A portable excitation device and method for controlling the characteristics of a seismic source

Abstract

The application discloses a portable excitation device capable of controlling the characteristics of a seismic source and a method. The device comprises a base plate, a height fixing mechanism and a swing mechanism. The base plate is arranged on a test site. The height fixing mechanism is vertically fixed and arranged on the base plate close to the edge side. One end of the swing mechanism is hinged to the upper part of the height fixing mechanism. The other end of the swing mechanism is arranged to swing and knock a wood block on the test site. The method comprises the following steps: obtaining the shear wave frequency corresponding to the soil type, calculating the required release height according to the relationship between the shear wave frequency and the release height, assembling the device, and releasing the excitation hammer according to the calculated release height each time, so that the shear wave with the same required frequency is generated each time. The application overcomes the problem that the traditional manual knocking of the wood block cannot guarantee the system of the test. The application can more accurately control the characteristics of the excitation source, has the advantages of high safety, easy assembly and simple operation, and the like.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of geotechnical in-situ test method, and particularly relates to a portable excitation device and method capable of controlling the characteristics of a seismic source. BACKGROUND

[0002] The down-hole method for measuring wave velocity is one of the traditional in-situ geotechnical test techniques. It only needs to use a large hammer to strike a wood block on the test ground to generate vertically propagating advantage shear waves. The relevant signals are received by the geophone under the hole, and the terminal equipment can be visualized, that is, the shear wave velocity of the test point can be calculated. The down-hole method has the advantages of small test workload, simple instrument equipment, easy operation, and low cost. However, the test depth is limited. When the test depth is too deep, the shear wave will be severely attenuated during propagation in the in-situ soil, resulting in a decrease in the signal-to-noise ratio, making it difficult to accurately calculate the propagation time and reducing the test accuracy.

[0003] Due to the non-uniform and nonlinear nature of soil in reality, the propagation speed of shear waves of different frequencies in soil is different. In some specific frequency range, the shear wave velocity may gradually decrease with the increase of frequency, which is called wave dispersion. Dispersion causes the separation of shear waves of different frequencies during propagation, resulting in changes in wave shape. This will have a certain impact on the test results of shear wave velocity.

[0004] In the traditional excitation method of the down-hole method test, a large hammer is generally used to strike a wood block manually. This operation has a certain risk. Moreover, manual striking has high randomness, which may cause system errors because the energy generated by the hammer striking the wood block each time cannot be guaranteed to be the same, and the position of the wood block struck each time cannot be guaranteed to be the same. These factors may cause large differences in the amplitude, frequency, and other characteristics of the vibration source, thereby causing large errors in the final measurement results, so multiple strikes may be required for testing. In addition, the shear wave energy generated by manual striking of the wood block is relatively small, and the energy is attenuated during propagation, which may not be sufficient to propagate to the geophone at a deeper position in the soil or the energy may be too small to be monitored, resulting in a decrease in the signal-to-noise ratio and affecting the test results. Finally, the excitation effect of different impulse hammers striking the same position of the wood block is different. This is closely related to factors such as the mass of the hammer, the material of the hammer, the movement speed during striking, and the contact area. The excitation frequency range is mainly determined by the stiffness of the contact surface. The harder the hammer head material, the shorter the duration of the excitation effect, and the higher the excitation frequency. In summary, the input energy of the excitation hammer determines the important characteristics of the output shear wave, such as frequency, amplitude, and propagation distance. The wave characteristics play a crucial role in the test results of the down-hole method wave velocity. SUMMARY

[0005] The present application aims at the deficiency of the existing excitation technology, and provides a portable excitation device capable of controlling the characteristics of a vibration source, so as to improve the accuracy and systematicness of the wave velocity measurement by the downhole method.

[0006] The technical scheme adopted by the present application to solve the technical problems is:

[0007] The present application is a portable excitation device capable of controlling the characteristics of a vibration source.

[0008] The device comprises a base plate, a height fixing mechanism and a swinging mechanism; the base plate is arranged on a test site; the height fixing mechanism is vertically fixed and arranged on the base plate near the edge side; one end of the swinging mechanism is hingedly connected to the upper part of the height fixing mechanism; and the other end of the swinging mechanism swings and strikes a wood block arranged on the test site.

[0009] The height fixing mechanism comprises a sleeve vertical rod, a height adjusting rod and a first pin; the bottom of the sleeve vertical rod is vertically arranged on the base plate near the edge side; the lower part of the height adjusting rod is coaxially sleeved in the upper part of the sleeve vertical rod through the first pin; and the top end of the height adjusting rod is hingedly connected to the swinging mechanism through the second pin.

