Device and method for monitoring springback deformation in whole excavation process of foundation pit

Abstract

The invention discloses a device and a method for monitoring springback deformation in the whole excavation process of a foundation pit. The device comprises a monitoring mechanism for layered springback above the bottom of the foundation pit and a monitoring mechanism for layered springback below the bottom of the foundation pit, the method comprises the following steps: 1, mounting the springback deformation monitoring device in the whole excavation process of the foundation pit; 2, measuring the initial reference elevation value of the rebound mark and the initial reference elevation value of the magnetic ring; and thirdly, layered excavation is conducted, and rebound deformation is monitored after each layer is excavated. The springback deformation of the soil layer below and above the bottom of the foundation pit can be monitored at the same time, whole-process springback deformation of the soil body in the excavation process of the foundation pit is achieved, the integrity of monitoring data can be effectively improved, the monitoring precision is improved, the springback condition of foundation pit layering is accurately measured, and a powerful guarantee is provided for engineering safety; and the magnetic ring measuring rod component can be recycled, so that the layered springback monitoring cost is reduced, the measurement accuracy is high, and the method is suitable for various geological conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of geotechnical engineering monitoring, and in particular relates to a device and method for monitoring rebound deformation during the whole process of foundation pit excavation. Background Art

[0002] As urban space becomes increasingly tight, engineering activities such as super-high-rise buildings and underground space development are increasing, forming a large number of deep foundation pit projects. After the excavation of deep foundation pits causes the self-weight stress of the soil in the foundation pit to decrease, the soil at the bottom of the pit will unload and rebound. The size of the foundation pit rebound is an important basis for judging the deformation and stability of the foundation pit, and it is also a prerequisite for accurately estimating the future settlement of buildings. At present, the rebound deformation of the foundation pit is mostly estimated by estimation methods, mainly including the layered summation method, the empirical formula method, and the residual stress method. Since the bottom rebound deformation is closely related to many factors such as the properties of the base soil, the size of the foundation pit, the depth and width of the foundation pit, the exposure time of the bottom pit, the form of the retaining structure, the support stiffness, and the construction quality, the base rebound deformation results obtained by the above estimation methods are often quite different from the measured values. Therefore, obtaining the rebound deformation of each soil layer under the foundation pit through on-site monitoring is currently the most direct, accurate, and reliable method.

[0003] The current foundation pit rebound deformation monitoring first buries rebound measuring marks in the foundation pit to be excavated, and conducts leveling measurement before and after the foundation pit excavation to measure the height difference changes of each measuring mark arranged on the bottom of the foundation pit, thereby obtaining the deformation of the rebound measuring mark. The main methods include: auxiliary rod method, steel ruler suspended hook method, and steel ruler with electromagnetic hammer (or electromagnetic probe) method. All three methods use leveling measurement, and the hole-making method and the method of burying the rebound measuring mark are basically the same. (1) Auxiliary rod method: Generally more suitable for shallow foundation pits. When implementing, press the rebound measuring mark into the bottom of the hole, lift the protective casing about 10 cm to temporarily fix it, and lower the pre-prepared auxiliary measuring rod (about 30 cm longer than the hole depth, with a round bubble level installed on the top) to the bottom of the hole, stand it upright on the rebound mark, keep it vertical (bubble concentrated in the center), and then place a level ruler on the auxiliary measuring rod to measure the elevation; (2) Steel ruler hanging hook method: Generally more suitable for medium-depth foundation pits. When implementing, the top of the rebound measuring mark is processed into a curved shape. Hook-shaped, the interface between the steel ruler head and the top of the rebound measuring mark is connected with a hook. After the steel ruler is tightened on the ground with a tripod, pulley and weight, a level is used to observe the height difference between the reference point and the rebound measuring mark; (3) The method of steel ruler equipped with an electromagnetic hammer (or electromagnetic probe): It is generally more suitable for deeper foundation pits. During implementation, a magnet block is set on the bottom of the weight in the hole so that it can be in close contact with the rebound mark head by the suction force of the magnet (the electromagnetic probe generates magnetic force after power is turned on). Its force exceeds the mass of the weight outside the hole. The weight is slowly lifted by hand to feel the contact. When the weight in the hole is in good contact with the rebound mark head, the weight is kept balanced, the steel ruler is kept vertical, and a level is used to observe the height difference between the reference point and the rebound measuring mark.

[0004] The above method still has the following shortcomings: (1) it can only monitor the final rebound deformation data of the bottom of the foundation pit after excavation, and cannot obtain the rebound deformation data of the bottom of the foundation pit during the excavation process; (2) it can only monitor the rebound deformation data of a certain depth at the same plane position, and cannot obtain the rebound deformation data of different depths at the same plane position. Therefore, a rebound deformation monitoring device and method for the whole process of foundation pit excavation is urgently needed. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a rebound deformation monitoring device for the whole process of foundation pit excavation in view of the deficiencies in the above-mentioned prior art. The device has a novel and reasonable design and can simultaneously monitor the rebound deformation of the soil layers below and above the bottom of the foundation pit, thereby realizing the whole process rebound deformation of the soil during the foundation pit excavation process. The device can effectively improve the integrity of the monitoring data, improve the monitoring accuracy, accurately measure the rebound of the foundation pit stratification, and provide strong guarantee for the safety of the project. After the foundation pit rebounds and stabilizes, the magnetic ring measuring rod components can be recycled and reused, thereby reducing the cost of stratified rebound monitoring. The device has high measurement accuracy, is suitable for a variety of geological conditions, and is easy to promote and use.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a rebound deformation monitoring device for the whole process of foundation pit excavation, characterized in that: it includes a monitoring mechanism for layered rebound above the bottom of the foundation pit and a monitoring mechanism for layered rebound below the bottom of the foundation pit; the layered rebound monitoring mechanism below the bottom of the foundation pit includes a plurality of hard plastic pipes centrally arranged in the borehole from bottom to top, two adjacent hard plastic pipes are connected by a hard plastic pipe joint, a magnetic ring fixing device for fixing the magnetic ring is sleeved on the hard plastic pipe, the magnetic ring fixing device includes an upper circular ring and a lower circular ring, the magnetic ring is arranged at the bottom of the lower circular ring, the inner diameter of the magnetic ring is smaller than the outer diameter of the hard plastic pipe joint, and the upper circular ring and the lower circular ring are fixed by a plurality of The upper and lower parts of the support leg are connected by a rod, a plurality of deformation mechanisms and a plurality of high-strength springs, wherein the deformation mechanism comprises a support leg hinged at one end on the upper circular ring and a support leg support rod hinged at one end on the lower circular ring, the other end of the support leg support rod is hinged to the middle part of the support leg, a limit block groove for installing a limit block which is wide at the top and narrow at the bottom is provided on the outer wall of the upper circular ring, the limit block abuts against the fixed rod, a card slot for installing a steel card is provided on the outer wall of the upper circular ring at the installation position of the limit block, and a lifting ring is provided on the top of the steel card; a plurality of electronic bins are arranged in sequence from bottom to top in the hard plastic tube, two adjacent electronic bins are connected by a measuring rod, and the data cable of the electronic bin extends out of the hard plastic tube and is connected to the demodulator on the original surface;

