Bypass hole reflected wave detection method and pile length and integrity evaluation method

Abstract

The invention discloses a side hole reflection wave detection method and a pile length and integrity evaluation method, and belongs to the technical field of engineering piles, pile body transmission direct waves and pile bottom reflection transmission waves are collected at a certain depth in a side hole, and the pile length can be analyzed through the travel time difference between the pile body transmission direct waves and the pile bottom reflection transmission waves and the depth of a detector; time and depth signal diagrams do not need to be arranged by collecting signals at certain intervals along the depth, and the signals only need to be detected and collected once in the test. According to the side hole reflected wave detection method and the pile length and integrity evaluation method, a time-depth signal graph does not need to be arranged by collecting signals at certain intervals along the depth, and only one-time signal detection and collection are needed in the test, so that a large amount of detection time is saved, and the detection efficiency is improved; the method can be used for detecting pile top connecting bearing platforms of existing building engineering piles and the like and the lower pile length and integrity of an upper structure in the urban renewal field, can also be used for detecting exposed free piles at the pile tops, and has high precision.

Description

Technical Field

[0001] The invention relates to the technical field of engineering piles, and in particular to a side-hole reflection wave detection method and a pile length and integrity assessment method. Background Art

[0002] Engineering piles are cast in the foundation through a specific construction method, or the pile body is driven or pressed into the foundation soil, so that the pile and the foundation soil together form a load-bearing structure to enhance the stability and bearing capacity of the building. It is mainly used to bear the load of the building and transfer these loads to the foundation soil. As an important foundation form, pile foundation is widely used in various building structures. The importance of its length and integrity detection is also widely recognized. Among the current pile foundation detection technologies, the low-strain reflection wave method and mechanical impedance method based on reflection waves have been widely used due to their advantages of fastness, low cost and good effect. It is widely used in the detection of various piles under construction. For existing engineering piles, when the top of the pile is connected to platforms such as beams, plates, and caps and the platform excitation method is adopted, the upper platform will cause a three-dimensional effect of the signal, and the waveform will present a low-frequency large swing form, so that the pile bottom or defect reflection is difficult to effectively identify, and the stress wave will be reflected multiple times at the upper and lower interfaces of the platform. Only a small amount of energy is transmitted to the pile body, and the pile bottom reflection is relatively weak. After the weak pile bottom reflection is superimposed with the interference signal, it is difficult to identify the position of the pile bottom reflection wave. When the existing engineering piles use pile side excitation, the upper structure reflection wave will also interfere with the identification of the pile bottom reflection wave.

[0003] In order to overcome the above defects, prior art 1 (application number CN201410188347.3, Chinese patent with application date of 2014-05-06) is a method for determining the bottom depth of an existing engineering pile based on the inflection point method of the side-hole transmission wave. This method is not affected by the waveform of the superstructure and is easy to detect. The bottom depth of the pile is determined by determining the inflection point position and correcting it with the recommended formula. The determination of the bottom depth of the pile is simple and intuitive. It is also easy to operate for technicians without engineering experience, and has solved the problem that it is difficult to determine the bottom depth of existing engineering piles. In addition, prior art 2 (Chinese patent with application number CN201610519601.2 and application date 2016-07-05) provides an effective pile foundation detection method for the case where the pile foundation and its upper foundation, pedestal, etc. are not under vibration conditions. It can also be used as a backup means for pile foundation detection under vibration conditions. It does not damage the upper structure and the pile foundation, does not require additional treatment of the pile, is simple to judge the integrity of the pile body, and does not require correction of the bottom depth of the pile. It is simple to operate and easy to promote and apply. Although the prior art can determine the bottom depth of the engineering pile, the hole depth must exceed the expected bottom depth of the pile or defect depth, otherwise effective testing cannot be performed. This will lead to poor detection efficiency in the later stage, affect its detection accuracy, and be very time-consuming and labor-intensive; and in the method for determining the bottom depth of existing engineering piles based on the side-hole transmission wave inflection point method of prior art 3 (application number CN201410188347.3, application date 2014-05-06 Chinese patent), compared with the method for determining the bottom depth of piles based on the intersection of two lines using the existing side-hole transmission wave method, the side-hole transmission wave inflection point method has lower requirements for the drilling depth, and only needs to exceed the pile to be tested by 2 to 3 meters, which reduces the requirements for the depth of the exploration hole, saves costs, and has good operability for technicians without engineering experience, and better solves the problem that it is difficult to determine the bottom depth of existing engineering piles. In the above technology, the depth of the measured hole must at least exceed a certain distance from the pile bottom, and during the test, signals must be collected at a certain distance along the measured hole, resulting in a larger testing workload and higher time cost.