[0010] The upper part of the sleeve vertical rod is provided with an external through hole for the insertion of the first pin; the height adjusting rod is provided with at least two internal through holes, which are arranged at intervals along the axial direction; one of the internal through holes is aligned with the external through hole of the sleeve vertical rod; and the first pin is inserted into the aligned internal through hole and external through hole.

[0011] The top end of the height adjusting rod is further provided with a pin through hole one for hingedly connecting to one end of the swinging mechanism; and the top part of the height adjusting rod is provided with a circular top cover to prevent the height adjusting rod from sliding into the sleeve vertical rod.

[0012] The swinging mechanism comprises a swinging telescopic rod, an excitation hammer and a second pin; the main body of the swinging telescopic rod is a telescopic rod which can freely extend and retract; the swinging telescopic rod is provided with a pin through hole two at one end; the pin through hole two of the swinging telescopic rod is hingedly connected to the pin through hole one of the height adjusting rod through the second pin; and the swinging telescopic rod is made of a material with high rigidity, such as stainless steel.

[0013] The excitation hammer is sleeved on the other end of the swinging telescopic rod and used for swinging and striking the wood block; the excitation hammer is detachable and replaceable, and used for exciting shear waves with different vibration characteristics; one side of the excitation hammer is a hammer head used for striking the wood block; a force sensor is embedded in the hammer head of the excitation hammer; the force sensor is electrically connected to an upper computer; and the other side of the excitation hammer is a counterweight head used for adjusting the counterweight of the excitation hammer; and the excitation hammer is one of a rubber excitation hammer, a metal excitation hammer and a nylon excitation hammer.

[0014] The wood block is cuboid, and the wood block is placed on one side of the base plate close to the height fixing mechanism, the height of the wood block is greater than the height from the wood block to the test site when the wood block is struck by the hammer, and the swinging telescopic rod and the surface of the wood block struck by the hammer are parallel and both in the vertical direction when the hammer strikes the wood block for the first time.

[0015] The portable excitation device further comprises a plurality of micro anchor rods, and the base plate is arranged on the test site by inserting the plurality of micro anchor rods. In a specific embodiment, four micro anchor rods are included and are respectively inserted and fixed at the four corners of the base plate.

[0016] Two, an excitation method of a portable excitation device

[0017] 1) According to the soil type of the test site, obtain the required shear wave frequency f of excitation, and select the corresponding excitation hammer.

[0018] 2) Obtain the parameters of the excitation hammer, the parameters of the wood block, and the parameters when the excitation hammer strikes the wood block.

[0019] 3) Construct the swinging excitation model f(h) of the shear wave frequency f of excitation and the release height h.

[0020] 4) Substitute the parameters of the excitation hammer, the parameters of the wood block, and the parameters t when the excitation hammer strikes the wood block obtained in step 2) into the swinging excitation model f(h) constructed in step 3), and solve the release height h.

[0021] 5) Assemble the portable excitation device, horizontally fix the portable excitation device on the test site, and place the wood block on one side of the base plate close to the height fixing mechanism, so that the swinging telescopic rod and the surface of the wood block struck by the excitation hammer are parallel and both in the vertical direction.

[0022] 6) Swing the excitation hammer of the portable excitation device to the release height h from the surface of the test site, loosen the excitation hammer, strike the wood block, and the required shear wave frequency f of excitation can be generated.

[0023] In step 2), the parameters of the excitation hammer are specifically: the radius r of the hammer head of the excitation hammer, the mass m of the excitation hammer, the deformation modulus E1 of the excitation hammer, and the Poisson's ratio v1 of the excitation hammer. The parameters of the wood block are specifically: the deformation modulus E2 of the wood block and the Poisson's ratio v2 of the wood block. The parameters when the excitation hammer strikes the wood block are specifically: the excitation time t of the excitation hammer and the wood block.

[0024] The step 4) is specifically: the hammer head radius r of the excitation hammer obtained in step 2), the mass m of the excitation hammer, the deformation modulus E1 of the excitation hammer, the Poisson's ratio v1 of the excitation hammer, the deformation modulus E2 of the wood block, the Poisson's ratio v2 of the wood block, the excitation time t of the excitation hammer and the wood block are substituted into the swing excitation model f(h) constructed in step 3), and the release height h is solved.

