KR20010044186A - method for standard penetration test and apparatus for performming the same - Google Patents

Abstract

PURPOSE: A method and a device for performing standard penetration test(SPT) are provided to automatically and collectively perform all test procedures after preparation of the SPT. CONSTITUTION: A method for automatically performing standard penetration test includes the steps of automatically pulling up and rising a hammer by an automatic pulling-up and falling device, separating the hammer from the automatic pulling-up and dropping device and freely lowering, measuring the number of strike of the hammer and accumulatively storing in a controller, measuring a penetration amount of a sampler and storing in the controller, comparing the penetration amount of the sampler with a standard value set in the controller and determining whether or not to progress the penetration test, calculating N value if the penetration amount reaches the standard value, and recording and outputting test data.

Description

Method for standard penetration test and apparatus for performming the same

The present invention relates to a method and apparatus for automatically performing a standard penetration test (SPT) for performing a standard penetration test (SPT), and specifically, free fall of the hammer by dropping only the hammer in the state of lifting the hammer mechanically It prevents additional penetration due to drop impact or load while maintaining constant dropping when hitting by. It makes it possible to inject the sampler by accurate hitting. It is possible to determine the continuation and interruption of the test by automatically measuring the penetration amount of the sampler, to calculate the final value of N, and to control the operation of the devices to perform the test automatically in a batch. Accurate test results can be obtained with a control unit that records and outputs the results. To shop.

According to KS F 2307, the standard penetration test (SPT) inserts a split barrel sampler into the ground and records its resistance (N value) while simultaneously taking representative samples for soil classification test and indoor test. Defined by the method. In detail, it measures the strength of the ground by measuring the N value, which is the number of strikes required to penetrate the sampler penetrated into the borehole at a constant depth of about 30 cm from the ground by a constant impact energy acting as the 63.5 kg hammer falls at a height of 75 cm. In situ test method to estimate soil constants such as relative density of soil and internal friction angle and to obtain disturbance samples for expansion and consolidation tests. This test method is widely used in various countries around the world due to the simplicity of the procedure, the accumulation of numerous data, and the low cost, and it is essential for most civil engineering and building projects in Korea.

Currently, most of the test methods adopted in the domestic standard penetration test are known test methods for lifting and dropping a hammer by a winch and an automatic trip hammer.

1A shows a standard penetration test apparatus using a winch in the related art.

The device referred to in this figure secures the winding drum 2 and the pulley 3 to the support 1 so that the rope 4 is wound around the winding drum 2 to 3 times to guide the pulley 3. The hammer 5 fixed to the end of the rope 4 is guided by the guide rod 6 and is installed to be elevated. A rod 8 having an anvil 7 fixed thereto is installed at a lower portion of the guide rod 6, and a sampler (not shown) for obtaining a disturbance sample of the ground is connected to the lower end of the rod 8. The sampler is mainly a split barrel sampler.

The device connects the rope 4 to the hammer 5 and winds the hammer 5 by winding the rope 4 on a winding drum 2 rotating in a constant direction to hit the anvil 7. To perform the test. At this time, the hammer 5 which is lifted by the rope 4 is guided to the guide rod 6 to achieve an effective hit and to lift within the track range for the hit. The impact of the hammer 5 is transmitted through the anvil 7 to the rod 8 so that the sampler is introduced.

Conventional methods using such winches and ropes are difficult to maintain a constant drop even if a skilled worker performs the test, and the friction characteristics of the rope in contact with the pulley and the winding drum vary depending on the characteristics of the rope connected to the hammer or the degree of aging. Many factors affect the final striking energy of the rope and cause initial tension on the rope due to inertia forces in the rope, pulley and winding drum, depending on how the worker lays the rope, causing the rope to swing or reduce the rate of fall. It is difficult to ensure the reliability of the test results. In addition, since the N-value counting operation also depends on the memory of the operator, the result may be incorrectly obtained by mistake, resulting in a completely different result even when the test is performed on the same ground. In order to solve such a problem, an automatic hammer drop device is often used outside the country.

