Deep foundation pit deformation trend prediction method based on multi-modal sensing data

Abstract

The invention relates to the technical field of construction monitoring, in particular to a deep foundation pit deformation trend prediction method based on multi-modal sensing data, and the method comprises the steps: calculating a pore water pressure difference value and predicting a settlement rate to determine a stratum settlement state, detecting the actual horizontal displacement condition of a diaphragm wall guide wall, and drawing a displacement curve of the diaphragm wall; determining the supporting condition of the inner support according to the curve diagnosis condition, and estimating the total horizontal displacement of a plurality of guide wall levels after the support is removed or checking the acting load of the inner support in the corresponding area; calculating the load loss amount, and determining the reason that the horizontal displacement does not conform to the curve diagnosis condition; calculating the horizontal total displacement of the diaphragm wall guide wall at the plurality of guide wall levels after the support is removed, and calculating a deformation evaluation value to determine the deformation trend of the foundation pit; and the displacement increment of the next guide wall level is adjusted according to the comparison result of the estimated total horizontal displacement and the actually detected actual horizontal displacement. The deformation trend of the foundation pit is determined by calculating the deformation evaluation value of the deep foundation pit.

Description

Technical Field

[0001] The present invention relates to the technical field of construction monitoring, and particularly to a method for predicting the deformation trend of a deep foundation pit based on multi-modal sensing data. Background Art

[0002] The excavation of deep foundation pits in urban areas will cause the deformation of the soil body in the excavation area and around the excavation area. Excessive deformation will damage adjacent buildings and infrastructure. To limit the deformation, the lateral displacement limit of the wall is usually set according to a certain proportion of the excavation depth, and deformation monitoring means are used to analyze and evaluate the deformation of the wall. When the monitoring data is less than the set limit, the deformation of the structure is within a relatively safe range, otherwise the structure will be in an unfavorable state. This evaluation method can directly reflect the current situation of the foundation pit and provide real-time monitoring information for decision-makers.

[0003] Chinese Patent Publication No.: CN118292498A discloses a method and system for real-time monitoring and early warning of the deformation of steel sheet piles in deep foundation pits. The method includes: reconstructing the three-dimensional real scene model of the deep foundation pit in real time based on UAV aerial photography and oblique photogrammetry technology; using the multi-scale model-to-model point cloud comparison algorithm (Multiscale Model to Model Cloud Comparison, M3C2) algorithm to compare the distance changes of the point cloud models of the deep foundation pit at different times to obtain the deformation cloud map of the deep foundation pit; measuring the deformation amount and deformation rate of the steel sheet piles based on the deformation cloud map, and predicting the deformation trend of the steel sheet piles, so as to realize the real-time monitoring and alarm of the deformation of the steel sheet piles in the deep foundation pit, and having the effect of improving the quality of construction monitoring and the level of project management. It can be seen that the method and system for real-time monitoring and early warning of the deformation of steel sheet piles in deep foundation pits have the following problems: The construction of deep foundation pit excavation includes the process of setting internal supports. Monitoring only the deformation of steel sheet piles without eliminating the axial support effect of internal supports on the deep foundation pit results in inaccurate deformation prediction. Summary of the Invention

[0004] Therefore, the present invention provides a method for predicting the deformation trend of a deep foundation pit based on multi-modal sensing data to overcome the problem in the prior art that only the deformation of steel sheet piles is monitored without eliminating the axial support effect of internal supports on the deep foundation pit, resulting in inaccurate deformation prediction.

[0005] To achieve the above object, the present invention provides a method for predicting the deformation trend of a deep foundation pit based on multi-modal sensing data, including: Detecting the actual pore water pressure according to the initial detection period, calculating the pore water pressure difference and predicting the settlement rate to determine the formation settlement state; Determine whether to continue monitoring the formation settlement state or detect the actual horizontal displacement of the diaphragm wall guide wall according to the formation settlement state, calculate the actual horizontal displacement based on the measured horizontal displacement, and draw the displacement curve of the diaphragm wall guide wall; Determine the support condition of the internal support according to the curve diagnosis condition of the displacement curve, estimate the total horizontal displacement of the diaphragm wall guide wall at several guide wall levels after removing the support, or check the acting load of the internal support in the corresponding area; Detect the acting loads of the internal support and the diaphragm wall, calculate the load loss, and determine whether the reason for the horizontal displacement not meeting the curve diagnosis condition is the load loss of the internal support; Calculate the total horizontal displacement of the diaphragm wall guide wall at several guide wall levels after removing the support according to the estimated displacement increment after removing the support, calculate the deformation evaluation value based on the total horizontal displacement and the current excavation depth, and determine the foundation pit deformation trend and the support removal sequence; Remove the internal supports at different guide wall levels according to the determined support removal sequence, and adjust the displacement increment of the next guide wall level according to the comparison result between the estimated total horizontal displacement and the actual measured horizontal displacement; Wherein, the guide wall levels are the level divisions made for the diaphragm wall guide wall according to the depth of the surrounding soil where the diaphragm wall guide wall is located.

