layer within the time t according to the corresponding relation between the matrix suction and the volume water content on the soil-water characteristic curve, and fitting to obtain a volume water content change curve from the bottom to the top of the sample within the time t.
According to the utility model discloses a testing device and infiltration principle are easily known, and in time t, the infiltration water yield Q/A through certain position soil sample on the unit area is promptly: the envelope area of the curve from the level to the top of the sample, i.e. the integral of the change of the water content in volume from the level to the top of the sample (equation 3). In the test process, the test result can be checked by integrating the change of the water content from the bottom to the top of the sample within the time t (by doing so, the distribution condition of the water in the device can be known), and comparing the change of the water quantity of the water tank measured by the water level meter within the same time period.
Wherein △ w is the variation of the volume water content, L is the height (cm) of the sample, h is the vertical distance (cm) from the layer to the bottom of the sample, and the unit which is not marked is dimensionless.
Consider the utility model discloses a penetration test device and atmosphere intercommunication, the inside atmospheric pressure of device equals atmospheric pressure, therefore matrix suction is negative pore water pressure promptly, and the ratio of pore water pressure and the weight of water is pressure head (formula 4). Therefore, the pressure water heads of soil samples at different positions at different moments can be obtained through the matrix suction sensor.
hp＝-uw/γw＝S/γw(formula 4)
In the formula: h ispIs a pressure head (cm); s is substrate suction (kPa); u. ofwPore water pressure (kPa); gamma raywIs the gravity of water (N/cm)3) The water gravity is the density of the water.
And calculating the total water head of the soil sample at a certain layer at any moment according to the formula 5.
H＝hv+hp+ h (formula 5)
In the formula: h is the total head (cm); h isvIs the velocity head (cm).
The velocity head can be ignored, considering that the flow rate of water in the unsaturated soil penetration test is extremely small. And calculating the hydraulic slope drop J of the soil sample at a certain position at any time according to the formula 6.
J＝dH/dh＝dhp/dh +1 (formula 6)
(7) And (3) acquiring the test temperature through a temperature sensor, and calculating according to the formula 7 to obtain the unsaturated permeability coefficient at the standard temperature.
In the formula: k is a radical of20The unsaturated permeability coefficient (cm/s) at the standard temperature (20 ℃), η the kinetic viscosity coefficient (kPa · s) of water at the test temperature, η20Is the dynamic viscosity coefficient (kPa. s) of water at the standard temperature (20 ℃), η/η20Can consult the regulations on road soil engineering tests.
(8) And establishing a corresponding relation between the permeability coefficient and the matrix suction measured by the matrix suction sensor at the same time, namely a relation between the permeability coefficient and the volume water content (saturation), so as to obtain a change rule of the unsaturated permeability coefficient along with the saturation. The penetration test process is easy to know, and the sample is gradually saturated from the bottom to the top, so that test data and change situations measured by matrix suction sensors at different layers are represented as time lag and regular consistency, and the measurement accuracy of the unsaturated permeability coefficient of the roadbed soil can be greatly improved through mutual inspection.
The results were compared with those of a matrix suction triaxial apparatus, and the test results are shown in FIG. 4. The permeability coefficient-matrix suction curve measured by 5 matrix suction sensors is quite consistent, the relative error is less than 1.9%, the relative error is consistent with the result of a triaxial apparatus, and the goodness-of-fit judgment coefficient is as high as 94.7%.
In addition, in the embodiment based on the utility model provides a road bed soil unsaturated permeability coefficient measuring device 22.75h when experimental usefulness of test method, 36.5h when conventional matrix suction triaxial apparatus penetration test shortens test time 37.7%, and obtains 5 experimental data of group, can provide experimental precision through mutual check-up, has further improved the accuracy of data.
To sum up, the utility model discloses various shortcomings in the prior art have effectively been overcome and high industry value has.