[0007] The monitoring mechanism for the layered rebound above the bottom of the foundation pit includes a plurality of rebound marks which are arranged in sequence from bottom to top in the exploration wells beside the borehole. A tripod is installed on the top of the exploration well, and a pulley block is arranged on the tripod. A steel wire rope is wound around the pulley block at one end with a counterweight, and the other end is connected to a steel ruler which extends into the exploration well and is connected to the rebound mark. A reference point for installing an indium tile ruler and a precision level for measuring the elevation are arranged on the original surface.

[0008] The above-mentioned rebound deformation monitoring device for the entire process of foundation pit excavation is characterized in that: a conical bottom pipe plug is provided at the bottom of the hard plastic pipe, and a hard plastic pipe centering ring and cement mortar are sequentially provided at the bottom of the drill hole from bottom to top, and the bottom pipe plug passes through the center position of the hard plastic pipe centering ring and extends into the cement mortar.

[0009] The above-mentioned rebound deformation monitoring device for the entire process of foundation pit excavation is characterized in that the magnetic ring is connected to the lower circular ring through a plurality of J-shaped slots and screws.

[0010] The above-mentioned rebound deformation monitoring device for the whole process of foundation pit excavation is characterized in that: the other end of the support leg is provided with a fixing claw that can be extended into the borehole wall; and a plurality of balls are provided on the outside of the limit block.

[0011] The above-mentioned rebound deformation monitoring device for the entire process of foundation pit excavation is characterized in that the bottom of the electronic warehouse is connected to the measuring rod through a measuring rod centering positioning ring, and the measuring rod centering positioning ring includes a centering ring and a hollow threaded rod arranged at the center position of the centering ring.

[0012] The above-mentioned rebound deformation monitoring device for the whole process of foundation pit excavation is characterized in that: the two measuring rods are connected by an extension rod, and the extension rod and the measuring rod are connected by an extension bolt.

[0013] The above-mentioned rebound deformation monitoring device for the entire process of foundation pit excavation is characterized in that the rebound mark includes a steel plate and a steel needle arranged at one end of the steel plate and inserted into the original soil, a circular ring is installed on the top of the steel plate, and a steel ruler is connected to the circular ring through a hook.

[0014] The above-mentioned rebound deformation monitoring device for the entire process of foundation pit excavation is characterized in that: the spacing between two adjacent rebound marks is 2m to 3m, the bottom of the exploration well is 10m to 15m lower than the bottom of the foundation pit, the exploration well is filled with backfill sand, and a lime layer is laid in the backfill sand at a position 0.3m above the rebound mark, and the thickness of each lime layer is 0.2m to 0.3m.

[0015] The above-mentioned rebound deformation monitoring device for the entire process of foundation pit excavation is characterized in that: after the foundation pit is excavated, the tripod is moved to the upper side of the exploration well at the surface position after excavation, and a hanger bracket for supporting the hanger is set on the original surface. The extended length of the hanger exceeds the slope line on the side of the foundation pit and is connected to another steel ruler through a wire rope, and a precision level is added on the surface after excavation.

[0016] At the same time, the present invention also discloses a method for monitoring rebound deformation during the whole process of foundation pit excavation, which is characterized in that the method comprises the following steps:

[0017] Step 1: Installation of the rebound deformation monitoring device during the whole process of foundation pit excavation. The process is as follows:

[0018] Step 101, drilling a hole at a monitoring point using a dry drilling method;

[0019] Step 102, place the magnetic ring on the bottom surface of the magnetic ring fixing device, pull up the upper ring until the top of the fixing rod reaches the lower side of the limit block slot, then put the limit block into the limit block slot, insert the steel card into the card slot, tie a thin rope on the lifting ring, tie each thin rope to a lifting rope and make corresponding marks;

[0020] Step 103, the hard plastic pipes are spliced ​​with hard plastic pipe joints. During the splicing process of the hard plastic pipes, the assembled magnetic rings and magnetic ring fixing devices are sleeved on the outside of the hard plastic pipes. After the hard plastic pipe joints are used to lower the hard plastic pipes into the drilled holes, the lower end of the magnetic ring fixing device contacts the upper end of the hard plastic pipe joints.

[0021] Step 104, pour cement mortar with a thickness of 20cm to 30cm to the bottom of the drill hole, lower the assembled hard plastic pipe into the hole section by section, and gradually lower the lifting rope into the hole during the lowering process, insert the bottom end of the hard plastic pipe into the cement mortar, and the center ring of the hard plastic pipe ensures that the entire device is in the center without horizontal deviation. After the cement mortar solidifies, pull up the lifting rope layer by layer. In the initial state, a limit block is installed in the card slot. When the lifting rope drives the steel card to be completely pulled out, the high-strength spring begins to contract from the tensioned state. The tension is provided and the contact surface between the limit block and the fixed rod is an inclined surface. The limit block will be squeezed out of the limit block groove by the fixed rod. The upper ring will move to the lower ring due to the loss of restriction. The support legs and the support leg support rods will be driven to extend outward, and the fixed claws will be squeezed onto the side wall of the borehole. During this movement, the positions of the lower ring and the magnetic ring are fixed and always in the initial position without relative displacement. As the spring continues to shrink, the support legs continue to open toward the hole wall until the support legs are firmly fixed to the hole wall. The entire device tends to be stable and reliably anchored on the hole wall.