[0006] Further, the process of determining the formation settlement state includes, Detect the actual pore water pressure according to the initial detection period, calculate the pore water pressure difference between the actual pore water pressure detected in the current initial detection period and the historical pore water pressure detected in the previous initial detection period, and calculate the predicted settlement rate of the soil around the foundation pit; If the pore water pressure difference is less than the standard pore water pressure difference and the predicted settlement rate is less than the standard settlement rate, it is determined that the deep foundation pit is in the first settlement state, and the actual horizontal displacement of the diaphragm wall guide wall is detected; If the pore water pressure difference is greater than or equal to the standard pore water pressure difference, or the predicted settlement rate is greater than or equal to the standard settlement rate, it is determined that the deep foundation pit is in the second settlement state, and the formation settlement state is continuously monitored.

[0007] Further, the process of drawing the displacement curve of the diaphragm wall guide wall includes, Calculate the actual horizontal displacement according to the measured horizontal displacement, temperature difference and measuring section length, draw the displacement curve of the diaphragm wall guide wall, divide the displacement curve into the wall top area, the excavation surface area and the wall bottom area, and obtain the horizontal displacement of the displacement curve in the corresponding area; If the horizontal displacements in the corresponding areas all meet the curve diagnosis conditions, it is determined that the support condition of the internal support is normal, and the total horizontal displacement of the diaphragm wall guide wall after removing the support is estimated; If the horizontal displacement of any area in the corresponding region does not meet the curve diagnosis condition, it is determined that the internal support in the corresponding region is loose, and the acting load of the internal support in the corresponding region is checked.

[0008] Further, the determination of not meeting the curve diagnosis condition is as follows: If the horizontal displacement at the top of the wall is greater than 0.2% of the excavation depth, it is determined that the support system fails, and the region at the top of the wall does not meet the curve diagnosis condition; If the maximum displacement at the excavation face is greater than 0.15% of the excavation depth, it is determined that the bending moment of the wall exceeds the limit, and the region at the excavation face does not meet the curve diagnosis condition; If the displacement increment at the bottom of the wall is greater than the standard displacement for three consecutive days, it is determined that the foundation heaves, and the region at the bottom of the wall does not meet the curve diagnosis condition.

[0009] Further, the process of checking the acting load of the internal support in the corresponding region includes: Detect the acting load of the internal support through an axial force meter, detect the acting load of the diaphragm wall guide wall through a concrete stress meter, and calculate the load loss generated during the conversion process between the two; Before the stage of removing the internal support, if the load loss is greater than 30% of the acting load, it is determined that the reason for the horizontal displacement not meeting the curve diagnosis condition is the load loss of the internal support, and compensation measures are taken for the internal support.

[0010] Further, the process of estimating the total horizontal displacement of the diaphragm wall guide wall after removing the support includes: Estimate the displacement increment after removing the support. The total horizontal displacement is equal to the sum of the displacement increment after removing the support and the initial displacement before removing the support. Calculate the deformation evaluation value based on the estimated total horizontal displacement and the current excavation depth.

[0011] Further, when the deformation evaluation value is less than or equal to the first-level evaluation value, it is determined that the deformation trend of the foundation pit is normal; When the deformation evaluation value is greater than the first-level evaluation value and less than the second-level evaluation value, it is determined that there is a risk in the deformation trend of the foundation pit; When the deformation evaluation value is greater than or equal to the second-level evaluation value, it is determined that the deformation trend of the foundation pit exceeds the safety range.

[0012] Further, during normal construction when the deformation trend of the foundation pit is normal, the internal support is removed step by step from bottom to top; When there is a risk in the deformation trend of the foundation pit, reduce the initial detection period and adjust the steps of removing the internal support; When the deformation trend of the foundation pit exceeds the safety range, stop construction.

[0013] Further, the internal supports at different diaphragm wall levels are demolished according to the determined demolition and bracing sequence, and the actual horizontal displacement of the diaphragm wall after demolishing the internal supports at the current diaphragm wall level is detected in real time. The estimated total horizontal displacement is compared with the actual horizontal displacement detected. If the displacement difference between the estimated total horizontal displacement of the current demolition and bracing layer and the actual horizontal displacement detected is less than the difference evaluation value, it is determined that the estimated result is within the normal range, and the demolition and bracing continue according to the determined demolition and bracing sequence. If the displacement difference between the estimated total horizontal displacement of the current demolition and bracing layer and the detected horizontal displacement is greater than or equal to the difference evaluation value, it is determined that the estimated result exceeds the normal range, and the predicted displacement increment of the diaphragm wall level in the next demolition and bracing sequence is adjusted.

