CN114720342A - Dynamic seepage device and method for impact load - Google Patents
Dynamic seepage device and method for impact load Download PDFInfo
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- CN114720342A CN114720342A CN202110013979.6A CN202110013979A CN114720342A CN 114720342 A CN114720342 A CN 114720342A CN 202110013979 A CN202110013979 A CN 202110013979A CN 114720342 A CN114720342 A CN 114720342A
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- 238000000034 method Methods 0.000 title claims abstract description 12
- 239000002689 soil Substances 0.000 claims abstract description 30
- 239000000523 sample Substances 0.000 claims description 92
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 71
- 239000011148 porous material Substances 0.000 claims description 35
- 239000004576 sand Substances 0.000 claims description 30
- 229910000831 Steel Inorganic materials 0.000 claims description 13
- 239000010959 steel Substances 0.000 claims description 13
- 229910052802 copper Inorganic materials 0.000 claims description 12
- 239000010949 copper Substances 0.000 claims description 12
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 11
- 229920001971 elastomer Polymers 0.000 claims description 7
- 238000002474 experimental method Methods 0.000 claims description 7
- 239000011521 glass Substances 0.000 claims description 4
- 238000012360 testing method Methods 0.000 claims description 4
- 239000011324 bead Substances 0.000 claims description 3
- 230000000903 blocking effect Effects 0.000 claims description 3
- 238000005520 cutting process Methods 0.000 claims description 3
- 238000001035 drying Methods 0.000 claims description 3
- 230000003116 impacting effect Effects 0.000 claims description 3
- 230000003287 optical effect Effects 0.000 claims description 3
- 238000002360 preparation method Methods 0.000 claims description 3
- 238000005070 sampling Methods 0.000 claims description 3
- 238000012216 screening Methods 0.000 claims description 3
- 102100036790 Tubulin beta-3 chain Human genes 0.000 claims description 2
- 102100036788 Tubulin beta-4A chain Human genes 0.000 claims description 2
- 230000003247 decreasing effect Effects 0.000 claims 1
- 238000005325 percolation Methods 0.000 claims 1
- 229920006395 saturated elastomer Polymers 0.000 abstract description 8
- 238000011160 research Methods 0.000 abstract description 7
- 230000004044 response Effects 0.000 abstract description 5
- 238000006073 displacement reaction Methods 0.000 abstract description 3
- 230000009471 action Effects 0.000 description 10
- 230000008859 change Effects 0.000 description 3
- 230000007547 defect Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000007789 sealing Methods 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- 230000003068 static effect Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000000740 bleeding effect Effects 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000009863 impact test Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
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Abstract
The invention discloses an impact load dynamic seepage device and method. The invention aims at solving the problems that most of the prior sandy soil liquefaction problems are researched under the conditions of vibration load or large shear displacement, the non-drainage state is mostly kept in the research, the technical requirement of liquefaction response after the bottom of saturated sandy soil is impacted is rarely considered, and a dynamic seepage device and a method under the impact load are provided.
Description
Technical Field
The invention relates to an impact load dynamic seepage device and method, and belongs to the technical field of geotechnical engineering and geological engineering.
Background
The liquefaction response mechanism of the saturated sandy soil under the bottom impact is as follows: under the action of different impact pressures and different impact frequencies, the saturated sandy soil can form different pore water pressures, and when the pore water pressure at the same height is equal to the total pressure of the sandy soil, the saturated sandy soil is liquefied (even if the impact pressure is small, the saturated sandy soil is not liquefied, but the pore water pressure is also increased). Therefore, the device judges the relation between the impact load and the sandy soil liquefaction by determining the relation between the pore water pressure and the total pressure.
