Bridge pier weathering steel casing grouting reinforcement construction method

Abstract

The application discloses a kind of bridge pier weathering steel casing grouting reinforcement construction methods, belong to bridge pier reinforcement construction technical field.The method includes: the cross-section ellipticity data of the reinforced pier to be collected, verticality deviation value and surface corrosion depth distribution parameter;According to the cross-section ellipticity data, the arrangement pitch of casing hoop stiffener is calculated, and the arrangement pitch is proportional to ellipticity;After coating corrosion-inhibiting isolation layer on the inside of casing, the casing is segmented hoisted to the periphery of pier, and the gap between the inner wall of casing and the surface of pier is homogenized by adjusting temporary support screw;Grout collecting ring groove is set in the bottom of casing and overflow valve is installed, and self-compacting micro-expansion grouting material is segmented pressure-injected from bottom to top, and the hoop strain value of the outer wall of casing and the temperature value of grouting material are collected in real time during pressure-injection process;Grouting pressure compensation is calculated according to the hoop strain value and the temperature value of grouting material, and the outlet pressure of grouting pump is dynamically adjusted by grouting pressure compensation.

Description

Technical Field

[0001] This invention relates to the field of bridge pier reinforcement construction technology, specifically a method for grouting reinforcement of bridge piers with weathering steel casing. Background Technology

[0002] When reinforcing bridge piers with weathering steel casings using grouting to enlarge the cross-section, conventional construction methods typically involve welding circumferential stiffening ribs at equal intervals on the inner side of the casing. The cross-section and spacing of the stiffening ribs are determined based on the nominal diameter of the pier and empirical formulas. However, due to long-term eccentric loading, construction errors, and environmental erosion, the actual cross-section of in-service piers is often elliptical, with significant differences in ellipticity at different heights. The uniform arrangement of stiffening ribs does not account for this geometric deviation, leading to drastic variations in the width of the annular gap between the casing and the pier in areas with greater ellipticity. The circumferential constraint stiffness provided by the evenly spaced stiffening ribs cannot match the gap distribution, resulting in localized insufficient constraint causing casing bulging or excessive constraint causing material redundancy during grouting. Furthermore, the grouting process generally relies on a constant pump outlet pressure, with personnel judging when to stop the pump based on the grout discharge status via the overflow valve. The heat released during grout hydration raises the casing temperature, and the grout pressure simultaneously induces circumferential strain in the casing. The coupling effect of temperature and strain causes dynamic changes in the actual stress state of the casing. Constant pressure cannot compensate for the additional stress caused by thermal expansion and strain. Excessive pressure can cause localized yielding of the casing or cracking of the welds, while insufficient pressure leads to incomplete filling and inadequate compaction, weakening the load-bearing capacity and durability of the reinforced pier. Existing monitoring methods are mostly limited to pressure gauge readings, failing to incorporate circumferential strain and grout temperature as feedback parameters for pressure control. Therefore, it is necessary to address how to rationally determine the arrangement of stiffening ribs based on the measured ellipticity distribution of the pier, ensuring the casing's constraint stiffness adapts to changes in cross-sectional ellipticity, and how to dynamically correct the grouting pressure during the grouting process using the real-time stress state and temperature field of the casing. Summary of the Invention

[0003] The purpose of this invention is to provide a method for grouting and reinforcing bridge piers with weathering steel casings, in order to solve the problems of mismatched constraint stiffness caused by neglecting the difference in ellipticity of the pier cross-section in the arrangement of stiffening ribs in existing reinforcement construction, and the inability of grouting pressure control to adapt to changes in the circumferential strain of the casing and the temperature of the grouting material in real time.

[0004] To achieve the above objectives, the present invention provides the following technical solution: The present invention provides a method for grouting reinforcement of weather-resistant steel casings for bridge piers, the method comprising the following steps:

[0005] Data on the ellipticity of the cross-section of the pier to be reinforced, its verticality deviation, and the distribution parameters of surface corrosion depth are collected to clarify the actual geometric shape and surface damage characteristics of the pier, providing a basis for the precise design and positioning of the subsequent casing. Preferably, a 3D laser scanner is used to acquire point cloud data of the pier surface. The point cloud data is then sliced ​​vertically, and an elliptical contour is fitted to each slice. The difference between the major and minor axes is calculated as the ellipticity of that layer. The horizontal offset of the center point of each ellipse is extracted, and the root mean square value of the offset is used as the verticality deviation of the entire pier. Simultaneously, an ultrasonic thickness gauge is used to collect corrosion depth values ​​at equal intervals along the circumference of the pier, generating a radial distribution curve of corrosion depth. This curve includes the rate of change of corrosion depth along the circumferential angle, thus comprehensively reflecting the cross-sectional variation, tilt state, and surface deterioration degree of the pier.

[0006] The spacing of the circumferential stiffening ribs of the casing is calculated based on the collected cross-sectional ellipticity data. The spacing is proportional to the ellipticity; that is, the larger the ellipticity, the denser the stiffening ribs need to be, in order to specifically resist local stress concentration caused by the irregularity of the cross-section. As a technical solution of this invention, the specific calculation method is as follows: the ellipticity of each layer of the cross-section is sorted by size, and the vertical height corresponding to the three largest ellipticities is taken as the critical section height; circumferential stiffening ribs are set at these critical section heights, and the width of the stiffening ribs is determined based on the product of the ellipticity of that layer and the casing wall thickness; at non-critical section heights, the spacing of the stiffening ribs is taken as the ratio of the casing diameter to the minimum ellipticity. The stiffening ribs adopt an I-shaped cross-section and are welded and fixed to the inner wall of the casing, thereby optimizing the amount of steel used while ensuring the overall rigidity of the casing, allowing the casing to better adapt to the irregular shape of the pier column.

[0007] After applying a corrosion-inhibiting isolation layer to the inner side of the casing, the casing is hoisted to the perimeter of the pier in sections. Temporary lifting lugs are welded to the outer wall of the casing, and four evenly distributed horizontal adjusting screws are installed at the upper end of each section, while eight evenly distributed vertical fine-tuning shims are installed at the lower end, enabling precise adjustment of the casing's spatial position. After hoisting into place, the horizontal adjusting screws are rotated sequentially to move the casing horizontally until the difference between the maximum and minimum distances between multiple measuring points on the inner wall of the casing and the pier surface is less than 2 mm, ensuring the uniformity of the annular gap. Simultaneously, wedge gauges are inserted into the gap, and the thickness of the vertical fine-tuning shims is adjusted based on the gauge readings to achieve a casing verticality accuracy of 0.1%. This process ensures the uniformity of the grout layer thickness, preventing uneven grouting or eccentric pressure on the casing due to uneven gaps.

