Portable excitation device and method capable of controlling seismic source characteristics

Abstract

The invention discloses a portable vibration excitation device and method capable of controlling vibration source characteristics. The device comprises a bottom plate, a height fixing mechanism and a swing mechanism, the bottom plate is arranged on a test site, the height fixing mechanism is vertically and fixedly arranged on the bottom plate close to the edge side, one end of the swing mechanism is hinged to the upper portion of the height fixing mechanism, and the other end of the swing mechanism swings to knock a wood block arranged on the test site; the method comprises the steps that the shear wave frequency corresponding to the soil body type is obtained firstly, then the needed release height is calculated according to the relation between the shear wave frequency and the release height, then the device is assembled, the excitation hammer is released according to the calculated release height every time, and therefore the shear waves with the same frequency are generated every time knocking is conducted. The device overcomes the problem that the systematicness of the test cannot be guaranteed due to the fact that a wood block is manually knocked to excite shear waves in the prior art, not only can the characteristics of an excitation vibration source be controlled more accurately, but also the device has the advantages of being high in safety, convenient to assemble, easy and convenient to operate and the like.

Description

Technical Field

[0001] The invention belongs to the field of geotechnical in-situ test methods, and in particular relates to a portable excitation device and method capable of controlling earthquake source characteristics. Background Art

[0002] The downhole method is one of the traditional in-situ geotechnical testing technologies. It only requires a sledgehammer to hit a wooden block on the test ground to generate a vertically propagating dominant shear wave. The relevant signal will be received by the detector under the hole and visualized by the terminal device, that is, the shear wave velocity at the test point can be calculated. The downhole method has the advantages of small testing workload, simple instruments and equipment, easy operation, and low cost. However, the test depth will be subject to certain restrictions. When the test depth is too deep, the shear wave will be severely attenuated during the propagation of 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] Since the soil in reality has non-uniform and nonlinear properties, shear waves of different frequencies propagate at different speeds in the soil. In some specific frequency ranges, the shear wave velocity may gradually decrease with the increase of frequency. This phenomenon is called wave dispersion. Dispersion causes shear waves of different frequencies to gradually separate during propagation, resulting in changes in the waveform. This will also have a certain impact on the test results of the shear wave velocity.

[0004] In the traditional excitation method of the downhole method test, a sledgehammer is generally used to hit the wood block, which is dangerous. In addition, human knocking has a high degree of randomness and will produce systematic errors, because human knocking of the wood block cannot guarantee that the energy generated by the sledgehammer is the same each time, nor can it guarantee that the position of the wood block is the same each time. These factors may cause large differences in the amplitude, frequency and other characteristics of the vibration source, which in turn leads to large errors in the final measurement results, so multiple knocking tests may be required. In addition, the shear wave energy generated by human knocking of the wood block is relatively small, and the energy decays during propagation. It may not be enough to propagate to the detector in the deeper part of the soil, or the energy is too small to be monitored, resulting in a decrease in the signal-to-noise ratio and affecting the test results. Finally, different pulse hammers hitting the same position of the same piece of wood also produce different excitation effects. This is closely related to factors such as the mass of the hammer, the material of manufacture, the speed of movement during knocking, and the contact area. The range of excitation frequencies generated is mainly determined by the stiffness of the contact surface. The harder the material of the hammer head, the shorter the duration of the excitation effect and the higher the excitation frequency. In short, 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 vital role in the test results of the downhole method wave velocity. Summary of the invention

[0005] The present invention aims at the shortcomings of the existing excitation technology and proposes a portable excitation device that can control the characteristics of the source to improve the accuracy and systematicness of the wave velocity measurement by the downhole method. The basic principle of the device and method described in this invention is to ensure the kinetic energy of each strike on the wooden board by controlling the gravitational potential energy of the excitation hammer.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] 1. A portable excitation device capable of controlling the characteristics of the source

[0008] It includes a base plate, a height fixing mechanism and a swing mechanism; the base plate is arranged on the test site, the height fixing mechanism is vertically fixed 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, and the other end of the swing mechanism swings and hits the wooden block arranged on the test site.

[0009] The height fixing mechanism includes an outer outer rod, a height adjustment rod and a latch; the bottom of the outer outer rod is vertically arranged on the bottom plate close to the edge side, the lower part of the height adjustment rod is coaxially sleeved in the upper part of the outer outer rod through the latch so as to be height-adjustable, and the top end of the height adjustment rod is hinged through the latch and the swing mechanism.

