Device and method for detecting the three-blow penetration of ram-expanded piles and measuring the pile bottom rebound

Abstract

The present application relates to the technical field of building construction, in particular to a device and method for detecting the three-blow penetration of ramming expansion piles and measuring the pile bottom rebound, which directly measures the distance of the hammer top surface each time through a laser range finder. Since the steel material of the non-standard column hammer is incompressible, it is equivalent to directly measuring the penetration of the carrier each time and the final rebound amount. The data is transmitted to the mobile phone in a timely manner through Bluetooth, so that the penetration of each ramming and the final rebound amount can be immediately grasped, the error problem caused by the tightness of the steel wire rope during manual measurement of the steel wire rope is avoided, the error reaches millimeter level, the detection accuracy is improved, the safety hidden danger caused by manual measurement of the lifting equipment is avoided, and the measurement of the three-blow penetration and the pile bottom rebound is fast, correct and safe.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building construction, and particularly relates to a device and method for detecting three-strike penetration of rammed piles and measuring pile bottom rebound. BACKGROUND

[0002] The hollow prefabricated pile rammed pile is a recommended carrier pile, and a working mechanism thereof is that dry-mixed mortar is filled into the inner cavity of the prefabricated hollow pile, and a cylindrical rammer is repeatedly rammed on the dry-mixed mortar filler to form a carrier composed of cement mortar mixture, compacted soil body and affected soil body. In order to control the quality of the carrier, the filler amount, three-strike penetration and pile bottom carrier rebound are required as main control indexes.

[0003] Currently, the measurement method of the last three-strike penetration is that a skilled worker marks the steel wire rope after each ramming of the hoisting column hammer at the discharge port, and finally the difference between the marks is obtained. When the volume of the dry-mixed mortar filler is close to and less than the design requirement, if the last three-strike penetration meets the requirement, the ramming is stopped, and if not, the filler ramming is continued until the requirement is met. When the volume of the dry-mixed mortar filler exceeds the design requirement but the three-strike penetration has not reached the design requirement, the design needs to be modified according to the specification. After the three-strike penetration meets the design requirement, the cylindrical rammer is raised by 1-2 meters and then gently lowered, the steel wire rope is marked, and the difference between the last mark of the three-strike penetration and the mark is taken as the value of the pile bottom carrier rebound.

[0004] The last three-strike penetration and the rebound value of the pile bottom carrier are obtained by converting the marks of the steel wire rope. Due to manual operation, it is difficult to standardize and quantify the tight state, and if the steel wire rope is in different tight states when marking each time, there will be errors, and inaccurate marking will result in inaccurate measurement values. When manually measuring the rebound value limit, if the steel wire rope is in a tight state, the cylindrical rammer is required to only contact the pile bottom carrier to meet the requirement, which can only be operated by a skilled person through feeling. If the steel wire rope is in a low-stress tight state, the cylindrical rammer will compress the rebound value, and if the steel wire rope is in a high-stress tight state, the cylindrical rammer may not contact the carrier, resulting in measurement errors that do not meet the specification requirements. Manual measurement does not meet the safety production requirements. SUMMARY

[0005] The present application aims to provide a device and method for detecting three-strike penetration of rammed piles and measuring pile bottom rebound, which solves the problems of inaccurate measurement values, measurement errors that do not meet the specification requirements and safety production requirements of manual measurement of three-strike penetration and the rebound value of the pile bottom carrier.

[0006] To achieve the above object, the application provides a method for detecting three-strike penetration of ramming expansion pile and measuring pile bottom rebound, comprising the following steps:

[0007] The prefabricated hollow pile is pretreated and pressed to a certain height.

[0008] A certain volume of dry-mixed mortar is poured into the inner cavity of the prefabricated hollow pile, the non-standard column hammer is allowed to freely fall at the maximum falling distance, and the dry-mixed mortar poured is rammed for multiple cycles.

[0009] The remaining 40% volume of dry-mixed mortar is equally divided into several portions, and poured into the inner cavity of the prefabricated hollow pile in sequence, and the lifting height of the non-standard column hammer is calculated.

[0010] The non-standard column hammer is lifted to the calculated lifting height and freely falls to ram for multiple times, the distance between the distance meter and the top surface of the hammer after each ramming is obtained, and the penetration of each hammering is calculated.

[0011] After the penetration meets the requirements, the distance between the distance meter and the carrier is measured, and the distance between the distance meter and the carrier is measured again after a certain time required by the specification, and the rebound of the pile bottom is obtained.

[0012] After the penetration meets the requirements, the distance between the distance meter and the carrier is measured, and the distance between the distance meter and the carrier is measured again after a certain time required by the specification, and the rebound of the pile bottom is obtained.

[0013] The prefabricated hollow pile is pretreated and pressed to a certain height, and the method further comprises:

[0014] After the prefabricated hollow pile arrives at the site, a special polisher is used to polish the floating mortar in the cavity of the prefabricated hollow pile to form a smooth cavity, a steel plate is welded at the bottom of the prefabricated hollow pile, the prefabricated hollow pile is pressed in by a static pressure machine, the prefabricated hollow pile is pre-pressed to the design elevation by a pile feeder, and the pile feeder is removed.