[0025] In the step 1), the corresponding relationship of the soil type of the test site and the excitation hammer is:

[0026] When the soil type of the test site is medium coarse sand layer, the steel excitation hammer is selected;

[0027] When the soil type of the test site is fine sand layer, the aluminum excitation hammer is selected;

[0028] When the soil type of the test site is silt layer, the nylon excitation hammer is selected;

[0029] When the soil type of the test site is clay layer, the rubber excitation hammer is selected.

[0030] The swing excitation model f(h) constructed in the step 4) is specifically:

[0031]

[0032] Wherein, f(h) is the swing excitation function of the shear wave frequency f and the release height h, f is the shear wave frequency, A is the test experience coefficient, r is the hammer head radius of the excitation hammer, m is the mass of the excitation hammer, E1 is the deformation modulus of the excitation hammer, v1 is the Poisson's ratio of the excitation hammer, h is the release height of the excitation hammer from the surface of the test site, E2 is the deformation modulus of the wood block, v2 is the Poisson's ratio of the wood block, t is the excitation time of the excitation hammer and the wood block, g is the gravity coefficient, and pi is a constant.

[0033] In the specific implementation of the present application, with the increase of the test depth, if the signal is not strong and the signal-to-noise ratio is not high, the weight of the excitation hammer can be increased, the hammer head can be replaced, and the release height of the excitation hammer can be increased, so that the purpose of enhancing the signal is achieved.

[0034] The innovation of the present application lies in that different materials of the excitation hammer can be used according to the soil type of the test site, the height of the excitation hammer can be stably adjusted, and the excitation method of swinging the excitation hammer to the same height each time is used, so that the shear wave frequency of each excitation is kept consistent, the characteristics of the excitation source are controlled, the advantages of quantitatively controlling the knocking force, angle and position are achieved, and the systematization of the test is ensured.

[0035] The beneficial effects of the present application are:

[0036] 1. The application adopts the detachable excitation hammer of different materials according to the soil type of the test site, and the structural characteristics of stably adjusting the height of the excitation hammer and the excitation method of swinging the excitation hammer to the same height each time, which brings the beneficial effect that the shear wave frequency of each excitation remains the same, controls the characteristics of the excitation source, realizes the advantages of quantitatively controlling the knocking force, angle and position, and ensures the systematicness of the test.

[0037] 2. The device of the application is small in size, common in material, low in cost, convenient to transport and can be well applied to various complex situations and environments.

[0038] 3. The application overcomes the problem of traditional manual knocking wood block excitation shear wave, which cannot quantitatively control the knocking force, angle and position, and cannot guarantee the systematicness of the test. The application not only can more accurately control the characteristics of the excitation source, but also has the advantages of high safety, easy assembly and simple operation. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 is the front view of the device of the application;

[0040] Figure 2 is the side view of the device of the application Figure 1 ;

[0041] Figure 3 is the side view of the device of the application Figure 2 ;

[0042] Figure 4 is the schematic diagram of the excitation hammer;

[0043] Figure 5 is the waveform diagram of the test sand layer and clay layer of the application.

[0044] In the figure: 1, base plate; 2, micro anchor rod; 3, wood block; 4, outer sleeve vertical rod; 5, bolt one; 6, height adjusting rod; 7, bolt two; 8, swinging telescopic rod; 9, excitation hammer. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the application will be described clearly and completely below with reference to the drawings in the embodiments of the application. Obviously, the described embodiments are only part of the embodiments of the application, not all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the application.

[0046] As Figure 1 , Figure 2 and Figure 3As shown, the device of the present application comprises a base plate 1, a height fixing mechanism and a swing mechanism; the base plate 1 is arranged on a test site, the bottom of the height fixing mechanism is fixed vertically on the base plate 1 near the edge side, one end of the swing mechanism is hinged with the upper part of the height fixing mechanism, and the other end of the swing mechanism is arranged to swing and strike a wood block 3 on the test site, thereby generating a shear wave. The base plate 1 is an iron block with large rigidity and density, so as to increase the stability of the whole device.

[0047] The height fixing mechanism comprises a sleeve vertical rod 4, a height adjusting rod 6 and a pin 5; the bottom of the sleeve vertical rod 4 is arranged vertically on the base plate 1 near the edge side through thread engagement, so as to facilitate disassembly, installation and transportation; the lower part of the height adjusting rod 6 is coaxially sleeved in the upper part of the sleeve vertical rod 4 through the pin, and the top end of the height adjusting rod 6 is hinged with the swing mechanism through the pin.