[0022] Step 105, the electronic compartment, the measuring rod and the measuring rod centering ring are connected section by section in sequence according to the designed position and placed in a hard plastic tube. During the installation process, the data cable is led to the ground and connected to the demodulator;

[0023] Step 106, excavate a test well next to the borehole, make the side wall of the test well tangent to the side wall of the borehole, and make the bottom of the test well 10m to 15m lower than the bottom of the foundation pit;

[0024] Step 107, set a rebound mark measuring point every 2m to 3m from bottom to top. When installing the rebound mark, connect the lower end of the steel ruler to the rebound mark, pass the upper end around the pulley block and hang a counterweight, adjust the steel ruler to keep it vertical, use a precision level to monitor the initial reference elevation values ​​of all rebound marks, and then backfill the exploration well in layers to make the filling density in the exploration well basically consistent with the surrounding original soil density. When backfilling to 0.3m above the rebound mark elevation, set a white lime layer with a thickness of 0.2m to 0.3m as a prompt layer during the foundation pit excavation process, and repeat the above steps when reaching the next measuring point until all rebound marks are installed and the filling in the exploration well is backfilled to the ground;

[0025] Step 2: Measure the initial reference elevation value of the rebound mark and the initial reference elevation value of the magnetic ring;

[0026] Step 3: Excavate in layers. The monitoring process of rebound deformation after each layer of excavation is the same. The monitoring process of rebound deformation after each layer of excavation is as follows:

[0027] Step 301, monitoring of layered rebound above the bottom of the foundation pit: When the foundation pit is excavated to 0.4m to 0.6m above the rebound mark position of the corresponding layer, excavate manually along the original exploration well range downward to the circular ring position of the rebound mark, hook the lower end of the steel ruler on the circular ring of the rebound mark, pass the upper end around the pulley and hang a hammer, adjust the steel ruler to keep it vertical, use a precision level to monitor the current elevation of the rebound mark, and calculate the height of the rebound mark according to the formula s j =H j -H 0j , calculate the rebound deformation s of the foundation soil below the rebound mark point of the jth layer j , where H j is the current elevation of the rebound measuring point on the jth layer, H 0j is the initial benchmark elevation value of the rebound measuring point of the jth layer;

[0028] Step 302, monitoring of layered rebound below the bottom of the foundation pit: Since the pipe bottom plug is reliably anchored to the cement mortar, the positions of the electronic compartment and the measuring rod will not change. After the foundation pit is excavated, the soil layer rebounds and deforms. During the soil layer rebound process, the magnetic ring will be driven to synchronously displace, changing the length of the measuring rod passing through the magnetic ring. The measuring rod is equipped with a waveguide wire. During measurement, the electronic compartment sends a starting pulse, which is transmitted along the waveguide wire. When the pulse meets the magnetic ring, a magnetostrictive effect current pulse is generated. The demodulator measures the current pulse and calculates the time difference between the two pulses, which is the absolute position of the magnetic ring. According to the formula s it =F it -F i0 , calculate the rebound deformation s of the foundation soil below the pit bottom at the i-th magnetic ring measuring point at time t it , where F it is the current elevation value of the i-th magnetic ring measuring point of the foundation soil below the bottom of the foundation pit at time t, F i0It is the initial benchmark elevation value of the i-th magnetic ring measuring point of the foundation soil below the bottom of the foundation pit at the initial moment.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] 1. The device used in the present invention is reliably anchored and can simultaneously monitor the rebound deformation of the soil layers below and above the bottom of the foundation pit, realizing the full-process rebound deformation of the soil during the foundation pit excavation process, which can effectively improve the integrity of the monitoring data and improve the monitoring accuracy.

[0031] 2. The device used in the present invention can recycle and reuse the magnetostrictive settlement instrument measuring device after the foundation pit rebound is stable, thereby reducing the cost of layered rebound monitoring.

[0032] 3. The device used in the present invention can accurately measure the rebound of foundation pit layers, providing a strong guarantee for engineering safety. By real-time monitoring of the rebound deformation of the soil below the bottom of the foundation pit, the foundation pit rebound problem can be discovered in time, and corresponding measures can be taken to deal with it to prevent the problem from further expanding.

[0033] 4. The method adopted by the present invention has simple steps, convenient installation, high measurement accuracy, is applicable to various geological conditions, and is easy to promote and use.

[0034] To sum up, the design of the present invention is novel and reasonable, and can simultaneously monitor the rebound deformation of the soil layers below and above the bottom of the foundation pit, and realize the full-process rebound deformation of the soil during the foundation pit excavation process. It can effectively improve the integrity of the monitoring data, improve the monitoring accuracy, and accurately measure the rebound of the foundation pit layers, providing strong protection for engineering safety. After the foundation pit rebounds and stabilizes, the magnetic ring measuring rod components can be recycled and reused, reducing the cost of layered rebound monitoring. The measurement accuracy is high, it is suitable for a variety of geological conditions, and is easy to promote and use.

[0035] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 This is a schematic diagram of measuring the rebound mark height in an exploration well according to the present invention;

[0037] Figure 2 It is a schematic diagram of measuring the rebound mark height during the foundation pit excavation process of the present invention;

[0038] Figure 3 It is a structural schematic diagram of the present invention;

[0039] Figure 4 It is a schematic diagram of the structure of the monitoring mechanism for layered rebound below the bottom of the foundation pit of the present invention;

[0040] Figure 5 This is a detailed schematic diagram of the bottom of the hard plastic pipe at location A of the present invention;

[0041] Figure 6 This is a schematic diagram of the magnetic ring fixing device of the present invention when it is not opened;

[0042] Figure 7 It is a detailed schematic diagram of the B portion when the magnetic ring fixing device of the present invention is not opened;

[0043] Figure 8 This is a schematic diagram of the magnetic ring fixing device of the present invention when it is opened;

[0044] Fig. 9 It is a detailed schematic diagram of the C position when the magnetic ring fixing device of the present invention is opened;

[0045] Fig.10 It is a schematic diagram of the rebound of the present invention;

[0046] Fig.11 It is a schematic diagram of the center ring of the present invention.