[0010] An external through hole is provided on the upper part of the outer outer rod for inserting a latch pin; at least two internal through holes are provided on the height adjustment rod, each of which is arranged at intervals along the axial direction, one of the internal through holes is aligned with the external through hole of the outer outer rod, and the latch pin is inserted into the aligned internal through hole and external through hole.

[0011] The top of the height adjustment rod is also provided with a latch through hole for being hinged with one end of the swing mechanism. The top of the height adjustment rod is provided with a round top cover to prevent the height adjustment rod from sliding into the outer coat vertical rod.

[0012] The swing mechanism includes a swing telescopic rod, an excitation hammer and a second latch; the main body of the swing telescopic rod is a freely retractable rod, and a second latch through hole is provided at one end of the swing telescopic rod. The second latch through hole of the swing telescopic rod is hinged to the first latch through hole of the height adjustment rod through the second latch; the swing telescopic rod is made of a material with relatively large rigidity, such as stainless steel.

[0013] The excitation hammer is mounted on the other end of the swing telescopic rod and is used to swing and hit the wood block; the excitation hammer is detachable and replaceable and is used to excite shear waves with different vibration characteristics; one side of the excitation hammer is a hammer head, which is used to hit the wood block, and a force sensor is embedded in the hammer head of the excitation hammer, which is electrically connected to the upper machine, and the other side of the excitation hammer is a counterweight head, which is used to adjust the counterweight of the excitation hammer. The excitation hammer is one of a rubber excitation hammer, a metal excitation hammer and a nylon excitation hammer.

[0014] The wooden block is in the shape of a rectangular block and is placed on one side of the bottom plate close to the height fixing mechanism. The height of the wooden block is greater than the height from the test site when the excitation hammer hits the wooden block. When the excitation hammer hits the wooden block for the first time, the swinging telescopic rod and the surface of the wooden block hit by the excitation hammer are parallel and both in the vertical direction.

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

[0016] 2. A vibration excitation method of a portable vibration excitation device

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

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

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

[0020] 4) Substitute the parameters of the excitation hammer, the parameters of the wooden block and the parameter t when the excitation hammer hits the wooden block obtained in step 2) into the swing excitation model f(h) constructed in step 3) to solve the release height h.

[0021] 5) Assemble the portable vibration excitation device, fix the portable vibration excitation device horizontally on the test site, and place the wooden block on one side of the bottom plate close to the height fixing mechanism, keeping the swing telescopic rod and the surface of the wooden block struck by the excitation hammer parallel and 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, release the excitation hammer, and strike the wooden block to generate the required excitation shear wave frequency f.

[0023] In step 2), the parameters of the excitation hammer are specifically: the hammer head radius r 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 between the excitation hammer and the wood block.

[0024] The step 4) is specifically as follows: the hammer head radius r of the excitation hammer, 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 wooden block, the Poisson's ratio v2 of the wooden block, and the excitation time t of the excitation hammer and the wooden block obtained in step 2) are substituted into the swing excitation model f(h) constructed in step 3) to solve the release height h.

[0025] In step 1), the corresponding relationship between 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, choose a steel excitation hammer;

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

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

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

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

[0031]

[0032] Among them, f(h) is the oscillation excitation function of the shear wave frequency f and the release height h, f is the shear wave frequency, A is the test empirical 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 π is a constant.

[0033] In the specific implementation of the present invention, 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, etc., and the release height of the excitation hammer can also be increased, so as to achieve the purpose of enhancing the signal.

[0034] The innovation of the present invention lies in the use of detachable excitation hammers of different materials according to the soil type of the test site, the structural characteristics of the excitation hammer that can stably adjust the height, and the excitation method of swinging the excitation hammer to the same height each time, which brings about the beneficial effect of keeping the shear wave frequency of each excitation consistent and controlling the characteristics of the excitation vibration source, realizing the advantage of quantitatively controlling the knocking force, angle and position, and ensuring the systematic nature of the test.

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

[0036] 1. The present invention adopts a detachable excitation hammer of different materials according to the soil type of the test site, and has a structural feature of stably adjusting the height of the excitation hammer and utilizing an excitation method of swinging the excitation hammer to the same height each time, thereby achieving the beneficial effect of keeping the shear wave frequency of each excitation consistent and controlling the characteristics of the excitation vibration source, achieving the advantage of quantitatively controlling the knocking force, angle and position, and ensuring the systematic nature of the test.

[0037] 2. The various parts of the device of the present invention are easy to disassemble and install, the device is small, the materials are common, the cost is low, and it is easy to transport. It can be well applied to various complex situations and environments.