[0014] Further, the process of adjusting the displacement increment includes When the estimated total horizontal displacement is less than or greater than the detected horizontal displacement, the predicted displacement increment after demolition of the internal supports at the diaphragm wall level in the next demolition and bracing sequence is reduced or increased according to the ratio of the displacement difference to the difference evaluation value.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows. Formation settlement is related to the deformation of the retaining wall and pore water pressure. It is inaccurate to judge the foundation pit settlement situation only through a single data of pore water pressure difference. Pore water pressure is affected by the distribution of the groundwater level and other factors. At the same time, due to the long period of settlement observation, this method predicts the foundation pit settlement speed through soil sensitivity, the speed of water pressure drop and the time decay effect. Whether the settlement state of the deep foundation pit is stable is reflected according to the pore water pressure difference and the predicted settlement rate, and corresponding treatment measures are taken accordingly, improving the stability of predicting the deformation trend of the deep foundation pit.

[0016] Further, due to the thermal expansion characteristics of the concrete forming the diaphragm wall, the horizontal displacement of the diaphragm wall at different depths is affected by temperature. After detecting the horizontal displacement, this method eliminates the influence of concrete thermal expansion on the measured value of the horizontal displacement of the diaphragm wall by calculating the actual horizontal displacement, improving the measurement accuracy of the horizontal displacement of the diaphragm wall. And corresponding judgment criteria are set in different areas of the diaphragm wall according to the displacement characteristics of the diaphragm wall. The displacement curve is diagnosed through the judgment of the horizontal displacement in the corresponding area to determine whether it meets the curve diagnosis conditions, and the support condition of the internal support is determined. According to the support condition of the internal support, the horizontal displacement of the diaphragm wall after the estimated removal of the support is determined or the acting load of the internal support in the corresponding area is checked, improving the adaptability and flexibility of predicting the deformation trend of the deep foundation pit.

[0017] Furthermore, due to factors such as installation clearance loss, deformation coordination loss, prestress relaxation, and temperature reduction, there is a load loss in the acting load of the internal support. When this load loss exceeds the preset allowable loss rate, this method determines that the reason for the horizontal displacement not meeting the curve diagnosis condition is the load loss of the internal support, and takes compensation measures for the internal support to prevent the internal support from being unable to provide normal load support to the diaphragm wall guide wall due to load loss, resulting in continuous horizontal displacement of the guide wall and causing deformation of the deep foundation pit or exacerbating the deformation trend of the deep foundation pit, thereby affecting the accuracy of subsequent prediction of the deformation trend of the deep foundation pit.

[0018] Furthermore, before removing the internal support of the deep foundation pit, when the deep foundation pit is in the first settlement state and all the horizontal displacements in the corresponding area meet the curve diagnosis conditions, this method estimates the total horizontal displacement of the diaphragm wall guide wall after removing the internal support, excluding the influencing factors that increase the accuracy of the estimated total horizontal displacement; calculates the deformation evaluation value of the deep foundation pit according to the total horizontal displacement and the current depth. By monitoring and calculating the deformation evaluation value in real time, the deformation trend of the foundation pit can be discovered in time, and corresponding measures can be taken to avoid the instability of the foundation pit or damage to surrounding buildings due to excessive deformation, providing a scientific and effective deformation evaluation method for the construction of deep foundation pits, which helps to improve construction safety, optimize construction progress, reduce construction costs, improve construction efficiency, and ensure the safety of the surrounding environment.

[0019] Furthermore, during the calculation process, the diaphragm wall guide wall is simplified as a vertically placed beam, while in reality, the width of the diaphragm wall guide wall is relatively large. Therefore, there is a certain difference between the theoretically calculated estimated total horizontal displacement and the actual measured value. This method compares the estimated total horizontal displacement with the actual horizontal displacement detected, and adjusts the predicted displacement increment after removing the support of the internal support at the guide wall level of the next support removal sequence according to the comparison result, improving the prediction accuracy of the estimated total horizontal displacement at different guide wall levels in the prediction of the deformation trend of the deep foundation pit, and avoiding the influence of guide wall deformation on formation displacement or the safety of foundation pit construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 is a flowchart of the steps of the method for predicting the deformation trend of a deep foundation pit based on multi-modal sensing data in an embodiment of the present invention; Figure 2 is a schematic diagram of the layout of the diaphragm wall guide wall and the internal support in the deep foundation pit in an embodiment of the present invention; Figure 3 is a schematic diagram of the calculation of the displacement increment in an embodiment of the present invention; Figure 4 is a schematic diagram of judging the deformation trend of the foundation pit according to the deformation evaluation value in an embodiment of the present invention; In the figure: 1 - diaphragm wall guide wall, 2 - internal support. Detailed implementation manners

[0021] In order to make the objectives and advantages of the present invention more clear and understandable, the present invention will be further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0022] The preferred implementation manners of the present invention will be described below with reference to the accompanying drawings. Those skilled in the art should understand that these implementation manners are only used to explain the technical principles of the present invention and do not limit the protection scope of the present invention.