[0047] Description of reference numerals:

[0048] 1—original surface; 2—well bottom; 3—demodulator;

[0049] 4—lime layer; 5—backfill sand; 6—original soil;

[0050] 7—Rebound mark; 7-1—Ring; 7-2—Steel plate;

[0051] 7-3—Steel needle; 8—Data cable; 9—Electronic compartment;

[0052] 10—Measuring rod centering ring; 10-1—Hollow threaded rod; 10-2—Centering ring;

[0053] 11—Measuring rod; 12—Hard plastic pipe joint; 13—Extension bolt;

[0054] 14—Extension rod; 15—Magnetic ring fixing device; 15-1—Supporting leg;

[0055] 15-2—Support leg support rod; 15-3—Fixed claw; 15-4—High-strength spring;

[0056] 15-5—Magnetic ring; 15-6—J-shaped slot; 15-7—Screw;

[0057] 15-8—upper ring; 15-9—steel card; 15-10—lifting ring;

[0058] 15-11—slot; 15-12—fixing rod; 15-13—lower ring;

[0059] 15-14—limit block; 15-15—ball bearing; 15-16—limit block slot;

[0060] 16—Hard plastic pipe; 16-1—Pipe bottom plug; 17—Hard plastic pipe centering ring;

[0061] 18—cement mortar; 19—pulley block; 20—tripod;

[0062] 21—precision level; 22—indium tile ruler; 23—reference point;

[0063] 24—Steel ruler; 25—Hook; 26—Exploration well;

[0064] 27—hanging rod; 28—slope line on the side of foundation pit; 29—hanging rod bracket. DETAILED DESCRIPTION

[0065] like Figures 1 to 11 As shown, a rebound deformation monitoring device for the whole process of foundation pit excavation described in the present invention includes a monitoring mechanism for layered rebound above the bottom of the foundation pit and a monitoring mechanism for layered rebound below the bottom of the foundation pit; the layered rebound monitoring mechanism below the bottom of the foundation pit includes a plurality of hard plastic pipes 16 centrally arranged in a borehole from bottom to top, two adjacent hard plastic pipes 16 are connected by a hard plastic pipe joint 12, a magnetic ring fixing device 15 for fixing a magnetic ring 15-5 is sleeved on the hard plastic pipe 16, the magnetic ring fixing device 15 includes an upper circular ring 15-8 and a lower circular ring 15-13, the magnetic ring 15-5 is arranged at the bottom of the lower circular ring 15-13, the inner diameter of the magnetic ring 15-5 is smaller than the outer diameter of the hard plastic pipe joint 12, the upper circular ring 15-8 and the lower circular ring 15-13 are connected by a plurality of fixing rods 15-12, a plurality of deformation mechanisms and a plurality of high-strength springs 15-4, the deformation mechanism The structure includes a support leg 15-1 hinged at one end on the upper circular ring 15-8 and a support leg support rod 15-2 hinged at one end on the lower circular ring 15-13, the other end of the support leg support rod 15-2 is hinged to the middle part of the support leg 15-1, the outer wall of the upper circular ring 15-8 is provided with a limit block groove 15-16 for installing a limit block 15-14 which is wide at the top and narrow at the bottom, the limit block 15-14 is abutted against the fixing rod 15-12, the outer wall of the upper circular ring 15-8 is provided with a card slot 15-11 for installing a steel card 15-9 at the installation position of the limit block 15-14, and a lifting ring 15-10 is provided on the top of the steel card 15-9; a plurality of electronic bins 9 are arranged in sequence from bottom to top in the hard plastic tube 16, two adjacent electronic bins 9 are connected by a measuring rod 11, and the data cable 8 of the electronic bin 9 extends out of the hard plastic tube 16 and is connected to the demodulator 3 on the original surface 1;

[0066] The monitoring mechanism for the layered rebound above the bottom of the foundation pit includes a plurality of rebound marks 7 arranged in sequence from bottom to top in a probe well 26 beside the borehole, a tripod 20 is installed on the top of the probe well 26, a pulley block 19 is arranged on the tripod 20, a steel wire rope is wound around the pulley block 19 at one end with a counterweight, and the other end is connected to a steel ruler 24 extending into the probe well 26 and connected to the rebound mark 7, a reference point 23 for installing an indium tile ruler 22 and a precision level 21 for measuring the elevation are arranged on the original surface 1.

[0067] It should be noted that the magnetic ring is fixed to the soil through a magnetic ring fixing device and is sleeved on the outside of the hard plastic tube. When the soil rebounds, the magnetic ring will be driven to move upward, changing the relative position of the magnetic ring and the measuring rod, thereby measuring the soil rebound deformation. The J-shaped slot is connected to the lower circular ring by screws and is used to fix the magnetic ring at the bottom of the lower circular ring. The support leg is fixed to the outside of the upper circular ring by a hinge, and a fixing claw is provided at the outer end; the fixing claw is used to fix the magnetic ring fixing device in the soil; the support leg is hingedly connected to the bottom circular ring by a support rod; the high-strength spring is connected to the upper and lower magnetic rings by welding, and the high-strength spring is long under normal conditions. The length is shorter than the fixing rod; the fixing rod is connected to the lower circular ring by welding, and the upper part of the fixing rod is an inclined surface inclined to the outside of the circular ring; the upper circular ring has three circular holes that pass through the upper and lower parts, and the weight of the holes can ensure that the fixing rod will not be bounced open when it pops out. The card slot is connected to the outside of the upper circular ring by welding, and there is a channel in the middle that is larger than the size of the limit block; the limit block is placed in the limit block slot, and the limit block slot is connected to the circular hole on the upper circular ring. One side of the limit block is an inclined surface that fits the top inclined surface of the fixing rod, and the other side is a ball groove for installing a ball; the upper part of the steel card is connected with a semicircular hanging ring and placed in the card slot.