[0038] 3. The present invention overcomes the problem that the traditional method of manually knocking on a wooden block to excite shear waves cannot quantitatively control the knocking force, angle and position, and cannot ensure the systematic nature of the test. The present invention can not only more accurately control the characteristics of the excitation vibration source, but also has the advantages of high safety, easy assembly, and simple operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a front view of the device of the present invention;

[0040] Figure 2 A side view of the device of the present invention Figure 1 ;

[0041] Figure 3 A side view of the device of the present invention Figure 2 ;

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

[0043] Figure 5 This is the waveform diagram of the sand layer and clay layer tested by the present invention.

[0044] In the figure: 1. base plate; 2. micro anchor rod; 3. wooden block; 4. outer sleeve vertical rod; 5. latch one; 6. height adjustment rod; 7. latch two; 8. swing telescopic rod; 9. excitation hammer. DETAILED DESCRIPTION

[0045] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] like Figure 1 , Figure 2 and Figure 3As shown, the device of the present invention comprises a bottom plate 1, a height fixing mechanism and a swing mechanism; the bottom plate 1 is arranged on the test site, the bottom of the height fixing mechanism is vertically fixed on the bottom plate 1 near the edge side, one end of the swing mechanism is hinged to the upper part of the height fixing mechanism, and the other end of the swing mechanism swings and strikes a wooden block 3 arranged on the test site, thereby generating shear waves. The bottom plate 1 is an iron block with high rigidity and density to increase the stability of the entire device.

[0047] The height fixing mechanism includes an outer outer rod 4, a height adjustment rod 6 and a latch 5; the bottom of the outer outer rod 4 is vertically arranged on the base plate 1 close to the edge side through threaded engagement, which is convenient for disassembly, installation and transportation, and the lower part of the height adjustment rod 6 is coaxially sleeved in the upper part of the outer outer rod 4 through a latch so as to be height-adjustable, and the top end of the height adjustment rod 6 is hinged through a latch and a swing mechanism.

[0048] The upper part of the outer sleeve rod 4 is provided with an external through hole for inserting a latch 5; at least two internal through holes are evenly provided on the height adjustment rod 6, each of which is radially provided along the height adjustment rod 6, and is used to adjust the swing mechanism to different heights. The internal through holes are arranged at intervals along the axial direction, and the hole size of one of the internal through holes is consistent with the external through hole, and the internal through hole is aligned with the external through hole of the outer sleeve rod 4. The latch 5 is inserted through the aligned internal through hole and the external through hole to fix the height fixing mechanism; the top of the height adjustment rod 6 is also provided with a latch through hole 1, which is used to be hinged with one end of the swing mechanism, and the latch through hole 1 and the internal through hole are in the same axial direction. A round top cover is provided on the top of the height adjustment rod 6 to prevent the height adjustment rod 6 from sliding into the outer sleeve rod 4.

[0049] The swing mechanism includes a swing telescopic rod 8, an excitation hammer 9 and a second latch 7; the main body of the swing telescopic rod 8 is a freely retractable rod, and a second latch through hole is radially opened at one end of the swing telescopic rod 8. The second latch through hole of the swing telescopic rod 8 is hinged to the first latch through hole of the height adjustment rod 6 through the second latch 7, and both ends of the latch are fixed with nuts to prevent slipping; the swing telescopic rod 8 is made of a material with greater rigidity, such as stainless steel.

[0050] The excitation hammer 9 is fixedly mounted on the other end of the swing telescopic rod 8, and is used to swing and strike the wooden block 3 arranged on the test site, thereby generating shear waves; the excitation hammer 9 is detachable and replaceable, and is used to excite shear waves with different vibration characteristics; one side of the excitation hammer 9 is a hammer head, which is used to strike the wooden block 3 arranged on the test site, and a force sensor is embedded in the hammer head of the excitation hammer 9, which is used to measure the force of the excitation hammer 9 striking the wooden block 3 on the test site. If the displayed striking force is small, a counterweight can be added to the excitation hammer 9 or the release height of the excitation hammer 9 can be increased. The circuit of the force sensor passes through the counterweight head of the excitation hammer 9 and is electrically connected to the upper computer. The other side of the excitation hammer 9 is a counterweight head, which is used to adjust the counterweight of the excitation hammer 9.