[0015] A certain volume of dry-mixed mortar is poured into the inner cavity of the prefabricated hollow pile, the non-standard column hammer is allowed to freely fall at the maximum falling distance, and the dry-mixed mortar poured is rammed for multiple cycles.

[0016] A sleeve is installed above the prefabricated hollow pile, a small volume V1 of dry-mixed mortar is poured into the inner cavity of the prefabricated hollow pile, a columnar body with a certain height is formed at the bottom of the cavity of the prefabricated hollow pile, and the non-standard column hammer is lifted to the bottom of the hammer by a steel wire rope through the steel wire rope by a gantry.

[0017] Wherein, a certain volume of dry mixed mortar is poured into the inner cavity of the precast hollow pile, the non-standard column hammer is freely dropped according to the maximum falling distance, and is cycled multiple times, the poured dry mixed mortar is rammed, and the method further comprises:

[0018] The gantry is provided with a telescopic arm rod with adjustable length, and a laser range finder is installed at the end of the telescopic arm rod, the non-standard column hammer is freely dropped according to the maximum falling distance for the first time to obtain the maximum impact energy, the dry mixed mortar is rammed into the soil layer after the welded steel plate is impacted, and the cement mortar mixture, the compacted soil body and the affected soil body are formed, and the non-standard column hammer is lifted to a certain height and repeatedly rammed for several times.

[0019] Wherein, the remaining 40% volume of dry mixed mortar is equally divided into several portions, and is poured into the inner cavity of the precast hollow pile in sequence, the lifting height of the non-standard column hammer is calculated, and the method further comprises:

[0020] The remaining 40% volume of dry mixed mortar is equally divided into several portions, each portion has a volume of Vn, the height of the dry mixed mortar in the inner cavity after each filling is a constant value hn2, the distance between the laser range finder and the top surface of the carrier formed by the dry mixed mortar is hn1, the falling distance of the non-standard column hammer is hn3, the length of the non-standard column hammer is hn4, and the lifting height hn5 of the non-standard column hammer is calculated according to the following formula:

[0021] Hn5=hn1-hn2-hn3-hn4.

[0022] Wherein, the non-standard column hammer is freely dropped and rammed multiple times after being lifted to the calculated lifting height, the distance between the range finder and the top surface of the hammer after each ramming is obtained, and the penetration of each hammering is calculated, and the method further comprises:

[0023] The non-standard column hammer is freely dropped and rammed after being lifted to Hn5, the distance L1 between the laser range finder and the top surface of the hammer is measured, then the non-standard column hammer is freely dropped and rammed n times after being lifted to Hn5 each time, the distance between the laser range finder and the top surface of the hammer is measured, and then the distance L2, L3,..., Ln-1, Ln between the range finder and the top surface of the hammer after each ramming is obtained, and the difference Ln-Ln-1 between the distances each time is the penetration of each hammering.

[0024] Wherein, after the penetration meets the requirement, the distance between the range finder and the carrier is measured, and after a certain time required by the specification, the distance between the range finder and the carrier is measured again to obtain the pile bottom rebound value, and the method further comprises:

[0025] After the penetration degree is met, the non-standard column hammer is lifted outside the sleeve, the distance H1 of the laser range finder from the carrier is measured, after a certain time required by the specification, the distance H2 of the laser range finder from the carrier is measured again, and the difference H1-H2 is the rebound of the pile bottom.

[0026] A three-hit penetration detection and pile bottom rebound measurement device of a rammed pile, comprising a lifting mechanism and a distance measurement device, the lifting mechanism comprising a gantry, a steel wire rope and a non-standard column hammer, one end of the steel wire rope being wound around the gantry, the other end of the steel wire rope being connected with the non-standard column hammer; the distance measurement device comprising an adjustable arm rod and a laser range finder, the adjustable arm rod being connected with the gantry, and the laser range finder being connected with the adjustable arm rod.

[0027] The three-hit penetration detection and pile bottom rebound measurement device and method of the rammed pile of the application directly measure the distance of the hammer top surface each time through the laser range finder, and due to the incompressibility of the non-standard column hammer made of steel material, the penetration degree and the final rebound amount of each ramming of the carrier are directly measured, data are transmitted to the mobile phone in time through Bluetooth, the penetration degree of each ramming and the final rebound amount are immediately grasped, the error problem caused by the tightness of the steel wire rope is avoided when the steel wire rope is measured manually, the error reaches millimeter level, the detection accuracy is improved, the safety hidden danger caused by manual measurement of the hoisting equipment is avoided, the three-hit penetration detection and pile bottom rebound measurement are fast, correct and safe. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced.

[0029] Figure 1 is a schematic diagram of precast hollow pile pressing to design elevation.

[0030] Figure 2 is a schematic diagram of pouring dry-mixed mortar into a replacement sleeve.

[0031] Figure 3 is a schematic diagram of adjusting the hammer center and maximum drop distance.

[0032] Figure 4 is a schematic diagram of forming a smaller carrier by hammering a steel plate.