1B is an example of an automatic hammer device. Automatic hammer devices, developed so far, are designed to strike at the correct height with a simple operation, with less variation than rope-pulled pulleys and can deliver more hammer drop energy to the rod. However, the existing automatic hammer devices not only cause inaccurate results due to the complicated mechanisms for dropping connected with hammers or rods, but also the hammers hitting the hammers after hitting them to maintain a certain drop. Since the attached equipments may cause friction during the aging of the equipment, and the equipment attached to the hammer has very little rigidity compared to the hammer, the impact energy to be transmitted to the rod when the equipment is vibrated during the impact is the vibration energy. There is also a problem that is not absorbed to obtain an accurate result.

In order to solve the above problems, in the present invention, a device for automatically lifting and dropping the hammer without using a rope, a pulley, and a winding drum, which act as obstacles to free fall of the hammer, as in the conventional standard penetration test apparatus, is separately provided. It is fixed to the support of to remove the secondary blow phenomenon by the lifting device to exert the prescribed blow energy, and by forming irregularities at a certain interval on the periphery of the hammer, even if the hammer descends as the sampler intrudes, the automatic lifting-dropping device The hammer can be continuously picked up, mechanically lifting and dropping the hammer, maintaining a constant drop, so that the same energy can be transferred to the anvil and rod during each test to ensure the reliability of the test. To prevent operator error in advance By accumulating and storing the number of hits, the sampler's penetration rate is automatically calculated and accumulated so that N value can be obtained at the end of the test, so that all test procedures can be performed automatically after preparation for the standard penetration test.

That is, the present invention has a structure of a hammer having an uneven portion so that the automatic lifting-falling device continuously picks up the hammer when the position of the hammer changes due to the penetration of the sampler, and mechanically lifts the hammer and drops only the hammer. Automatic lifting and dropping device of hammer that can precisely test by eliminating friction factor of rope and winding drum to help free fall of hammer and to maintain constant dropping during each hit to prevent additional penetration due to drop impact or load of lifting device Weighing counting means to automatically measure the number of blows during hammer strike, and to prevent the operator's error in advance, and to automatically measure the penetration of the sampler to determine the continuation and interruption of the test. Penetration measurement means for calculating an N value as a result; The present invention provides a standard penetration test method capable of performing a smooth test by providing a control device that records and outputs a test result by controlling the driving of the above devices and performs a test automatically and collectively.

1A is a perspective view of a conventional standard penetration test apparatus

1B is a cross-sectional view showing another example of a conventional standard penetration test apparatus.

2 is a perspective view of the installation state of the present invention

3 is a front view of the present invention

4 is a perspective view of a portion of the present invention;

5 is a front view showing a part of the present invention;

Figure 6 is a plan view of the hammer portion of the present invention

7A is a cross-sectional view of the main part of the present invention in a state where a hammer is raised;

Figure 7b is a cross-sectional view of the main part of the hammer in the present state cut off

8 is a process flow chart of the present invention.

In order to achieve the above object, the present invention provides a method for performing a standard penetration test, comprising automatically lifting and raising a hammer by an automatic lifting-dropping device (S1); Separating the raised hammer from the lifting device to free fall (S2); Measuring the number of hits of the hammer by the step and accumulating and storing the hammer in the control device (S3); Simultaneously measuring the amount of penetration of the sampler and storing it in the control device (S4); Determining whether the penetration test proceeds by comparing the penetration amount of the sampler measured in the step with a reference value set in the control device (S5); Calculating an N value when the penetration amount of the sampler reaches the set reference value in the step (S6); In step S7, the test data is recorded and output as the N value is calculated.

In the measurement of the number of hits, a detection signal of a sensor that detects a hammer drop is transmitted to the control device to automatically accumulate and store the hits, and when the penetration amount of the sampler reaches a prescribed value, N value is calculated from the hit hits up to that point.

In the measurement of the penetration amount of the sampler, the signal generated from the sensor for detecting the movement amount of the hammer after each hit is input to the control device and used as data for output of the test result and control of the test.

An apparatus for performing such a test method includes an automatic lifting-dropping device installed in a housing rotatably fixed to a fixed shaft formed in a known boring equipment to raise and free fall a hammer; A hammer is formed in a space in which the anvil is accommodated from the lower portion, and an upper end portion is formed of a striking portion striking the anvil, and a plurality of protrusions having a circular shape are formed in a layer shape on an outer circumferential surface thereof; Blow recovery counting means for counting the number of times the hammer falling hits the anvil by the operation of the automatic lifting-dropping device; Penetration amount measuring means for measuring the penetration amount of a sampler introduced by the hammer hitting the anvil by the operation of the automatic lifting-dropping device; Control of driving of the automatic lifting-falling device by determining the continuation of the test by comparing the hit recovery counting means and the signal of the penetration measuring means with the set reference value, and controlling the calculation of the N value and recording and outputting the test result. An apparatus is provided.