[0023] It should be noted that in the description of the present invention, the terms indicating directions or positional relationships such as "upper", "lower", "left", "right", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings. This is only for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation of the present invention.

[0024] In addition, it should also be noted that in the description of the present invention, unless otherwise clearly specified and defined, the terms "installation", "connection", and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0025] Please refer to Figures 1-4 as shown in Figure 1 the step flow chart of the deep foundation pit deformation trend prediction method based on multi-modal sensing data in the embodiment of the present invention; Figure 2 the layout schematic diagram of the diaphragm wall guide wall and internal support in the deep foundation pit in the embodiment of the present invention; Figure 3 the schematic diagram of displacement increment calculation in the embodiment of the present invention; Figure 4 the schematic diagram of judging the foundation pit deformation trend according to the deformation evaluation value in the embodiment of the present invention.

[0026] Among them, Figure 2 where h is the excavation depth.

[0027] The present invention provides a deep foundation pit deformation trend prediction method based on multi-modal sensing data, including: Step S1, constructing a monitoring device for wall deformation, mechanical response and environmental factors; Step S2, detecting the actual pore water pressure according to the initial detection period, calculating the pore water pressure difference and predicting the settlement rate to determine the formation settlement state; Step S3: Determine whether to continue monitoring the formation settlement state or detect the actual horizontal displacement of the diaphragm wall guide wall 1 according to the formation settlement state. Calculate the actual horizontal displacement based on the measured horizontal displacement, and draw the displacement curve of the diaphragm wall. Step S4: Determine the support condition of the internal support 2 according to the curve diagnosis condition of the displacement curve, estimate the total horizontal displacement of the diaphragm wall guide wall 1 at several guide wall levels after removing the support, or check the acting load of the internal support in the corresponding area. Step S5: Detect the acting load of the internal support 2 and the diaphragm wall guide wall 1, calculate the load loss, and determine whether the reason for the horizontal displacement not meeting the curve diagnosis condition is the load loss of the internal support. Step S6: Calculate the total horizontal displacement of the diaphragm wall guide wall 1 at several guide wall levels after removing the support according to the estimated displacement increment after removing the support. Calculate the deformation evaluation value based on the total horizontal displacement and the current excavation depth, and determine the foundation pit deformation trend and the order of removing the support. Step S7: Remove the internal supports at different guide wall levels according to the determined order of removing the support, and adjust the displacement increment of the next guide wall level according to the comparison result between the estimated total horizontal displacement and the actual horizontal displacement detected.

[0028] The deformation of a deep foundation pit refers to the displacement and settlement phenomena that occur to the retaining structure and the surrounding soil during the excavation of the foundation pit, mainly including various forms such as horizontal displacement, vertical settlement, and inclination deformation.

[0029] In this embodiment, a diaphragm wall guide wall is provided for the deep foundation pit. The deep foundation pit adopts a layered excavation construction method, and several internal supports are provided inside the deep foundation pit. For the observation of the layered settlement of the foundation soil, the diaphragm wall guide wall of the deep foundation pit is hierarchically divided according to the depth of the surrounding soil, and is divided into several guide wall levels. During the construction pre - period of the deep foundation pit, excavation construction is carried out according to the guide wall levels, and displacement and settlement observations are carried out on different guide wall levels.

[0030] A pore water pressure gauge group is arranged at the bottom of the diaphragm wall guide wall and the deep foundation pit, and a total station is set at the top of the diaphragm wall guide wall to obtain the measured value of the settlement rate. Detect the actual pore water pressure according to the initial detection period, and calculate the pore water pressure difference between the actual pore water pressure detected in the current initial detection period and the historical pore water pressure detected in the previous initial detection period. Calculate the predicted settlement rate of the soil around the foundation pit to determine the formation settlement state. The predicted settlement rate = k×(du / dt)×e^(-αt); Where, du / dt is the pore pressure change rate, that is, the change speed of the pore water pressure within the initial detection period, k is the seepage settlement coefficient, α is the attenuation coefficient, t is the excavation duration, and e is a constant. In this embodiment, k = 0.5 mm / (day·kPa) reflects the influence of soil permeability on settlement, α = 0.1 / day represents the degree of natural attenuation of the settlement rate with time, and e^(-αt) is the exponential attenuation term, considering the effect that the settlement rate gradually slows down during the soil consolidation process.