[0033] Figure 5 is lifting the column hammer to the sleeve outside the filler volume V2 to the pile bottom.

[0034] Figure 6 is the column hammer falling freely according to the larger drop distance.

[0035] Figure 7is a converted hammer distance schematic diagram.

[0036] Figure 8 is a three-strike penetration detection schematic diagram.

[0037] Figure 9 is a pile bottom rebound detection schematic diagram.

[0038] Figure 10 is a lumen plug body schematic diagram.

[0039] Figure 11 is a step diagram of the three-strike penetration detection and pile bottom rebound measurement method of the rammed pile of the present application.

[0040] In the figure: 201-gantry, 202-steel wire rope, 203-non-standard column hammer, 204-adjustable arm rod, 205-laser range finder. DETAILED DESCRIPTION

[0041] The embodiments of the present application are described in detail below, examples of which are shown in the accompanying drawings, the embodiments described below by referring to the accompanying drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0042] The first embodiment of the present application is:

[0043] Please refer to Figure 11 , wherein, Figure 11 is a step diagram of the three-strike penetration detection and pile bottom rebound measurement method of the rammed pile of the present application.

[0044] The present application provides a three-strike penetration detection and pile bottom rebound measurement method of a rammed pile, comprising the following steps:

[0045] S101: pretreating a prefabricated hollow pile and pressing the prefabricated hollow pile to a certain height.

[0046] Specifically, after the prefabricated hollow pile arrives, a special polisher is used to polish the floating slurry in the hollow cavity of the hollow pile to form a smooth cavity, so that the cylindrical rammer can smoothly descend when ramming and will not produce eccentricity; a steel plate is welded at the bottom of the prefabricated hollow pile to prevent soil plug and underground water from entering the inner cavity of the prefabricated hollow pile. When constructing, the static pressure installation machine presses the prefabricated hollow pile, and then the pile feeder is used to press the hollow prefabricated pile to the design elevation, and then the pile feeder is removed.

[0047] S102: pouring a certain volume of dry mixed mortar into the inner cavity of the prefabricated hollow pile, making the non-standard column hammer 203 freely fall according to the maximum drop distance, and repeating multiple times to ram the poured dry mixed mortar.

[0048] Specifically, a sleeve is installed above the prefabricated hollow pile to prevent soil around the hole from entering the inner cavity of the hollow pile. A small volume V1 of dry-mixed mortar is poured into the inner cavity of the prefabricated hollow pile to form a columnar body of a certain height at the bottom of the cavity of the prefabricated pile. The non-standard hammer is lifted to the bottom of the sleeve by 30-50 mm through the steel wire rope 202 of the gantry 201, and the steel wire rope 202 is required to be aligned with the center of the prefabricated hollow pile to ensure that the plumb body can freely fall in the sleeve and the inner cavity. At the same time, the maximum plumb body falling distance can make the plumb body obtain the maximum impact energy, and ensure that the steel plate welded at the bottom of the prefabricated hollow pile can be impacted and opened by the first free fall. The telescopic arm rod installed on the gantry 201 can be adjusted in length, and the end of the telescopic arm rod is provided with a laser range finder 205 that can be purchased on the market. The range finder can send measurement data to a mobile phone through Bluetooth function, and has a remote control switch for turning on and off the range finder through the mobile phone software. The range finder is turned on, and the telescopic arm rod is adjusted to ensure that the range finder can measure the plumb body. The laser range finder 205 is an instrument for measuring the distance of the target by modulating a certain parameter of the laser. According to the distance measuring method, it is divided into phase method range finder and pulse method range finder. The measurement level product of the pulse method laser range finder 205 shows the accuracy of 0.1 meters, and the measurement accuracy is ±0.15 meters. The accuracy of the phase type laser range finder 205 can reach 1 millimeter error, and is suitable for various high-precision measurement purposes. The working principle of the phase method laser range finder 205 is to detect the distance by detecting the phase difference between the emitted light and the reflected light in space. The non-standard column hammer 203 is freely dropped for the first time according to the maximum falling distance to obtain the maximum impact energy, and the welded steel plate is impacted and opened. Then the dry-mixed mortar is rammed into the bearing layer soil to form a cement mortar mixture, a compacted soil body, and an affected soil body. The column hammer is lifted to a certain height and repeatedly rammed several times.

[0049] S103: Continue to pour a certain volume of dry-mixed mortar into the prefabricated hollow pile, and repeat the ramming of the non-standard column hammer 203 and the pouring of the dry-mixed mortar until the volume of the poured dry-mixed mortar reaches 60% of the designed volume.

[0050] Specifically, the non-standard column hammer 203 is lifted out of the sleeve, a certain volume V2 of dry-mixed mortar is poured into the sleeve, and a columnar body of a certain height is formed at the bottom of the cavity of the prefabricated pile. The non-standard column hammer 203 is freely dropped according to a larger falling distance, the volume V2 of dry-mixed mortar is rammed into the carrier that has been formed, the column hammer is lifted to a certain height and repeatedly rammed several times. At this time, due to the ramming of the volume V2 of dry-mixed mortar into the carrier, the range of the cement mortar mixture, the compacted soil body, and the affected soil body has gradually expanded. The dry-mixed mortar is repeatedly poured and rammed several times until the volume of the dry-mixed mortar reaches 60% of the designed volume. At this time, due to the several times of filling, the range of the cement mortar mixture, the compacted soil body, and the affected soil body has further expanded.

