An ultra-deep cone probe grouting pressure self-adaptive regulation method

Abstract

The application discloses a kind of super deep cone probe grouting pressure self-adapting regulation and control methods, it is related to grouting pressure regulation and control field, comprising: obtaining the hole depth of super deep cone probe grouting hole and cone probe rod initial position, and set hole bottom target pressure value;Real-time acquisition orifice pressure value and grouting flow value in the process of cone probe grouting;In the process of subsection lifting or moving down of cone probe rod, simultaneously collect grouting flow variation, orifice pressure variation and cone probe rod displacement;The application synchronously collects grouting flow variation, orifice pressure variation and displacement in the movement of cone probe rod, and the actual pressure of hole bottom is calculated back by on-line fitting slurry along the way resistance coefficient and density, and the output of grouting pump is adjusted by hole bottom pressure deviation signal closed loop, improve the accuracy of hole bottom pressure control.

Description

Technical Field

[0001] This invention relates to the field of grouting pressure control technology, specifically to an adaptive control method for grouting pressure in ultra-deep cone grouting. Background Technology

[0002] Cone drilling grouting is a common engineering method used in dam seepage prevention and reinforcement as well as soft soil foundation treatment. It involves drilling a hole with a cone and then injecting grout into the pores or fissures of the strata to improve soil density and impermeability. In recent years, grouting depths have been continuously increasing. Deep strata have high ground stress, high pore water pressure, and complex geological conditions, making the control of grouting pressure a direct determinant of grouting effectiveness and construction safety.

[0003] An invention patent application with application number 202010838981.2 discloses an adaptive grouting control method. This application uses the grouting pressure and flow rate at the wellhead during the trial grouting stage to determine the groutability of the formation. Then, based on the change in grouting flow rate, the grouting pressure is gradually increased and maintained to achieve adaptive grouting under different geological conditions. The pressure monitoring point of this method is located in the grout return pipeline at the wellhead, and the wellhead pressure is used as the control basis.

[0004] Currently, most existing technologies in ultra-deep grouting use orifice pressure as the control benchmark. The pressure loss along the grout path changes dynamically with the hole depth, grout viscosity, and flow rate. There is a significant and time-varying deviation between the actual pressure at the orifice and the bottom of the hole, which cannot be corrected in real time. This results in insufficient grouting when the bottom pressure is too low, and grout leakage when it is too high, making it difficult to achieve adaptive control of the actual bottom pressure. Summary of the Invention

[0005] In view of the above-mentioned shortcomings of the existing technology, the present invention provides an adaptive control method for grouting pressure in ultra-deep cone grouting, which can effectively solve the problems of the existing technology.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions;

[0007] This invention discloses an adaptive control method for grouting pressure in ultra-deep cone grouting, comprising the following steps:

[0008] Obtain the depth of the ultra-deep cone grouting hole and the initial position of the cone probe, and set the target pressure value at the bottom of the hole;

[0009] Real-time acquisition of borehole pressure and grouting flow rate during cone grouting;

[0010] During the segmented lifting or lowering of the cone probe, the changes in grouting flow rate, orifice pressure, and cone probe displacement are collected simultaneously.

[0011] The friction coefficient of the grout is determined based on the relationship between the change in grouting flow rate and the change in orifice pressure. The density of the grout is determined based on the relationship between the displacement of the cone probe and the change in orifice pressure. The actual pressure value at the bottom of the hole is obtained by subtracting the friction pressure loss and the static pressure of the grout column from the orifice pressure value.

[0012] The difference between the actual pressure value at the bottom of the hole and the target pressure value at the bottom of the hole is used to generate a pressure deviation signal at the bottom of the hole.

[0013] Adjust the output pressure of the grouting pump according to the pressure deviation signal at the bottom of the hole, so that the actual pressure value at the bottom of the hole approaches the target pressure value at the bottom of the hole.

[0014] Furthermore, the target pressure value at the bottom of the borehole is dynamically adjusted according to the formation's grout suction status:

[0015] Collect the return flow rate value, and obtain the formation grout intake value from the difference between the injection flow rate value and the return flow rate value. When the formation grout intake value satisfies the following formula, adjust the target pressure value at the bottom of the hole.

[0016] ;

[0017] In the formula: This refers to the amount of grout absorbed by the formation. The formation's grout absorption coefficient; This represents the actual pressure value at the bottom of the hole. This represents the initial in-situ stress in the deep strata. It is a non-linear exponent;

[0018] When the aforementioned inequality holds, it is determined that the formation's grout absorption has weakened, and the target pressure value at the bottom of the borehole is adjusted according to the following formula:

[0019] ;

[0020] In the formula; The adjusted target pressure value at the bottom of the hole; The target pressure value at the bottom of the hole before adjustment; The preset maximum pressure adjustment step size is defined as follows: the percentage of insufficient formation grout intake is indicated within square brackets. When the inequality does not hold, the formation grout intake is determined to be normal, and the target pressure value at the bottom of the borehole is kept constant.

[0021] Furthermore, the sampling interval for real-time acquisition of orifice pressure and grouting flow rate during the conical grouting process is dynamically adjusted according to the following formula:

[0022] ;

[0023] In the formula: For dynamic sampling interval; The reference sampling interval; is the first-order rate of change of the orifice pressure; The second rate of change of the orifice pressure value. The first-order rate of change weighting coefficient. The second-order rate of change weighting coefficient;

[0024] The first-order rate of change and the second-order rate of change are calculated by the difference in orifice pressure values ​​at adjacent sampling times.

[0025] Furthermore, the change in grouting flow rate is the difference in grouting flow rate before and after the cone probe is lifted or lowered, the change in orifice pressure is the difference in orifice pressure before and after the cone probe is lifted or lowered, and the displacement of the cone probe is the difference between the current position of the cone probe and the initial position of the cone probe.

[0026] The time difference between the sampling times of the grouting flow rate change, the orifice pressure change, and the cone probe displacement does not exceed the preset sampling synchronization threshold.

[0027] Furthermore, during the lifting or lowering of the cone probe... The grouting flow rate, orifice pressure, and cone probe position were collected at each time period. The ratio of the change in orifice pressure to the change in grouting flow rate within each time period was used as the sample value of the grout friction coefficient for that time period. The time-varying grout friction coefficient was then obtained by fitting the data using the following formula:

[0028] ;

[0029] In the formula: For a moment The friction coefficient of the slurry; This is the initial friction coefficient of the slurry. The hydration rate coefficient of the slurry; This refers to the time from the moment the current batch of slurry is prepared until the sampling time of the corresponding period.