[0031] If the pore water pressure difference is less than the standard pore water pressure difference and the predicted settlement rate is less than the standard settlement rate, it is determined that the deep foundation pit is in the first settlement state, and the actual horizontal displacement of the diaphragm wall guide wall is detected. If the pore water pressure difference is greater than or equal to the standard pore water pressure difference, or the predicted settlement rate is greater than or equal to the standard settlement rate, it is determined that the deep foundation pit is in the second settlement state, and the formation settlement state is continuously monitored. Among them, the standard pore water pressure difference is 10 kPa, and the standard settlement rate is 2 mm / d.

[0032] Compare the predicted settlement rate with the measured value of the settlement rate. When the predicted settlement rate is more than 30% smaller than the measured value, the seepage settlement coefficient k is corrected, and the corrected seepage settlement coefficient k = original k × (measured value / predicted settlement rate).

[0033] Specifically, the formation settlement is related to the deformation of the retaining wall and the pore water pressure. Judging the settlement of the foundation pit only through the single data of the pore water pressure difference is inaccurate. The pore water pressure is affected by the distribution of the groundwater level and other factors. At the same time, due to the long period of settlement observation, this method predicts the settlement speed of the foundation pit through the soil sensitivity, the water pressure drop speed, and the time decay effect. According to the pore water pressure difference and the predicted settlement rate, it reflects whether the settlement state of the deep foundation pit is stable, and corresponding different treatment measures are taken to improve the stability of the deformation trend prediction of the deep foundation pit.

[0034] When the deep foundation pit is in the first settlement state, inclinometers buried at different depths are used to measure the actual horizontal displacement of the diaphragm wall guide wall before the internal support is removed. During implementation, the inclinometer tubes of the inclinometers are tied to the reinforcement cage of the diaphragm wall and cast in sync with the wall to ensure coordinated deformation with the wall. The actual horizontal displacement is equal to the measured horizontal displacement - the coefficient of thermal expansion of concrete × temperature difference × length of the measured section. During implementation, the coefficient of thermal expansion of the concrete is 12×10 -6 / ℃; The temperature difference is the difference between the temperature of the diaphragm wall detected by the temperature sensor and the preset temperature. The preset temperature is the measured temperature after the concrete solidifies. The length of the measured section is the excavation depth where the measurement point is located. Draw the displacement curve of the diaphragm wall. The horizontal axis of the curve is the horizontal displacement, and the positive direction of the horizontal axis is the inside of the foundation pit. The vertical axis of the curve is the depth. The displacement curve is divided into the top-wall region, the excavation-face region, and the bottom-wall region according to the excavation depth, and the horizontal displacements of the displacement curve in the corresponding regions are obtained. If the horizontal displacements in the corresponding regions all meet the curve diagnosis conditions, it is determined that the support condition of the internal support is normal, and the total horizontal displacement of the diaphragm wall guide wall after the support is removed is estimated. If any of the horizontal displacements in the corresponding regions does not meet the curve diagnosis conditions, it is determined that the internal support in the corresponding region is loose, and the acting load of the internal support in the corresponding region is checked.

[0035] Specifically, the determination situation of not meeting the curve diagnosis conditions is as follows. If the horizontal displacement at the top of the wall is greater than 0.2% of the excavation depth, it is determined that the support system fails, and the top-wall region does not meet the curve diagnosis conditions. If the maximum displacement at the excavation face is greater than 0.15% of the excavation depth, it is determined that the bending moment of the wall exceeds the limit, and the excavation-face region does not meet the curve diagnosis conditions. If the displacement increment at the bottom of the wall is greater than the standard displacement for three consecutive days, it is determined that the foundation heaves, and the bottom-wall region does not meet the curve diagnosis conditions. Wherein, the standard displacement is 2 mm.

[0036] It can be understood that the implementer can divide the top-wall region, the excavation-face region, and the bottom-wall region according to the excavation depth, which will not be elaborated here.