The automatic lifting-dropping device includes: a hydraulic cylinder fixed vertically downward to an upper portion of a housing rotatably fixed to the boring equipment and having horizontal fixed ends on both ends of the piston rod; A pair of pincers contacting the outer circumferential surface of the hammer by forming a projection for lifting the hammer in a layered manner while the upper end is rotatably fixed below the fixed end of the hydraulic cylinder; A hydraulic cylinder actuating in both directions to push the niche away from the hammer so that the niche grips and releases the hammer; In order to cooperate with the gripping operation of the narrowing zone, a protrusion corresponding to the protrusion of the narrowing zone may be formed in a layered manner on the outer peripheral surface of the hammer.

The blow recovery counting means is constituted by a switch which is switched to the operation of the piston rod of the bidirectional hydraulic cylinder which operates the pincers which grip and lift the hammer.

The penetration measuring means consists of a sensor, for example an ultrasonic sensor, which detects the distance traveled by the hammer after each strike.

The control device is provided with basic data for the penetration test, is responsible for driving and controlling the mechanical configuration such as automatic lifting-dropping device, and accumulatively converts and stores the signals transmitted from the impact recovery counting means and the penetration measurement means. Analyze and record and output these test results.

In the apparatus of the present invention, the hydraulic cylinder lifts the hammer to a predetermined position during the test, and when the hammer is raised to the predetermined position, the narrowing zone is opened by the forward operation of the bidirectional cylinder to drop the hammer. At this time, the elements that hinder the falling of the hammer, for example, a winding drum, a roadway, a rope, and the like, which are found in the conventional apparatus, are not connected to the hammer, thereby allowing free free fall. The hammer strike energy is transmitted through the anvil and rod and used by the sampler to penetrate the ground. When the sampler, the rod and the hammer stop after injecting the sampler, the narrowing zone is lowered to a certain position according to the reciprocating motion of the reciprocating cylinder, and the narrowing zone is gripped again by the backward operation of the bidirectional cylinder. This procedure is repeated until the cumulative penetration of the sampler reaches the specified value and the test is terminated.

In this case, irregularities are formed in the peripheral part of the hammer so that the restraining device can continuously pick up the hammer even if the hammer descends according to the penetration of the sampler, and the automatic lifting-falling device is separated from the hammer and the rod to a separate support. The absolute position at which the restraining device picks up the hammer is always the same because it is held in place. Lamellar projections are formed on the outer circumferential surface of the hammer at regular intervals so that after a single hit, the pincers grasp a portion above the sampler penetration from the previously picked up position. Thus, even if the hammer descends, unlike the other automatic hammer device, the lifting-falling device does not need to be lowered to maintain a constant drop, so that the secondary collision problem can be eliminated accordingly and always maintain a constant lifting and falling.

The blow recovery counting means detects the operation of the two-way cylinder in which the pincers restraining the hammer, including the switch and the wire attached to the two-way cylinder, and the control device, release the hammer. The number of hits is automatically accumulated and stored. When the penetration amount of the sampler exceeds the prescribed value due to the accumulated blow of the hammer, the N value is calculated from the number of hits until then.

The penetration measurement means comprises a distance measuring sensor that targets the sensor to be installed downward from the inside of the lifting device. An ultrasonic sensor for distance measurement fixed in position will measure the penetration of the sampler from the amount of movement descending as the hammer strikes the anvil from the initial position of the hammer's test start. The signal generated from the ultrasonic sensor is transmitted to the controller and used as data for output of test results and control of the test.

The control unit controls the sequence of operation of the automatic running device and calculates the penetration amount after the start of the test to continue the test until the specified penetration amount and obtain N value. If the test termination criteria given in the regulations are met, the test is stopped and the results are output.

This embodiment of the present invention will be described with reference to the accompanying drawings.

2 shows a perspective view of a state in which the apparatus of the present invention is installed.

Referring to this figure, the housing 400 is fixed to the brackets 300 and 300a rotatably fixed to the fixed shaft 200 formed in the boring equipment 100.