[0051] like Figure 4 As shown, the excitation hammer 9 is one of a rubber excitation hammer, a metal excitation hammer and a nylon excitation hammer; the wooden block 3 is a rectangular block, and the wooden block 3 is placed on one side of the bottom plate 1 close to the height fixing mechanism. The height of the wooden block 3 is greater than the height from the test site when the excitation hammer 9 hits the wooden block 3, the length of the wooden block 3 is greater than the diameter of the hammer head of the excitation hammer 9, and the width of the wooden block 3 is slightly smaller than the length of the wooden block 3. When the excitation hammer 9 hits the wooden block 3 for the first time, the swing telescopic rod 8 and the surface of the wooden block 3 hit by the excitation hammer 9 are parallel and both in the vertical direction, and the wooden block 3 is a sleeper.

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

[0053] The embodiments of the present invention and the steps thereof are as follows:

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

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

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

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

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

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

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

[0061] In step 2), the parameters of the excitation hammer 9 are specifically: the hammer head radius r 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 between the excitation hammer 9 and the wood block 3.

[0062] 3) Construct a oscillating excitation model f(h) of the excited shear wave frequency f and the release height h.

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

[0064]

[0065] Among them, f(h) is the oscillation excitation function of the shear wave frequency f and the release height h, f is the shear wave frequency, A is the test empirical coefficient, ranging from 0.02 to 0.1, which is related to the soil properties, r is the hammer head radius 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.

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

[0067] Step 4) is specifically as follows: the hammer head radius r 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 for the release height h.

[0068] 5) Assemble the portable vibration excitation device, fix the portable vibration excitation device horizontally on the test site, and place the wooden block 3 on one side of the bottom plate 1 close to the height fixing mechanism, keeping the swing telescopic rod 8 and the surface of the wooden block 3 struck by the excitation hammer 9 parallel and in 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, release the excitation hammer 9, and strike the wooden block 3 to generate the required excitation shear wave frequency f.

[0070] In the specific implementation of the present invention, 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, etc., and the release height of the excitation hammer can also be increased, so as to achieve the purpose of enhancing the signal.

[0071] After the test is completed, the various equipment components should be disassembled for easy storage and transportation.

[0072] The specific embodiments of the present invention are as follows:

[0073] Embodiment 1

[0074] For a certain actual site, the soil survey data of the site are as follows: the sand layer within 8.2m below the ground surface is coarse-grained soil, and the clay layer between 8.2m and 16.3m is fine-grained soil. The water level is 0.5m underground. Shear wave velocity tests are performed every 1m.

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

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

[0077] The swing telescopic rod 8 is made of a material with relatively high rigidity, such as stainless steel. A second latch hole is radially provided at one end of the swing telescopic rod 8. The second latch hole of the swing telescopic rod 8 is hinged to the first latch hole of the height adjustment rod 6 through a second latch 7, so that the swing path of the excitation hammer 9 can be constrained. An engineering plastic protective layer is also provided inside the second latch hole to reduce friction and wear, and its inner diameter is about 3 mm larger than the diameter of the latch. In addition, the length of the swing telescopic rod 8 is retractable to match height adjustment rods 6 of different heights. A threaded hole is engraved at the bottom of the swing telescopic rod 8 to connect the excitation hammer 9.

[0078] The bottom plate 1 is a block of iron with high rigidity and density to increase the stability of the entire device. The bottom plate 1 is about 40 cm long, about 10 cm wide, and about 5 cm thick. Holes are opened on the inner side of the four corners of the bottom plate 1 for anchoring the entire device. Threaded holes are opened on the inner side of the long side for fixing the outer cover rod 4.

[0079] The wooden block 3 is a rectangular sleeper 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 base plate 1 close to the outer sleeve vertical rod 4. The height of the wooden block 3 is greater than the height from the test site when the excitation hammer 9 hits the wooden block 3. When the excitation hammer 9 hits the wooden block 3 for the first time, the swing telescopic rod 8 and the surface of the wooden block 3 hit by the excitation hammer 9 are parallel and both in the vertical direction.

[0080] The excitation hammer 9 is detachable. Hammers of different shapes and materials can be replaced. One side of the excitation hammer 9 is a hammer head, which is used to strike the wooden block 3 arranged on the test site. The contact surface between the excitation hammer 9 and the wooden block 3 should be a relatively flat plane to prevent the possibility of rebound after impact. A force sensor is embedded in the hammer head of the excitation hammer 9 to measure the magnitude of the striking force. The other side of the excitation hammer 9 is a counterweight head, and different counterweights can be selected. The hammer handle is short and engraved with threads for connecting the swing telescopic rod 8.