[0037] Specifically, due to the thermal expansion characteristics of the concrete that makes up the diaphragm wall guide wall, the horizontal displacement of the guide wall at different depths is affected by temperature. After detecting the horizontal displacement, this method eliminates the influence of concrete thermal expansion on the measured value of the horizontal displacement of the diaphragm wall guide wall by calculating the actual horizontal displacement, improving the measurement accuracy of the horizontal displacement of the diaphragm wall guide wall; and sets corresponding evaluation criteria in different regions of the guide wall according to the displacement characteristics of the guide wall, diagnoses the displacement curve through the evaluation of the horizontal displacements in the corresponding regions, determines whether it meets the curve diagnosis conditions, determines the support condition of the internal support, and accordingly decides to estimate the horizontal displacement of the diaphragm wall guide wall after the support is removed or check the acting load of the internal support in the corresponding region, improving the adaptability and flexibility of predicting the deformation trend of deep foundation pits.

[0038] Stress gauges and axial force gauges are set at different depths on the inner and outer sides of the diaphragm wall guide wall to detect the acting loads of the diaphragm wall at different depths and the acting loads of several internal supports. The acting load Fn of the internal support is detected by the axial force gauge, and the acting load Fb of the diaphragm wall is detected by the concrete stress gauge, and the load loss amount Fs generated during their conversion is calculated. During the inner support removal stage, the load loss amount $Fs = \beta(Fn - Fb)$, where $\beta$ is the conversion coefficient, and its magnitude is related to factors such as the inner support removal time and method, the strength of the structural slab at the time of removal, etc.; Before the inner support removal stage, if the load loss amount $Fs$ is greater than 30% of the applied load $Fn$, it is determined that the reason for the horizontal displacement not meeting the curve diagnosis condition is the inner support load loss, and compensation measures are taken for the inner support; Specifically, the compensation measure is to use a jack for re - jacking or temporarily add a spare support.

[0039] Specifically, due to reasons such as installation clearance loss, deformation coordination loss, prestress relaxation, and temperature reduction of the inner support's applied load, there is a load loss in the applied load on the diaphragm wall guide wall. When the load loss in this method exceeds the preset allowable loss rate, it is determined that the reason for the horizontal displacement not meeting the curve diagnosis condition is the inner support load loss, and compensation measures are taken for the inner support to prevent the inner support from being unable to provide normal load support to the diaphragm wall guide wall due to load loss, resulting in continuous horizontal displacement of the guide wall and causing deformation of the deep foundation pit or exacerbating the deformation trend of the deep foundation pit, thereby affecting the accuracy of subsequent prediction of the deep foundation pit deformation trend.

[0040] When the deep foundation pit is in the first settlement state and all the horizontal displacements in the corresponding area meet the curve diagnosis conditions, estimate the total horizontal displacement of the diaphragm wall guide wall at several guide wall levels after removing the support; The initial displacement is the measured value, and the displacement increment after removing the support = $Pb$ 2 (3a + 2b) / 6WI, where $\delta$ is the horizontal displacement increment, $W$ is the elastic modulus of the diaphragm wall guide wall, $I$ is the moment of inertia of the inner support, $P$ is the measured support axial force, and $a$ and $b$ are the layer lengths of different guide wall levels; The total horizontal displacement is equal to the sum of the displacement increment after removing the support and the initial displacement before removing the support. Calculate the deformation evaluation value $E$ based on the estimated total horizontal displacement and the current excavation depth; ( + η·ln(h)), In the formula, is the soil parameter, η is the construction influence coefficient, $\delta$ is the measured horizontal displacement value, and $h$ is the current excavation depth; The value range is 0.8 - 1.0, and the η value range is 0.1 - 0.15. In this embodiment, takes 1.0, and η takes 0.1.

[0041] If the deformation evaluation value is less than or equal to the first - level evaluation value, it is determined that the deformation trend of the foundation pit is normal, and the inner support is removed in the conventional construction steps from bottom to top; If the deformation evaluation value is greater than the first-level evaluation value and less than the second-level evaluation value, it is determined that there is a risk in the foundation pit deformation trend, and the initial detection period is reduced to adjust the internal support removal steps; If the deformation evaluation value is greater than or equal to the second-level evaluation value, it is determined that the foundation pit deformation trend exceeds the safe range, and the construction is stopped; Among them, the first-level evaluation value is 0.3, and the second-level evaluation value is 0.6.

[0042] Specifically, before removing the internal support of the deep foundation pit, when the deep foundation pit is in the first settlement state and the horizontal displacements in the corresponding area all meet the curve diagnosis conditions, the total horizontal displacement of the diaphragm wall guide wall after removing the internal support is estimated, and the influencing factors are excluded to increase the accuracy of the total horizontal displacement estimation; according to the total horizontal displacement and the current depth, the deformation evaluation value of the deep foundation pit is calculated. By real-time monitoring and calculating the deformation evaluation value, the deformation trend of the foundation pit can be discovered in time, and corresponding measures can be taken to avoid the instability of the foundation pit or the damage of surrounding buildings caused by excessive deformation, providing a scientific and effective deformation evaluation method for the construction of deep foundation pits, which helps to improve construction safety, optimize construction progress, reduce construction costs, improve construction efficiency and ensure the safety of the surrounding environment.