Saturated sandy soil can be liquefied under the action of vibration, impact, explosion and other dynamic loads, and is accompanied with the settlement of a sand surface, and in severe cases, a sand blasting and water bleeding phenomenon can also occur. The result is severe damage to the earthworks in mines, dams, docks, etc., resulting in significant casualties and property loss. At present, the device is rarely researched on equipment for liquefying the sand on the upper layer caused by the underground shock wave, and the device is favorable for simulating the research of liquefying saturated sand caused by the impact on the bottom.
At present, most of sandy soil liquefaction problem researches are completed under the conditions of vibration load or large shear displacement, a non-drainage state is mostly kept in the researches, and liquefaction response of the bottom of saturated sandy soil after impact is rarely considered. The impact equipment provided by the patent can well observe the sand sample change and liquefaction response when the sand is impacted at the bottom.
At present, the research on seepage action is mostly finished under a static load state, the influence of impact action on sandy soil on the seepage action is rarely considered, and the experimental device can analyze the change of the seepage speed under a dynamic load through data recorded by a sensor.
Disclosure of Invention
The technical problem to be solved by the invention is to overcome the defects of the prior art, and to overcome the defects in the prior equipment, the invention provides the device which has low manufacturing cost and simple structure and can carry out the impact test in the seepage state, thereby not only solving the problem of liquefying the sample by impacting the sample with specific frequency and size; the dynamic seepage problem under the impact action can be further researched by the device, and the impact load dynamic seepage device and the method are provided.
In order to solve the technical problem, the invention provides an impact load dynamic seepage device which comprises a loading device, a device main body and a water supply system, wherein the loading device is arranged in the device main body, and the water supply system is connected with the device main body.
As a preferred embodiment, the loading device comprises a speed-adjustable motor, a crankshaft, a connecting rod and an impact rod, wherein the output end of the speed-adjustable motor is connected with the crankshaft in a matching mode, the speed-adjustable motor drives the crankshaft to rotate, one end of the connecting rod is connected with the crankshaft, the other end of the connecting rod is connected with the impact rod, the head of the impact rod is provided with an impact head, a detachable spring is placed on the impact head, and a copper cap is installed above the spring.
As a better embodiment, the device main body comprises a sample cylinder, a box body base and a threaded rod, wherein the bottom of the box body base is fixedly connected with the threaded rod to form an integral support, and an optical axis for placing a balance weight is arranged in the box body base; the upper part of the integral bracket is provided with a steel hoop matched with the outer diameter of the sample cylinder; the integral bracket is provided with an upper flange and a lower flange which are symmetrically distributed up and down, the upper flange and the lower flange are vertically matched on the threaded rod through a first nut and a second nut to move and adjust the positioning height, and the side part of the lower flange is externally connected with a water inlet pipeline; the lower end of the sample cylinder is connected with the upper flange, and the inner bottom of the sample cylinder is provided with a filter box.
As a better embodiment, the box base is provided with a box base sliding rail at the opening position of the upper part of the box body, so as to ensure that the copper cap in the loading device runs smoothly up and down.
As a better embodiment, the aperture of the reserved threaded hole of the sample cylinder is respectively matched with the diameter of a sensor and the diameter of a drainage pipeline used for experiments, the threaded hole reserved at the topmost part of the sample cylinder is connected with the drainage pipeline, one side of the threaded holes with the symmetrical heights on the sample cylinder is inserted into a hole pressure sensor, and the other side of the threaded holes with the symmetrical heights on the sample cylinder is inserted into a pressure sensor.
As a preferred embodiment, a mesh copper cap is additionally arranged outside the probe of the pore pressure sensor.
As a preferred embodiment, the interior of the filter box consists of a layer of glass beads and a screen, so that not only is the sand sample prevented from falling into the upper flange, but also the water flow is ensured to uniformly flow through the sand surface.
As a preferred embodiment, the steel hoop is used for avoiding the shaking of the upper part of the sample cylinder caused by the overhigh height, and the rubber cushion layer is designed in the steel hoop and used for increasing the friction force between the steel hoop and the sample cylinder and increasing the stability.