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

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

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

[0084] The excitation hammer 9 is a steel excitation hammer with a counterweight of 0.3 kg. The rotation radius of the excitation hammer 9 is 1.5 m, the radius r of the hammer head of the excitation hammer 9 is 2 cm, the mass m of the excitation hammer 9 is 0.8 kg, the deformation modulus E1 of the excitation hammer 9 is 200 GPa, the Poisson's ratio v1 of the excitation hammer 9 is 0.285, the deformation modulus E2 of the wood block 3 is 15 GPa, 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 0.013 s, and the empirical coefficient A is taken as 0.07.

[0085] Substitute the above-obtained parameters into the following swing excitation model f(h) formula:

[0086]

[0087] Among them, f(h) is the oscillation 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, ranging from 0.05 to 0.15, which is related to the soil properties, r is the hammer head radius 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] When the calculated release height h is 1.5 m, the expected effect can be achieved. The excitation hammer 9 is released at the calculated release height every 30 seconds, so that each strike generates a shear wave of the same required frequency.

[0089] Embodiment 2

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

[0091] The test site and the device in the first embodiment are used, and only the excitation hammer 9 is changed.

[0092] The excitation hammer 9 is a rubber excitation hammer, the hammer head radius r 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 empirical coefficient A is taken as 0.11.

[0093] Substitute the above-obtained parameters into the following swing excitation model f(h) formula:

[0094]

[0095] It can be calculated that when the release height is h = 1.8m, the expected effect can be achieved. Every 30 seconds, the excitation hammer 9 is swung to the release height of 1.8m to strike the wood block 3, so that each strike generates a shear wave of the same frequency as required.

[0096] The test results of the medium-coarse sand layer at a depth of 5 to 8.2 m are as follows: Figure 5 As shown, the frequency of the shear wave in the medium-coarse sand layer is approximately 50 Hz, the shear wave velocity propagation is clear and the waveform is relatively uniform, which shows that the present invention controls the characteristics of the excitation vibration source by controlling the falling height and movement trajectory of the excitation hammer.

[0097] The test results of the clay layer at a depth of 8.2 to 12 m are as follows: Figure 5 As shown, the frequency of the shear wave of the clay layer is approximately 10 Hz, the shear wave velocity propagation is clear and the waveform is relatively uniform, which shows that the present invention controls the characteristics of the excitation vibration source by controlling the falling height and movement trajectory of the excitation hammer.

[0098] The innovation of the present invention lies in the use of detachable excitation hammers of different materials according to the soil type of the test site, the structural characteristics of the excitation hammer that can stably adjust the height, and the excitation method of swinging the excitation hammer to the same height each time, which brings about the beneficial effect of keeping the shear wave frequency of each excitation consistent and controlling the characteristics of the excitation vibration source, realizing the advantage of quantitatively controlling the knocking force, angle and position, and ensuring the systematic nature of the test.

[0099] The various parts of the device of the present invention are easy to disassemble and install, the device is small, the materials are common, the cost is low, the transportation is convenient, and it can be well applied to various complex situations and environments.

[0100] The present invention adopts detachable excitation hammers of different materials, and different excitation hammers can be replaced for different strata to achieve the desired excitation frequency, thereby meeting the needs of various environments.

[0101] The present invention overcomes the problem that the traditional method of manually knocking a wooden block to excite shear waves cannot quantitatively control the knocking force, angle and position, and thus cannot ensure the systematic nature of the test. The present invention can not only more accurately control the characteristics of the excitation vibration source, but also has the advantages of high safety, easy assembly, and simple operation.

Claims

1. A portable excitation device capable of controlling the characteristics of a seismic source, characterized in that: The invention comprises a base plate (1), a height fixing mechanism and a swing mechanism; the base plate (1) is arranged on a test site, the height fixing mechanism is vertically fixed on the base plate (1) near an edge side, one end of the swing mechanism is hinged to the upper part of the height fixing mechanism, and the other end of the swing mechanism swings and strikes a wooden block (3) arranged on the test site.

2. The portable vibration excitation device according to claim 1, characterized in that: The height fixing mechanism comprises an outer outer rod (4), a height adjustment rod (6) and a latch (5); the bottom of the outer outer rod (4) is vertically arranged on the bottom plate (1) close to the edge side, the lower part of the height adjustment rod (6) is coaxially sleeved in the upper part of the outer outer rod (4) through the latch so as to be height-adjustable, and the top end of the height adjustment rod (6) is hinged to the swing mechanism through the latch.