[0030] Furthermore, during the lifting or lowering of the cone probe, [the following is taken]: The average density of the slurry is obtained by fitting the corresponding values ​​of the displacement of the cone probe and the change in orifice pressure using the following formula:

[0031] ;

[0032] In the formula: The average density of the slurry; For the first Displacement of the cone probe in the group; For the first The change in orifice pressure of the group; It is the acceleration due to gravity; This represents the number of measurement groups.

[0033] Furthermore, the actual pressure value at the bottom of the hole is obtained by the following formula:

[0034] ;

[0035] In the formula: This represents the actual pressure value at the bottom of the hole. This refers to the orifice pressure value. The friction coefficient of the time-varying slurry; The grouting flow rate value; This is the flow area of ​​the annular gap between the probe wall and the borehole wall when the cone probe is located at the bottom of the borehole. The cone probe is located at depth The flow area of ​​the annular gap at that location; Area correction index; The average density of the slurry. It is the acceleration due to gravity. The depth of the hole.

[0036] Furthermore, in the stage of calculating the actual pressure value at the bottom of the borehole, the pressure value at the borehole opening and the grouting flow rate are taken after a delay from the current moment. The corresponding value, the delay duration The time it takes for the pressure wave to propagate from the orifice to the bottom of the orifice. , The velocity of the pressure wave in the slurry.

[0037] Furthermore, the bottom pressure value predicted based on the time-varying grout friction coefficient is compared with the calculated actual bottom pressure value. When the deviation between the two exceeds the preset threshold, the current result is determined to be invalid and the process is returned to the synchronous acquisition stage of grouting flow rate change, orifice pressure change and cone probe displacement for re-execution.

[0038] The preset allowable deviation threshold is determined by the following formula:

[0039] ;

[0040] In the formula, The preset allowable deviation threshold; The baseline deviation threshold; This represents the current number of fitted samples; The number of fitted samples is used as a reference. This is the slurry stabilization rate coefficient.

[0041] Furthermore, after adjusting the output pressure of the grouting pump based on the bottom hole pressure deviation signal, the delay time is waited for. Then, the orifice pressure value and the grouting flow rate value are collected again, and the actual pressure value at the bottom of the hole is calculated.

[0042] If the absolute value of the bottom hole pressure deviation signal still exceeds the preset deviation threshold, the process of simultaneously collecting the changes in grouting flow rate, the changes in borehole pressure, and the displacement of the cone probe is repeated until the output pressure of the grouting pump is adjusted according to the bottom hole pressure deviation signal.

[0043] Compared with the known prior art, the technical solution provided by this invention has the following beneficial effects:

[0044] This invention simultaneously collects changes in grouting flow rate, orifice pressure, and cone rod displacement during the segmented lifting or lowering of the cone probe. It then online fits the friction coefficient and density of the grout and calculates the actual pressure at the bottom of the borehole by subtracting the friction loss and static pressure of the grout column from the orifice pressure value. This reflects the time-varying characteristics of the grout in ultra-deep boreholes and the influence of annular flow resistance on the bottom pressure. Furthermore, the bottom pressure deviation signal generated by the actual bottom pressure value and the target bottom pressure value is used to adjust the output pressure of the grouting pump in a closed loop, so that the control directly acts on the key parameter of bottom pressure.

[0045] Simultaneously, the target pressure value at the bottom of the borehole is dynamically adjusted based on the formation grouting status, the sampling interval is adaptively adjusted according to the pressure change rate, and pressure wave propagation delay compensation and effectiveness verification are introduced. This allows the control to adapt to the dynamic changes in formation and grout properties during ultra-deep cone grouting. Compared with the existing fixed parameter open-loop control, this effectively improves the accuracy and timeliness of borehole pressure control. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 This is a flowchart illustrating an adaptive control method for grouting pressure in ultra-deep cone grouting.

[0048] Figure 2 This is a schematic diagram of the segmented movement curve of the cone probe with "fixed-distance pause" in this invention;

[0049] Figure 3 This is a schematic diagram of the grouting flow rate time sequence curve (time-sequence acquisition strategy) in this invention. Detailed Implementation

[0050] 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, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0051] The present invention will be further described below with reference to embodiments.

[0052] Example:

[0053] This embodiment presents an adaptive control method for ultra-deep cone grouting pressure, such as... Figure 1 As shown, it includes the following steps:

[0054] Obtain the depth of the ultra-deep cone grouting hole and the initial position of the cone probe, and set the target pressure value at the bottom of the hole;

[0055] The target pressure value at the bottom of the borehole is dynamically adjusted according to the formation's grouting condition.

[0056] Collect the return slurry flow rate value, and obtain the formation slurry absorption amount from the difference between the injection slurry flow rate value and the return slurry flow rate value;

[0057] When the stratum absorbs grout When the calculated value is negative, it is determined to be due to abnormal slurry return flow measurement or discharge of slurry accumulated in the pipeline. The formation slurry suction status determination is not performed, and the target pressure value at the bottom of the borehole is not adjusted. Under this condition, the slurry return flow is continuously monitored until three consecutive sampling cycles have been completed. After the value is restored to non-negative, the suction status determination process is restarted. If If the negative value persists for more than 10 sampling cycles, an abnormality warning for the slurry return pipeline will be issued, prompting on-site inspection to check whether the slurry return flow meter is blocked or whether there is cross-contamination in the pipeline;

[0058] It should be noted that:

[0059] The slurry return flow rate is collected at the slurry return pipeline at the orifice, measured using an electromagnetic flowmeter or a volumetric flowmeter. The flowmeter is installed on a straight pipe section between the orifice slurry return outlet and the slurry return pool, with the installation position no more than 2m from the orifice outlet. Straight pipe sections of at least 5 times and 3 times the pipe diameter are reserved before and after the flowmeter, respectively, to eliminate the influence of vortex flow on measurement accuracy. The sampling interval for the slurry return flow rate is consistent with the sampling interval for the grouting flow rate, and both sampling times are synchronously triggered using the same time base to ensure the temporal correspondence of the formation slurry absorption calculation.