[0048] The upper part of the sleeve vertical rod 4 is provided with an external through hole for the insertion of the pin 5; the height adjusting rod 6 is uniformly provided with at least two internal through holes, each of which is radially arranged along the height adjusting rod 6, for adjusting the swing mechanism to different heights, and the internal through holes are arranged in an axial direction at intervals, wherein the size of the hole of one of the internal through holes is consistent with that of the external through hole, the internal through hole is aligned with the external through hole of the sleeve vertical rod 4, and the pin 5 is inserted through the aligned internal through hole and external through hole, so as to fix the height fixing mechanism; the top end of the height adjusting rod 6 is further provided with a pin through hole 1 for hinging with one end of the swing mechanism, and the pin through hole 1 is in the same axial direction as the internal through hole. The top of the height adjusting rod 6 is provided with a circular top cover, so as to prevent the height adjusting rod 6 from sliding into the sleeve vertical rod 4.

[0049] The swing mechanism comprises a swing telescopic rod 8, an excitation hammer 9 and a pin 7; the main body of the swing telescopic rod 8 is a freely extendable rod, one end of the swing telescopic rod 8 is provided with a pin through hole 2 in a radial direction, the pin through hole 2 of the swing telescopic rod 8 is hinged with the pin through hole 1 of the height adjusting rod 6 through the pin 7, and the pin is fixed at both ends with a nut, so as to prevent it from falling off; the swing telescopic rod 8 is made of a material with large rigidity, such as stainless steel.

[0050] The excitation hammer 9 is fixedly sleeved on the other end of the swing telescopic rod 8, for swinging and striking the wood block 3 arranged on the test site, thereby generating a shear wave; the excitation hammer 9 is detachable and replaceable, for exciting shear waves with different vibration characteristics; one side of the excitation hammer 9 is a hammer head, for striking the wood block 3 arranged on the test site, and a force sensor is embedded in the hammer head of the excitation hammer 9, for measuring the force of the excitation hammer 9 striking the wood block 3 on the test site; if the displayed striking force is small, the excitation hammer 9 can be increased in weight or the release height of the excitation hammer 9 can be increased; the line of the force sensor goes out through the weight head of the excitation hammer 9 and is electrically connected with an upper computer, and the other side of the excitation hammer 9 is a weight head, for adjusting the weight of the excitation hammer 9.

[0051] As shown in Figure 4 The excitation hammer 9 is one of a rubber excitation hammer, a metal excitation hammer and a nylon excitation hammer; the wood block 3 is a cuboid, is placed on one side of the base plate 1 close to the height fixing mechanism, has a height greater than the height from the test site when the excitation hammer 9 strikes the wood block 3, has a length greater than the diameter of the hammer head of the excitation hammer 9, and has a width slightly smaller than the length of the wood block 3, the surface of the swinging telescopic rod 8 and the wood block 3 is parallel and in the vertical direction when the excitation hammer 9 strikes the wood block 3 for the first time, and the wood block 3 is a sleeper.

[0052] The portable excitation device further comprises a plurality of micro anchor rods 2; the base plate 1 is fixedly arranged on the test site by inserting the plurality of micro anchor rods 2. In a specific embodiment, four micro anchor rods 2 are included and are respectively inserted and fixed at the four corners of the base plate 1.

[0053] Embodiments of the present application and steps thereof are as follows:

[0054] 1) According to the soil type of the test site, the required shear wave frequency f of excitation is obtained, and the corresponding excitation hammer 9 is selected.

[0055] In step 1), the correspondence between the soil type of the test site and the excitation hammer 9 is as follows:

[0056] When the soil type of the test site is a medium-coarse sand layer, a steel excitation hammer is selected;

[0057] When the soil type of the test site is a fine sand layer, an aluminum excitation hammer is selected;

[0058] When the soil type of the test site is a silt layer, a nylon excitation hammer is selected;

[0059] When the soil type of the test site is a clay layer, a rubber excitation hammer is selected.

[0060] 2) The parameters of the excitation hammer 9, the parameters of the wood block 3 and the parameters when the excitation hammer 9 strikes the wood block 3 are obtained.

[0061] In step 2), the parameters of the excitation hammer 9 are specifically: the radius r of the hammer head of the excitation hammer 9, the mass m of the excitation hammer 9, the deformation modulus E1 of the excitation hammer 9 and the Poisson's ratio v1 of the excitation hammer 9. The parameters of the wood block 3 are specifically: the deformation modulus E2 of the wood block 3 and the Poisson's ratio v2 of the wood block 3; the parameters when the excitation hammer 9 strikes the wood block 3 are specifically: the excitation time t of the excitation hammer 9 and the wood block 3.