[0068] The demodulator can measure the electronic pulse data. The pulse electronic compartment sends a signal along the waveguide wire, and generates a magnetostrictive current pulse after encountering the magnetic ring. The signal is transmitted to the demodulator through the data cable, and the collected data is uploaded to the cloud platform to collect and analyze the deep rebound deformation data of the foundation soil below the bottom of the foundation pit. The waveguide wire is made of iron-nickel alloy with a diameter of 0.5mm to 0.8mm. During measurement, the excitation module in the pulse electronic compartment applies a query pulse to both ends of the waveguide wire. The pulse forms a circumferential Ampere annular magnetic field around the waveguide wire at the speed of light. When the Ampere annular magnetic field is coupled with the biased permanent magnetic field of the vernier magnetic ring, a Widman effect torsional stress wave is formed on the surface of the waveguide wire. The torsional wave propagates from the generation point to the two ends of the waveguide wire at the speed of sound. The torsional wave transmitted to the end is absorbed by the damping device, and the signal transmitted to the excitation end is received by the detection device. The control module in the electronic warehouse calculates the time difference between the query pulse and the received signal, and then multiplies it by the propagation speed of the torsional stress wave in the waveguide material, so as to calculate the distance between the torsional wave occurrence position and the measurement reference point, that is, the absolute distance between the magnetic ring and the measurement reference point at that moment, thereby realizing real-time and accurate measurement of the magnetic ring position. The electronic warehouse can generate excitation pulses and process related electrical signals, and connect with the demodulator to realize long-distance transmission. The number of electronic warehouses is consistent with the number of layers of rebound soil layers at the bottom of the foundation pit, and is arranged at the top of each layer of soil. When the soil layer rebounds and deforms, the magnetic ring fixing device is driven to move by the fixed claw, and a vertical relative displacement is generated between the magnetic ring and the measuring rod. The electronic warehouse emits a wave signal, and the soil layer rebound amount is transmitted to the demodulator through the wave signal, thereby obtaining the rebound amount of each layer of soil below the bottom of the foundation pit; the measuring rod is made of stainless steel and is equipped with a waveguide wire inside. It is connected with the electronic warehouse, and the electronic warehouse transmits wave signals through the waveguide wire in the measuring rod at the speed of sound; the extension rod is made of stainless steel, and is threadedly connected with the electronic warehouse and the measuring rod through an extension bolt, so as to adjust the relative distance between the upper and lower electronic warehouses; the measuring rod centering ring includes a centering ring and a hollow threaded rod; the inner diameter of the middle circular hole of the hollow threaded rod is the same as the outer diameter of the measuring rod and the extension rod, and is threadedly connected with the measuring rod and the extension rod through the middle circular hole; the centering ring is fixed on the hollow threaded rod by threads, and the outer diameter of the centering ring is 2mm to 3mm smaller than the inner diameter of the hard plastic tube.

[0069] The inner diameter of the hard plastic tube is slightly larger than the center positioning ring of the measuring tube, and the outer diameter is slightly smaller than the inner diameters of the upper and lower rings in the magnetic ring fixing device. It is sleeved on the outside of the measuring rod, and a hard plastic tube plug is installed at the bottom. The hard plastic tube plug is connected to the hard plastic tube by adhesive. The conical circular hole inside the hard plastic tube plug is used for installation and centering of the measuring device.

[0070] The cement mortar is poured at the bottom of the drill hole, the cement mortar is graded M10, and the lower end of the hard plastic pipe is inserted into the cement mortar as a relatively fixed point.

[0071] In this embodiment, a conical bottom plug 16-1 is provided at the bottom of the hard plastic tube 16, and a hard plastic tube centering ring 17 and cement mortar 18 are provided in sequence at the bottom of the drill hole from bottom to top. The bottom plug 16-1 passes through the center position of the hard plastic tube centering ring 17 and extends into the cement mortar 18.

[0072] In this embodiment, the magnetic ring 15-5 is connected to the lower circular ring 15-13 through a plurality of J-shaped slots 15-6 and screws 15-7.

[0073] In this embodiment, the other end of the support leg 15 - 1 is provided with a fixing claw 15 - 3 that can extend into the wall of the drill hole; a plurality of balls 15 - 15 are provided on the outer side of the limit block 15 - 14.

[0074] It should be noted that when the magnetic ring fixing device 15 is not installed, the high-strength spring 15-4 in the device is in a stretched state. After the magnetic ring fixing device is hoisted to the specified position as a whole through the lifting ring 15-10, the steel card 15-9 is slowly pulled out from the card slot 15-11; in the initial state, a limit block 15-14 is installed in the card slot 15-11. When the steel card 15-9 is completely pulled out, the high-strength spring 15-4 begins to contract from a tensioned state. As the spring continues to contract, the support leg 15-1 continues to open toward the hole wall until the support leg 15-1 is firmly fixed to the hole wall. The entire device becomes stable and is reliably anchored on the hole wall.

[0075] In this embodiment, the bottom of the electronic compartment 9 is connected to the measuring rod 11 through the measuring rod centering positioning ring 10, and the measuring rod centering positioning ring 10 includes a centering ring 10-2 and a hollow threaded rod 10-1 arranged at the center position of the centering ring 10-2.

[0076] In this embodiment, the two measuring rods 11 are connected via an extension rod 14 , and the extension rod 14 and the measuring rod 11 are connected via an extension bolt 13 .

[0077] In this embodiment, the rebound mark 7 includes a steel plate 7-2 and a steel needle 7-3 arranged at one end of the steel plate 7-2 and inserted into the original soil 6. A ring 7-1 is installed on the top of the steel plate 7-2, and a steel ruler 24 is connected to the ring 7-1 through a hook 25.

[0078] In this embodiment, the distance between two adjacent rebound marks 7 is 2m to 3m, the bottom of the exploration well 2 is 10m to 15m lower than the bottom of the foundation pit, the exploration well 26 is filled with backfill sand 5, and a lime layer 4 is laid in the backfill sand 5 at a position 0.3m above the rebound mark 7, and the thickness of each lime layer 4 is 0.2m to 0.3m.