[0060] Adjust the target pressure value at the bottom of the borehole when the grout intake of the formation meets the following formula;

[0061] ;

[0062] In the formula: This refers to the amount of grout absorbed by the formation. The formation's grout absorption coefficient; This represents the actual pressure value at the bottom of the hole. This represents the initial in-situ stress in the deep strata. It is a non-linear exponent;

[0063] At the implementation level, formation grout intake The grouting flow rate and return flow rate should use the same unit, and the actual pressure value at the bottom of the hole should be used. Initial geostress of deep strata Using the same pressure unit, the formation slurry absorption coefficient The dimensions are automatically determined based on the selected flow rate and pressure units, ensuring that inequalities are maintained. The physical dimensions on both sides are consistent;

[0064] Fitting during trial irrigation stage During the process, the units of flow rate and pressure for input data should be consistent with those used in the subsequent formal grouting stage to avoid issues caused by unit switching. Value mismatch;

[0065] This formula combines the internal stress conditions of the formation to establish a nonlinear relationship between the formation grout absorption and the effective grouting pressure at the bottom of the borehole. It abandons the simple linear grout absorption judgment logic and fully considers the nonlinear characteristics of grout penetration and filling in fractured formations. It can truly reflect the actual grout absorption capacity of the formation under different fracture conditions. This can be used as a criterion for judging whether the formation grout absorption has weakened, which facilitates the subsequent dynamic correction of the target pressure and avoids ineffective grouting under the fixed pressure mode.

[0066] On the other hand, when the actual pressure value at the bottom of the hole Less than or equal to the initial geostress of deep strata At that time, effective grouting pressure Not greater than zero, right side of the decision equation Loss of physical meaning—when nonlinear exponents When the integer is not an integer, the expression is undefined in the real number domain; when... When the result is an integer, the calculation result does not conform to the physical meaning of the formation's slurry absorption capacity;

[0067] Under this condition, the formation grout intake determination formula is not performed, nor is the target pressure value at the bottom of the borehole adjusted downwards, to avoid further reduction of the target pressure leading to... Persistently below The positive feedback loop directly issues an early warning of insufficient formation groutability, prompting on-site operators to check formation conditions, grout ratio and grouting equipment status.

[0068] when Restore to greater than And all three consecutive sampling periods satisfy Afterwards, it automatically re-enters the normal process of determining the amount of slurry sucked and dynamically adjusting the target pressure; if If the status continues for more than 10 control cycles, it is determined that the grouting section has poor groutability under the current grout ratio and pressure parameters. It is suggested that on-site engineering measures such as reducing the water-cement ratio of the grout, adding accelerators, increasing the initial grouting pressure, or increasing the density of the hole layout should be taken before automatic control is restored.

[0069] When the inequality holds, it is determined that the formation's grout absorption has weakened, and the target pressure value at the bottom of the borehole is adjusted according to the following formula:

[0070] ;

[0071] In the formula; The adjusted target pressure value at the bottom of the hole; The target pressure value at the bottom of the hole before adjustment; The step size for adjusting the maximum pressure is set in square brackets, which represents the proportion of insufficient formation grout intake. When the inequality does not hold, the formation grout intake is considered normal, and the target pressure value at the bottom of the borehole is kept constant.

[0072] The determination of formation grout absorption status and the adjustment of the target pressure value at the bottom of the borehole are executed every 5 control cycles, or immediately after the cone probe completes a segment movement and refits the resistance coefficient and density, whichever comes first. The time interval between two target pressure adjustments is no less than 30 seconds to avoid frequent oscillations in the target pressure due to instantaneous flow fluctuations. After each adjustment, the adjusted target pressure value at the bottom of the borehole is used as the deviation comparison benchmark for the next control cycle until the next target pressure adjustment.

[0073] The above formula uses the proportion of insufficient grout intake in the formation as the core weight for pressure adjustment. Combined with the preset maximum pressure adjustment step size, it completes the dynamic reduction of the target pressure at the bottom of the hole. It can adaptively change the pressure correction amplitude according to the degree of deviation of the actual grout intake from the theoretical grout intake level. It will not directly use a fixed amplitude to reduce the pressure. It can reduce the target pressure in time when the grout intake capacity decays, and can also prevent sudden pressure changes from causing disturbance and damage to the deep formation.

[0074] At the implementation level, the dynamic adjustment of the target pressure value at the bottom of the borehole is subject to a lower limit constraint, which determines the adjusted target pressure value at the bottom of the borehole. It shall not be lower than the initial in-situ stress of the deep strata. The larger of the two values: 30% of the design grouting pressure and the adjusted formula. When the pressure is below the lower limit, the lower limit value is taken as the adjusted target pressure, and the formation grouting status is monitored in the next control cycle. If the lower limit is reached for three consecutive cycles, it is determined that the formation section has poor grouting ability. It is suggested that engineering measures such as increasing the number of holes, reducing the water-cement ratio of the grout, or adding a coagulant be taken on site before automatic control is restored.

[0075] The initial target pressure value at the bottom of the borehole is determined by the design grouting pressure.

[0076] ;

[0077] In the formula: This is the initial target pressure value at the bottom of the hole; To design the grouting pressure; To prepare the density of the slurry; It is the acceleration due to gravity; For the depth of the hole;

[0078] The above formula starts from the influence of the self-weight of the grout column under ultra-deep grouting conditions. It calculates the initial target pressure at the bottom of the hole by subtracting the static pressure generated by the grout column at the corresponding depth from the design grouting pressure given by the project. This solves the problem that the design pressure at the hole opening cannot be directly equivalent to the actual working pressure at the bottom of the hole under deep hole conditions, and provides an initial pressure benchmark that conforms to the actual working conditions of deep holes for the entire adaptive control process.

[0079] The data were obtained through nonlinear fitting of the grouting flow rate and the actual pressure at the bottom of the hole during the trial grouting stage.

[0080] The actual pressure value at the bottom of the borehole during the trial grouting phase was estimated using a simplified method: before the trial grouting began, the grout was prepared according to the designed grout mix ratio and its density was measured. During the trial irrigation process, the flow rate was maintained constant for no less than 10 baseline sampling intervals at each set flow rate level. The steady-state orifice pressure value at that level was recorded. Estimate the actual pressure at the bottom of the hole, among which The empirical resistance coefficient value for conventional grouting in this type of formation should be used, or it should be pre-determined through a small-scale annular flow test in the field. The actual pressure value at the bottom of the borehole obtained during the trial grouting phase is only used for the formation grout absorption coefficient. With nonlinear exponent The initial fitting is performed, and after the formal grouting stage begins, the online fitting method of this invention updates the actual pressure at the bottom of the hole in real time and gradually corrects it. and The value of ;

[0081] The initial estimated value before the first dynamic adjustment is obtained by subtracting the static pressure of the slurry column from the initial orifice pressure value, which is obtained from the execution steps of the previous control cycle. It is obtained from the geostress test during the geological exploration stage, or estimated by the product of the average unit weight of the overlying strata and the depth of the grouting hole; The value is determined by fitting the grout intake data at different pressure levels during the trial injection phase, or by taking empirical values ​​based on the degree of formation fracture development.