[0008] A trapezoidal grout collection groove is installed at the bottom of the casing, with an upper base width of 30 mm, a lower base width of 50 mm, and a depth of 20 mm. This groove runs along the bottom inner side of the casing. An overflow valve is installed at the lowest point of the groove, with the opening pressure set to 1.2 times the grouting pressure. The overflow valve outlet guides the overflowing grout into a recovery tank via a recovery pipe. This structure effectively collects the wetting water and thin grout ejected by air during the initial grouting process, ensuring the quality of the bottom grouting. After completing the above preparations, each 3-meter-high section of the casing is used as a grouting unit, and self-compacting micro-expansion grout is injected in sections from bottom to top. Before injection, clean water is injected to moisten the surface of the pier and the inner wall of the casing. The volume of clean water injected is 5% of the grout volume to wet the interface and expel air. During the injection process, the end of the grout delivery pipe is always buried 0.5 meters below the grouting surface to achieve continuous and stable bottom-up injection. Excess air and water are discharged through the overflow valve until pure grout flows out and then the valve is closed, ensuring the dense filling and interface bonding of the grout.

[0009] During the injection process, the circumferential strain value of the outer wall of the casing and the temperature value of the grout are collected in real time. Preferably, eight resistance strain gauges are evenly attached to the outer wall of the casing along the circumferential direction, and two temperature sensors are arranged every meter along the height of the casing. The sampling frequency is set to twice per second. The arithmetic mean of the circumferential strain value at each sampling moment is taken as the representative value of the current circumferential strain. At the same time, the temperature values ​​collected by the temperature sensors are processed by linear interpolation to obtain the instantaneous temperature distribution at each height position of the casing. Through this dynamic monitoring method, the stress state of the casing and the temperature change of the grout can be grasped in real time.

[0010] The grouting pressure compensation is calculated based on the monitored circumferential strain and grout temperature, and the outlet pressure of the grouting pump is dynamically adjusted accordingly to achieve closed-loop control of the grouting process. Specifically, the difference between the current representative circumferential strain value and the representative circumferential strain value at the previous sampling time is taken as the strain increment, and the difference between the temperature distribution and the grout reference temperature of 20 degrees Celsius is taken as the temperature deviation. The strain increment is multiplied by the elastic modulus of the casing material to obtain the stress increment, and the temperature deviation is multiplied by the linear expansion coefficient of the casing material to obtain the thermal stress change. The sum of the stress increment and the thermal stress change is divided by the friction coefficient of the grout-casing interface, and the result is the grouting pressure compensation. This calculation method integrates structural mechanical constraints and thermal effects, enabling pressure regulation to simultaneously compensate for the increase in circumferential tension caused by the rise of grout and the thermal expansion force caused by the temperature rise due to hydration heat.

[0011] As a technical solution of this invention, an electric regulating valve is installed on the outlet pipe of the grouting pump. The grouting pressure compensation is converted into an opening adjustment value of the electric regulating valve, which is proportional to the compensation. The opening adjustment value is corrected based on the measured consistency value of the grout material. The consistency value is measured in real time using a slump cone. When the consistency value exceeds a preset range, the opening adjustment value is multiplied by a consistency correction coefficient. The corrected opening adjustment value is sent to the controller of the electric regulating valve, so that the outlet pressure of the grouting pump is continuously adjusted within the range of 0.2 MPa to 0.8 MPa. This dynamic control mechanism effectively prevents the casing from yielding and deforming due to excessive pressure or from being incompletely filled due to insufficient pressure, ensuring a safe and efficient construction state throughout the grouting process.

[0012] The technical effects and advantages provided by the present invention in the above technical solution are as follows: The ellipticity data of the cross-section of the pier to be reinforced is collected, and the spacing of the circumferential stiffening ribs of the casing is determined based on the ellipticity calculation results, ensuring that the spacing is proportional to the ellipticity. Stiffening ribs are densely spaced at critical cross-sections with high ellipticity. The width of the stiffening ribs is the product of the ellipticity of that layer and the casing wall thickness, allowing the circumferential constraint stiffness of the casing for non-circular cross-sections to adaptively adjust with changes in the actual ellipticity of the pier. In areas with high ellipticity, where the spacing differences are significant, the densely spaced stiffening ribs effectively distribute the circumferential tensile stress, suppressing local bending deformation of the casing wall caused by uneven lateral pressure during grouting. This avoids abrupt changes in grout layer thickness and stress concentration caused by insufficient constraint stiffness, resulting in a more uniform constraint effect in the circumferential direction for the reinforced pier, improving its overall load-bearing capacity and durability. At non-critical cross-sections, the stiffening rib spacing is taken as the ratio of the casing diameter to the minimum ellipticity, reducing steel consumption in areas with lower constraint requirements, balancing structural safety and economy.

[0013] After coating the inner side of the casing with an anti-corrosion isolation layer and adjusting the gap in sections during segmented hoisting, the circumferential strain value output by the resistance strain gauges attached to the outer wall of the casing and the temperature value of the grout collected by temperature sensors deployed along the height are collected in real time during the injection of self-compacting micro-expansion grout. The difference between the current representative value of circumferential strain and the previous sampling time is taken as the strain increment, which is multiplied by the elastic modulus of the casing material to obtain the stress increment; the difference between the temperature distribution and the reference temperature of the grout is multiplied by the linear expansion coefficient of the casing material to obtain the thermal stress change; the sum of the two and divided by the friction coefficient of the interface between the grout and the casing, the result is taken as the grouting pressure compensation amount. This compensation amount directly reflects the real-time stress demand change of the casing caused by the coupling of mechanical load and thermal effect, and is used to continuously adjust the opening of the electric regulating valve on the outlet pipe of the grouting pump, so that the injection pressure dynamically follows the evolution of the stress state of the casing. This pressure control method, based on measured physical field feedback, eliminates pressure overshoot caused by thermal expansion under constant pressure or insufficient pressure caused by grout shrinkage due to water loss. It effectively prevents defects such as plastic bulging of the casing, circumferential cracking, and voids and honeycombing in the grout layer, enhancing the density of the grout filling and the overall integrity of the interface bonding. Correcting the valve opening based on the measured consistency value of the grout slump cylinder further suppresses pressure control deviations caused by fluctuations in grout flowability, maintains stable injection process parameters, and improves the consistency of reinforcement construction quality. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0015] Figure 1 This is a flowchart of the construction method for grouting and reinforcing bridge piers with weather-resistant steel casings; Figure 2 This is a flowchart of a grouting pressure compensation control method based on circumferential strain and temperature. Figure 3 This is a schematic diagram of the segmented grouting and injection structure for reinforcing the pier column casing; Figure 4 This is a diagram showing the distribution of the major and minor axes radii of the bridge pier cross-section. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] See Figure 1 This invention provides a method for grouting reinforcement of weathering steel casings for bridge piers, comprising: collecting cross-sectional ellipticity data, verticality deviation values, and surface corrosion depth distribution parameters of the pier to be reinforced; calculating the arrangement spacing of the circumferential stiffening ribs of the casing based on the cross-sectional ellipticity data, wherein the arrangement spacing is proportional to the ellipticity; after coating the inner side of the casing with a corrosion-inhibiting isolation layer, hoisting the casing in sections to the periphery of the pier, and uniformizing the gap between the inner wall of the casing and the surface of the pier by adjusting the temporary support screws; setting a grout collection groove at the bottom of the casing and installing an overflow valve, and injecting self-compacting micro-expansion grout in sections from bottom to top, collecting the circumferential strain value of the outer wall of the casing and the temperature value of the grout in real time during the injection process; calculating the grouting pressure compensation amount based on the circumferential strain value and the grout temperature value, wherein the grouting pressure compensation amount is used to dynamically adjust the outlet pressure of the grouting pump.