[0079] In this embodiment, after the foundation pit is excavated, the tripod 20 is moved to the upper side of the exploration well 26 at the surface position after excavation, and a hanger bracket 29 for supporting the hanger 27 is set on the original surface 1. The extension length of the hanger 27 exceeds the slope line 28 of the side of the foundation pit and is connected to another steel ruler 24 through a wire rope, and a precision level 21 is added to the surface after excavation.

[0080] A method for monitoring rebound deformation during the entire process of foundation pit excavation, comprising the following steps:

[0081] Step 1: Installation of the rebound deformation monitoring device during the whole process of foundation pit excavation. The process is as follows:

[0082] Step 101, drilling a hole at a monitoring point using a dry drilling method;

[0083] Step 102, place and install the magnetic ring 15-5 on the bottom surface of the magnetic ring fixing device 15, pull up the upper ring 15-8 until the top of the fixing rod 15-12 reaches the lower side of the limit block slot 15-16, then put the limit block 15-14 into the limit block slot 15-16, then insert the steel card 15-9 into the card slot 15-11, and tie a thin rope on the hanging ring 15-10, tie each thin rope to a hanging rope and make corresponding marks;

[0084] Step 103, the hard plastic pipe 16 is spliced ​​with the hard plastic pipe joint 12, and during the splicing process of the hard plastic pipe 16, the assembled magnetic ring 15-5 and the magnetic ring fixing device 15 are sleeved on the outside of the hard plastic pipe 16, and after the hard plastic pipe joint 12 is used to lower the hard plastic pipe 16 into the drilled hole, the lower end of the magnetic ring fixing device 15 contacts the upper end of the hard plastic pipe joint 12;

[0085] Step 104, pour cement mortar 18 with a thickness of 20cm to 30cm to the bottom of the drill hole, lower the assembled hard plastic tube 16 into the hole section by section, and gradually lower the lifting rope into the hole during the lowering process, insert the bottom end of the hard plastic tube 16 into the cement mortar 18, and the hard plastic tube centering ring 17 ensures that the entire device is in the center without horizontal deviation. After the cement mortar 18 solidifies, pull up the lifting rope layer by layer. In the initial state, the limit block 15-14 is installed in the card slot 15-11. When the lifting rope drives the steel card 15-9 to be completely pulled out, the high-strength spring 15-4 begins to contract from the tensioned state. Due to the tension provided by the high-strength spring 15-4 and the limit block 15-14 The contact surface with the fixing rod 15-12 is an inclined surface, and the limit block 15-14 will be squeezed out of the limit block groove 15-16 by the fixing rod 15-12. The upper ring 15-8 will move toward the lower ring 15-13 due to the loss of restriction, and the support leg 15-1 and the support leg support rod 15-2 will be driven to extend outward, squeezing the fixing claw 15-3 onto the side wall of the borehole; during this movement, the lower ring 15-13 and the magnetic ring 15-5 are fixed in position and are always in the initial position without any relative displacement. As the spring continues to shrink, the support leg 15-1 continues to open toward the hole wall until the support leg is firmly fixed to the hole wall, and the entire device tends to be stable and reliably anchored on the hole wall;

[0086] Step 105, the electronic compartment 9, the measuring rod 11 and the measuring rod centering ring 10 are connected section by section in sequence according to the designed position and placed in the hard plastic tube 16. During the installation process, the data cable 8 is led to the ground and connected to the demodulator 3;

[0087] Step 106, excavate a test well 26 next to the borehole, so that the side wall of the test well is tangent to the side wall of the borehole, and the bottom of the test well is 10m to 15m lower than the bottom of the foundation pit;

[0088] Step 107, set a rebound mark measuring point every 2m to 3m from bottom to top. When installing the rebound mark 7, connect the lower end of the steel ruler to the rebound mark, and the upper end passes through the pulley block 19 and hangs a counterweight. Adjust the steel ruler 24 to keep it vertical. Use the precision level 21 to monitor the initial reference elevation values ​​of all rebound marks. Then, backfill the exploration well 26 in layers so that the density of the filling in the exploration well is basically consistent with the density of the surrounding original soil. When backfilling to 0.3m above the rebound mark elevation, set a lime layer 4 with a thickness of 0.2m to 0.3m as a prompt layer during the foundation pit excavation process. Repeat the above steps when reaching the next measuring point until all the rebound marks 7 are installed and the filling in the exploration well is backfilled to the ground.

[0089] Step 2: Measure the initial reference elevation value of the rebound mark and the initial reference elevation value of the magnetic ring;

[0090] Step 3: Excavate in layers. The monitoring process of rebound deformation after each layer of excavation is the same. The monitoring process of rebound deformation after each layer of excavation is as follows:

[0091] Step 301, monitoring of layered rebound above the bottom of the foundation pit: When the foundation pit is excavated to 0.4m to 0.6m above the rebound mark position of the corresponding layer, excavate manually along the original exploration well range downward to the position of the circular ring 7-1 of the rebound mark, hook the lower end hook 25 of the steel ruler 24 on the circular ring 7-1 on the rebound mark, pass the upper end around the pulley and hang a hammer, adjust the steel ruler to keep it vertical, use the precision level 21 to monitor the current elevation of the rebound mark, and according to the formula s j =H j -H 0j , calculate the rebound deformation s of the foundation soil below the rebound mark point of the jth layer j , where H j is the current elevation of the rebound measuring point on the jth layer, H 0j is the initial benchmark elevation value of the rebound measuring point of the jth layer;

[0092] Step 302, monitoring of layered rebound below the bottom of the foundation pit: Since the pipe bottom plug 16-1 and the cement mortar 18 are reliably anchored, the positions of the electronic chamber 9 and the measuring rod 11 will not change. After the foundation pit is excavated, the soil layer rebounds and deforms. During the soil layer rebound process, the magnetic ring 15-5 will be driven to synchronously shift, changing the length of the measuring rod passing through the magnetic ring. The measuring rod 11 is equipped with a waveguide wire. During measurement, the electronic chamber 9 sends a starting pulse, which is transmitted along the waveguide wire. When the pulse meets the magnetic ring, a magnetostrictive effect current pulse is generated. The demodulator measures the current pulse and calculates the time difference between the two pulses, which is the absolute position of the magnetic ring. According to the formula s it =F it -F i0 , calculate the rebound deformation s of the foundation soil below the pit bottom at the i-th magnetic ring measuring point at time t it , where F it is the current elevation value of the i-th magnetic ring measuring point of the foundation soil below the bottom of the foundation pit at time t, F i0 It is the initial benchmark elevation value of the i-th magnetic ring measuring point of the foundation soil below the bottom of the foundation pit at the initial moment.