[0004] Therefore, we proposed a side-hole reflection wave detection method and a pile length and integrity assessment method to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to provide a side-hole reflection wave detection method and a pile length and integrity assessment method to solve the problem raised by the above-mentioned background technology that during detection in the current market, the hole depth must be measured to exceed the expected pile bottom or defect depth, otherwise effective testing cannot be carried out, which will lead to poor subsequent detection efficiency, affect its detection accuracy, and be very time-consuming and labor-intensive.

[0006] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a side-hole reflection wave detection method and a pile length and integrity assessment method, which is based on collecting the direct wave transmitted through the pile body and the reflected transmission wave from the pile bottom at a certain depth in the side-hole, and the pile length can be analyzed through the travel time difference between the two and the depth of the detector; there is no need to collect signals at certain intervals along the depth to arrange a time and depth signal diagram, and only one detection and one signal collection are required during the test.

[0007] Preferably, the side-hole reflected wave detection method includes an exciting hammer, a signal analyzer and a detector, wherein the exciting hammer is connected to the signal analyzer via a wiring harness, and the signal analyzer is connected to the detector via a wiring harness.

[0008] Preferably, a side hole is drilled below the ground, and a detector is placed inside the side hole, and the depth of the detector is higher than the depth of the bottom of the pile body.

[0009] Preferably, the ground has a pedestal, the pedestal is placed above the ground, and a pile body is constructed at the bottom of the pedestal, and the bottom of the pile body extends through to the inner side of the bottom of the pedestal, and the vibration hammer strikes the top and side surfaces of the pedestal during testing.

[0010] Preferably, the side-hole reflection wave detection method is almost not restricted by pile type and material during detection, and can be used for pile types of round piles, square piles, sheet piles, pile walls, and steel, wood, concrete and cement soil materials.

[0011] Preferably, the method comprises the following steps: Step 1: Drill test holes and bury test tubes. Before testing, test holes and test tubes must be drilled near the pile body. The depth of the test holes does not need to exceed the expected pile bottom. Fill the tube with clean water to couple the detector with water. The bottom of the tube should be tightly sealed, or no water should be injected into the test hole. However, reliable means should be used to ensure that the detector is in stable contact with the wall of the test tube during the test. Step 2: Measure the hole. The measuring hole should be as close to the pile side as possible to reduce the influence of soil stratification and energy attenuation on the waveform. Step 3: Backfill the gap between the casing and the borehole with sand and cement slurry to make it dense; Step 4: Test. During the test, use a vibration hammer to hit the base, beam, and plate structure on the top of the pile. Only one vibration and detection is required to complete the signal collection.

[0012] Preferably, for the first arrival wave of the pile length transmission side hole, at a certain depth in the side hole z The travel time of the first arrival wave is calculated as follows: ,in V P is the wave velocity of the pile body, V S is the ground P wave velocity.

[0013] Preferably, for the first arrival wave reflected from the pile bottom and transmitted through the side hole, the travel time of the first arrival wave at a certain depth z in the side hole is calculated according to the following formula 2: , Formula 3: , Formula 4 is the pile length .

[0014] Compared with the prior art, the present invention has the following beneficial effects: (1) There is no need to collect signals at certain intervals along the depth to arrange a time-depth signal diagram. During the test, it is only necessary to detect and collect the signal once, which saves a lot of detection time and improves detection efficiency.

[0015] (2) This method can be used to detect the length and integrity of piles at the top of existing construction projects such as piles in the urban renewal field, such as the connection pedestal and the pile under the superstructure, with high accuracy. It can also be used to detect exposed free piles at the top of the piles. (3) By using a vibration hammer to strike the pile cap, beam, plate and other structures, signal collection is completed after only one vibration and detection. The pile depth and pile integrity can be analyzed based on the first arrival wave characteristics of the signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the detection principle of the present invention; Figure 2 It is a simplified model of pile-soil wave propagation path of the present invention; Figure 3 The side hole reflection wave test signal 1 of the present invention; Figure 4 It is the side hole reflection wave test signal 2 of the present invention.