[0051] S104: The remaining 40% volume of dry-mixed mortar is divided into several portions and poured into the inner cavity of the precast hollow pile in turn, and the lifting height of the non-standard column hammer 203 is calculated.

[0052] Specifically, the remaining 40% is divided into several portions, each portion having a volume Vn. The purpose of this is to make the height hn2 of the dry-mixed mortar in the wall a constant value hn2 after each filling, and to calculate the conversion hammer distance: The national industry standard "Technical Standard for Carrier Pile" JGJ135 stipulates that a column hammer with a diameter of 355 mm and a mass of 3500 kg is used, with a drop distance of 6.0 m, and the cumulative settlement of three consecutive hammer blows is three blow penetration. When the inner diameter of the precast hollow pile is greater than 355 mm + 20 mm + 20 mm = 395 mm (20 mm is the gap between the column hammer and the inner wall of the hollow pile), the standard hammer can be used. Taking a national standard pipe pile with a diameter of 600 mm as an example, the minimum wall thickness is 110, and the maximum inner diameter of the cavity is 380 mm, which cannot be used with a standard column hammer. The diameter of such a precast pipe pile is 700 mm, which is less commonly used in general engineering and is not economical. Therefore, the "Technical Standard for Carrier Pile" provides the conversion principle of non-standard hammer for engineering quality assurance: The impact energy per unit area of the non-standard hammer is the same as the impact energy of the standard hammer when the three blow penetration is reached, i.e.

[0053] The mass of the non-standard hammer (kg) x the drop distance (M) / π x the radius of the non-standard hammer (mm) 2 = 3500 kg x 6.0 (M) / π x 177.5 (mm) 2

[0054] The drop distance hn3 of the non-standard hammer is calculated according to the above formula,

[0055] The distance between the distance meter and the carrier top surface formed by the dry-mixed mortar is hn1, the volume of the dry-mixed mortar is Vn, the height of the dry-mixed mortar is hn2, the drop distance of the non-standard hammer is hn3, and the length of the non-standard hammer is hn4. The lifting height hn5 of the non-standard column hammer 203 can be obtained according to the following formula:

[0056] Hn5 = hn1 - hn2 - hn3 - hn4

[0057] So every time the hammer is lifted to a height hn5 and then freely falls, it can ensure that each ramming meets the required drop distance. The non-standard column hammer 203 is lifted outside the sleeve, the mobile phone opens the remote control switch of the distance meter, measures the distance hn1 between the distance meter and the carrier, the distance meter Bluetooth sends the hn1 data to the mobile phone APP, and the distance meter is closed to prevent sending invalid data. A certain volume Vn of dry mixed mortar is poured, the mobile phone opens the remote control switch of the distance meter, measures the distance hn2 between the distance meter and the carrier, the distance meter Bluetooth sends the hn2 data to the mobile phone APP, and the distance meter is closed to prevent sending invalid data. The mobile phone APP gives the lifting height Hn5 of the non-standard hammer after processing the above data.

[0058] S105: The non-standard column hammer 203 is lifted to the calculated lifting height and freely falls to ram several times, the distance between the distance meter and the top surface of the hammer after each ramming is obtained, and the penetration of each hammering is calculated.

[0059] Specifically, the non-standard column hammer 203 is lifted to Hn5 and freely falls to ram, the distance L1 between the distance meter and the top surface of the hammer is measured, and then the non-standard column hammer 203 is lifted to Hn5 and freely falls to ram n times, the distance between the distance meter and the top surface of the hammer after each ramming is measured to obtain the distance L2, L3,..., Ln-1, Ln between the distance meter and the top surface of the hammer after each ramming. The difference Ln-Ln-1 between each distance is the penetration of each hammering; after the distance Ln between the distance meter and the top surface of the hammer is measured each time, the data is sent to the mobile phone APP through Bluetooth, and the mobile phone APP can display the penetration through calculation; after the volume Vn of dry mixed mortar is poured and hammered several times, if the penetration displayed by the mobile phone APP meets the design requirements, the hammering can be stopped; if the penetration does not meet the design, the next volume Vn of dry mixed mortar should be poured, and then the non-standard column hammer 203 is lifted to Hn5 and freely falls to ram several times, the distance between the distance meter and the top surface of the hammer after each ramming is measured to obtain Ln, Ln+1, Ln+2,..., and the data is sent to the mobile phone APP through Bluetooth after the distance L between the distance meter and the top surface of the hammer is measured each time. The mobile phone APP can display the penetration through calculation; if the penetration displayed by the mobile phone APP meets the design requirements, the hammering can be stopped; if the penetration does not meet the design, the next volume Vn of dry mixed mortar should be poured, and the above process should be continued until the penetration meets the position; however, the prerequisite is that when the dry mixed mortar is filled to 1.0 to 1.1 times the volume required by the design, the penetration still does not meet the design requirements, which indicates that the design scheme is unreasonable and should be modified.