[0093] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A rebound deformation monitoring device for the whole process of foundation pit excavation, characterized in that: The invention comprises a monitoring mechanism for layered rebound above the bottom of a foundation pit and a monitoring mechanism for layered rebound below the bottom of the foundation pit; the monitoring mechanism for layered rebound below the bottom of the foundation pit comprises a plurality of hard plastic pipes (16) centrally arranged in a borehole from bottom to top, two adjacent hard plastic pipes (16) are connected by a hard plastic pipe joint (12), a magnetic ring fixing device (15) for fixing a magnetic ring (15-5) is sleeved on the hard plastic pipe (16), and the magnetic ring fixing device (15) comprises an upper circular ring ( The invention relates to a plastic pipe joint (15-8) and a lower circular ring (15-13), wherein the magnetic ring (15-5) is arranged at the bottom of the lower circular ring (15-13), the inner diameter of the magnetic ring (15-5) is smaller than the outer diameter of the hard plastic pipe joint (12), the upper circular ring (15-8) and the lower circular ring (15-13) are connected by a plurality of fixing rods (15-12), a plurality of deformation mechanisms and a plurality of high-strength springs (15-4), wherein the deformation mechanism comprises a support leg with one end hinged on the upper circular ring (15-8) (15-1) and a support leg support rod (15-2) with one end hinged on the lower circular ring (15-13), the other end of the support leg support rod (15-2) is hinged to the middle of the support leg (15-1), the outer wall of the upper circular ring (15-8) is provided with a limit block groove (15-16) for installing a limit block (15-14) with a width at the top and a narrowness at the bottom, the limit block (15-14) is in contact with the fixing rod (15-12), and the outer wall of the upper circular ring (15-8) is located at the limit block groove (15-16). A card slot (15-11) for installing a steel card (15-9) is provided at the installation position of the block (15-14), and a lifting ring (15-10) is provided on the top of the steel card (15-9); a plurality of electronic bins (9) are arranged in sequence from bottom to top in the hard plastic tube (16), two adjacent electronic bins (9) are connected by a measuring rod (11), and a data cable (8) of the electronic bin (9) extends out of the hard plastic tube (16) and is connected to a demodulator (3) on the original ground surface (1); The monitoring mechanism for layered rebound above the bottom of the foundation pit comprises a plurality of rebound marks (7) arranged in sequence from bottom to top in a pilot well (26) beside a borehole, a tripod (20) is installed on the top of the pilot well (26), a pulley block (19) is arranged on the tripod (20), a steel wire rope is wound around the pulley block (19) and provided with a counterweight at one end, and a steel ruler (24) extending into the pilot well (26) and connected to the rebound mark (7) at the other end, and a reference point (23) for installing an indium tile ruler (22) and a precision level (21) for measuring elevation are arranged on the original ground surface (1).

2. A device for monitoring rebound deformation during the whole process of foundation pit excavation according to claim 1, characterized in that: A conical bottom plug (16-1) is provided at the bottom of the hard plastic pipe (16), and a hard plastic pipe centering ring (17) and cement mortar (18) are sequentially provided at the bottom of the drill hole from bottom to top, and the bottom plug (16-1) passes through the center position of the hard plastic pipe centering ring (17) and extends into the cement mortar (18).

3. A device for monitoring rebound deformation during the whole process of foundation pit excavation according to claim 1, characterized in that: The magnetic ring (15-5) is connected to the lower circular ring (15-13) via a plurality of J-shaped slots (15-6) and screws (15-7).

4. A device for monitoring rebound deformation during the whole process of foundation pit excavation according to claim 1, characterized in that: The other end of the support leg (15-1) is provided with a fixing claw (15-3) that can extend into the wall of the drill hole; and a plurality of balls (15-15) are provided on the outside of the limit block (15-14).

5. A device for monitoring rebound deformation during the whole process of foundation pit excavation according to claim 1, characterized in that: The bottom of the electronic compartment (9) is connected to a measuring rod (11) via a measuring rod centering positioning ring (10), and the measuring rod centering positioning ring (10) comprises a centering ring (10-2) and a hollow threaded rod (10-1) arranged at the center of the centering ring (10-2).

6. A device for monitoring rebound deformation during the whole process of foundation pit excavation according to claim 5, characterized in that: The two measuring rods (11) are connected via an extension rod (14), and the extension rod (14) and the measuring rod (11) are connected via an extension bolt (13).

7. A device for monitoring rebound deformation during the whole process of foundation pit excavation according to claim 1, characterized in that: The rebound mark (7) comprises a steel plate (7-2) and a steel needle (7-3) arranged at one end of the steel plate (7-2) and inserted into the original soil (6); a circular ring (7-1) is installed on the top of the steel plate (7-2); and a steel ruler (24) is connected to the circular ring (7-1) via a hook (25).

8. A device for monitoring rebound deformation during the whole process of foundation pit excavation according to claim 1, characterized in that: The spacing between two adjacent rebound marks (7) is 2m to 3m, the bottom of the exploration well (2) is 10m to 15m lower than the bottom of the foundation pit, the exploration well (26) is filled with backfill sand (5), and a lime layer (4) is laid in the backfill sand (5) at a position 0.3m above the rebound mark (7), and the thickness of each lime layer (4) is 0.2m to 0.3m.

9. A device for monitoring rebound deformation during the whole process of foundation pit excavation according to claim 1, characterized in that: After the foundation pit is excavated, the tripod (20) is moved to the upper side of the exploration well (26) at the surface position after the excavation, and a suspension rod bracket (29) for supporting a suspension rod (27) is arranged on the original surface (1). The extension length of the suspension rod (27) exceeds the slope line (28) on the side of the foundation pit and is connected to another steel ruler (24) through a steel wire rope, and a precision level (21) is additionally arranged on the surface after the excavation.