[0018] Example 1: In practice, the process of acquiring point cloud data of the pier surface using a 3D laser scanner is as follows: The 3D laser scanner is set up on stable ground within a range of 5 to 15 meters from the pier to be reinforced. The vertical angular resolution of the laser beam emitted by the scanner is set to 0.02 degrees, and the horizontal angular resolution is set to 0.02 degrees. A 360-degree surround scan of the pier is performed to obtain raw point cloud data containing three-dimensional coordinates and reflection intensity. The raw point cloud data is imported into point cloud processing software, noise points more than 50 mm away from the main surface of the pier are removed, and voxel downsampling is performed on the point cloud data, with the voxel grid size set to 5 mm.

[0019] In some embodiments, the process of vertically slicing point cloud data is as follows: taking the top surface of the pier foundation as the elevation zero point, a point cloud slice is taken vertically upwards at 100 mm intervals, with each slice being 10 mm thick. All point cloud data falling within the thickness range of the same slice are considered as the point set of that slice. For each slice point set, the least squares method is used to fit an elliptical contour. The general equation of the ellipse is:

[0020] in, and These are the two orthogonal coordinates of a point in the slice point set within the horizontal plane, with the origin being the origin of the scan coordinate system. Parameters , , , , , The coefficients of the elliptic equation are to be determined. This is solved by minimizing the sum of squared algebraic distances from all points in the slice point set to the elliptic curve, under the following constraints: To ensure the fitted result is an ellipse, the coefficients of the ellipse equation are obtained, and then the coordinates of the ellipse's center are calculated. Major axis radius and minor axis radius The calculation of the major and minor axis radii is based on the geometric parameter transformation formula of the ellipse equation. The difference between the major and minor axis radii is taken as the ellipticity of the cross-section of that layer.

[0021] In practice, the process of calculating the ellipticity correction coefficient is as follows: based on each point in the slice point set... The algebraic residuals between the fitted ellipse and the fitted ellipse are represented by the root mean square of the sum of the squares of the algebraic residuals at all points, where... The index of the slice point set is 1, representing the total number of slice points in that layer. The circumference of the ellipse is approximated using a formula. The ratio of the fitted residual to the ellipse's circumference is calculated and is called the ellipticity correction coefficient. This coefficient measures the reliability of the ellipse fit; a smaller coefficient indicates a more reliable fit.

[0022] Optionally, the process of extracting the horizontal offset of the center point of each layer ellipse is as follows: For the ellipse center coordinates of all layer slices... Calculate the horizontal distance between the pier and the designed axis of the column, which is determined by the coordinates of the bottom center of the pier. This horizontal distance is used as the horizontal offset of the center point of the corresponding layer ellipse. The process of calculating the verticality deviation of the entire column is as follows: sum the squares of the horizontal offsets of all layer ellipses, divide by the total number of layers, and then take the square root to obtain the root mean square of the offset of each layer, which is used as the verticality deviation of the entire column.

[0023] In practice, the process of collecting corrosion depth values ​​at equal intervals along the circumference of the pier using an ultrasonic thickness gauge is as follows: Several test sections are selected vertically on the pier surface, with a spacing of 500 mm between adjacent test sections. On each test section, a measuring point is marked every 30 degrees along the circumference, for a total of 12 measuring points. The thickness of the protective layer of the pier is measured at each measuring point using an ultrasonic thickness gauge. The corrosion depth value at that measuring point is obtained by subtracting the measured protective layer thickness from the designed protective layer thickness. The corrosion depth values ​​of the 12 measuring points on the same test section are arranged in circumferential angle order to generate a radial distribution curve of corrosion depth. The radial distribution curve of corrosion depth includes the rate of change of corrosion depth along the circumferential angle, which is calculated by dividing the difference in corrosion depth between adjacent measuring points by the angular interval. The radial distribution curve of corrosion depth is used to visually display the circumferential non-uniformity of corrosion on the pier surface.

[0024] Example 2: In specific implementation, the process of sorting the ellipticity of each layer's cross-section by size is as follows: Obtain the ellipticity values ​​of all vertical slices calculated in Example 1, and map each ellipticity value to its corresponding vertical height to generate an ellipticity-height dataset. Using a numerical sorting method, the ellipticity values ​​in the ellipticity-height dataset are sorted in descending order from largest to smallest, and the vertical heights corresponding to the three largest ellipticity values ​​after sorting are recorded as the key cross-section heights.

[0025] In some embodiments, the process of setting stiffening ribs at critical section heights is as follows: circumferential position lines corresponding to three critical section heights are marked on the inner wall of the casing. At each critical section height position line, a circumferential stiffening rib is set along the circumferential direction of the inner wall of the casing. The width of the stiffening rib is calculated by multiplying the ellipticity value of the section at that level by the casing wall thickness. The casing wall thickness is a known parameter determined during the casing structure design and is pre-selected based on the pier diameter and corrosion protection requirements; the commonly used range for the casing wall thickness is 6 mm to 16 mm. The ellipticity value is the difference between the major axis radius and the minor axis radius of the fitted ellipse at the critical section height, expressed in units of length. The width of the stiffening rib extends radially along the casing, and the thickness of the stiffening rib is 0.8 times the casing wall thickness.