As a preferred embodiment, the water supply system comprises a speed-adjustable water pump, a flow meter and a needle valve, wherein the left end of the needle valve is connected with the speed-adjustable water pump through a water inlet pipeline, the right end of the needle valve is connected with the flow meter, and the flow meter is connected with the device main body through the water inlet pipeline.
The invention also provides an impact load dynamic seepage method, which comprises the following steps:
step SS 1: preparing a sandy soil sample at a field sampling point by using a cutting ring, screening different types of sandy soil, and drying and storing;
step SS 2: the dry density of the sandy soil is measured according to the geotechnical test rule, the required volume of the sandy soil is obtained by calculation according to the inner diameter of the sample cylinder and the height of the highest position of the pore pressure sensor arranged on the sample cylinder, and the required dry sand mass is calculated according to the dry density of the sandy soil, wherein the formula is as follows:
m＝ρdv＝ρπr2h
wherein m is the dry sand mass required in sample preparation, rhodThe dry density of natural sand, v is the volume of the required dry sand, pi is the circumferential rate, r is the inner radius of the sample cylinder, and h is the highest position height of a pore pressure sensor arranged on the sample cylinder;
step SS 3: respectively connecting a hole pressure sensor and a pressure sensor into reserved threaded holes in the side wall of a sample cylinder, placing a filter box at the bottom of the sample cylinder, then, filling weighed sand samples into the sample cylinder in batches through a funnel, then, opening a needle valve, filling water into the sample cylinder until the water level reaches the position of the reserved threaded holes at the top of the sample cylinder, blocking the reserved threaded holes at two symmetrical positions at the top, and stopping water flow;
step SS 4: starting a speed-adjustable motor, impacting a lower flange plate by an impact rod, recording data of a sensor probe at each position by a computer, comparing total pressure and pore water pressure of the sensor at each position after impact, judging whether a sand sample is liquefied according to an effective stress principle, and calculating to obtain hydraulic slope drop i between two holes at the momentnThe correlation formula is:
σ′n＝σn-un
in the formula, σnFor the total stress, u, displayed by the pressure sensor at the location of the nth preformed holenPore water pressure, σ ', displayed by pore pressure sensor at nth reserved pore position'nLiquefying when the effective stress at the position of the nth reserved hole is equal to 0;
in the formula, hnExcess pore water pressure head, h, at the nth preformed hole positionn+1Excess pore water pressure head at the (n + 1) th preformed hole position, HnFor the height between the nth and the (n + 1) th reserved threaded hole, inThe hydraulic gradient between the two holes;
step SS 5: opening a needle valve, disassembling rubber plugs of two reserved holes at symmetrical positions at the top of the side wall of the sample cylinder, connecting a drainage pipeline at the reserved threaded hole at the top, keeping the other parts of the sample cylinder running, and then adjusting the water flow speed to keep the height of the water level in the sample cylinder unchanged at the height of the threaded hole at the top;
step SS 6: reading out the current seepage velocity v through a flowmeter, and respectively recording the pore water pressure u 'of the sensors at the nth preformed hole position and the (n + 1) th preformed hole position when the seepage state is maintained through the computer again'nAnd calculating the dynamic hydraulic slope i 'at that time'nAccording to Darcy's lawCalculating the dynamic seepage coefficient k at the moment, wherein the correlation formula is as follows:
k＝v/(i′n-in)
the invention achieves the following beneficial effects: the invention provides a dynamic seepage device and method under impact load aiming at solving the problem that most of the existing sandy soil liquefaction problems are researched under the conditions of vibration load or large shear displacement, most of the researches are kept in a non-drainage state, and the technical requirements of liquefaction response after the bottom of saturated sandy soil is impacted are rarely considered. Aiming at solving the technical requirements that the current research on seepage action is mostly finished in a static load state, the influence of the impact action on the seepage action of sandy soil is rarely considered, and the change of the seepage speed under the dynamic load is analyzed by recording data through a sensor.