10. A method for monitoring rebound deformation during the whole process of foundation pit excavation using the device as claimed in claim 1, characterized in that: The method comprises the following steps: Step 1: Installation of the rebound deformation monitoring device during the whole process of foundation pit excavation. The process is as follows: Step 101, drilling a hole at a monitoring point using a dry drilling method; Step 102, place and install the magnetic ring (15-5) on the bottom surface of the magnetic ring fixing device (15), pull up the upper ring (15-8) until the top of the fixing rod (15-12) reaches the lower side of the limit block slot (15-16), then put the limit block (15-14) into the limit block slot (15-16), then insert the steel card (15-9) into the card slot (15-11), and tie a thin rope on the hanging ring (15-10), tie each thin rope to a hanging rope and make corresponding marks; Step 103, the hard plastic pipe (16) is spliced ​​with the hard plastic pipe joint (12), and during the splicing process of the hard plastic pipe (16), the assembled magnetic ring (15-5) and the magnetic ring fixing device (15) are sleeved on the outside of the hard plastic pipe (16), and after the hard plastic pipe (16) is lowered into the drilled hole by using the hard plastic pipe joint (12), the lower end of the magnetic ring fixing device (15) contacts the upper end of the hard plastic pipe joint (12); Step 104, pour cement mortar (18) with a thickness of 20 cm to 30 cm at the bottom of the drill hole, lower the assembled hard plastic pipe (16) into the hole section by section, and gradually lower the lifting rope into the hole during the lowering process, insert the bottom end of the hard plastic pipe (16) into the cement mortar (18), and the hard plastic pipe centering ring (17) ensures that the entire device is in the center without horizontal deviation. After the cement mortar (18) solidifies, pull up the lifting rope layer by layer. In the initial state, the limit block (15-14) is installed in the card slot (15-11). When the lifting rope drives the steel card (15-9) to be completely pulled out, the high-strength spring (15-4) begins to contract from the tension state. Due to the tension provided by the high-strength spring (15-4) and the limit block (15-14) The contact surface with the fixing rod (15-12) is an inclined surface, the limit block (15-14) is squeezed out of the limit block groove (15-16) by the fixing rod (15-12), the upper ring (15-8) moves toward the lower ring (15-13) due to the loss of restriction, the support leg (15-1) and the support leg support rod (15-2) are driven to extend outward, and the fixing claw (15-3) is squeezed onto the side wall of the borehole; during this movement, the position of the lower ring (15-13) and the magnetic ring (15-5) is fixed and always in the initial position, and no relative displacement occurs. As the spring continues to shrink, the support leg (15-1) continues to open toward the hole wall until the support leg is firmly fixed to the hole wall, and the entire device tends to be stable and reliably anchored on the hole wall; Step 105, the electronic compartment (9), the measuring rod (11) and the measuring rod centering ring (10) are connected section by section in sequence according to the designed position and placed in the hard plastic tube (16). During the installation process, the data cable (8) is led to the ground and connected to the demodulator (3); Step 106, excavating a test well (26) beside the borehole, making the side wall of the test well tangent to the side wall of the borehole, and the bottom of the test well being 10m to 15m lower than the bottom of the foundation pit; Step 107, a rebound mark measuring point is set every 2m to 3m from bottom to top. When the rebound mark (7) is installed, the lower end of the steel ruler is connected to the rebound mark, and the upper end is passed through the pulley block (19) and a counterweight is hung. The steel ruler (24) is adjusted to keep it vertical. The initial reference elevation values ​​of all rebound marks are monitored by a precision level (21). Then, the exploration well (26) is backfilled in layers so that the filling density in the exploration well is basically consistent with the surrounding original soil density. When the backfill is 0.3m above the rebound mark elevation, a white lime layer (4) with a thickness of 0.2m to 0.3m is set as a prompt layer during the foundation pit excavation process. When the next measuring point is reached, the above steps are repeated until all the rebound marks (7) are installed and the filling in the exploration well is backfilled to the ground. Step 2: Measure the initial reference elevation value of the rebound mark and the initial reference elevation value of the magnetic ring; Step 3: Excavate in layers. The monitoring process of rebound deformation after each layer of excavation is the same. The monitoring process of rebound deformation after each layer of excavation is as follows: Step 301, monitoring of layered rebound above the bottom of the foundation pit: When the foundation pit is excavated to 0.4m to 0.6m above the rebound mark position of the corresponding layer, excavate manually along the original exploration well range downward to the position of the circular ring (7-1) of the rebound mark, hook the lower end hook (25) of the steel ruler (24) on the circular ring (7-1) on the rebound mark, pass the upper end around the pulley and hang a hanging hammer, adjust the steel ruler to keep it vertical, use a precision level (21) to monitor the current elevation of the rebound mark, and according to the formula s j =H j -H 0j , calculate the rebound deformation s of the foundation soil below the rebound mark point of the jth layer j , where H j is the current elevation of the rebound measuring point on the jth layer, H 0j is the initial benchmark elevation value of the rebound measuring point of the jth layer; Step 302, monitoring of layered rebound below the bottom of the foundation pit: Since the pipe bottom plug (16-1) and the cement mortar (18) are reliably anchored, the positions of the electronic chamber (9) and the measuring rod (11) will not change. After the foundation pit is excavated, the soil layer rebounds and deforms. During the soil layer rebound process, the magnetic ring (15-5) will be driven to synchronously shift, changing the length of the measuring rod passing through the magnetic ring. The measuring rod (11) is equipped with a waveguide wire. During measurement, the electronic chamber (9) sends a starting pulse, which is transmitted along the waveguide wire. When the pulse meets the magnetic ring, a magnetostrictive effect current pulse is generated. The demodulator measures the current pulse and calculates the time difference between the two pulses, which is the absolute position of the magnetic ring. According to the formula s it =F it -F i0 , calculate the rebound deformation s of the foundation soil below the pit bottom at the i-th magnetic ring measuring point at time t it , where F it is the current elevation value of the i-th magnetic ring measuring point of the foundation soil below the bottom of the foundation pit at time t, F i0 It is the initial benchmark elevation value of the i-th magnetic ring measuring point of the foundation soil below the bottom of the foundation pit at the initial moment.

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