[0017] In the figure: 1. Ground; 2. Capping platform; 3. Excitation hammer; 4. Pile body; 5. Signal analyzer; 6. Detector; 7. Side hole. DETAILED DESCRIPTION

[0018] 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.

[0019] The present invention provides the following technical solutions: Embodiment 1, in order to solve the existing problem, discloses: based on collecting the direct wave transmitted through the pile body and the reflected wave transmitted through the pile bottom at a certain depth in the side hole, the pile length can be analyzed through the travel time difference between the two and the depth of the detector; there is no need to collect signals at a certain distance along the depth to arrange a time and depth signal diagram, and only one detection and one signal collection is required in the test.

[0020] The side hole reflection wave detection method includes an exciting hammer 3, a signal analyzer 5 and a detector 6, wherein the exciting hammer 3 is connected to the signal analyzer 5 through a wire harness, and the signal analyzer 5 is connected to the detector 6 through a wire harness. The ground 1 has a side hole 7 drilled below the ground 1, and a detector 6 is placed inside the side hole 7, and the depth of the detector 6 is higher than the depth of the bottom of the pile body 4. The ground 1 has a cap 2, the cap 2 is placed above the ground 1, and a pile body 4 is constructed at the bottom of the cap 2, and the bottom of the pile body 4 extends through and extends to the inner side of the bottom of the cap 2. During detection, the exciting hammer 3 knocks the top surface and side surface of the cap 2.

[0021] The side-hole reflection wave detection method is almost not restricted by pile type and material during detection. It can be used for round piles, square piles, sheet piles, pile walls and steel, wood, concrete and cement soil materials.

[0022] The steps include: Step 1: Drill test holes and bury test tubes. Before testing, test holes and test tubes must be drilled near the pile body. The depth of the test holes does not need to exceed the expected pile bottom. Fill the tube with clean water to couple the detector with water. The bottom of the tube should be tightly sealed, or no water should be injected into the test hole. However, reliable means should be used to ensure that the detector is in stable contact with the wall of the test tube during the test. Step 2: Measure the hole. The measuring hole should be as close to the pile side as possible to reduce the influence of soil stratification and energy attenuation on the waveform. Step 3: Backfill the gap between the casing and the borehole with sand and cement slurry to make it dense; Step 4: Testing: During the test, a vibration hammer is used to strike the cap 2, beam and plate structure on the top of the pile body 3. Only one vibration and detection is required to complete the signal collection.

[0023] For the first arrival wave of the pile body through the side hole, at a certain depth in the side hole, z The travel time of the first arrival wave is calculated as follows: ,in V P is the wave velocity of the pile body, V S is the ground P wave velocity.

[0024] For the first arrival wave reflected from the pile bottom and transmitted through the side hole, the travel time of the first arrival wave at a certain depth z in the side hole is calculated according to Formula 2: , Formula 3: , Formula 4 is the pile length .

[0025] like Figure 1-Figure 4As shown, before the test, a measuring hole needs to be drilled near the pile body 4 and a measuring pipe needs to be buried. The depth of the measuring hole does not need to exceed the depth of the pile body 4, and it can be about half the length of the pile parallel to the pile body 4. Then, the pipe is filled with clean water to couple the detector 6 with the water. The bottom of the pipe should also be tightly sealed to avoid leakage and seepage in the later stage, thereby improving the sealing of the measuring pipe. When the hole is not filled with water, the reliability of the contact between the detector 6 and the hole wall needs to be ensured during the test. The measuring hole should be as close to the outside of the pile body 4 as possible to reduce the influence of soil stratification and energy attenuation on the waveform. Then, the gap between the casing and the borehole should be backfilled with sand or The cement slurry is poured densely, and during the test, the exciting hammer 3 is used to knock the pedestal 2, beams, plates and other structures on the top of the pile body 4. The detector 6 is placed at a certain depth z in the side hole. Only one excitation and detection is required to complete the signal collection. There is no need to collect signals at a certain distance along the depth to arrange the time and depth signal diagram, which saves a lot of detection time and improves the detection efficiency. It can be used for the pile length and integrity detection when the top of the existing construction engineering piles is connected to the pedestal 2 and the upper structure in the field of urban renewal. It has higher accuracy, practicability and wider application range, thereby completing a series of tasks.