[0062] 3) A swinging excitation model f(h) of the shear wave frequency f and the release height h of excitation is constructed.

[0063] The swinging excitation model f(h) constructed in step 3) is specifically:

[0064]

[0065] Wherein, f(h) is the swing excitation function of the shear wave frequency f and the release height h, f is the shear wave frequency, A is a test empirical coefficient, ranging from 0.02 to 0.1, and related to soil properties, r is the radius of the hammer head of the excitation hammer 9, m is the mass of the excitation hammer 9, E1 is the deformation modulus of the excitation hammer 9, v1 is the Poisson's ratio of the excitation hammer 9, h is the release height of the excitation hammer 9 from the surface of the test site, E2 is the deformation modulus of the wood block 3, v2 is the Poisson's ratio of the wood block 3, t is the excitation time of the excitation hammer 9 and the wood block 3, g is the gravity coefficient, and pi is a constant.

[0066] 4) The parameters of the excitation hammer 9, the parameters of the wood block 3 and the parameter t when the excitation hammer 9 strikes the wood block 3 obtained in step 2) are substituted into the swing excitation model f(h) constructed in step 3) to solve the release height h.

[0067] Step 4) is specifically: the radius r of the hammer head of the excitation hammer 9, the mass m of the excitation hammer 9, the deformation modulus E1 of the excitation hammer 9, the Poisson's ratio v1 of the excitation hammer 9, the deformation modulus E2 of the wood block 3, the Poisson's ratio v2 of the wood block 3, and the excitation time t of the excitation hammer 9 and the wood block 3 obtained in step 2) are substituted into the swing excitation model f(h) constructed in step 3) to solve the release height h.

[0068] 5) Assemble the portable excitation device, fix the portable excitation device horizontally on the test site, and place the wood block 3 on one side of the bottom plate 1 close to the height fixing mechanism, so that the swing telescopic rod 8 and the wood block 3 are struck by the excitation hammer 9, and the faces are parallel and along the vertical direction.

[0069] 6) Swing the excitation hammer 9 of the portable excitation device to a release height h from the surface of the test site, loosen the excitation hammer 9, strike the wood block 3, and the required excitation shear wave frequency f can be generated.

[0070] In the specific implementation of the present application, as the test depth increases, if the signal is not strong and the signal-to-noise ratio is not high, the counterweight of the excitation hammer can be increased, the hammer head can be replaced, and the release height of the excitation hammer can be increased, so as to achieve the purpose of enhancing the signal.

[0071] After the test is completed, each equipment part should be disassembled for storage and transportation.

[0072] The specific implementation of the present application is as follows:

[0073] Example 1

[0074] The actual site is a certain piece of land, and the site soil layer geological survey data is as follows: the sand layer within 8.2 m below the ground surface belongs to coarse-grained soil, and the clay layer from 8.2 m to 16.3 m belongs to fine-grained soil. The water level is located at 0.5 m underground. The shear wave velocity test is conducted every 1 m interval.

[0075] The outer sleeve vertical rod 4 is made of a material with large rigidity, such as stainless steel. The length of the vertical rod is about 1.0 m, the outer diameter is about 2 cm, and the inner diameter is about 1.5 cm. The bottom of the outer sleeve vertical rod is provided with a 4 cm thread for connecting the bottom plate. The outer sleeve vertical rod 4 needs to be located at the edge of the bottom plate, so as to ensure the excitation of the horizontal shear force. The upper part of the outer sleeve vertical rod 4 is provided with a latch 5, and the inside of the latch is provided with a spring, which can easily pull out the latch, and the other end is tightened and reinforced by a nut;

[0076] The height adjusting rod 6 is made of a material with large rigidity, such as stainless steel. The length of the height adjusting rod 6 is about 1.0 m, the outer diameter is about 1.4 cm, and the inner diameter is about 1 cm. The outer diameter of the height adjusting rod 6 cannot be too different from the inner diameter of the outer sleeve vertical rod 4 to prevent violent shaking. The top of the height adjusting rod 6 is provided with a circular top cover with a diameter of about 2 cm and a thickness of about 2 mm, which can prevent the height adjusting rod 6 from sliding into the outer sleeve vertical rod 4. At the same time, the top end of the height adjusting rod 6 is also provided with a latch hole 1 for inserting a latch 7 to adjust the height.