[0026] In practical implementation, the process of setting stiffening ribs at non-critical section heights is as follows: In the remaining vertical sections of the casing, excluding the three critical section heights, multiple circumferential stiffening ribs are evenly arranged according to the stiffening rib spacing. The formula for calculating the stiffening rib spacing is:

[0027] in, The spacing of the stiffening ribs is in millimeters. The inner diameter of the casing is in millimeters. The inner diameter of the casing is the diameter of the inner wall circular surface after the casing is designed and manufactured, and is obtained from the design drawings. The minimum ellipticity is expressed in millimeters. The minimum ellipticity is the minimum value among all cross-sectional ellipticity values ​​in the ellipticity-height dataset, obtained by iterating through the ellipticity-height dataset and taking the minimum value.

[0028] The stiffening ribs have an I-shaped cross-section, consisting of a web and flanges at both ends of the web. The web is arranged radially along the casing, and the two flanges extend circumferentially along the casing. The height of the I-shaped cross-section is equal to the width of the stiffening rib. The web thickness is one-tenth of the height of the I-shaped cross-section, the flange width is three times the web thickness, and the flange thickness is the same as the web thickness. The stiffening ribs are welded to the inner wall of the casing. The welding method involves welding along the entire length of the two circumferential lines where the stiffening rib contacts the inner wall of the casing. The weld type is a fillet weld, and the weld leg size is 0.7 times the casing wall thickness.

[0029] Example 3: In practice, the process of welding temporary lifting lugs to the outer wall of the casing is as follows: Four temporary lifting lugs are welded evenly in a circumferential direction at a position 200 mm from the top end of each section of the casing's outer wall. The temporary lifting lugs are made of 20 mm thick Q235B steel plates, cut into triangular shapes with lifting holes of 30 mm in diameter. The welding method between the lifting lugs and the outer wall of the casing is a double-sided fillet weld, with a weld leg size of 8 mm.

[0030] In some embodiments, the process of installing four evenly distributed horizontal adjusting screws at the upper end of each section of the casing is as follows: An adjusting support is welded every 90 degrees along the circumferential direction on the upper end face of the casing. The adjusting support has a radially penetrating M24 threaded hole. The horizontal adjusting screw is an M24 fully threaded screw, 400 mm in length. A rotating handle is installed at one end of the screw, and the other end passes through the threaded hole of the adjusting support and abuts against the pier surface. An arc-shaped steel plate is installed at the end of the screw that abuts against the pier surface. The radius of curvature of the arc-shaped steel plate matches the pier surface. The arc-shaped steel plate is connected to the end of the screw via a ball joint, allowing the arc-shaped steel plate to adapt to local tilting of the pier surface.

[0031] In practice, the process of setting eight evenly distributed vertical fine-tuning shims at the lower end of each section of the casing is as follows: On the contact surface between the bottom end of the casing and the lower structure, a set of vertical fine-tuning shims is set every 45 degrees along the circumference, for a total of eight sets. Each set of vertical fine-tuning shims is composed of stacked stainless steel sheets with thicknesses of 0.5 mm, 1 mm, and 2 mm. The total thickness of the set of shims is adjusted by increasing or decreasing the number of shims.

[0032] In practice, the process of sequentially rotating the horizontal adjusting screws to move the casing after hoisting and positioning is as follows: After the lifting equipment lowers the casing to the predetermined position outside the pier, the lifting hook is released. The operator uses a torque wrench to sequentially rotate the handles of the four horizontal adjusting screws, controlling the rotation angle within 30 degrees each time, causing the casing to move radially. After each adjustment, a gap measuring ruler with a range of 30 mm and a graduation of 0.5 mm is used to measure the radial gap at eight evenly distributed measuring points along the circumference between the inner wall of the casing's upper end and the pier surface. The gap measurements at the eight measuring points are recorded, and the difference between the maximum and minimum gap measurements is calculated. When the difference between the maximum and minimum values ​​is greater than or equal to 2 mm, the horizontal adjusting screws are rotated sequentially to adjust the casing position until the difference between the maximum and minimum values ​​is less than 2 mm.

[0033] In some embodiments, the process of inserting a wedge gauge into the gap between the casing and the pier is as follows: After the casing is horizontally positioned, the wedge gauge is inserted from the top and bottom of the casing into the annular gap between the inner wall of the casing and the surface of the pier. The wedge gauge has a measuring range of 1 mm to 15 mm, the slope of the wedge is 1:10, and the surface of the gauge is engraved with graduations corresponding to the gap width value. The wedge gauge is inserted at eight evenly distributed points along the circumference at both the upper and lower ends of the casing, and the gap width value at each point is read.

[0034] In practice, the process of adjusting the thickness of the vertical fine-tuning shims to achieve a casing verticality accuracy of 0.1% based on wedge gauge readings is as follows: The average value of the wedge gauge readings at eight positions on the upper end is taken as the average upper clearance, and the average value of the wedge gauge readings at eight positions on the lower end is taken as the average lower clearance. Based on the difference between the upper and lower average clearances, and considering the relationship between the casing's designed inner diameter and the pier's designed diameter, the horizontal offset of the casing's top center relative to its bottom center is calculated. The formula for calculating the percentage deviation of the casing verticality is:

[0035] in, The percentage of casing verticality deviation is expressed in % %. The horizontal offset of the center of the top end of the casing relative to the center of the bottom end is expressed in millimeters. The vertical length of the casing section is measured in millimeters, obtained from the measured length from the upper end to the lower end of the casing.

[0036] When calculated When the value is greater than 0.1%, determine the direction and amount of adjustment required. Correct the casing tilt by increasing or decreasing the number of vertical fine-tuning shims at the corresponding location to alter the total shim thickness. Repeat the gap measurement and calculation. Value, until When the value is less than or equal to 0.1%, the verticality adjustment of the casing is completed.

[0037] Example 4: In specific implementation, please refer to Figure 2The process of uniformly attaching eight resistance strain gauges circumferentially to the outer wall of the casing is as follows: On the same horizontal circumferential surface 500 mm above the bottom of each section of the casing, surface grinding and rust removal are performed. The grinding area is 40 mm × 40 mm, achieving a surface roughness of Ra 3.2 micrometers. After wiping the grinding area with anhydrous ethanol, a 0.2 mm thick cyanoacrylate adhesive is applied. Foil-type resistance strain gauges with a resistance of 120 ohms and a grid length of 10 mm are then attached circumferentially to the casing. The eight strain gauges are distributed at 45-degree intervals along the circumference. Each strain gauge is covered with a 0.5 mm thick silicone rubber protective layer. After the protective layer cures, PVC insulating tape is wrapped around it for mechanical protection.