[0026] Embodiment 2, which is different from Embodiment 1, discloses a case, such as Figure 3 As shown: The designed pile length of an existing engineering pile is L The pile body is 30m high, the pile body concrete is C30, and the wave velocity of the pile body is 3700m / s. Due to doubts about the quality of the pile body, the pile is tested using the side hole transmission reflection wave method. The side hole is 2m away from the side of the pile body and the side hole is 15m deep. During the test, a vibration hammer is used to hit the pile top cap, and a detector is placed at a depth of 12m in the side hole to collect the side hole signal. Figure 1 As shown. According to the signal, the travel time of the first arrival wave and the reflected wave are t 1=0.00454s, t 2=0.00967s. According to Formula 4, the length of the test pile can be determined to be 0.5×3700(0.00967-0.00454)+12=21.5m. Therefore, it can be judged that the pile has serious defects or broken piles at 21.5m.

[0027] Embodiment 3 is different from Embodiment 2 in that another case is disclosed: The designed pile length of an existing engineering pile is L The pile body is 31m high, the pile body concrete is C30, and the wave velocity of the pile body is 3690m / s. Due to doubts about the quality of the pile body, the pile is tested using the side hole transmission reflection wave method. The side hole is 1.8m away from the side of the pile body and the side hole is 14m deep. During the test, a vibration hammer is used to hit the pile top cap, and the detector is placed at a depth of 13m in the side hole to collect the side hole signal.

[0028] Embodiment 4 is different from Embodiment 3 in that another case is disclosed: The designed pile length of an existing engineering pile is L The pile body is 29m high, the pile body concrete is C30, and the pile body wave velocity is 3710m / s. Due to doubts about the quality of the pile body, the pile is tested using the side hole transmission reflection wave method. The side hole is 2.2m away from the side of the pile body and the side hole is 16m deep. During the test, a vibration hammer is used to hit the pile top cap, and the detector is placed at a depth of 13m in the side hole to collect the side hole signal.

[0029] Embodiment 5 is different from Embodiment 4 in that another case is disclosed: The designed pile length of an existing engineering pile is L The pile body is 32m high, the concrete of the pile body is C30, and the wave velocity of the pile body is 3720m / s. Due to doubts about the quality of the pile body, the pile is tested using the side hole transmission reflection wave method. The side hole is 2.2m away from the side of the pile body and the side hole is 16m deep. During the test, a vibration hammer is used to hit the pile top cap, and the detector is placed at a depth of 13m in the side hole to collect the side hole signal.

[0030] Embodiment 6, which is different from Embodiment 5, discloses another case, such as Figure 4 As shown: The designed pile length of an existing engineering pile is L The pile is 22m high, the pile body concrete is C30, and the wave velocity of the pile body is 3700m / s. The pile is tested using the side hole transmission reflection wave method. The side hole is 2m away from the side of the pile body and the side hole is 10m deep. During the test, a vibration hammer is used to hit the pile top cap. The detector is placed at a depth of 8m in the side hole to collect the side hole signal. The signal is as follows: Figure 2 As shown. According to the signal, the travel time of the first arrival wave and the reflected wave are t 1=0.0033s, t 2=0.0108s. According to Formula 4, the test pile length can be determined to be 0.5×3700(0.0108-0.0033)+8=21.9m. The test pile length is consistent with the design pile length.

[0031] Embodiment 7 is different from Embodiment 6 in that another case is disclosed: For an existing engineering pile, the designed pile length L is 21m, the pile body concrete is C30, and the pile body wave velocity is 3690m / s. The pile is tested using the side hole transmission reflection wave method. The side hole is 2m away from the side of the pile body and the side hole is 10m deep. During the test, a vibration hammer is used to hit the pile top cap, and a detector is placed 8m deep in the side hole to collect the side hole signal.

[0032] The above is the working process of the detection principle, and the contents not described in detail in this specification belong to the existing technology known to professional and technical personnel in this field.