[0060] S106: After the penetration meets the requirements, the distance between the distance meter and the carrier is measured, and after a certain time required by the specification, the distance between the distance meter and the carrier is measured again to obtain the pile bottom rebound.

[0061] Specifically, after the penetration degree is satisfied, the non-standard column hammer 203 is lifted out of the sleeve, the mobile phone is turned on to open the remote control switch of the range finder, the distance H1 between the range finder and the carrier is measured, after a certain time required by the specification, the distance H2 between the range finder and the carrier is measured again, and the difference between H1 and H2 is the rebound value of the pile bottom. If the difference between H1 and H2 is greater than the design requirement or the specification requirement, it indicates that the soil body is not effectively compacted, and the three-impact penetration degree must be measured again after ramming. If the difference between H1 and H2 is less than the design requirement or the specification requirement, it indicates that the soil body is compacted, and subsequent construction is carried out. The non-standard column hammer 203 is lifted into the sleeve, the volume of the dry-mixed mortar to be poured in is calculated according to the height and inner diameter of the prefabricated hollow pile cavity plug body required by the design, the dry-mixed mortar is poured in, the non-standard column hammer 203 is lifted into the sleeve and gently placed down, and the dry-mixed mortar is lightly pressed for 3-5 times to compact the dry-mixed mortar.

[0062] The distance from the top surface of the column hammer is directly measured by the laser range finder 205 each time. Due to the incompressibility of the steel column hammer, the penetration degree and the final rebound value of each ramming of the carrier are directly measured. The data is transmitted to the mobile phone APP in a timely manner through Bluetooth, so that the penetration degree and the final rebound value of each ramming are immediately mastered, the error caused by the tightness of the steel wire rope 202 is avoided when the steel wire rope 202 is measured manually, the error is reduced to millimeters, the detection accuracy is improved, the safety hidden danger caused by manual measurement of the hoisting equipment is avoided, the three-impact penetration degree detection and the pile bottom rebound measurement are fast, correct and safe.

[0063] The second embodiment of the present application is:

[0064] Based on the first embodiment, please refer to Figures 1 to 10 , wherein, Figure 1 is a schematic diagram of a prefabricated hollow pile being pressed to a design elevation. Figure 2 is a schematic diagram of a replacement sleeve pouring dry-mixed mortar. Figure 3 is a schematic diagram of adjusting the hammer center and the maximum drop distance. Figure 4 is a schematic diagram of a hammer impacting a steel plate to form a smaller carrier. Figure 5 is lifting the column hammer to the sleeve outside to fill the volume V2 to the pile bottom. Figure 6 is the column hammer freely falling and ramming according to a larger drop distance. Figure 7 is a conversion hammer distance schematic diagram. Figure 8 is a three-impact penetration degree detection schematic diagram. Figure 9 is a pile bottom rebound detection schematic diagram. Figure 10 is an inner cavity plug body schematic diagram.

[0065] A kind of ramming pile three hit penetration detection and the measuring device of pile bottom rebound, including lifting mechanism and distance measuring device, the lifting mechanism includes portal frame 201, steel wire rope 202 and non-standard column hammer 203, the distance measuring device includes adjustable arm lever 204 and laser range finder 205.

[0066] For this specific embodiment, one end of the steel wire rope 202 is wound around the portal frame 201, the other end of the steel wire rope 202 is connected with the non-standard column hammer 203, the adjustable arm lever 204 is connected with the portal frame 201, and the laser range finder 205 is connected with the adjustable arm lever 204. A pulley is arranged between the top of the portal frame 201, and the non-standard column hammer 203 can be lifted by the winch through the steel wire rope 202 around the pulley and can freely fall. The filler at the bottom of the rammed pile forms a carrier, which is continuously rammed and compacted by repeated ramming, forming a cement mortar mixture, a compacted soil body, and an affected soil carrier from the inside out. The adjustable arm lever 204 is used to fix the position of the laser range finder 205. One end of the adjustable arm lever 204 can be fixed at any height position of the portal frame 201 body through bolts, and the other end fixes the laser range finder 205. By adjusting the horizontal length, the laser beam emitted by the laser range finder 205 can be irradiated on the upper surface of the non-standard column hammer 203 to measure the distance. The laser range finder 205 is a phase range finder with Bluetooth data transmission function, which can send the measured data to a mobile phone. The laser range finder 205 has a wireless remote control switch, which can be turned on or off by the mobile phone.

[0067] A kind of ramming pile three hit penetration detection and the measuring device of pile bottom rebound using the embodiment is as shown in Figure 1 、 2 After the prefabricated hollow pile is put into place, the special polisher is used to polish the floating slurry in the hollow cavity of the hollow pile according to the size of the inner diameter of the prefabricated hollow pile to form a smooth cavity, so that the cylindrical rammer can smoothly descend during ramming without eccentricity. A 5mm thick steel plate is welded at the bottom of the prefabricated hollow pile to prevent soil plug and underground water from entering the inner cavity of the prefabricated hollow pile. After the prefabricated hollow pile is pressed into place by the static pressure pressing machine, the pile is sent to the design elevation and the pile sender is removed.