The housing 400 is placed on top of a sampler (not shown below) to be introduced by receiving the automatic drop-lifting device 10 of the present invention and rotating it about the fixed shaft 200 to perform a test.

The automatic drop-lifting device 500 is composed of a hydraulic cylinder 10 fixed to the housing 400, a pair of pincers 20 and 20a, and a bidirectional hydraulic cylinder 30.

The hydraulic cylinder 10 is fixed to vertically coincide with the rod 50 on which the anvil 40 is installed while the piston rod 11 is downwardly reciprocated at a 75 cm height section at the upper portion of the housing 400. do.

A horizontal fixed end portion 12 is formed at the end of the piston rod 11, and the bidirectional hydraulic cylinder 30 is fixed to the lower center of the fixed end portion 12 so that the piston rods 31 and 31a face outwards. The upper ends of the pincers 20 and 20a are rotatably fixed to the hinges 13 and 13a at positions facing the piston rods 31 and 31a of the bidirectional hydraulic cylinder 30.

The narrow strip 20, 20a is formed with a layered serrated projection 21, 21a on the inner side in order to hold the hammer 60, and brackets 22, 22a on the upper inner side. The end portions of the piston rods 31 and 31a of the bidirectional hydraulic cylinders 30 and 30a are fixed to the rotatable hinges 22 and 22a, respectively.

The blow coefficient measuring switch 70 is fixed to the upper portion of the bidirectional hydraulic cylinder 30.

The blow coefficient measuring switch 70 is a rotation piece 72 in which a roller 71 contacting the protrusion 32 of one piston rod 31a of the bidirectional hydraulic cylinder 30 is rotatably fixed to the hinge 73. Is fixed to the roller rod 31 when the piston rod 31a makes a single retracting operation, and the rotating piece 72 pivots about the hinge 73 while the roller 71 is engaged with the switch contact. The signal 60 falls once to be transmitted to the control device.

The hammer 60 is made of a weight of 63.5 kg to form a space 61 for accommodating the anvil 40 from the bottom, the upper portion is blocked and a striking portion 62 for hitting the anvil 40 is formed, automatic lifting- In order to cooperate with the lifting operation of the dropping device, the projections 63 corresponding to the projections 21 and 21a of the narrow strip 20, 20a are formed in a layered manner on the outer circumferential surface thereof.

The hammer 60 is lifted by the narrow strip 20 and 20a and then dropped and hits the anvil 40 so that the sampler is infiltrated. In order to measure the penetration amount of the sampler, an ultrasonic wave inside the upper portion of the housing 400 is applied. The sensor 80 is fixed, and the ultrasonic wave transmitted from the ultrasonic sensor 80 reaches the upper surface of the hammer 60 through the space 14 drilled in the fixed end 12.

In the present invention configured as described above, the pincer strips 20 and 21 pinch and lift the hammer 60 placed on the anvil 40.

This lifting operation is as shown in FIG. 7A, when the piston rods 31 and 31a of the bidirectional hydraulic cylinder 30 are reversed, the pincers 20 and 21 are placed vertically by their own weight, so that both projections 20a ( 21a) is coupled to the projection () on the hammer 60, the piston rod 11 of the hydraulic cylinder 10 is reversed and ascended so that the space between the striking portion 62 of the hammer 60 and the anvil 40 Is formed.

Then, as shown in FIG. 7B, when the piston rods 31 and 31a of the bidirectional hydraulic cylinder 30 are advanced to push the narrow strips 20 and 20a to the outside, the narrow strips 20 and 20a are hinged 13. As the projections 20a and 21a move away from the hammer 60 while rotating about 13a, the hammer 60 falls freely, and the striking portion 62 strikes the anvil 40, and the impact energy The sampler is introduced by passing it through the rod 50 to the sampler.

When the single stroke of the hammer 60 is completed, the piston rods 31 and 31a of the bidirectional cylinder 30 retreat again so that the pincer 20 and 20a clamp the hammer 60 and then the hydraulic cylinder 10 Piston rod 11 of the) is reversed to rise with the hammer to prepare for the second blow.