[0043] Remove the internal supports at different guide wall levels according to the determined support removal order, and real-time detect the actual horizontal displacement of the diaphragm wall guide wall after removing the internal support at the current guide wall level, and compare the estimated total horizontal displacement with the actual horizontal displacement detected; If the displacement difference between the estimated total horizontal displacement of the current support removal layer and the actual horizontal displacement detected is less than the difference evaluation value, it is determined that the estimated result is within the normal range, and continue to remove the support according to the determined support removal order; If the displacement difference between the estimated total horizontal displacement of the current support removal layer and the horizontal displacement detected is greater than or equal to the difference evaluation value, it is determined that the estimated result exceeds the normal range, and adjust the predicted displacement increment after support removal of the internal support at the next support removal order at the guide wall level; Specifically, when the estimated total horizontal displacement is less than or greater than the actual horizontal displacement detected, reduce or increase the predicted displacement increment after support removal of the internal support at the next support removal order at the guide wall level according to the ratio of the displacement difference to the difference evaluation value; Among them, the difference evaluation value is 2% of the total horizontal displacement.

[0044] Specifically, during the calculation process, the diaphragm wall guide wall is simplified as a beam placed vertically. However, in reality, the width of the diaphragm wall guide wall is relatively large. Therefore, there is a certain difference between the predicted total horizontal displacement in the theoretical calculation and the actual measured value. This method compares the predicted total horizontal displacement with the actual horizontal displacement detected, and adjusts the predicted displacement increment after bracing of the internal support at the guide wall level in the next bracing sequence according to the comparison result, improving the prediction accuracy of the predicted total horizontal displacement at different guide wall levels in the prediction of the deformation trend of deep foundation pits, and avoiding the influence of guide wall deformation on formation displacement or the safety of foundation pit construction.

[0045] So far, the technical solution of the present invention has been described in combination with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the protection scope of the present invention.

[0046] The above are only the preferred embodiments of the present invention and are not used to limit the present invention; for those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent substitution, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for predicting the deformation trend of deep foundation pits based on multi-modal sensing data, characterized in that Including: Detect the actual pore water pressure according to the initial detection period, and determine the formation settlement state based on the calculated pore water pressure difference and the predicted settlement rate; Determine whether to continue monitoring the formation settlement state or detect the actual horizontal displacement of the diaphragm wall guide wall according to the formation settlement state, calculate the actual horizontal displacement based on the measured horizontal displacement, and draw the displacement curve of the diaphragm wall guide wall; Determine the support condition of the internal support according to the curve diagnosis condition of the displacement curve, estimate the total horizontal displacement of the diaphragm wall guide wall at several guide wall levels after removing the support, or check the acting load of the internal support in the corresponding area; Detect the acting loads of the internal support and the diaphragm wall, calculate the load loss, and determine whether the reason for the horizontal displacement not meeting the curve diagnosis condition is the load loss of the internal support; Calculate the total horizontal displacement of the diaphragm wall guide wall at several guide wall levels after removing the support according to the predicted displacement increment after removing the support, calculate the deformation evaluation value based on the total horizontal displacement and the current excavation depth, and determine the foundation pit deformation trend and the support removal sequence; Remove the internal supports at different guide wall levels according to the determined support removal sequence, and adjust the displacement increment of the next guide wall level according to the comparison result between the predicted total horizontal displacement and the actual horizontal displacement actually detected; Among them, the guide wall level is the level division of the diaphragm wall guide wall according to the depth of the surrounding soil where the diaphragm wall guide wall is located.

2. The method for predicting the deformation trend of deep foundation pits based on multi-modal sensing data according to claim 1, characterized in that, The process of determining the formation settlement state includes, Detect the actual pore water pressure according to the initial detection period, calculate the pore water pressure difference between the actual pore water pressure detected in the current initial detection period and the historical pore water pressure detected in the previous initial detection period, and calculate the predicted settlement rate of the soil around the foundation pit; If the pore water pressure difference is less than the standard pore water pressure difference and the predicted settlement rate is less than the standard settlement rate, it is determined that the deep foundation pit is in the first settlement state, and the actual horizontal displacement of the diaphragm wall guide wall is detected; If the pore water pressure difference is greater than or equal to the standard pore water pressure difference, or the predicted settlement rate is greater than or equal to the standard settlement rate, it is determined that the deep foundation pit is in the second settlement state, and the formation settlement state is continuously monitored.