[0038] In some embodiments, the process of arranging two temperature sensors per meter along the height of the casing is as follows: A temperature sensor mounting point is set every 500 mm from the bottom of the casing upwards. At each mounting point, the sensing element of a Pt100 platinum resistance temperature sensor is tightly attached to the outer wall of the casing. Thermally conductive silicone grease with a thermal conductivity of 3 Kelvin per meter is applied between the sensing element and the outer wall of the casing. The sensing element is covered with a 20 mm thick layer of 80 mm × 80 mm rubber-plastic insulation cotton to isolate the temperature sensor readings from ambient temperature interference.

[0039] In practice, the process of leading the strain gauges and temperature sensors out from the top of the casing is as follows: the leads of the eight resistance strain gauges are divided into two groups, with four leads in each group corresponding to four resistance strain gauges, and connected to the bridge box of the dynamic strain gauge using a 1 / 4 bridge three-wire connection method. The three leads of the temperature sensor are connected to the input channel of the temperature acquisition module. All leads are run vertically along the outer wall of the casing, and every 300 mm, high-temperature resistant aluminum foil tape is used to fix the lead bundle to the outer wall of the casing. The lead bundles converge at the top of the casing and are then passed through a waterproof gland into the data acquisition box. The data acquisition box contains the dynamic strain gauge and the temperature acquisition module. The dynamic strain gauge has a range of ±20,000 microstrains and a resolution of 0.5 microstrains; the temperature acquisition module has a resolution of 0.1 degrees Celsius and an accuracy of ±0.2 degrees Celsius.

[0040] In the specific implementation, the process of setting the sampling frequency to twice per second is as follows: the central controller in the data acquisition box sends sampling trigger pulses to the dynamic strain gauge and temperature acquisition module. The period of the sampling trigger pulse is 500 milliseconds. At each sampling moment, data is synchronously acquired once for the eight resistance strain gauge channels and all temperature sensor channels and stored in the memory card.

[0041] In some embodiments, the process of taking the arithmetic mean of eight measuring points for the circumferential strain value at each sampling moment as the current representative value of circumferential strain is as follows: For a certain sampling moment, the circumferential strain values ​​collected by the eight resistance strain gauges are denoted as follows: to The unit is microstrain. The formula for calculating the representative value of the current circumferential strain is:

[0042] in, This represents the current circumferential strain value, in microstrain. The value of the circumferential strain measured by the first resistance strain gauge at the circumferential position of 0 degrees; The value of the circumferential strain measured by the second resistance strain gauge at a circumferential position of 45 degrees. The value of the circumferential strain measured by the third resistance strain gauge at a circumferential position of 90 degrees. The value of the circumferential strain measured at 135 degrees circumferentially by the fourth resistance strain gauge. The value of the circumferential strain measured at 180 degrees in the circumferential position by the fifth resistance strain gauge; The value of the circumferential strain measured at 225 degrees circumferentially by the sixth resistance strain gauge. The circumferential strain value measured at 270 degrees circumferentially by the seventh resistance strain gauge; The value of the circumferential strain measured at 315 degrees circumferentially by the eighth resistance strain gauge is given.

[0043] In practice, the process of obtaining the instantaneous temperature distribution at various height positions of the casing by linear interpolation of the temperature values ​​collected by the temperature sensors is as follows: Temperature sensors arranged along the height direction of the casing are sorted from smallest to largest according to their height position. Within the height interval between two adjacent temperature sensors, the temperature value at any height is obtained by linear interpolation between the measured temperature values ​​of the two adjacent temperature sensors. The temperature value of the lowest temperature sensor is taken at the lowest position of the casing, and the temperature value of the highest temperature sensor is taken at the highest position of the casing, thus obtaining the instantaneous temperature distribution at various height positions throughout the entire height range of the casing.

[0044] In some embodiments, the process of using the difference between the current representative value of circumferential strain and the representative value of circumferential strain at the previous sampling time as the strain increment is as follows: subtract the representative values ​​of circumferential strain at two adjacent sampling times read from the memory card of the central controller. Let the current sampling time number be denoted as... , The value is an integer greater than or equal to 2, and the current circumferential strain represents the value. The circumferential strain at the previous sampling time is represented by the value. Strain increment for minus The difference is expressed in microstrain.

[0045] In practice, the process of using the difference between the temperature distribution and the 20-degree Celsius reference temperature of the grout as the temperature deviation is as follows: Extract the temperature values ​​at each height position within the entire height range of the casing from the instantaneous temperature distribution. Subtract the reference temperature of 20 degrees Celsius from the temperature value at each height position to obtain the temperature deviation value at that height position. The temperature deviation values ​​at all height positions constitute the temperature deviation distribution along the height direction. The reference temperature of 20 degrees Celsius is set based on the standard curing temperature of the self-compacting micro-expansion grout, at which the hydration reaction rate and expansion performance of the grout are at their standard state.

[0046] In some embodiments, the process of multiplying the strain increment by the elastic modulus of the casing material to obtain the stress increment is as follows: stress increment equal to the strain increment Multiply by the elastic modulus of the casing material Elastic modulus of casing material The value is determined based on the grade of weathering steel used in the casing. The elastic modulus of Q355NH weathering steel is taken as 206 gigapascals.

[0047] In practical implementation, the process of multiplying the temperature deviation by the linear expansion coefficient of the casing material to obtain the change in thermal stress is as follows: Change in thermal stress Equals temperature deviation multiplied by the linear expansion coefficient of the casing material Multiply by the elastic modulus of the casing material. The coefficient of linear expansion of the casing material Values This value represents the average linear expansion coefficient of Q355NH weathering steel in the range of 20 to 100 degrees Celsius.

[0048] In some embodiments, the process of summing the stress increment and the thermal stress change and dividing the result by the friction coefficient of the grout-casing interface as the grouting pressure compensation amount is as follows: Grouting pressure compensation amount equal to stress increment With thermal stress change Sum of the sum divided by the coefficient of friction Coefficient of friction The value is 0.4. This value is based on the static friction coefficient between the self-compacting micro-expansion grout before hardening and the inner wall of the casing after being coated with an anti-corrosion isolation layer, which is determined by indoor inclined plane slip test.