[0068] A sleeve is installed to prevent soil around the hole from entering the inner cavity of the hollow pile. A small amount of dry mortar with volume V1 is poured through the inner cavity of the prefabricated hollow pile to form a columnar body with a certain height at the bottom of the cavity of the prefabricated pile.

[0069] As shown in Figure 3 、 4As shown, the winch passes through the steel wire rope 202 around the top pulley of the gantry 201 to hoist the column hammer vertically, ensuring that the steel wire rope 202 is centered with the prefabricated hollow pile to ensure that the column hammer can freely fall in the sleeve and inner cavity; the column hammer is lifted to the bottom of the hammer just entering the sleeve 30-50mm, at this time the column hammer obtains the maximum impact energy with the maximum drop distance, to ensure that the first free-falling ramming can impact the steel plate welded at the bottom of the prefabricated hollow pile to be opened; the filler rammed at the bottom of the pile forms a carrier, which is continuously rammed and compacted by repeated ramming, forming a cement mortar mixture, a compacted soil body, and a carrier affecting the soil body from the inside out.

[0070] The gantry 201 is provided with an adjustable length telescopic arm for fixing the position of the laser range finder 205. One end of the telescopic arm 204 can be fixed at any height position of the gantry 201 body through a bolt, and the other end is fixed with the laser range finder 205. By adjusting the horizontal length, the laser beam emitted by the range finder can be irradiated on the upper surface of the ramming column hammer to measure the distance. The laser range finder 205 has the function of sending data through Bluetooth, and can send the measured data to the mobile phone. The laser range finder 205 has a wireless remote control switch, which can be turned on or off through the mobile phone. When the distance needs to be measured, the switch of the laser range finder 205 is turned on through the mobile phone, and the range finder sends data to the mobile phone APP through Bluetooth. When the distance does not need to be measured, the switch of the laser range finder 205 is turned off through the mobile phone to avoid sending useless data.

[0071] As shown in Figure 5 , 6 , the column hammer is lifted out of the sleeve and a certain volume V2 of dry mixed mortar is poured to form a columnar body of a certain height at the bottom of the prefabricated pile cavity; the column hammer is freely dropped with a larger drop distance, and the volume V2 of dry mixed mortar is rammed into the carrier that has been formed, and the column hammer is lifted to a certain height and repeatedly rammed several times; at this time, since the volume V2 of dry mixed mortar is rammed into the carrier, the range of cement mortar mixture, compacted soil body, and carrier affecting the soil body gradually expands; the repeated filling is continuously rammed n times until the volume of the dry mixed mortar filling reaches 60% of the design volume; that is, the volume of each filling V1+V2+...+Vn≤60% of the design, at this time, due to the several fillings, the range of cement mortar mixture, compacted soil body, and carrier affecting the soil body further expands;

[0072] As shown in Figure 7 , it is a conversion hammer distance schematic diagram; the national industry standard "carrier pile technical standard" JGJ135 gives the conversion principle of non-standard hammer to ensure engineering quality: the impact energy per unit area of non-standard hammer is the same as that of standard hammer with three impact degrees, that is:

[0073] Mass of non-standard hammer (kg) x drop distance (M) / π x radius of non-standard hammer (mm) 2 = 3500 kg x 6.0 (M) / π x 177.5 (mm) 2

[0074] The drop distance hn3 of the non-standard hammer is calculated according to the above formula.

[0075] The distance between the distance finder and the top surface of the carrier formed by the dry-mixed mortar is hn1; the remaining 40% is divided into several portions, each portion having a volume Vn, and the purpose of this is to make the height hn2 of the dry-mixed mortar in the wall a constant value hn2 after each filling.

[0076] The drop distance hn3 of the non-standard hammer, the length of the non-standard hammer hn4, and the lifting height hn5 of the non-standard column hammer 203 can be obtained according to the following formula:

[0077] Hn5 = hn1 - hn2 - hn3 - hn4

[0078] This ensures that each ramming meets the required drop distance.

[0079] As shown in Figure 8 The remaining 40% is divided into several portions, each portion having a volume Vn, and the purpose of this is to make the height hn2 of the dry-mixed mortar in the wall a constant value after each filling. After the non-standard column hammer 203 is lifted to Hn5 and freely falls for ramming, the distance L1 between the distance finder and the top surface of the hammer is measured, the laser distance finder 205 is turned on by the mobile phone, and the distance L1 between the distance finder and the top surface of the hammer is sent to the mobile phone APP through Bluetooth. Thereafter, the column hammer is lifted to Hn5 and freely falls for ramming n times, and the distance between the distance finder and the top surface of the hammer after each ramming, L2, L3,..., Ln-1, Ln, is obtained. The difference Ln-Ln-1 between each distance is the penetration depth of each hammering. After the distance Ln between the distance finder and the top surface of the hammer is measured each time, the data is sent to the mobile phone APP through Bluetooth, and the penetration depth is displayed by the mobile phone APP through calculation.