[0077] The swing telescopic rod 8 is made of a material with large rigidity, such as stainless steel. One end of the swing telescopic rod 8 is provided with a latch hole 2 in the radial direction, and the latch hole 2 of the swing telescopic rod 8 is hinged with the latch hole 1 of the height adjusting rod 6 through the latch 7, so as to constrain the swing path of the excitation hammer 9. The inside of the latch hole 2 is also provided with an engineering plastic protective layer for reducing friction and wear, and the inner diameter is about 3 mm larger than the diameter of the latch. In addition, the length of the swing telescopic rod 8 is telescopic, which is used to match the height adjusting rod 6 of different heights. The bottom of the swing telescopic rod 8 is provided with a threaded hole for connecting the excitation hammer 9.

[0078] The bottom plate 1 is a block of iron with large rigidity and density to increase the stability of the whole device. The length of the bottom plate 1 is about 40 cm, the width is about 10 cm, and the thickness is about 5 cm. The inside of the four corner points of the bottom plate 1 is provided with a hole for anchoring the whole device. The inside of the long side is provided with a threaded hole for fixing the outer sleeve vertical rod 4.

[0079] The wooden block 3 is a rectangular wooden block with a length of 30 cm, a width of 40 cm, and a height of 50 cm. The wooden block 3 is placed on one side of the bottom plate 1 close to the outer sleeve vertical rod 4, and the height of the wooden block 3 is greater than the height from the test site when the excitation hammer 9 strikes the wooden block 3. When the excitation hammer 9 strikes the wooden block 3 for the first time, the swing telescopic rod 8 and the wooden block 3 are struck by the excitation hammer 9 in parallel and in the vertical direction.

[0080] The excitation hammer 9 is detachable. Different shapes and materials of the hammer can be replaced. One side of the excitation hammer 9 is a hammer head for knocking the wood block 3 arranged on the test site. The contact surface of the excitation hammer 9 and the wood block 3 should be a relatively flat plane to prevent the possibility of rebound after impact. The hammer head of the excitation hammer 9 is embedded with a force sensor to measure the size of the knocking force. The other side of the excitation hammer 9 is a counterweight head. Different counterweights can be selected. The hammer handle is short and has threads for connecting the swing telescopic rod 8.

[0081] According to the soil exploration data, the corresponding relationship between the soil type and the required shear wave frequency f is as follows:

[0082] For sand layer, the corresponding shear wave frequency f is 30-60Hz; for silt layer, the corresponding shear wave frequency f is 20-30Hz; for clay layer, the corresponding shear wave frequency f is 10-20Hz.

[0083] When testing the coarse sand layer, the required shear wave frequency f for excitation is 50Hz.

[0084] The excitation hammer 9 is a steel excitation hammer with a counterweight of 0.3kg. The radius of gyration of the excitation hammer 9 is 1.5m, the radius r of the hammer head of the excitation hammer 9 is 2cm, the mass m of the excitation hammer 9 is 0.8kg, the deformation modulus E1 of the excitation hammer 9 is 200GPa, the Poisson's ratio v1 of the excitation hammer 9 is 0.285, the deformation modulus E2 of the wood block 3 is 15GPa, the Poisson's ratio v2 of the wood block 3 is 0.4, the excitation time t of the excitation hammer 9 and the wood block 3 is 0.013s, and the experience coefficient A is taken as 0.07.

[0085] The above obtained parameters are substituted into the following swing excitation model f(h) formula:

[0086]

[0087] Wherein, f(h) is the swing excitation function of the shear wave frequency f and the release height h, f is the shear wave frequency, A is the test experience coefficient, the range is 0.05-0.15, and it is related to soil properties, r is the radius of the hammer head of the excitation hammer 9, m is the mass of the excitation hammer 9, E1 is the deformation modulus of the excitation hammer 9, v1 is the Poisson's ratio of the excitation hammer 9, h is the release height of the excitation hammer 9 from the surface of the test site, E2 is the deformation modulus of the wood block 3, v2 is the Poisson's ratio of the wood block 3, t is the excitation time of the excitation hammer 9 and the wood block 3, g is the gravity coefficient, and π is a constant.

[0088] The calculation shows that the release height h is 1.5m, which can achieve the expected effect. The excitation hammer 9 is released at the calculated release height every 30s, so that each time the shear wave of the same frequency is generated.

[0089] Example two

[0090] For the clay layer, the shear wave frequency f is taken as 10 Hz.

[0091] The test site and device in Example 1 are adopted, and only the excitation hammer 9 is changed.