[0033] Embodiment 8 is different from Embodiment 7 in that another case is disclosed: The designed pile length of an existing engineering pile isL The pile is 20m high, the pile body concrete is C30, and the wave velocity of the pile body is 3710m / s. The pile is tested using the side hole transmission reflection wave method. The side hole is 2m away from the side of the pile body and the side hole is 10m deep. During the test, a vibration hammer is used to hit the pile top cap, and the detector is placed at a depth of 8m in the side hole to collect the side hole signal.

[0034] Embodiment 9 is different from Embodiment 8 in that another case is disclosed: The designed pile length of an existing engineering pile is L The pile is 23m high, the pile body concrete is C30, and the wave velocity of the pile body is 3720m / s. The pile is tested using the side hole transmission reflection wave method. The side hole is 2m away from the side of the pile body and the side hole is 10m deep. During the test, a vibration hammer is used to hit the pile top cap, and the detector is placed at a depth of 8m in the side hole to collect the side hole signal.

[0035] The above is the working process of the detection principle, and the contents not described in detail in this specification belong to the existing technology known to professional and technical personnel in this field.

[0036] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A side hole reflection wave detection method, characterized in that Based on collecting the direct wave transmitted by the pile body and the reflected wave from the pile bottom at a certain depth in the side hole, the pile length can be analyzed through the travel time difference between the two and the depth of the detector; There is no need to collect signals at certain intervals along the depth to arrange a time and depth signal diagram. In the test, it is only necessary to detect and collect the signal once.

2. A side hole reflection wave detection method according to claim 1, characterized in that: The side-hole reflected wave detection method comprises an exciting hammer (3), a signal analyzer (5) and a detector (6), wherein the exciting hammer (3) is connected to the signal analyzer (5) via a wiring harness, and the signal analyzer (5) is connected to the detector (6) via a wiring harness.

3. A side hole reflection wave detection method according to claim 2, characterized in that: A ground surface (1), wherein a side hole (7) is drilled below the ground surface (1), and a geophone (6) is placed inside the side hole (7), and the depth of the geophone (6) is higher than the depth of the bottom of the pile body (4).

4. A side hole reflection wave detection method according to claim 3, characterized in that: The ground (1) has a cap (2), the cap (2) is placed above the ground (1), and a pile body (4) is constructed at the bottom of the cap (2), and the bottom of the pile body (4) extends through and extends to the inner side of the bottom of the cap (2). During detection, the exciting hammer (3) strikes the top surface and side surfaces of the cap (2).

5. A side hole reflection wave detection method according to claim 1, characterized in that: The side-hole reflection wave detection method is almost not restricted by pile type and material during detection. It can be used for round piles, square piles, sheet piles, pile walls and steel, wood, concrete and cement soil materials.

6. A side hole reflection wave detection method according to claim 1, characterized in that: The steps include: Step 1: Drill test holes and bury test tubes. Before testing, test holes and test tubes must be drilled near the pile body. The depth of the test holes does not need to exceed the expected pile bottom. Fill the tube with clean water to couple the detector with water. The bottom of the tube should be tightly sealed, or no water should be injected into the test hole. However, reliable means should be used to ensure that the detector is in stable contact with the wall of the test tube during the test. Step 2: Measure the hole. The measuring hole should be as close to the pile side as possible to reduce the influence of soil stratification and energy attenuation on the waveform. Step 3: Backfill the gap between the casing and the borehole with sand and cement slurry to make it dense; Step 4: Testing: During the testing, a vibration hammer is used to strike the cap (2), beam and plate structure at the top of the pile body (3). Only one vibration and detection is required to complete the signal collection.

7. A method for evaluating pile length and pile integrity, characterized in that: The side hole reflection wave detection method according to claim 1, for the pile body transmitting the side hole transmission first arrival wave, at a certain depth in the side hole z The travel time of the first arrival wave is calculated as follows: ,in V P is the wave velocity of the pile body, V S is the ground P wave velocity.

8. The depth and pile integrity assessment method according to claim 7, characterized in that: For the first arrival wave reflected from the pile bottom and transmitted through the side hole, the travel time of the first arrival wave at a certain depth z in the side hole is calculated according to Formula 2: , Formula 3: , Formula 4 is the pile length .

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