[0080] After each volume Vn of dry-mixed mortar is poured and hammered several times, if the penetration depth displayed by the mobile phone APP meets the design requirements, the hammering is stopped; if the penetration depth does not meet the design requirements, the next volume Vn of dry-mixed mortar is poured, and thereafter the column hammer is lifted to Hn5 and freely falls for ramming several times, and the distance between the distance finder and the top surface of the hammer after each ramming is measured to obtain Ln, Ln+1, Ln+2,.... After the distance L between the distance finder and the top surface of the hammer is measured each time, the data is sent to the mobile phone APP through Bluetooth, and the penetration depth is displayed by the mobile phone APP through calculation. If the penetration depth displayed by the mobile phone APP meets the design requirements, the hammering is stopped; if the penetration depth does not meet the design requirements, the next volume Vn of dry-mixed mortar is poured, and thereafter the column hammer is lifted to Hn5 and freely falls for ramming several times, and the distance between the distance finder and the top surface of the hammer after each ramming is measured to obtain Ln, Ln+1, Ln+2,.... After the distance L between the distance finder and the top surface of the hammer is measured each time, the data is sent to the mobile phone APP through Bluetooth, and the penetration depth is displayed by the mobile phone APP through calculation.

[0081] If the design requirements are met, hammering can be stopped. If the penetration does not meet the design requirements, the next batch of dry-mixed mortar with a volume of Vn should be poured in, and the above process should be continued until the penetration meets the requirements. However, the prerequisite is that if the penetration still does not meet the design requirements after the dry-mixed mortar has been filled to 1.0 to 1.1 times the design requirements, it indicates that the design scheme is unreasonable and the design should be modified.

[0082] like Figure 9 As shown, after the penetration requirement is met, the pile hammer is lifted out of the sleeve. The remote control switch of the rangefinder is turned on using a mobile phone, and the distance H1 between the rangefinder and the carrier is measured. After a certain period of time as required by the specifications, the distance H2 between the rangefinder and the carrier is measured again. The difference between H1 and H2 is the rebound amount at the pile bottom. If the difference between H1 and H2 is greater than the design requirement or specification requirement, it indicates that the soil has not been effectively compacted, and the three-blow penetration must be measured again after compaction. If the difference between H1 and H2 is less than the design requirement or specification requirement, it indicates that the soil has been compacted, and subsequent construction can proceed.

[0083] like Figure 10 As shown, lift the non-standard column hammer 203 out of the sleeve. Calculate the final volume of dry-mixed mortar to be poured in based on the height and diameter of the precast hollow pile's inner cavity plug as required by the design. Pour in the dry-mixed mortar, lift the non-standard column hammer 203 into the sleeve, and gently lower it. Repeat this gentle pressing 3-5 times to compact the dry-mixed mortar.

[0084] The laser rangefinder 205 directly measures the distance to the top of the hammer each time. Due to the incompressibility of the non-standard column hammer 203 made of steel, this is equivalent to directly measuring the penetration and final rebound of each impact on the carrier. The data is transmitted to the mobile phone in real time via Bluetooth, allowing for immediate monitoring of the penetration and final rebound of each impact. This avoids the error caused by manually measuring the tension of the steel wire rope 202, reducing the error to the millimeter level, improving detection accuracy, and avoiding the safety hazards of manual measurement on lifting equipment. This makes the three-impact penetration test and pile bottom rebound measurement quick, accurate, and safe.

[0085] The above-disclosed embodiments are merely one or more preferred embodiments of this application and should not be construed as limiting the scope of this application. Those skilled in the art can understand that all or part of the processes for implementing the above embodiments and equivalent changes made in accordance with the claims of this application still fall within the scope of this application.

Claims

1. A method for detecting the three-blow penetration and measuring the rebound at the bottom of a rammed and expanded pile, characterized in that, Includes the following steps: The precast hollow piles are pre-treated and then pressed to a certain height. A certain volume of dry-mixed mortar is poured into the inner cavity of the precast hollow pile, and a non-standard column hammer is allowed to fall freely at the maximum drop distance, and the process is repeated multiple times to tamp the poured dry-mixed mortar. Continue to pour a certain volume of dry-mixed mortar into the precast hollow pile, repeat the tamping of the non-standard column hammer and the pouring of dry-mixed mortar until the volume of dry-mixed mortar poured in reaches 60% of the design requirement. Divide the remaining 40% volume of dry-mixed mortar into several equal portions and pour them into the inner cavity of the precast hollow pile in sequence. Calculate the lifting height of the non-standard column hammer. The non-standard column hammer was raised to the calculated lifting height and then dropped freely to pound the hammer multiple times. The distance between the laser rangefinder and the top surface of the hammer was obtained after each pounding, and the penetration degree of each hammering was calculated. After the penetration is satisfied, the distance between the laser rangefinder and the carrier is measured. After a certain period of time as required by the specification, the distance between the laser rangefinder and the carrier is measured again to obtain the rebound amount at the bottom of the pile.