At this time, while the piston rod 31a of the bidirectional hydraulic cylinder 30 operates the reciprocating operation to operate the narrow strip 20, 21, the protrusion 32 of the piston rod 31a continuously switches the switch 70. Is transmitted as a single drop of the hammer 60 to the control device, and the penetration amount of the sampler due to the drop of the hammer 60 is lowered by the ultrasonic sensor 80 every time at the initial position of the hammer. It is measured by measuring altitude.

The signal generated from the ultrasonic sensor 80 is transmitted to the control device.

The control device (not shown) receives the signals received from the blow count measurement switch 30 and the ultrasonic sensor 80 and compares them with the set reference value to determine whether to continue the test. When the hammer 60 hits by the automatic drop-lifting device is repeated repeatedly until the test is completed and the value is reached, and the penetration amount of the sampler exceeds the prescribed value, N value is obtained from the number of hits until then and the test is stopped. , Print the result.

The present invention carried out by the above configuration has the following effects.

The fall of the hammer can be kept constant by the operation of the automatic lifting drop device. The automatic lifting drop device is separated from the hammer and the rod, and is supported by a separate supporting means, and only the hammer is released freely as the narrowing zone is released. There is no energy loss or secondary collision.

In addition, while automatically measuring the number of hits of the hammer by using a counting device, the injection amount of the sampler by the hammer hit is also automatically measured by using an ultrasonic sensor, and by the control device that determines the continuation and termination of the test and calculates the N value. All test procedures are performed automatically.

Claims (7)

In performing a standard penetration test that injects a sampler into the ground using a falling hammer, Automatically lifting and raising the hammer by the automatic lifting drop device (S1); Separating the raised hammer from the automatic lifting drop device to free fall (S2); Measuring the number of hits of the hammer by the step and accumulating and storing the hammer in the control device (S3); Simultaneously measuring the amount of penetration of the sampler and storing it in the control device (S4); Determining whether the penetration test proceeds by comparing the penetration amount of the sampler measured in the step with a reference value set in the control device (S5); Calculating an N value when the penetration amount of the sampler reaches the set reference value in the step (S6); And (S7) recording and outputting test data as the N value is calculated in the step. 2. A method according to claim 1, wherein the automatic lifting drop device employs a switch that switches to a mechanical action of releasing the hammer to drop the hammer. The method according to claim 1, wherein the measurement of penetration of the sampler measures the penetration of the sampler from the change amount of the hammer moving with respect to the hammer. In forming a standard penetration test apparatus for injecting a sampler into the ground using a falling hammer, it is installed in a housing rotatably fixed to a fixed shaft formed in a known boring equipment. A dropping device; A hammer is formed in a space where the anvil is accommodated from the lower part, and an upper end portion is formed with a hitting part that strikes the anvil, and a plurality of protrusions having a circular shape are formed in a layer shape on an outer circumferential surface thereof; Blow recovery counting means for counting the number of times the hammer falling hits the anvil by the operation of the automatic lifting-dropping device; Penetration amount measuring means for measuring the penetration amount of a sampler introduced by the hammer hitting the anvil by the operation of the automatic lifting-dropping device; The control device for controlling the driving of the automatic lifting and dropping device by determining the continuation of the test by comparing the hit recovery counting means and the signal of the penetration measuring means with the set reference value, and calculating and outputting the N value and recording the test result. Standard penetration test automatic performance device comprising a. The hydraulic lifting device according to claim 4, further comprising: a hydraulic cylinder fixed vertically downward to an upper portion of the housing rotatably fixed to the boring equipment and having horizontal fixed ends on both ends of the piston rod; A pair of pincers contacting the outer circumferential surface of the hammer by forming a projection for lifting the hammer in a layered manner while the upper end is rotatably fixed below the fixed end of the hydraulic cylinder; A hydraulic cylinder actuating in both directions to push the niche away from the hammer so that the niche grips and releases the hammer; A standard penetration test automatic performance device, characterized in that to form a layer of projections coincident with the projections of the narrow zone on the outer peripheral surface of the hammer to cooperate with the narrow zone. 5. The apparatus according to claim 4, wherein the hit recovery counting means is composed of a switch which is switched to the operation of the piston rod of the bidirectional hydraulic cylinder which operates the pincer grip which grips, lifts and drops the hammer. 5. The apparatus of claim 4, wherein the penetration measurement means comprises an ultrasonic sensor for sensing the distance traveled by the hammer after each strike.