Drawings
FIG. 1 is a schematic view of the loading device of the present invention;
FIG. 2 is a schematic view of the sample loading device of the present invention;
FIG. 3 is a schematic structural view of the base of the case of the present invention;
FIG. 4 is a schematic structural view of an impact loading test under seepage conditions in accordance with the present invention.
The meanings of the symbols in the figures: 1-adjustable speed motor, 2-impact rod, 3-connecting rod, 4-crankshaft, 5-spring, 6-copper cap, 7-counterweight, 8-impact head, 9-box base, 10-steel hoop, 11-pore pressure sensor, 12-pressure sensor, 13-threaded rod, 14-sample barrel, 15-filter box, 16-upper flange, 17-lower flange, 18-box base slide rail, 19-water inlet pipeline, 20-water discharge pipeline, 21-first nut, 22-second nut, 23-bolt, 24-adjustable speed water pump, 25-needle valve and 26-flowmeter.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
Example 1: as shown in fig. 1, fig. 2, fig. 3 and fig. 4, the present invention provides a dynamic seepage device under impact load, which comprises a loading device, a device body and a water supply system.
Referring to fig. 1, the loading device is placed in a box body base 9 and comprises a speed-adjustable motor 1, a crankshaft 4, a connecting rod 3 and an impact rod 2, the speed-adjustable motor 1 drives the crankshaft 4 to rotate, one end of the connecting rod 3 is connected with the crankshaft 2, the other end of the connecting rod 3 is connected with the impact rod 2, a wide impact head 8 is designed at the head of the impact rod, a detachable spring 5 is placed on the impact head 8, and a replaceable copper cap 6 is arranged above the spring 5.
With reference to fig. 3, the device main body comprises a sample cylinder 14, a box body base 9 and a threaded rod 13, the selected box body base 9 can prevent water discharge and ensure the use safety of the device main body, the bottom of the box body base 9 is provided with a threaded hole and fixedly connected with the threaded rod 13 to form an integral support, and an optical axis placing counterweight 7 is designed in the box body base 9 to increase the stability of the device main body; the upper part of the integral bracket is provided with a steel hoop 10 matched with the outer diameter of a sample cylinder 14; the upper flange plate 16 and the lower flange plate 17 are provided with unthreaded holes to be connected with the integral support, the positioning height is adjusted by moving the first nut 21 on the threaded rod 13, the integral sealing performance of the device main body is ensured by the up-and-down matching action of the first nut 21 and the second nut 22, and the side surface of the lower flange plate 17 is provided with a threaded hole to be connected with the water inlet pipeline 19; the sample cylinder 14 is transparent, the lower end of the sample cylinder 14 is connected with an upper flange 16, the cylinder wall of the sample cylinder 14 is provided with two rows of symmetrical reserved threaded holes along a bus, and a filter box 15 is arranged at the bottom in the sample cylinder 14.
Referring to fig. 4, the water supply system includes a speed-adjustable water pump 24, a flow meter 26, and a needle valve 25, wherein the left end of the needle valve 25 is connected to the speed-adjustable water pump 24 through a water inlet pipe 19, the right end of the needle valve 2 is connected to the flow meter 26, and the flow meter 26 is connected to the apparatus main body through the water inlet pipe 19.
Optionally, the sample cylinder 14 is made of organic glass, and the lower flange 17, the threaded rod 13 and the box base 9 are made of stainless steel.
Optionally, the box base 9 is provided with a box base slide rail 18 at an opening position at the upper part of the box, so as to ensure that the copper cap 6 in the loading device runs smoothly up and down.
Optionally, the copper cap 6 is made of a copper material, and the lower flange 17 is made of a softer material, so that the bottom surface of the lower flange 17 can be protected.