The above embodiments are merely illustrative of the principles and effects of the present invention, and are not to be construed as limiting the invention. Modifications and variations can be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which may be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (10)
1. The system for measuring the unsaturated permeability coefficient of the roadbed soil is characterized by comprising a sample accommodating device (1) and a water supply device (2), wherein the sample accommodating device (1) comprises a sample accommodating part (11), the sample accommodating part (11) comprises a sample accommodating cavity (111) with an upper opening, a porous buffer layer (112) is arranged at the bottom of the sample accommodating cavity (111), a temperature measuring device (12) and a matrix suction measuring device (13) are further arranged in the sample accommodating cavity (111), a top cover (14) for covering the upper opening of the sample accommodating part (11) is further included, and the top cover (14) is detachably connected with the sample accommodating part (11);
the sample accommodating piece (11) further comprises an air guide channel (114), a water inlet channel (115) and a water drainage channel (116), the water supply device is communicated with the porous buffer layer (112) through the water inlet channel (115), the porous buffer layer (112) is further communicated with the outside through the water drainage channel (116), and the top of the sample accommodating cavity (111) is communicated with the outside through the air guide channel (114).
2. The roadbed soil unsaturated permeability coefficient measuring system according to claim 1, wherein the porous buffer layer (112) comprises a permeable stone layer (1121) and a filter paper layer (1122), and the filter paper layer (1122) covers the surface of the permeable stone layer (1121);
and/or a detection device accommodating cavity (113) is arranged on the side wall of the sample accommodating part (11), and the temperature measuring device (12) and the matrix suction measuring device (13) are positioned in the detection device accommodating cavity (113).
3. The system for measuring the unsaturated permeability coefficient of subgrade soil according to claim 2, characterized in that the detection device accommodating cavity (113) penetrates through the side wall of the sample accommodating part (11), and the temperature measuring device (12) and the matrix suction measuring device (13) are tightly attached to the detection device accommodating cavity (113).
4. The system for measuring the unsaturated permeability coefficient of subgrade soil according to claim 1, characterized by comprising more than three matrix suction measuring devices (13), wherein the matrix suction measuring devices (13) are uniformly distributed in the extending direction of the sample accommodating cavity (111) in a staggered mode.
5. The system for measuring the unsaturated permeability coefficient of roadbed soil according to claim 4, wherein the interval between the matrix suction measuring devices (13) in the extending direction of the sample holding cavity (111) is 5-10 cm.
6. The system for measuring the unsaturated permeability coefficient of subgrade soil according to claim 1, characterized in that the top cover (14) is detachably connected with the sample accommodating part (11) through a fixing part (15).
7. The system for measuring the unsaturated permeability coefficient of subgrade soil according to claim 6, characterized in that the fixing piece (15) is a fixing rod with the extending direction consistent with the extending direction of the sample accommodating piece (11), one end of the fixing rod is fixedly connected with the sample accommodating piece (11), and the other end is detachably connected with the top cover (14).
8. The system for measuring the unsaturated permeability coefficient of subgrade soil according to claim 1, characterized in that a flow control device (117) is arranged on the water inlet channel (115) and/or the water outlet channel (116).
9. The system for measuring the unsaturated permeability coefficient of roadbed soil according to claim 1, wherein the height of the sample accommodating cavity (111) is 20-40 cm, and the volume is 1570cm3～12560cm3The permeability coefficient of the permeable stone layer is more than or equal to 10-3cm/s, and the permeability coefficient of the filter paper layer is more than or equal to 10-3cm/s, the sample accommodating cavity (111) is cylindrical, and the diameter of the cylindrical section is 10-20 cm.
10. The system for measuring the unsaturated permeability coefficient of the subgrade soil according to the claim 1, further comprising a data acquisition device (3), wherein the data acquisition device (3) is in signal connection with the temperature measurement device (12) and the matrix suction measurement device (13).
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN110426336A (en) * | 2019-08-15 | 2019-11-08 | 同济大学 | A kind of subgrade soils Unsaturated Hydraulic Conductivity measuring system and its relevant measurement method |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110426336A (en) * | 2019-08-15 | 2019-11-08 | 同济大学 | A kind of subgrade soils Unsaturated Hydraulic Conductivity measuring system and its relevant measurement method |
| CN110426336B (en) * | 2019-08-15 | 2024-10-01 | 同济大学 | Roadbed soil unsaturated permeability coefficient measurement system and related measurement method thereof |
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