[0082] Preset maximum pressure adjustment step , This is a proportionality coefficient, and its value is determined according to the degree of fracture development in the strata: 0.1~0.15 for intact strata with no fracture development, 0.07~0.1 for strata with moderate fracture development, and 0.05~0.07 for fractured strata with well-developed fractures.

[0083] Based on the design grouting pressure, this formula introduces a proportional coefficient that matches the degree of formation fracture development to determine the maximum pressure adjustment step size. It incorporates the geological conditions of the formation into the pressure adjustment amplitude constraint. Different adjustment upper limits are corresponding to fractured, intact and other formations to prevent formation splitting caused by excessive pressure adjustment step size, or lag in control response caused by excessive step size.

[0084] Real-time acquisition of borehole pressure and grouting flow rate during cone grouting;

[0085] The sampling interval for real-time acquisition of borehole pressure and grouting flow rate during cone grouting is dynamically adjusted according to the following formula:

[0086] ;

[0087] In the formula: For dynamic sampling interval; The reference sampling interval; is the first-order rate of change of the orifice pressure; The second rate of change of the orifice pressure value. The first-order rate of change weighting coefficient. The second-order rate of change weighting coefficient;

[0088] The above formula dynamically changes the sampling interval based on the first and second order rates of change of the overall orifice pressure. When the pressure fluctuates violently, the sampling interval is automatically reduced, and when the pressure tends to be stable, the sampling interval is enlarged. It takes into account the data acquisition accuracy and sampling calculation overhead of the dynamic grouting process, and is suitable for the data acquisition needs of various working conditions such as cone probe movement, pressure change, and constant pressure grouting.

[0089] The first and second rates of change are calculated by the difference in orifice pressure values ​​at adjacent sampling times;

[0090] Optionally, to avoid abnormal operating conditions where the denominator is non-positive in the dynamic sampling interval formula, a lower limit protection is set for the denominator term: when the calculated value is... When the value is less than 0.5, the denominator is set to 0.5, and the dynamic sampling interval is then determined. No more than twice the reference sampling interval ;

[0091] This protection measure ensures that the sampling interval does not increase abnormally during the rapid pressure drop phase, maintaining a basic data acquisition density; at the same time, the calculation results of the first and second rate of change are filtered by moving average, with a window length of 3 sampling points, to suppress drastic jumps in the rate of change caused by pressure measurement noise.

[0092] Among them, the reference sampling interval , The sampling interval coefficient is determined based on the grouting stage: 0.01~0.02 for the trial grouting and cone probe movement stage, and 0.03~0.05 for the normal constant pressure grouting stage. For the depth of the hole; The propagation velocity of the pressure wave in the slurry is calculated from the slurry density and bulk modulus, or determined by field pressure wave propagation test.

[0093] This formula combines the hole depth, the propagation velocity of the grout pressure wave, and the sampling interval coefficient corresponding to the grouting stage to calculate the benchmark sampling interval. It incorporates the propagation characteristics of the grout pressure wave in the borehole into the process of determining the sampling benchmark, so that the benchmark sampling interval matches the physical propagation characteristics of the ultra-deep borehole and avoids sampling timing misalignment in deep boreholes with a fixed benchmark sampling interval.

[0094] First-order rate of change weighting coefficient and second-order rate of change weighting coefficient Determine by the following formula:

[0095] ;

[0096] In the formula: To pre-set a reference value for pressure fluctuation amplitude, the value is determined based on the degree of formation fracture development: 1% to 2% of the design grouting pressure for fractured formations with well-developed fractures, 2% to 4% of the design grouting pressure for moderately developed fractures, and 4% to 5% of the design grouting pressure for intact formations without well-developed fractures.

[0097] The above formula uses the benchmark sampling interval and the preset pressure fluctuation amplitude reference value to determine the weighting coefficients of the first and second order rates of change, binds the pressure fluctuation reference level and the sampling benchmark, and completes the synchronous adaptation of the weighting coefficients with the formation conditions and the sampling benchmark, ensuring that the constraint effect of the pressure change rate of each order on the sampling interval under different formation conditions is within a reasonable range.

[0098] During the segmented lifting or lowering of the cone probe, the changes in grouting flow rate, orifice pressure, and cone probe displacement are collected simultaneously.

[0099] The segmented lifting or lowering of the cone probe is performed using a "fixed-distance pause" method. The distance of each segmented movement is 0.5m to 1.0m, and the moving speed is controlled at 0.1m / min to 0.3m / min. After each segment is completed, the cone probe is paused for at least three reference sampling intervals to allow the borehole pressure and grouting flow rate to stabilize before collecting steady-state data at the start and end points of that segment. The total stroke of the segmented movement covers the length of the current grouting segment. When lifting upwards, the segmented movement proceeds from deep to shallow; when moving downwards, the segmented movement proceeds from shallow to deep. During the movement, the grouting pump maintains continuous grout supply without interruption.

[0100] The change in grouting flow rate is the difference between the grouting flow rate before and after the cone probe is lifted or lowered; the change in orifice pressure is the difference between the orifice pressure before and after the cone probe is lifted or lowered; and the displacement of the cone probe is the difference between the current position and the initial position of the cone probe.

[0101] The initial position of the cone probe refers to its depth position at the moment data acquisition begins using this method. This position serves as the zero point for displacement calculation and is recorded and latched by the depth measuring instrument at the instant data acquisition starts. The cone probe displacement is positive downwards; displacement is positive when the current depth is greater than the initial depth and negative when it is less than the initial depth. During density fitting data acquisition, the cone probe should move continuously in a single direction from its initial position to avoid cumulative displacement errors caused by back-and-forth movement.

[0102] The time difference between the sampling times of the grouting flow rate change, the orifice pressure change, and the cone probe displacement does not exceed the preset sampling synchronization threshold.

[0103] The preset sampling synchronization threshold is set to half of the baseline sampling interval;

[0104] The friction coefficient of the grout is determined based on the relationship between the change in grouting flow rate and the change in orifice pressure. The density of the grout is determined based on the relationship between the displacement of the cone probe and the change in orifice pressure. The actual pressure value at the bottom of the hole is obtained by subtracting the friction pressure loss and the static pressure of the grout column from the orifice pressure value.