Optionally, the aperture of the reserved threaded hole of the sample cylinder 14 is respectively matched with the diameter of a sensor and a drain pipe used for an experiment, a rubber plug is used for sealing in the sample loading process, the reserved threaded hole at the topmost part of the sample cylinder is connected with the drain pipe 20 in the experiment process, the threaded holes with the symmetrical heights are arranged on one side of the threaded hole, the hole pressure sensor 11 is inserted into the threaded hole, and the pressure sensor 12 is inserted into the other side of the threaded hole.
Optionally, drain line 20 may ensure that the water level within sample cartridge 14 is constant.
Optionally, the filter box 15 is made of stainless steel, and is composed of a layer of glass beads and a screen inside, so that sand samples can not fall into the upper flange 16, and water flow can be guaranteed to flow across the sand surface uniformly.
Optionally, the steel hoop 10 can avoid shaking of the sample tube 14 due to the excessively high upper portion, and a rubber cushion layer is designed inside the steel hoop 10 and used for increasing the friction force between the steel hoop 10 and the sample tube 14, so that the stability is increased.
Optionally, the spring 5 may act as a buffer during impact loading to prevent the loading device from jamming.
Optionally, a mesh copper cap is added outside the probe of the pore pressure sensor 11, which is different from the pressure sensor 12.
Optionally, the speed-adjustable water pump 24 can adjust the water flow speed and the water flow size, so as to ensure that the flow speed is unchanged in the experiment.
Optionally, the speed-adjustable motor 1 can adjust the size and frequency of the impact load, and the load in the experiment is guaranteed to be kept unchanged.
Example 2: the invention also discloses an impact load dynamic seepage method, which comprises the following steps:
(1) preparing a sandy soil sample at a field sampling point by using a cutting ring, screening different types of sandy soil, and drying and storing;
(2) the dry density of the sandy soil is measured according to the geotechnical test rule, the required volume of the sandy soil is obtained by calculation according to the inner diameter of the sample cylinder 14 and the height of the highest position of the pore pressure sensor 11 distributed on the sample cylinder 14, and the required dry sand mass is calculated according to the dry density of the sandy soil, and the formula is as follows:
m＝ρdv＝ρπr2h；
wherein m is the dry sand mass required in sample preparation, rhodThe dry density of natural sand, v is the volume of the required dry sand, pi is the circumferential rate, r is the inner radius of the sample cylinder 14, and h is the highest position height of the pore pressure sensor 11 distributed on the sample cylinder;
(3) respectively connecting a pore pressure sensor 11 and a pressure sensor 12 into reserved threaded holes in the side wall of the sleeve according to the connection mode, placing a filter box 15 at the bottom of a sample cylinder 14, then loading the weighed sand sample into the sample cylinder 14 in batches through a funnel, then opening a needle valve 25, injecting water into the sample cylinder 14 until the water level reaches the position of the reserved threaded holes at the top of the sample cylinder 14, blocking the reserved threaded holes at two symmetrical positions at the top, and stopping water flow;
(4) the adjustable speed motor 1 is started, the impact rod 2 impacts the lower flange 17, the data of the sensor probe at each position is recorded by the computer, the total pressure and the pore water pressure of the sensor at each position after impact are compared, whether the sand sample is liquefied or not is judged according to the effective stress principle, and the hydraulic slope drop i at the moment is obtained by calculationnThe correlation formula is:
σ′n＝σn-un；
in the formula, σnFor the total stress, u, displayed by the pressure sensor at the location of the nth preformed holenPore water pressure, σ ', displayed by the pore water pressure sensor at the n-th reserved hole position'nFor the effective stress at the nth preformed hole position, liquefaction occurs when it equals 0;
in the formula, hnExcess pore water pressure head, h, at the nth preformed hole positionn+1Excess pore water pressure head at the (n + 1) th preformed hole position, HnFor the height between the nth and the (n + 1) th reserved threaded hole, inThe hydraulic gradient between the two holes; (5) opening the needle valve 25, removing rubber plugs of two reserved holes at symmetrical positions at the top of the side wall of the sample cylinder 14, connecting the drain pipeline 20 at the reserved threaded hole at the top, keeping the other parts of the instrument running, and then adjusting the water flow speed to keep the height of the water level in the sample cylinder 14 unchanged at the height of the threaded hole at the top;
(6) the current seepage velocity v is read out by the flowmeter 26, and the pore water pressure u 'of the sensors at the nth reserved hole position and the (n + 1) th reserved hole position respectively at the time of maintaining the seepage state is recorded again by the computer'nAnd calculates the dynamic hydraulic slope i 'at that time'nAccording to Darcy's law, the dynamic seepage coefficient k at this time can be calculated, and the correlation formula is:
k＝v/(i′n-in)
through the experiment, the relation between the total pressure of the sand sample and the pore water pressure under impact loads of different sizes can be effectively measured, meanwhile, the relation between liquefaction of the sand sample and the impact loads can be established, and meanwhile, the k value of the dynamic seepage coefficient under the impact loads can be calculated.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (10)
1. The dynamic impact load seepage device is characterized by comprising a loading device, a device main body and a water supply system, wherein the loading device is arranged in the device main body, and the water supply system is connected with the device main body.