3. The portable vibration excitation device according to claim 2, characterized in that: The upper part of the outer sleeve upright rod (4) is provided with an external through hole for inserting the first latch pin (5); the height adjustment rod (6) is provided with at least two internal through holes, each of which is arranged at intervals along the axial direction, one of the internal through holes is aligned with the external through hole of the outer sleeve upright rod (4), and the first latch pin (5) is inserted into the aligned internal through hole and external through hole; The top end of the height adjustment rod (6) is also provided with a latch through hole for being hinged to one end of the swing mechanism.

4. The portable vibration excitation device according to claim 2, characterized in that: The swing mechanism comprises a swing telescopic rod (8), an excitation hammer (9) and a second latch (7); the main body of the swing telescopic rod (8) is a freely retractable rod, one end of the swing telescopic rod (8) is provided with a second latch through hole, and the second latch through hole of the swing telescopic rod (8) is hingedly connected to the first latch through hole of the height adjustment rod (6) through the second latch (7); The excitation hammer (9) is sleeved on the other end of the swing telescopic rod (8) and is used for swinging and striking the wooden block (3); one side of the excitation hammer (9) is a hammer head for striking the wooden block (3); a force sensor is embedded in the hammer head of the excitation hammer (9), and the force sensor is electrically connected to the upper computer; the other side of the excitation hammer (9) is a counterweight head for adjusting the counterweight of the excitation hammer (9).

5. The portable excitation device according to claim 4, characterized in that: The excitation hammer (9) is one of a rubber excitation hammer, a metal excitation hammer and a nylon excitation hammer; The wooden block (3) is in the shape of a rectangular parallelepiped. The wooden block (3) is placed on one side of the bottom plate (1) close to the height fixing mechanism. 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 surface of the wooden block (3) struck by the excitation hammer (9) are parallel and both in the vertical direction. The portable excitation device also includes a plurality of micro anchor rods (2); the base plate (1) is arranged on a test site by inserting a plurality of the micro anchor rods (2).

6. A vibration excitation method using a portable vibration excitation device according to any one of claims 1 to 5, characterized in that: 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) obtaining parameters of the excitation hammer (9), parameters of the wooden block (3), and parameters when the excitation hammer (9) strikes the wooden block (3); 3) Construct a sway excitation model f(h) of the excitation shear wave frequency f and the release height h; 4) Substituting the parameters of the excitation hammer (9), the parameters of the wooden block (3) and the parameter t when the excitation hammer (9) strikes the wooden block (3) obtained in step 2) into the swing excitation model f(h) constructed in step 3) to solve for the release height h; 5) Assembling the portable vibration excitation device, fixing the portable vibration excitation device horizontally on the test site, and placing the wooden block (3) on one side of the bottom plate (1) close to the height fixing mechanism, keeping the swing telescopic rod (8) and the surface of the wooden block (3) struck by the excitation hammer (9) parallel and in the vertical direction; 6) Swing the exciting hammer (9) of the portable exciting device to a release height h from the surface of the test site, release the exciting hammer (9), and strike the wooden block (3) to generate the required exciting shear wave frequency f.

7. The vibration excitation method of a portable vibration excitation device according to claim 6, characterized in that: In the step 2), the parameters of the excitation hammer (9) are specifically: the hammer head radius r 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 wooden block (3) are specifically: the deformation modulus E2 of the wooden block (3) and the Poisson's ratio v2 of the wooden block (3); and the parameters when the excitation hammer (9) strikes the wooden block (3) are specifically: the excitation time t between the excitation hammer (9) and the wooden block (3).

8. The vibration excitation method of a portable vibration excitation device according to claim 6, characterized in that: The step 4) is specifically as follows: the hammer head radius r 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 for the release height h.

9. The vibration excitation method of a portable vibration excitation device according to claim 6, characterized in that: In the step 1), the corresponding relationship between the soil type of the test site and the excitation hammer (9) is: When the soil type of the test site is medium-coarse sand layer, choose a steel excitation hammer; When the soil type of the test site is fine sand layer, choose an aluminum excitation hammer; When the soil type of the test site is silt layer, choose nylon excitation hammer; When the soil type of the test site is clay layer, choose a rubber excitation hammer.

10. The vibration excitation method of a portable vibration excitation device according to claim 6, characterized in that: The swing excitation model f(h) constructed in step 4) is specifically: Wherein, f(h) is the oscillation excitation function of the shear wave frequency f and the release height h, f is the shear wave frequency, A is the test empirical coefficient, r is the hammer head radius 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.

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