[0105] During the lifting or lowering of the cone probe... Grouting flow rate, orifice pressure, and cone probe position were collected at each time period. The ratio of the change in orifice pressure to the change in grouting flow rate within each time period was used as the sample value of the grout friction coefficient for that time period (where the number of time periods is...). The ratio of the single segmented movement distance of the cone probe to the data sampling interval during that movement is determined, rounded down. To ensure sufficient sample coverage for fitting the time-varying drag coefficient, when the single movement distance of the cone probe is short, leading to inaccurate calculations... When doing so, the single movement distance should be appropriately extended or the sampling interval shortened to ensure that the number of fitted samples meets the statistical requirements for least squares parameter identification. Then, the time-varying slurry friction coefficient is obtained by fitting using the following formula:

[0106] ;

[0107] In the formula: For a moment The friction coefficient of the slurry; This is the initial friction coefficient of the slurry. The hydration rate coefficient of the slurry; The time from the moment the current batch of slurry was prepared to the moment of sampling in the corresponding time period is expressed in hours.

[0108] At the implementation level, to obtain effective resistance coefficient samples, during the movement of each segment of the cone probe, a stable flow rate of at least one benchmark sampling interval is maintained at the start and end positions of that segment using a grouting pump. The difference between two adjacent stable flow rate values ​​is not less than 15% of the current rated grouting flow rate, ensuring that the flow rate variation... Significantly higher than the noise level of flow measurement; orifice pressure variation within each time period Changes in grouting flow rate The difference between the measured average values ​​under two stable operating conditions at the beginning and end of the time period is taken to eliminate the interference of the transient process of the cone probe's acceleration and deceleration on the pressure-flow correspondence; the position of the cone probe is kept fixed during the collection of resistance coefficient samples to eliminate the influence of the annular area change on the orifice pressure;

[0109] It should be noted that the completion time of grout preparation is defined as the moment when the grout in the mixing tank is uniformly mixed according to the design ratio, passes the on-site density test, and begins to be pumped into the grouting pipeline, as indicated by the on-site construction records. When a new batch of grout is introduced during the grouting process, the timing is reset from the moment the new batch of grout begins pumping, and the initial friction coefficient of the grout is refitted based on the first batch of sampling data from the new batch. With hydration rate coefficient To avoid the accumulation of time-varying resistance coefficients caused by differences in the properties of different batches of slurry. distortion;

[0110] The above formula uses an exponential function to characterize the change law of the friction coefficient of the grout along the time. Considering the engineering reality that the viscosity of the grout continues to increase due to hydration and solidification, it is different from the traditional constant resistance coefficient treatment method. It can reflect the time-varying characteristics of the flow resistance of the same batch of grout increasing with the hydration time and restore the real pipeline resistance change throughout the grouting process.

[0111] in, and The value of follows:

[0112] Let the first The sample values ​​of the slurry friction coefficient for each time period are as follows: The corresponding time is ( (Take the reference slurry friction coefficient) ,but and Calculate using the following formula:

[0113] ;

[0114] This formula solves the slurry hydration rate coefficient based on multiple sets of measured samples using the least squares fitting approach. It relies on resistance coefficient samples obtained at different sampling times to complete parameter identification. It does not require pre-given empirical values ​​of hydration rate. It completes the model parameter solution based on field measured data, thereby improving the adaptability of the time-varying resistance model to the actual hydration characteristics of the slurry in the field.

[0115] ;

[0116] In the formula, To refer to the friction coefficient of the slurry, take Alternatively, the friction coefficient of the slurry measured for the first time during the trial grouting phase can be used;

[0117] The above formula, combined with the hydration rate coefficient already obtained, uses multiple sets of field sampling samples to fit the initial slurry friction coefficient, and completes the numerical conversion with the help of the reference friction coefficient. The initial flow resistance of the batch slurry is directly determined from the field measured data, thereby getting rid of the excessive dependence on indoor test parameters and adapting to the parameter changes caused by the fluctuation of field slurry ratio.

[0118] During the lifting or lowering of the cone probe, take... The average density of the slurry is obtained by fitting the corresponding values ​​of the displacement of the cone probe and the change in orifice pressure using the following formula:

[0119] ;

[0120] In the formula: The average density of the slurry; For the first Displacement of the cone probe in the group; For the first The change in orifice pressure of the group; It is the acceleration due to gravity; For the number of measurement groups, The value is determined by the ratio of the cone probe's moving distance to the sampling interval, rounded down.

[0121] At the implementation level, to ensure the consistency of the physical correspondence between displacement and pressure change in density fitting, in the formula... Take the first The cumulative displacement of the cone probe relative to its initial position during group measurements. The cumulative change in orifice pressure at the corresponding moment relative to the orifice pressure at the initial moment is taken, rather than the instantaneous difference before and after a single movement.

[0122] The data sets were sorted from shallowest to deepest according to the location of the cone probe, and the grouting flow rate was kept constant during the data collection period to eliminate the interference of flow rate fluctuations on the orifice pressure. It only reflects the contribution of the static pressure of the grout column to the change of the cone probe depth;

[0123] The above formula uses the displacement change caused by the movement of the cone probe and the corresponding change in orifice pressure to obtain the average density of the grout through the least squares algorithm. There is no need to set up additional density detection sensors. The density identification is completed by relying on the displacement and pressure data collected in situ during the grouting process. It can capture the density change caused by the fluctuation of the grout ratio on site and provide real density parameters for the calculation of the bottom hole pressure.

[0124] To avoid the coupling interference of flow rate and position changes on orifice pressure during the movement of the cone probe, a time-sequential acquisition strategy is adopted for fitting the friction coefficient and density of the grout: at the start and end points of each segment of movement, a set of steady-state orifice pressure values ​​is first collected at the current fixed flow rate for density fitting (at this time, the flow rate is constant, and pressure changes are only caused by position changes). Then, the flow rate is stepped to the next set value by the grouting pump. After stabilization, another set of steady-state data is collected for friction coefficient fitting (at this time, the position of the cone probe is fixed, and pressure changes are only caused by flow rate changes).

[0125] Two types of fitted data are acquired and processed alternately to ensure that their respective independent variables are singular and to eliminate the influence of cross terms on the fitting accuracy.

[0126] The actual pressure value at the bottom of the hole is obtained by the following formula:

[0127] ;

[0128] In the formula: This represents the actual pressure value at the bottom of the hole. This refers to the orifice pressure value. The friction coefficient of the time-varying slurry; This represents the grouting flow rate. This is the flow area of ​​the annular gap between the probe wall and the borehole wall when the cone probe is located at the bottom of the borehole. The cone probe is located at depth The flow area of ​​the annular gap at that location; Area correction index; The average density of the slurry. It is the acceleration due to gravity. For the depth of the hole;

[0129] Annular gap flow area according to Calculation, where For depth The diameter of the borehole at that location The outer diameter of the cone probe;

[0130] Drilling diameter The value is obtained by logging the borehole diameter segmentally along the borehole depth during the borehole formation stage, or by taking values ​​segmentally according to the designed borehole diameter and in conjunction with the formation diameter reduction empirical coefficient under conditions where borehole diameter logging is not available. The annular flow area when the cone probe is at the bottom of the borehole. correspond place value;

[0131] When the borehole diameter is approximately uniform along the hole depth We can approximate it as a constant, in which case the area correction term... ;

[0132] The above formula calculates the actual pressure at the bottom of the hole by successively deducting the time-varying friction loss, the additional pressure loss caused by the change in the flow area of ​​the annular gap, and the static pressure of the grout column from the measured pressure at the borehole opening. It takes into account the influence of the change in the flow cross section of the annular gap caused by the change in the position of the cone probe, and introduces the resistance coefficient that varies with the hydration time, thus solving the engineering problem that the pressure at the bottom of ultra-deep cone probe grouting holes cannot be directly measured.