2. The dynamic impact load seepage device according to claim 1, wherein the loading device comprises a speed-adjustable motor (1), a crankshaft (4), a connecting rod (3) and an impact rod (2), the output end of the speed-adjustable motor (1) is connected with the crankshaft (4) in a matching manner, the speed-adjustable motor (1) drives the crankshaft (4) to rotate, one end of the connecting rod (3) is connected with the crankshaft (2), the other end of the connecting rod (3) is connected with the impact rod (2), the head of the impact rod (2) is provided with an impact head (8), a detachable spring (5) is placed on the impact head (8), and a copper cap (6) is installed above the spring (5).
3. The dynamic seepage device with impact load according to claim 1, wherein the device body comprises a sample tube (14), a box base (9) and a threaded rod (13), the bottom of the box base (9) is fixedly connected with the threaded rod (13) to form an integral support, and an optical axis for placing a counterweight (7) is arranged in the box base (9); the upper part of the integral bracket is provided with a steel hoop (10) matched with the outer diameter of the sample cylinder (14); the integral support is provided with an upper flange (16) and a lower flange (17) which are vertically and symmetrically distributed, the upper flange (16) and the lower flange (17) are vertically matched on the threaded rod (13) through a first nut (21) and a second nut (22) to move and adjust the positioning height, and the side part of the lower flange (17) is externally connected with a water inlet pipeline (19); the lower end of the sample cylinder (14) is connected with the upper flange plate (16), and a filter box (15) is arranged at the inner bottom of the sample cylinder (14).
4. The dynamic seepage device of impact load according to claim 3, wherein the box base (9) is provided with a box base slide rail (18) at the position of the upper opening of the box body, so as to ensure that the copper cap (6) in the loading device runs smoothly up and down.
5. The dynamic seepage device with impact load according to claim 3, wherein the diameter of the prepared threaded hole of the sample cylinder (14) is matched with the diameter of a sensor and a drainage pipeline (20) used for experiments respectively, the threaded hole prepared at the topmost part of the sample cylinder (14) is connected with the drainage pipeline (20), one side of the rest of highly symmetrical threaded holes on the sample cylinder (14) is inserted into the hole pressure sensor (11), and the other side of the rest of highly symmetrical threaded holes on the sample cylinder (14) is inserted into the pressure sensor (12).
6. A dynamic seepage device under impact load according to claim 5, characterized in that a mesh copper cap is added on the outside of the probe of the pore pressure sensor (11).
7. A dynamic seepage device under impact load according to claim 3, wherein the filter box (15) is internally composed of a layer of glass beads and a screen mesh, which ensures that the sand sample does not fall into the upper flange (16) and that the water flow uniformly flows over the sand surface.