[0049] In practice, the process of installing an electric regulating valve on the outlet pipeline of the grouting pump is as follows: disconnect the pipeline 500 mm away from the outlet flange of the pump body and install a flange-type electric regulating valve. The nominal diameter of the electric regulating valve is the diameter of the outlet pipeline of the grouting pump. The input signal of the electric regulating valve is a current signal of 4 mA to 20 mA, corresponding to a valve opening of 0% to 100%, and the actuator response time is 2 seconds.

[0050] In some embodiments, the process of converting the grouting pressure compensation amount into the opening adjustment value of the electric regulating valve is as follows: grouting pressure compensation amount The adjustment value is directly proportional to the valve opening. A pressure transmitter installed on the grouting pump outlet pipe provides real-time feedback of the current outlet pressure. When the grouting pressure compensation is positive, the valve opening adjustment value is positive, increasing the valve opening to raise the outlet pressure. When the grouting pressure compensation is negative, the valve opening adjustment value is negative, decreasing the valve opening to lower the outlet pressure. The proportionality coefficient between the valve opening adjustment value and the grouting pressure compensation is 0.5% per kPa. This coefficient is based on the fact that the outlet pressure of the electric regulating valve has an approximately linear relationship with the valve opening across its full range. Calibration tests have shown that a 1% change in valve opening corresponds to a 2 kPa change in outlet pressure.

[0051] In practice, the process of correcting the opening adjustment value based on the measured consistency value of the grout's fluidity is as follows: The consistency value of the grout is measured in real time using a slump cone, expressed as slump spread in millimeters. The preset slump spread range is 600 mm to 750 mm. When the measured consistency value exceeds this preset range, the opening adjustment value is multiplied by a consistency correction factor. The consistency correction factor is obtained as follows: when the measured consistency value is less than 600 mm, the consistency correction factor is 1.2, based on the principle that insufficient grout fluidity requires increased grouting pressure to ensure dense filling; when the measured consistency value is greater than 750 mm, the consistency correction factor is 0.8, based on the principle that excessive grout fluidity requires reduced grouting pressure to avoid segregation. When the measured consistency value is within the preset range, the consistency correction factor is 1.0.

[0052] In some embodiments, the process of sending the corrected opening adjustment value to the controller of the electric regulating valve is as follows: the central controller calculates the corrected opening adjustment value, converts it into a current signal value in the range of 4 mA to 20 mA, and sends the current signal to the controller of the electric regulating valve through the analog output module, so that the outlet pressure of the grouting pump is continuously adjusted in the range of 0.2 MPa to 0.8 MPa. The upper limit of the outlet pressure of 0.8 MPa is set based on the allowable stress limit of the circumferential weld of the casing, and the lower limit of the outlet pressure of 0.2 MPa is set based on the minimum pressure required for the grouting material to overcome the pipe resistance and fill the gap.

[0053] Example 5: In specific implementation, please refer to Figure 3The grouting process, with each casing section having a height of 3 meters as a grouting unit, is as follows: A single casing section is divided vertically along its entire length into an independent grouting unit, with the vertical height of the grouting unit equal to the length of the casing section (3 meters). For casing sections longer than 3 meters, several grouting units are divided within the casing section at 3-meter intervals. The remaining sections less than 3 meters are treated as a separate grouting unit. The grouting sequence, from bottom to top, is as follows: starting with the first casing section at the bottom of the pier, after completing the grouting of the first casing section, the grouting of the adjacent casing sections above it is carried out. This process continues upwards until the grouting of all casing sections in the pier reinforcement section is completed.

[0054] In practice, the process of installing water-stop rubber rings at the junction of adjacent units is as follows: When dividing the injection units, water-stop rubber rings are pre-installed in the annular gap between the inner wall of the casing and the surface of the pier at the interface between two adjacent injection units. The cross-section of the water-stop rubber ring is circular, and its diameter is 3 mm larger than the width of the gap between the inner wall of the casing and the surface of the pier. The material of the water-stop rubber ring is water-swellable rubber, with a volume expansion rate of 200% to 300% after contact with water. When installing the water-stop rubber ring, it is wrapped around the surface of the pier and joined end to end. The joint is bonded with cyanoacrylate adhesive, and the outer edge of the water-stop rubber ring is tightly attached to the inner wall of the casing. The function of the water-stop rubber ring is to prevent water in the grout from seeping and migrating into the gap of the un-grouted injection unit above after the lower injection unit has been grouted.

[0055] In some embodiments, the process of injecting clean water to moisten the surface of the pier and the inner wall of the casing before grouting each injection unit is as follows: Before grouting, clean water is injected from the grouting hole reserved at the bottom of the casing into the annular gap between the inner wall of the casing and the surface of the pier using a grouting pump. The amount of clean water injected is calculated as 5% of the grout volume, and the grout volume is equal to the sum of the annular gap volume corresponding to the injection unit and the volume of the grout collection groove arranged on the inner wall of the casing. The annular gap volume is equal to the inner diameter cross-sectional area of ​​the casing minus the average cross-sectional area of ​​the pier within the range of the injection unit, multiplied by the height of the injection unit. The average cross-sectional area is calculated from the cross-sectional ellipticity data obtained in Embodiment 1. The clean water injection process continues until the clean water flows out from the overflow valve at the top of the casing. During the flow of clean water, it moistens the surface of the pier and the inner wall of the casing, reducing the water migration rate between the grout and the contact surface.

[0056] In practice, the process of keeping the end of the grout delivery pipe buried 0.5 meters below the grouted surface during injection is as follows: The grout delivery pipe is inserted into the annular gap through the grouting hole at the bottom of the casing, with the initial position of the pipe end 100 mm from the bottom of the casing. As the grout is injected, the grout level in the annular gap gradually rises, and the delivery pipe is lifted upwards synchronously with the rise in grout level. The burial depth of the pipe end below the grouted surface is observed through graduations marked every 0.1 meters on the outer wall of the pipe. The operator controls the lifting speed of the delivery pipe according to the rising speed of the grout level, ensuring that the burial depth of the pipe end remains at 0.5 meters. The rising speed of the grout level is determined by the ratio of the grout pump outlet flow rate to the cross-sectional area of ​​the annular gap. The adjustment of the grout pump outlet flow rate is linked to the opening control of the electric regulating valve in Example 4.