[0133] in, Take 1.5~2, calibrated by annular flow test, or selected according to the rheological characteristics of slurry. Take a larger value when the slurry viscosity is high and the rheological characteristics deviate from those of Newtonian fluid, and take a smaller value when the slurry viscosity is low and the rheological characteristics are close to those of Newtonian fluid.

[0134] In the calculation stage of the actual pressure value at the bottom of the borehole, the pressure value at the borehole opening and the grouting flow rate value are taken after a delay from the current moment. The corresponding value, delay duration The time it takes for the pressure wave to propagate from the orifice to the bottom of the orifice. , The propagation velocity of pressure waves in the slurry;

[0135] The difference between the actual pressure value at the bottom of the hole and the target pressure value at the bottom of the hole is used to generate a pressure deviation signal at the bottom of the hole.

[0136] Adjust the output pressure of the grouting pump according to the pressure deviation signal at the bottom of the hole, so that the actual pressure value at the bottom of the hole approaches the target pressure value at the bottom of the hole;

[0137] The bottom pressure value predicted based on the time-varying grout friction coefficient is compared with the calculated actual bottom pressure value. When the deviation between the two exceeds the preset threshold, the current result is determined to be invalid and the process is returned to the synchronous acquisition stage of grouting flow rate change, orifice pressure change and cone probe displacement to be re-executed.

[0138] The bottom hole pressure value predicted based on the time-varying slurry friction coefficient is determined as follows:

[0139] The time-varying slurry friction coefficient obtained from the fitting of the previous control cycle is taken. and average density of slurry Substitute the values ​​into the actual pressure calculation formula at the bottom of the hole, using the measured pressure value at the hole opening and the grouting flow rate at the current moment. The predicted borehole bottom pressure value is calculated using the input; the actual borehole bottom pressure value is calculated using data re-acquired and fitted in the current cycle. and calculate;

[0140] The physical difference between the two is that the predicted value reflects the theoretical value of the bottom pressure when the resistance coefficient does not change, while the calculated value reflects the actual value after the resistance coefficient is updated in real time. By comparing the deviation between the two, it can be determined whether the fitting result of the resistance coefficient has an abnormal jump.

[0141] The preset allowable deviation threshold is determined by the following formula:

[0142] ;

[0143] In the formula, The preset allowable deviation threshold; The basic deviation threshold is determined based on the degree of formation fracture development: 2% of the design grouting pressure for fractured formations with well-developed fractures, 3% for formations with moderately developed fractures, and 4% for intact formations with no developed fractures. This represents the current number of fitted samples (samples fitted for the resistance coefficient). To use as a reference for the number of fitted samples, we take 3 to 5 times the number of fitted parameters. The fitted parameters are the initial slurry friction coefficient and the slurry hydration rate coefficient, a total of 2. Take 6~10;

[0144] The above formula integrates formation conditions, the number of fitted samples, and the hydration time of slurry to construct a dynamic allowable deviation threshold. The more samples there are, the stricter the threshold becomes. The threshold converges synchronously after the slurry stabilizes over time. A fixed deviation threshold is not used throughout the process. This is used to verify the effectiveness of the resistance coefficient fitting results and filter out invalid calculation results when there are insufficient samples or drastic changes in the slurry state.

[0145] The slurry stabilization rate coefficient is determined by the following formula:

[0146] ;

[0147] In the formula, This is the proportionality coefficient; The standard setting time of the slurry is determined by the setting time test. The time is from the moment the current batch of slurry was prepared.

[0148] The above formula combines the slurry setting time with the corresponding proportional coefficient to solve the slurry stabilization rate coefficient. The setting and solidification characteristics of the slurry itself are introduced into the calculation of the attenuation of the deviation threshold. Different types of slurries, such as fast-setting and slow-setting, are distinguished. The attenuation rhythm of the deviation threshold is matched with the actual solidification process of the slurry, ensuring the rationality of the verification logic under different slurry conditions.

[0149] in, The values ​​are as follows: 3-4 for fast-setting grout with a setting time of less than 2 hours, and 4-5 for slow-setting grout with a setting time of 2 hours or more.

[0150] After adjusting the grouting pump output pressure based on the borehole bottom pressure deviation signal, wait for the delay period. Afterwards, the orifice pressure and grouting flow rate were re-collected, and the actual pressure at the bottom of the hole was calculated.

[0151] If the absolute value of the bottom hole pressure deviation signal still exceeds the preset deviation threshold, the process of simultaneously collecting the changes in grouting flow rate, the changes in borehole pressure, and the displacement of the cone probe will be repeated until the output pressure of the grouting pump is adjusted according to the bottom hole pressure deviation signal.

[0152] The repetitive process specifically includes: re-executing the segmented movement and synchronous data acquisition of the cone probe, and refitting the time-varying slurry friction coefficient based on the newly acquired data. With average density of slurry Recalculate the actual pressure value at the bottom of the hole. The bottom hole pressure deviation signal is regenerated, and the grouting pump output pressure is adjusted again based on the new deviation signal; each time this process is repeated, the number of times the grouting pump output pressure adjustment has been performed is recorded. Cumulative increment, preset deviation threshold Updated synchronously according to the exponential decay formula;

[0153] If the deviation requirement is not met after 5 consecutive repetitions, the automatic adjustment is paused and an early warning is issued. The on-site operator then checks the formation conditions, equipment status, and slurry properties to decide whether to continue.