[0092] The excitation hammer 9 is a rubber excitation hammer, the radius r of the hammer head of the excitation hammer 9 is 3 cm, the mass m of the excitation hammer 9 is 0.22 kg, the excitation time t of the excitation hammer 9 and the wood block 3 is 0.021 s, the deformation modulus E1 of the excitation hammer 9 is 0.01 Gpa, the Poisson's ratio v1 of the excitation hammer 9 is 0.475, the deformation modulus E2 of the wood block 3 is 15 GPa, and the Poisson's ratio v2 of the wood block 3 is 0.4. The experience coefficient A is taken as 0.11.

[0093] The above obtained parameters are substituted into the following swing excitation model f(h) formula:

[0094]

[0095] It can be calculated that the expected effect can be achieved when the release height is h=1.8 m. The excitation hammer 9 is swung to the release height of 1.8 m every 30 s, and the wood block 3 is knocked, so that the same frequency shear wave is generated every time.

[0096] The test results of the medium-coarse sand layer 5-8.2 m in depth are shown in Figure 5 The frequency of the shear wave of the medium-coarse sand layer is about 50 Hz, the shear wave speed propagation is clear and uniform, and it is shown that the characteristics of the excitation source are controlled by controlling the falling height and the motion trajectory of the excitation hammer.

[0097] The test results of the clay layer 8.2-12 m in depth are shown in Figure 5 The frequency of the shear wave of the clay layer is about 10 Hz, the shear wave speed propagation is clear and uniform, and it is shown that the characteristics of the excitation source are controlled by controlling the falling height and the motion trajectory of the excitation hammer.

[0098] The innovation of the present application is that the excitation hammer of different materials can be disassembled according to the type of the soil of the test site, the height of the excitation hammer can be stably adjusted, and the excitation method of swinging the excitation hammer to the same height every time is used, so that the frequency of the shear wave of each excitation is kept consistent, the characteristics of the excitation source are controlled, the advantages of quantitatively controlling the knocking force, the angle and the position are realized, and the system of the test is ensured.

[0099] The device of the present application is small in size, common in material, low in cost, convenient to transport, and can be well applied to various complex situations and environments.

[0100] The present application adopts the detachable exciting hammer of different materials, and different exciting hammers can be replaced according to different strata to achieve the desired exciting frequency, so as to meet the needs of various environments.

[0101] The present application overcomes the problem that the traditional manual knocking wood block cannot quantitatively control the knocking strength, angle and position, and cannot guarantee the system of the test. The present application can more accurately control the characteristics of the exciting vibration source, and has the advantages of high safety, convenient assembly and simple operation.

Claims

1. A portable excitation device excitation method, characterized in that: the method comprises the following steps: 1) according to the soil type of the test site, the shear wave frequency f required for excitation is obtained, and the corresponding excitation hammer (9) is selected; 2) the parameters of the excitation hammer (9), the parameters of the wood block (3), and the parameters when the excitation hammer (9) strikes the wood block (3) are obtained; 3) a swing excitation model f(h) of the shear wave frequency f and the release height h is constructed; 4) the parameters of the excitation hammer (9), the parameters of the wood block (3), and the parameters when the excitation hammer (9) strikes the wood block (3) obtained in step 2) are substituted into the swing excitation model f(h) constructed in step 3), and the release height h is solved; 5) the portable excitation device is assembled, the portable excitation device is fixed horizontally on the test site, and the wood block (3) is placed on one side of the bottom plate (1) close to the height fixing mechanism, so that the swing telescopic rod (8) and the wood block (3) are kept parallel and in the vertical direction; 6) the excitation hammer (9) of the portable excitation device is swung to the release height h from the surface of the test site, the excitation hammer (9) is loosened, the wood block (3) is struck, and the shear wave frequency f required for excitation is generated; the swing excitation model f(h) constructed in step 4) is specifically: f(h)=fAπr2mE1v1hE2v2t2g, wherein f(h) is a swing excitation function of the shear wave frequency f and the release height h, f is the shear wave frequency, A is a test empirical coefficient, r is the radius of the hammer head of the excitation hammer (9), m is the mass of the excitation hammer (9), E1 is the deformation modulus of the excitation hammer (9), v1 is the Poisson's ratio of the excitation hammer (9), h is the release height of the excitation hammer (9) from the surface of the test site, E2 is the deformation modulus of the wood block (3), v2 is the Poisson's ratio of the wood block (3), t is the excitation time of the excitation hammer (9) and the wood block (3), g is the gravity coefficient, and π is a constant. 2.The portable excitation device excitation method according to claim 1, characterized in that: in step 2), the parameters of the excitation hammer (9) are specifically the radius r of the hammer head of the excitation hammer (9), the mass m of the excitation hammer (9), the deformation modulus E1 of the excitation hammer (9), and the Poisson's ratio v1 of the excitation hammer (9); the parameters of the wood block (3) are specifically the deformation modulus E2 of the wood block (3) and the Poisson's ratio v2 of the wood block (3); and the parameters when the excitation hammer (9) strikes the wood block (3) are specifically the excitation time t of the excitation hammer (9) and the wood block (3). 3.The portable excitation device excitation method according to claim 1, characterized in that: step 4) is specifically that the radius r of the hammer head of the excitation hammer (9), the mass m of the excitation hammer (9), the deformation modulus E1 of the excitation hammer (9), the Poisson's ratio v1 of the excitation hammer (9), the deformation modulus E2 of the wood block (3), the Poisson's ratio v2 of the wood block (3), and the excitation time t of the excitation hammer (9) and the wood block (3) obtained in step 2) are substituted into the swing excitation model f(h) constructed in step 3), and the release height h is solved. 4.The portable excitation device excitation method according to claim 1, characterized in that: ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ In the step 1), the correspondence between the soil type of the test site and the excitation hammer (9) is as follows: When the soil type of the test site is medium-coarse sand layer, a steel excitation hammer is selected; When the soil type of the test site is fine sand layer, an aluminum excitation hammer is selected; When the soil type of the test site is silt layer, a nylon excitation hammer is selected; When the soil type of the test site is clay layer, a rubber excitation hammer is selected.