[0057] In some embodiments, the process of discharging excess air and water through the overflow valve is as follows: an overflow valve is installed at the top of the casing of each injection unit, and the overflow valve communicates with an overflow hole opened in the inner wall of the casing, the diameter of which is 20 mm. During the filling of the grout from the bottom of the annular gap upwards, the air and injected water in the annular gap are pushed upwards by the grout and discharged from the overflow valve at the top of the casing. The overflow valve remains open until the discharged medium changes from a mixture of air and water to pure grout. When the medium flowing out of the overflow valve changes from turbid water to continuous and uniform pure grout, it indicates that the air and water in the annular gap have been completely discharged, and the overflow valve is closed at this time. The criterion for determining pure grout is that at least 5 liters of grout flow continuously from the overflow valve outlet and there are no visible air bubbles or water mixed in.

[0058] In practice, the process of setting the grout collection groove at the bottom of the casing is as follows: A grout collection groove is formed along the inner circumference of the casing, 20 mm above the bottom surface of the casing. The groove has a trapezoidal cross-section with an upper base width of 30 mm, a lower base width of 50 mm, and a depth of 20 mm. The opening of the trapezoidal section faces the annular gap inside the casing. The groove is fabricated before the casing steel plate is rolled; a planer is used to machine a trapezoidal groove on the inner side of the lower edge of the rolled-out steel plate. After the casing is rolled, the trapezoidal groove naturally forms the annular grout collection groove. The grout collection groove is continuously set along the bottom inner side of the casing. It collects the grout that leaks downwards along the annular gap during grouting, preventing excessive local pressure caused by the accumulation of leaked grout at the bottom of the casing.

[0059] In practical implementation, the process of installing the overflow valve at the lowest point of the grout collection ring groove is as follows: A through hole is drilled at the lowest point of the grout collection ring groove along its circumference on the casing wall plate corresponding to the bottom of the casing. The diameter of the through hole matches the interface pipe diameter of the overflow valve. The overflow valve is installed at the through hole via a threaded connection or flange connection, and the inlet of the overflow valve communicates with the inside of the grout collection ring groove. The opening pressure of the overflow valve is set to 1.2 times the grouting pressure, and this is achieved by adjusting the spring preload inside the overflow valve. The spring preload is calibrated using a pressure testing bench. The grouting pressure is taken as the real-time value of the grouting pump outlet pressure during the grouting process of this injection unit. The formula for calculating the opening pressure of the overflow valve is:

[0060] in, The opening pressure of the overflow valve is expressed in megapascals (MPa). The grouting pressure is expressed in megapascals (MPa) and is the current outlet pressure value fed back in real time by the pressure transmitter on the grouting pump outlet pipeline. The reason for setting the overflow valve opening pressure to 1.2 times the grouting pressure is as follows: During normal grouting, the pressure in the grout collection groove is close to the grouting pressure, and the overflow valve opening pressure needs to be higher than the normal operating pressure to remain closed. When the pressure in the grout collection groove rises to 1.2 times the grouting pressure due to abnormal accumulation of grout, the overflow valve automatically opens to release pressure, preventing excessive local pressure from causing casing deformation or seal failure.

[0061] In practice, the process of connecting the overflow valve outlet to the recovery pipe to guide the overflowing grout into the recovery tank is as follows: A transparent steel wire hose with an inner diameter of 25 mm is connected to the outlet end of the overflow valve as a recovery pipe, and the other end of the recovery pipe is inserted into a 50-liter recovery tank. The recovery tank is placed on the ground outside the bottom of the casing, and a filter screen is covered at the opening of the recovery tank to filter out any impurities that may be mixed in. When the pressure in the grout collection ring groove reaches the opening pressure of the overflow valve, the overflow valve opens, and the overflowing grout flows into the recovery tank through the recovery pipe. The grout collected in the recovery tank, if its fluidity still meets the requirements, can be added back into the grouting pump hopper for subsequent injection unit grouting.

[0062] See Figure 4 In the figure, the horizontal axis represents time (in seconds) and the vertical axis represents grouting pressure (in megapascals). The curves show the real-time grouting pressure changes of the three injection units during the grouting reinforcement process from bottom to top according to the injection unit segment in Example 5. The curve colors correspond to the bottom injection unit 1 (blue), the middle injection unit 2 (orange), and the upper injection unit 3 (green), respectively.

[0063] As shown in the figure, the grouting pressure of all injection units exhibits an overall upward trend, starting at approximately 0.25 MPa and gradually increasing over time before stabilizing. Specifically, the initial pressure of the bottom injection unit 1 is relatively low, and its overall pressure level is lower than that of the middle injection unit 2 and the upper injection unit 3. The pressure curve of the middle injection unit 2 is in the middle, while the pressure of the upper injection unit 3 is the highest, approaching 0.8 MPa. This trend conforms to the bottom-up, unit-by-unit injection sequence of the casing, with the bottom unit pressure increasing first, followed by the middle and upper units.

[0064] The pressure curves of each injection unit exhibited sharp fluctuations within a short period during the pressurization phase, with a fluctuation range of approximately 0.05 MPa. This reflects the dynamic changes in the grout pump outlet pressure during the grouting process, influenced by the material's rheological properties and the lifting operation of the delivery pipe. Subsequently, the pressure stabilized, fluctuating within the corresponding pressure range. The pressure of the bottom unit remained stable at approximately 0.55 MPa, the middle unit at approximately 0.65 MPa, and the upper unit at approximately 0.75 MPa. This indicates a significant hierarchical difference in grouting pressure among different injection units, consistent with the differences in stress and density requirements across different injection zones during reinforcement construction.

[0065] Furthermore, no pressure exceeding 0.8 MPa was observed in the figure, which conforms to the upper limit of the grouting pump outlet pressure in Example 5, ensuring the stress safety of the circumferential weld of the casing. The entire injection process controlled the grouting pressure to increase uniformly, avoiding casing deformation or grout segregation due to sudden pressure increases, demonstrating the effective application of dynamic pressure compensation and segmented injection technology.

[0066] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application.

Claims

1. A method for grouting reinforcement of weather-resistant steel casings for bridge piers, characterized in that, The method includes: Collect cross-sectional ellipticity data, verticality deviation values, and surface corrosion depth distribution parameters of the pier column to be reinforced; The arrangement spacing of the circumferential stiffening ribs of the casing is calculated based on the ellipticity data of the cross section, and the arrangement spacing is proportional to the ellipticity. After coating the inner side of the casing with an anti-corrosion isolation layer, the casing is hoisted to the outer perimeter of the pier in sections, and the gap between the inner wall of the casing and the surface of the pier is made uniform by adjusting the temporary support screws. A grout collection groove is set at the bottom of the casing and an overflow valve is installed. Self-compacting micro-expansion grout is injected in sections from bottom to top. During the injection process, the circumferential strain value of the outer wall of the casing and the temperature value of the grout are collected in real time. The grouting pressure compensation is calculated based on the circumferential strain value and the grouting material temperature value. The grouting pressure compensation is used to dynamically adjust the outlet pressure of the grouting pump.