[0154] Among them, the preset deviation threshold ;

[0155] In the formula: The initial control deviation threshold is determined based on the degree of formation fracture development: 3% of the design grouting pressure for fractured formations with well-developed fractures, 4% for formations with moderately developed fractures, and 5% for intact formations without well-developed fractures. The convergence coefficient is determined based on the degree of fracture development in the formation: 0.4~0.5 for fractured strata with well-developed fractures, 0.3~0.4 for strata with moderately developed fractures, and 0.2~0.3 for intact strata without well-developed fractures. This refers to the number of times the grouting pump output pressure has been adjusted, starting with the first adjustment. Each adjustment Increment by 1;

[0156] The above formula uses the number of adjustments as a variable and adopts an exponential decay form to obtain the dynamic control deviation threshold. As the number of grouting pump pressure adjustments increases, the control deviation requirement gradually tightens. Combined with a convergence coefficient that matches the formation fractures, the control process gradually converges. This allows for both a moderate deviation in the initial stage to ensure the adjustment response speed and a reduction in deviation in the later stage to achieve high-precision and stable control of the bottom hole pressure.

[0157] In this embodiment, before the ultra-deep cone grouting operation is started, the actual depth of the grouting hole is measured and the initial position of the cone probe is recorded. At the same time, the initial target pressure value at the bottom of the hole is set after deducting the static pressure of the grout column from the designed grouting pressure. After entering the grouting stage, the system continuously collects the orifice pressure and grouting flow rate at a dynamic sampling interval. This interval is adjusted in real time according to the first and second order rates of change of the orifice pressure. When the pressure fluctuates violently, the sampling is intensified to capture transient characteristics, and the sampling frequency is reduced during the stable stage to reduce the data burden.

[0158] When the cone probe is raised or lowered in sections, the changes in grouting flow rate, orifice pressure, and displacement are recorded synchronously at each stage of the probe's movement. The sampling time difference of the three types of data is controlled within half of the reference sampling interval to ensure synchronicity. The friction coefficient of the grout is obtained by using the ratio of the orifice pressure change to the grouting flow rate change in each stage. Then, the friction coefficient that changes with aging is fitted according to the exponential growth model to reflect the law of gradual increase in viscosity during the grout hydration process. At the same time, no less than three sets of data corresponding to the displacement and orifice pressure change are taken, and the average density of the grout is obtained by linear fitting.

[0159] After obtaining the above parameters, the actual pressure value at the bottom of the hole is obtained by taking the orifice pressure and grouting flow rate delayed by one pressure wave propagation time before the current time as the benchmark, and deducting the friction loss and static pressure of the grout column self-weight. In the friction loss calculation, the area correction index is introduced to compensate for the change of the annular gap flow area with the position of the rod and the non-Newtonian fluid effect. The calculation results also need to be cross-validated with the predicted value based on the time-varying resistance coefficient. When the deviation exceeds the allowable threshold, the data is deemed invalid and returned for re-acquisition. The threshold gradually narrows as the number of fitted samples increases and the grout tends to stabilize.

[0160] The deviation signal is generated by subtracting the actual pressure at the bottom of the borehole from the target pressure. The output pressure of the grouting pump is adjusted accordingly. After each adjustment, the pressure wave is allowed to propagate to the bottom of the borehole before the actual pressure at the bottom of the borehole is recalculated. If the deviation still exceeds the control threshold, the acquisition and adjustment process is repeated. The control threshold converges exponentially with the number of adjustments to avoid overshoot oscillation. The return flow rate is continuously monitored during the grouting process. The formation grout intake is obtained from the difference between the grouting flow rate and the return flow rate. When the grout intake is lower than the formation grout intake capacity, it indicates that the formation grout intake is weakened. At this time, the target pressure value at the bottom of the borehole is reduced according to the proportion of insufficient grout intake, so as to achieve adaptive adjustment of the target pressure according to the formation grout intake state.

[0161] See Figure 2 As shown in the figure, the horizontal axis represents time t, and the vertical axis represents the depth position of the cone probe. The curve is stepped, consisting of alternating moving sections and pause platforms, illustrating the segmented downward movement of the cone probe from shallow to deep. The distance of each segmented movement is 0.5m to 1.0m, and the moving speed is controlled at 0.1m / min to 0.3m / min. After each segment is completed, the cone probe pauses for at least 3 reference sampling intervals (the pause platform in the figure is marked as ≥3Ts). Steady-state data of the start and end points of that segment are collected after the orifice pressure and grouting flow rate stabilize. There are 5 pause points in the figure. The total stroke of the segmented movement covers the length of the current grouting segment. During the movement, the grouting pump maintains continuous grout supply without interruption. This "fixed-distance pause" method provides stable and synchronous sampling conditions for online fitting of the grout friction coefficient and density.

[0162] See Figure 3As shown in the figure, the horizontal axis represents time t, and the vertical axis represents the grouting flow rate. The curves exhibit a step-like change, demonstrating the strategy of alternating time-series data acquisition for density fitting and resistance coefficient fitting. The density fitting window (constant flow rate) corresponds to the constant flow rate stage, where a fixed flow rate is maintained at each pause point to collect steady-state orifice pressure values. Pressure changes are only caused by changes in the position of the cone probe, and this is used for fitting the average density of the grout. The resistance coefficient fitting window (variable flow rate) corresponds to the stage of step-adjustment of the grouting pump flow rate. The cone probe position is fixed, and data is collected after a step change in flow rate and the condition stabilizes. Pressure changes are only caused by changes in flow rate, and this is used for fitting the friction coefficient of the time-varying grout. The two types of data are acquired and processed alternately to ensure that each independent variable is singular and to eliminate the influence of cross terms on the fitting accuracy. The figure is marked with key elements such as the steady-state holding time, the synchronization threshold Δt≤Ts / 2, and the step-adjustment flow rate.

[0163] In summary, the method described in the above embodiments simultaneously collects changes in grouting flow rate, orifice pressure, and cone rod displacement during the segmented lifting or lowering of the cone probe. It then online fits the grout friction coefficient and grout density, and calculates the actual bottom pressure by subtracting friction loss and static pressure from the grout column's own weight from the orifice pressure value. This reflects the time-varying characteristics of the grout in ultra-deep holes and the influence of annular flow resistance on the bottom pressure. Furthermore, the bottom pressure deviation signal generated by the actual bottom pressure value and the target bottom pressure value is used to adjust the grouting pump output pressure in a closed loop, allowing control to directly act on the key parameter of bottom pressure. Simultaneously, it dynamically adjusts the target bottom pressure value based on the formation's grout absorption status, adaptively adjusts the sampling interval based on the pressure change rate, and introduces pressure wave propagation delay compensation and effectiveness verification. This allows the control to adapt to the dynamic changes in formation and grout properties during ultra-deep cone grouting, effectively improving the accuracy and responsiveness of bottom pressure control compared to existing fixed-parameter open-loop control.