2. The method for detecting the three-blow penetration and measuring the rebound at the bottom of the pile in claim 1, characterized in that, The method further includes pre-treating the precast hollow piles and pressing them to a certain height. After the precast hollow piles arrive on site, a special grinder is used to grind the slurry inside the cavity of the precast hollow pile to form a smooth cavity. A steel plate is welded to the bottom of the precast hollow pile. After the precast hollow pile is pressed in using a static pressure machine, a pile driver is used to pre-press the precast hollow pile to the design elevation, and then the pile driver is removed.

3. The method for detecting the three-blow penetration and measuring the rebound at the bottom of the pile in claim 1, characterized in that, A certain volume of dry-mixed mortar is poured into the inner cavity of the precast hollow pile, and a non-standard column hammer is allowed to fall freely at its maximum drop distance, and this process is repeated multiple times to compact the poured dry-mixed mortar. The method further includes: A sleeve is installed above the precast hollow pile. A small amount of dry-mixed mortar of volume V1 is poured into the inner cavity of the precast hollow pile to form a columnar body of a certain height at the bottom of the cavity of the precast hollow pile. The non-standard column hammer is lifted by steel wire rope through a gantry frame until the bottom of the hammer just enters the sleeve by 30-50mm.

4. The method for detecting the three-blow penetration and measuring the rebound at the bottom of the pile in claim 3, characterized in that, A certain volume of dry-mixed mortar is poured into the inner cavity of the precast hollow pile, and a non-standard column hammer is allowed to fall freely at its maximum drop distance, and this process is repeated multiple times to compact the poured dry-mixed mortar. The method further includes: An adjustable telescopic boom is installed on the gantry frame. A laser rangefinder is installed at the end of the telescopic boom. The non-standard column hammer is dropped freely at its maximum drop distance for the first time to obtain the maximum impact energy. After the welded steel plate is broken open, the dry-mixed mortar is driven into the bearing soil layer to form a cement mortar mixture, which compacts and affects the soil. The non-standard column hammer is then raised to a certain height and repeatedly driven several times.

5. The method for detecting the three-blow penetration and measuring the rebound at the bottom of the pile in claim 4, characterized in that, The remaining 40% volume of dry-mixed mortar is divided into several equal portions and poured sequentially into the inner cavity of the precast hollow pile. The lifting height of the non-standard column hammer is calculated. The method further includes: The remaining 40% volume of dry-mixed mortar is divided into several equal portions, each with a volume of Vn. The height of the dry-mixed mortar in the inner cavity after each filling is a fixed value hn2. The distance between the laser rangefinder and the top surface of the carrier formed by the dry-mixed mortar is hn1. The drop distance of the non-standard hammer is hn3, the length of the non-standard hammer is hn4, and the lifting height of the non-standard hammer is hn5, calculated using the following formula: Hn5 = hn1 - hn2 - hn3 - hn4.

6. The method for detecting the three-blow penetration and measuring the rebound at the bottom of the pile in claim 5, characterized in that, The non-standard column hammer is raised to a calculated height and then dropped freely to strike the hammer multiple times. The distance between the laser rangefinder and the top surface of the hammer is obtained after each strike, and the penetration depth of each strike is calculated. The method also includes: The non-standard hammer is raised to Hn5 and then dropped freely to strike the hammer. The distance L1 between the laser rangefinder and the top surface of the hammer is measured. Subsequently, the non-standard hammer is raised to Hn5 and dropped freely to strike the hammer n times each time. The distance between the laser rangefinder and the top surface of the hammer is measured again. The distances L2, L3, ..., Ln-1, Ln between the laser rangefinder and the top surface of the hammer after each strike can be obtained. The difference between each distance, Ln-Ln-1, is the penetration depth of each strike.

7. The method for detecting the three-blow penetration and measuring the rebound at the bottom of the pile in claim 6, characterized in that, After the penetration depth is satisfied, the distance between the laser rangefinder and the carrier is measured. After a certain period of time as required by the specification, the distance between the laser rangefinder and the carrier is measured again to obtain the pile bottom rebound amount. The method further includes: After the penetration is satisfied, the non-standard pile hammer is lifted outside the sleeve, and the distance H1 between the laser rangefinder and the carrier is measured. After a certain period of time as required by the specification, the distance H2 between the laser rangefinder and the carrier is measured again. The difference between H1 and H2 is the rebound amount at the bottom of the pile.

8. A measuring device for detecting the three-blow penetration and the rebound at the bottom of a rammed and expanded pile, applicable to the method for detecting the three-blow penetration and the rebound at the bottom of a rammed and expanded pile as described in claim 1, characterized in that, The device includes a lifting mechanism and a distance measuring device. The lifting mechanism includes a gantry frame, a wire rope, and a non-standard drop hammer. One end of the wire rope passes around the gantry frame, and the other end of the wire rope is connected to the non-standard drop hammer. The distance measuring device includes an adjustable boom and a laser rangefinder. The adjustable boom is connected to the gantry frame, and the laser rangefinder is connected to the adjustable boom.

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