2. The method for grouting reinforcement of bridge piers with weathering steel casings according to claim 1, characterized in that, The data collected on the cross-sectional ellipticity, verticality deviation, and surface corrosion depth distribution of the pier to be reinforced include: The point cloud data of the pier surface was acquired using a 3D laser scanner. The point cloud data was then sliced ​​vertically, and each slice was fitted with an elliptical profile. The difference between the major axis and the minor axis was calculated as the ellipticity of the cross section of that layer. Extract the horizontal offset of the center point of each ellipse and calculate the root mean square of the verticality deviation of the entire column. An ultrasonic thickness gauge is used to collect corrosion depth values ​​at equal intervals along the circumference of the pier column, generating a radial distribution curve of corrosion depth. The radial distribution curve of corrosion depth includes the rate of change of corrosion depth along the circumferential angle.

3. The method for grouting reinforcement of weathering steel casing for bridge piers according to claim 1, characterized in that, The calculation of the circumferential stiffening rib spacing of the casing based on the cross-sectional ellipticity data includes: Sort the ellipticity of each section by size, and take the vertical height corresponding to the three largest ellipticities as the critical section height; Stiffening ribs are installed at the critical section height, and the width of the stiffening ribs is the product of the ellipticity of the layer and the thickness of the casing wall. At non-critical section heights, the spacing of stiffening ribs is taken as the ratio of the casing diameter to the minimum ellipticity. The stiffening ribs adopt an I-shaped section and are welded and fixed to the inner wall of the casing.

4. The method for grouting reinforcement of bridge piers with weathering steel casings according to claim 1, characterized in that, The process of hoisting the casing in sections to the perimeter of the pier, and adjusting the temporary support bolts to uniformly distribute the gap between the inner wall of the casing and the surface of the pier, includes: Temporary lifting lugs are welded to the outer wall of the casing. Four evenly distributed horizontal adjusting screws are set at the upper end of each section of the casing, and eight evenly distributed vertical fine-tuning shims are set at the lower end. After hoisting into place, rotate the horizontal adjusting screw one by one to push the casing to move horizontally until the difference between the maximum and minimum distances between multiple measuring points on the inner wall of the casing and the surface of the pier is less than 2 mm. Insert a wedge gauge into the gap between the casing and the pier, and adjust the thickness of the vertical fine-tuning shim according to the gauge reading to achieve a casing verticality accuracy of 0.1%.

5. The method for grouting reinforcement of weathering steel casing for bridge piers according to claim 1, characterized in that, The circumferential strain value of the outer wall of the casing and the temperature value of the grout are collected in real time during the injection process, including: Eight resistance strain gauges are evenly pasted along the circumferential direction on the outer wall of the casing. Two temperature sensors are arranged every meter along the height of the casing. The leads of the strain gauges and temperature sensors are led out from the top of the casing to the data acquisition instrument. The sampling frequency is set to twice per second, and the arithmetic mean of eight measuring points is taken as the current representative value of circumferential strain at each sampling time. The temperature values ​​collected by the temperature sensor are processed by linear interpolation to obtain the instantaneous temperature distribution at each height position of the casing.

6. The method for grouting reinforcement of weathering steel casing for bridge piers according to claim 1, characterized in that, The calculation of grouting pressure compensation based on the circumferential strain value and the grout temperature value includes: The difference between the current representative value of circumferential strain and the representative value of circumferential strain at the previous sampling time is taken as the strain increment, and the difference between the temperature distribution and the reference temperature of grouting material of 20 degrees Celsius is taken as the temperature deviation. The stress increment is obtained by multiplying the strain increment by the elastic modulus of the casing material, and the thermal stress change is obtained by multiplying the temperature deviation by the linear expansion coefficient of the casing material. The sum of the stress increment and the thermal stress change is divided by the friction coefficient of the grout-casing interface, and the result is used as the grouting pressure compensation.

7. The method for grouting reinforcement of weathering steel casing for bridge piers according to claim 6, characterized in that, The grouting pressure compensation amount is used to dynamically adjust the outlet pressure of the grouting pump, including: An electric regulating valve is installed on the outlet pipeline of the grouting pump to convert the grouting pressure compensation amount into the opening adjustment value of the electric regulating valve. The opening adjustment value is proportional to the compensation amount. The opening adjustment value is corrected based on the measured consistency value of the grout's fluidity. The consistency value is measured in real time using a slump cone. When the consistency value exceeds the preset range, the opening adjustment value is multiplied by the consistency correction coefficient. The corrected opening adjustment value is sent to the controller of the electric regulating valve, so that the outlet pressure of the grouting pump can be continuously adjusted within the range of 0.2 MPa to 0.8 MPa.

8. The method for grouting reinforcement of bridge piers with weathering steel casings according to claim 1, characterized in that, The bottom-up segmented injection self-compacting micro-expansion grouting material includes: Each section of the casing is 3 meters high and is used as a pressure injection unit. Pressure injection is carried out unit by unit from bottom to top. Water-stop rubber rings are set at the junction of adjacent units. Before each injection unit is injected, clean water is injected to moisten the surface of the pier column and the inner wall of the casing. The amount of clean water injected is 5% of the volume of the grout. During the injection process, the end of the grout delivery pipe should always be buried 0.5 meters below the grouted surface. Excess air and water should be discharged through the overflow valve until pure grout flows out of the overflow valve and then it should be closed.

9. The method for grouting reinforcement of bridge piers with weathering steel casings according to claim 1, characterized in that, The method also includes setting a slurry collecting ring groove at the bottom of the casing and installing an overflow valve. The cross-section of the slurry collecting ring groove is trapezoidal, with an upper base width of 30 mm, a lower base width of 50 mm, and a depth of 20 mm. The slurry collecting ring groove is set around the bottom of the inner side of the casing. The overflow valve is installed at the lowest point of the grout collection ring groove. The opening pressure of the overflow valve is set to 1.2 times the grouting pressure. The outlet of the overflow valve is connected to a recovery pipe to guide the overflowing grout into the recovery tank.

10. A method for grouting and reinforcing bridge piers with weathering steel casings according to claim 2, characterized in that, The fitted elliptical profile is obtained using the least squares method, and an ellipticity correction coefficient is calculated. The correction coefficient is equal to the ratio of the fitted residual to the ellipse circumference.

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