[0164] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for adaptive control of grouting pressure in ultra-deep cone grouting, characterized in that, Includes the following steps: Obtain the depth of the ultra-deep cone grouting hole and the initial position of the cone probe, and set the target pressure value at the bottom of the hole; Real-time acquisition of borehole pressure and grouting flow rate during cone grouting; During the segmented lifting or lowering of the cone probe, the changes in grouting flow rate, orifice pressure, and cone probe displacement are collected simultaneously. The friction coefficient of the grout is determined based on the relationship between the change in grouting flow rate and the change in orifice pressure. The density of the grout is determined based on the relationship between the displacement of the cone probe and the change in orifice pressure. The actual pressure value at the bottom of the hole is obtained by subtracting the friction pressure loss and the static pressure of the grout column from the orifice pressure value. The difference between the actual pressure value at the bottom of the hole and the target pressure value at the bottom of the hole is used to generate a pressure deviation signal at the bottom of the hole. Adjust the output pressure of the grouting pump according to the pressure deviation signal at the bottom of the hole, so that the actual pressure value at the bottom of the hole approaches the target pressure value at the bottom of the hole.

2. The method for adaptive control of grouting pressure in ultra-deep cone grouting according to claim 1, characterized in that, The target pressure value at the bottom of the borehole is dynamically adjusted according to the formation's grout suction status. Collect the return flow rate value, and obtain the formation grout intake value from the difference between the injection flow rate value and the return flow rate value. When the formation grout intake value satisfies the following formula, adjust the target pressure value at the bottom of the hole. ； In the formula: This refers to the amount of grout absorbed by the formation. The formation's grout absorption coefficient; This represents the actual pressure value at the bottom of the hole. This represents the initial in-situ stress in the deep strata. It is a non-linear exponent; When the aforementioned inequality holds, it is determined that the formation's grout absorption has weakened, and the target pressure value at the bottom of the borehole is adjusted according to the following formula: ； In the formula; The adjusted target pressure value at the bottom of the hole; The target pressure value at the bottom of the hole before adjustment; The preset maximum pressure adjustment step size is defined as follows: the percentage of insufficient formation grout intake is indicated within square brackets. When the inequality does not hold, the formation grout intake is determined to be normal, and the target pressure value at the bottom of the borehole is kept constant.

3. The method for adaptive control of grouting pressure in ultra-deep cone grouting according to claim 1, characterized in that, The sampling interval for real-time acquisition of orifice pressure and grouting flow rate during the cone grouting process is dynamically adjusted according to the following formula: ； In the formula: For dynamic sampling interval; The reference sampling interval; is the first-order rate of change of the orifice pressure; The second rate of change of the orifice pressure value. The first-order rate of change weighting coefficient. The second-order rate of change weighting coefficient; The first-order rate of change and the second-order rate of change are calculated by the difference in orifice pressure values ​​at adjacent sampling times.

4. The adaptive control method for ultra-deep cone grouting pressure according to claim 1, characterized in that, The change in grouting flow rate is the difference between the grouting flow rate before and after the cone probe is lifted or lowered; the change in orifice pressure is the difference between the orifice pressure before and after the cone probe is lifted or lowered; and the displacement of the cone probe is the difference between the current position of the cone probe and its initial position. The time difference between the sampling times of the grouting flow rate change, the orifice pressure change, and the cone probe displacement does not exceed the preset sampling synchronization threshold.

5. The adaptive control method for ultra-deep cone grouting pressure according to claim 4, characterized in that, During the lifting or lowering of the cone probe... The grouting flow rate, orifice pressure, and cone probe position were collected at each time period. The ratio of the change in orifice pressure to the change in grouting flow rate within each time period was used as the sample value of the grout friction coefficient for that time period. The time-varying grout friction coefficient was then obtained by fitting the data using the following formula: ； In the formula: For a moment The friction coefficient of the slurry; This is the initial friction coefficient of the slurry. The hydration rate coefficient of the slurry; This refers to the time from the moment the current batch of slurry is prepared until the sampling time of the corresponding period.

6. The method for adaptive control of grouting pressure in ultra-deep cone grouting according to claim 5, characterized in that, During the lifting or lowering of the cone probe, take... The average density of the slurry is obtained by fitting the corresponding values ​​of the displacement of the cone probe and the change in orifice pressure using the following formula: ； In the formula: The average density of the slurry; For the first Displacement of the cone probe in the group; For the first The change in orifice pressure of the group; It is the acceleration due to gravity; This represents the number of measurement groups.

7. The method for adaptive control of grouting pressure in ultra-deep cone grouting according to claim 6, characterized in that, The actual pressure value at the bottom of the hole is obtained by the following formula: ； In the formula: This represents the actual pressure value at the bottom of the hole. This refers to the orifice pressure value. The friction coefficient of the time-varying slurry; The grouting flow rate value; This is the flow area of ​​the annular gap between the probe wall and the borehole wall when the cone probe is located at the bottom of the borehole. The cone probe is located at depth The flow area of ​​the annular gap at that location; Area correction index; The average density of the slurry. It is the acceleration due to gravity. The depth of the hole.

8. The method for adaptive control of grouting pressure in ultra-deep cone grouting according to claim 7, characterized in that, During the calculation of the actual pressure value at the bottom of the borehole, the pressure value at the borehole opening and the grouting flow rate are taken after a delay from the current moment. The corresponding value, the delay duration The time it takes for the pressure wave to propagate from the orifice to the bottom of the orifice. , The velocity of the pressure wave in the slurry.

9. The method for adaptive control of grouting pressure in ultra-deep cone grouting according to claim 7, characterized in that, The bottom pressure value predicted based on the time-varying grout friction coefficient is compared with the calculated actual bottom pressure value. When the deviation between the two exceeds the preset threshold, the current result is determined to be invalid and the process is returned to the synchronous acquisition stage of grouting flow rate change, orifice pressure change and cone probe displacement to be re-executed. The preset allowable deviation threshold is determined by the following formula: ； In the formula, The preset allowable deviation threshold; The baseline deviation threshold; This represents the current number of fitted samples; The number of fitted samples is used as a reference. This is the slurry stabilization rate coefficient.

10. The method for adaptive control of grouting pressure in ultra-deep cone grouting according to claim 8, characterized in that, After adjusting the grouting pump output pressure according to the bottom hole pressure deviation signal, wait for the specified delay time. Then, the orifice pressure value and the grouting flow rate value are collected again, and the actual pressure value at the bottom of the hole is calculated. If the absolute value of the bottom hole pressure deviation signal still exceeds the preset deviation threshold, the process of simultaneously collecting the changes in grouting flow rate, the changes in borehole pressure, and the displacement of the cone probe is repeated until the output pressure of the grouting pump is adjusted according to the bottom hole pressure deviation signal.

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