5. A portable excitation device for implementing the excitation method of any one of claims 1-4, wherein: a base plate (1), a height fixing mechanism, and a swinging mechanism are included; the base plate (1) is arranged on the test site, the height fixing mechanism is vertically fixed and arranged on the base plate (1) near the edge side, one end of the swinging mechanism is hinged to the upper part of the height fixing mechanism, and the other end of the swinging mechanism swings and strikes the wood block (3) arranged on the test site.

6. The portable excitation device according to claim 5, wherein: the swinging mechanism includes a swinging telescopic rod (8), an excitation hammer (9), and a second plug (7); the main body of the swinging telescopic rod (8) is a telescopic rod that can be freely extended and retracted, one end of the swinging telescopic rod (8) is provided with a second plug through hole, and the second plug through hole of the swinging telescopic rod (8) is hinged to the first plug through hole of the height adjusting rod (6) through the second plug (7); the excitation hammer (9) is sleeved on the other end of the swinging telescopic rod (8) and used for swinging and striking the wood block (3); one side of the excitation hammer (9) is a hammer head used for striking the wood block (3), a force sensor is embedded in the hammer head of the excitation hammer (9), the force sensor is electrically connected to the upper computer, and the other side of the excitation hammer (9) is a counterweight head used for adjusting the counterweight of the excitation hammer (9).

7. The portable excitation device according to claim 6, wherein: the excitation hammer (9) is one of a rubber excitation hammer, a metal excitation hammer, and a nylon excitation hammer; the wood block (3) is a cuboid, the wood block (3) is placed on one side of the base plate (1) near the height fixing mechanism, the height of the wood block (3) is greater than the height from the test site when the excitation hammer (9) strikes the wood block (3), and the surface of the swinging telescopic rod (8) and the wood block (3) struck by the excitation hammer (9) is parallel and in the vertical direction when the excitation hammer (9) strikes the wood block (3) for the first time; the portable excitation device further includes a plurality of micro anchor rods (2); the base plate (1) is arranged on the test site by inserting the plurality of micro anchor rods (2).

8. The portable excitation device according to claim 5, wherein: the height fixing mechanism includes a sleeve vertical rod (4), a height adjusting rod (6), and a first plug (5); the bottom of the sleeve vertical rod (4) is vertically arranged on the base plate (1) near the edge side, the lower part of the height adjusting rod (6) is coaxially sleeved in the upper part of the sleeve vertical rod (4) through the plug, and the top end of the height adjusting rod (6) is hinged to the swinging mechanism through the plug.

9. The portable excitation device according to claim 8, wherein: The upper part of the outer sleeve vertical rod (4) is provided with an external through hole for inserting the first latch (5); the height adjusting rod (6) is provided with at least two internal through holes, each of which is arranged axially and spaced apart, one of which is aligned with the external through hole of the outer sleeve vertical rod (4), and the first latch (5) is inserted into the aligned internal through hole and external through hole; The top end of the height adjusting rod (6) is further provided with a latch through hole one for hinging with one end of the swing mechanism.

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