3. The method for predicting the deformation trend of deep foundation pits based on multi-modal sensing data according to claim 1, characterized in that, The process of drawing the displacement curve of the diaphragm wall guide wall includes, Calculate the actual horizontal displacement according to the measured horizontal displacement, temperature difference and section length, draw the displacement curve of the diaphragm wall guide wall, divide the displacement curve into the wall top area, the excavation surface area and the wall bottom area, and obtain the horizontal displacement of the displacement curve in the corresponding area; If the horizontal displacements in the corresponding areas all meet the curve diagnosis conditions, it is determined that the support condition of the internal support is normal, and the total horizontal displacement of the diaphragm wall guide wall after removing the support is estimated; If any of the horizontal displacements in the corresponding areas does not meet the curve diagnosis conditions, it is determined that the internal support in the corresponding area is loose, and the acting load of the internal support in the corresponding area is checked.

4. The method for predicting the deformation trend of deep foundation pits based on multi-modal sensing data according to claim 3, wherein, The determination situation of not meeting the curve diagnosis conditions is, If the horizontal displacement of the wall top is greater than 0.2% of the excavation depth, it is determined that the support system fails, and the wall top area does not meet the curve diagnosis conditions; If the maximum displacement of the excavation surface is greater than 0.15% of the excavation depth, it is determined that the wall moment is excessive, and the excavation surface area does not meet the curve diagnosis conditions; If the increment of the wall bottom displacement is greater than the standard displacement for three consecutive days, it is determined that the foundation heaves, and the wall bottom area does not meet the curve diagnosis condition.

5. The method for predicting the deformation trend of deep foundation pits based on multi-modal sensing data according to claim 3, wherein, The process of checking the acting loads of the internal supports in the corresponding area includes detecting the acting loads of the internal supports through axial force gauges, detecting the acting loads of the diaphragm wall guide walls through concrete stress gauges, and calculating the load loss generated during their conversion; Before the stage of removing the internal supports, if the load loss is greater than 30% of the acting load, it is determined that the reason for the horizontal displacement not meeting the curve diagnosis condition is the load loss of the internal supports, and compensation measures are taken for the internal supports.

6. The method for predicting the deformation trend of deep foundation pits based on multi-modal sensing data according to claim 3, wherein, The process of predicting the total horizontal displacement of the diaphragm wall guide wall after removing the supports includes predicting the displacement increment after removing the supports, where the total horizontal displacement is equal to the sum of the displacement increment after removing the supports and the initial displacement before removing the supports, and calculating the deformation evaluation value based on the predicted total horizontal displacement and the current excavation depth.

7. The method for predicting the deformation trend of a deep foundation pit based on multi-modal sensing data according to claim 6, characterized in that when the deformation evaluation value is less than or equal to the first-level evaluation value, it is determined that the deformation trend of the foundation pit is normal; when the deformation evaluation value is greater than the first-level evaluation value and less than the second-level evaluation value, it is determined that there is a risk in the deformation trend of the foundation pit; when the deformation evaluation value is greater than or equal to the second-level evaluation value, it is determined that the deformation trend of the foundation pit exceeds the safe range.

8. The method for predicting the deformation trend of a deep foundation pit based on multi-modal sensing data according to claim 7, characterized in that during normal construction when the deformation trend of the foundation pit is normal, the internal supports are removed step by step from bottom to top; when there is a risk in the deformation trend of the foundation pit, the initial detection period is reduced to adjust the steps of removing the internal supports; when the deformation trend of the foundation pit exceeds the safe range, the construction is stopped.

9. The method for predicting the deformation trend of a deep foundation pit based on multi-modal sensing data according to claim 8, characterized in that the internal supports at different guide wall levels are removed according to the determined support removal sequence, and the actual horizontal displacement of the diaphragm wall guide wall after removing the internal supports of the current guide wall level is detected in real time, and the predicted total horizontal displacement is compared with the actual horizontal displacement detected; if the displacement difference between the predicted total horizontal displacement of the current support removal layer and the actual horizontal displacement detected is less than the difference evaluation value, it is determined that the prediction result is within the normal range, and the support removal continues according to the determined support removal sequence; if the displacement difference between the predicted total horizontal displacement of the current support removal layer and the horizontal displacement detected is greater than or equal to the difference evaluation value, it is determined that the prediction result exceeds the normal range, and the predicted displacement increment of the guide wall level in the next support removal sequence is adjusted.

10. The method for predicting the deformation trend of deep foundation pits based on multi-modal sensing data according to claim 9, wherein The process of adjusting the displacement increment includes when the predicted total horizontal displacement is less than or greater than the actually detected horizontal displacement, the displacement increment after removing the supports predicted for the guide wall level where the internal supports in the next support removal sequence are located is reduced or increased according to the ratio of the displacement difference to the difference evaluation value.

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