8. An impact load dynamic seepage device as claimed in claim 3, wherein said steel hoop (10) is used for avoiding the shaking of the upper part of the sample tube (14) caused by the overhigh height, and the inside of said steel hoop (10) is designed with a rubber cushion layer for increasing the friction force between the steel hoop (10) and the sample tube (14) and increasing the stability.
9. A dynamic percolation device in impact loading according to claim 1 characterized by that the water supply system comprises a speed adjustable water pump (24), a flow meter (26), a needle valve (25), the left end of the needle valve (25) is connected to the speed adjustable water pump (24) through a water inlet pipe (19), the right end of the needle valve (25) is connected to the flow meter (26), the flow meter (26) is connected to the device body through the water inlet pipe (19).
10. An impact load dynamic seepage method is characterized by comprising the following steps:
step SS 1: preparing a sandy soil sample at a field sampling point by using a cutting ring, screening different types of sandy soil, and drying and storing;
step SS 2: the dry density of the sandy soil is measured according to the geotechnical test rule, the required sandy soil volume is calculated according to the inner diameter of a sample cylinder (14) and the height of the highest position of a pore pressure sensor (11) arranged on the sample cylinder (14), and the required dry sand mass is calculated according to the dry density of the sandy soil, wherein the formula is as follows:
m＝ρdv＝ρπr2h
wherein m is the dry sand mass required in sample preparation, rhodThe dry density of natural sand, v is the volume of the required dry sand, pi is the circumferential rate, r is the inner radius of the sample cylinder (14), and h is the height of the highest position of a pore pressure sensor (11) arranged on the sample cylinder (14);
step SS 3: respectively connecting a hole pressure sensor (11) and a pressure sensor (12) into reserved threaded holes in the side wall of a sample cylinder (14), placing a filter box (15) at the bottom of the sample cylinder (14), then loading weighed sand samples into the sample cylinder (14) in batches through a funnel, then opening a needle valve (25), injecting water into the sample cylinder (14) until the water level reaches the position of the reserved threaded holes at the top of the sample cylinder (14), blocking the reserved threaded holes at two symmetrical positions at the top, and stopping water flow;
step SS 4: turning on a speed-adjustable motor (1), impacting a lower flange plate (17) by an impact rod (2), recording the probe data of the sensor at each position by a computer, comparing the total pressure of the sensor at each position after impact with the pore water pressure, judging whether a sand sample is liquefied according to the effective stress principle, and calculating to obtain the hydraulic slope drop i at the momentnThe correlation formula is:
σ′n＝σn-un
in the formula, σnFor the total stress, u, displayed by the pressure sensor at the location of the nth preformed holenPore water pressure, σ ', displayed by pore pressure sensor at nth reserved pore position'nFor the effective stress at the nth preformed hole position, liquefaction occurs when it equals 0;
in the formula, hnUltra-hole at the nth preformed hole positionGap water pressure head, hn+1Excess pore water pressure head at the (n + 1) th reserved hole position, HnFor the height between the nth and the (n + 1) th reserved threaded hole, inThe hydraulic slope between the two holes is decreased;
step SS 5: opening a needle valve (25), disassembling rubber plugs of two reserved holes at symmetrical positions at the top of the side wall of the sample cylinder (14), connecting a drainage pipeline (20) at the reserved threaded hole at the top, keeping the other parts of the sample cylinder (14) in operation, and then adjusting the water flow speed to keep the water level height in the sample cylinder (14) unchanged at the threaded hole at the top;
step SS 6: reading out the current seepage velocity v through a flowmeter (26), and respectively recording the pore water pressure u 'of the sensor at the n-th reserved hole position and the n + 1-th reserved hole position when the seepage state is maintained through the computer again'nAnd calculating the dynamic hydraulic slope i 'between the two holes at the moment'nAnd calculating the dynamic seepage coefficient k at the moment according to Darcy's law, wherein the correlation formula is as follows:
k＝v/(i′n-in)。
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