Precise control method for micro-deformation of deep foundation pit

Abstract

The invention discloses an accurate control method for micro-deformation of a deep foundation pit. The method comprises the steps that a first concrete support is constructed between foundation pit support structures; the method comprises the following steps: sequentially constructing subsequent concrete supports between a foundation pit support structure along with excavation of a soil body of a foundation pit, and mounting an active servo control device between each concrete support of the subsequent concrete supports and the foundation pit support structure, grouting reinforcement is carried out on the soil body in the pit which is not excavated below the two ends of each concrete support of each subsequent concrete support; according to a formula (1), micro-deformation of the foundation pit support structure generated in the foundation pit excavation process is accurately controlled through a cooperative control mode of active compensation of servo supporting force applied by the active servo control device and passive compensation of grouting reinforcement of soil in the pit. Micro-deformation generated in the excavation process of the foundation pit can be accurately controlled, the construction safety of the foundation pit is effectively guaranteed, and the dynamic intelligent regulation and control effect on the micro-deformation of the foundation pit is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of foundation pit construction, and particularly relates to a precise control method for micro-deformation of deep foundation pits. Background Art

[0002] During the excavation of deep foundation pits, the control of micro-deformation of foundation pits is the key and difficult point of construction projects. The traditional technology has insufficient passive earth pressure compensation, relies on the initial strength of the soil in the pit, and cannot dynamically compensate for the deformation of the foundation pit retaining structure, resulting in lateral displacement of the foundation pit retaining structure and excessive bottom heave of the pit (>5 mm), threatening the safety of surrounding sensitive facilities, low efficiency of the support system, rough grouting process, single material function, and lagging risk control. Summary of the Invention

[0003] The purpose of the present invention is to provide a precise control method for micro-deformation of deep foundation pits to solve the problem of poor precision in controlling micro-deformation of foundation pits.

[0004] To solve the above technical problems, the present invention provides a precise control method for micro-deformation of deep foundation pits, including: Construct the first concrete support between the foundation pit retaining structures; As the soil in the foundation pit is excavated, construct the subsequent concrete supports between the foundation pit retaining structures in sequence. Install active servo control devices between each concrete support of the subsequent concrete supports and the foundation pit retaining structures. Grout and reinforce the unexcavated soil in the pit under both ends of each concrete support of the subsequent concrete supports. According to formula (1), precisely control the micro-deformation generated by the foundation pit retaining structure during the excavation of the foundation pit through the active compensation of the servo support force applied by the active servo control device and the passive compensation of grouting and reinforcement of the soil in the pit; (1); In formula (1), ΔD is the micro-deformation amount of the foundation pit, k is the soil compression coefficient, ΔV is the grouting volume expansion amount, S is the area of the grouting influence zone, β is the servo support force sensitivity coefficient of the active servo control device, ΔF is the real-time adjustment amount of the servo support force of the active servo control device, F 0 is the initial servo support force of the active servo control device.

[0005] Furthermore, for the precise control method for micro-deformation of deep foundation pits provided by the present invention, during the on-site grouting test stage, record the relationship between the micro-deformation amount ΔD of the foundation pit and the grouting volume expansion amount ΔV in formula (1), and calculate the soil compression coefficient through a linear regression functionk 。

[0006] Furthermore, for the deep foundation pit micro-deformation precise control method provided by the present invention, during the activation stage of the active servo control device, the grouting volume expansion ΔV is set to 0, and the real-time adjustment amount ΔF of the servo support force of the active servo control device and the micro-deformation amount ΔD are recorded, and the servo support force sensitivity coefficient is calculated according to formula (2) β； (2); In formula (2), β is the servo support force sensitivity coefficient of the active servo control device, ΔD is the micro-deformation amount of the foundation pit, F 0 is the initial servo support force of the active servo control device, ΔF is the real-time adjustment amount of the servo support force of the active servo control device.

[0007] Furthermore, for the deep foundation pit micro-deformation precise control method provided by the present invention, the method for grouting and reinforcing the unexcavated soil mass in the pit includes: Drilling construction is carried out in the unexcavated soil mass in the pit under both ends of each concrete support of the subsequent concrete supports on the inner side of the foundation pit enclosure structure to form multiple rows of grouting holes, and the grouting hole depth is determined according to formula (3); D = 1.2L p + d (3); In formula (3), D is the grouting hole depth, L p is the excavation depth of the soil mass in the foundation pit, d is the allowable deformation value of the foundation pit enclosure structure; The grouting density is calculated according to formula (4); (4); In formula (4), D(x,y) is the grouting density, is the number of grouting holes per unit area, P p (x,y) is the passive earth pressure value after grouting, and k(x,y) is the permeability coefficient; By inserting a grouting pipe into each grouting hole and winding geotextile around the periphery of the grouting pipe; The soil mass in the pit is grouted through the grouting pipe wound with geotextile according to the predetermined slurry mixing ratio of three slurries: cement slurry, water glass mixture and slurry containing an expansion agent.

[0008] Furthermore, for the precise control method of deep foundation pit micro-deformation provided by the present invention, the spacing between grouting holes is adjusted according to formula (5) to adjust the grouting density; (5); In formula (5), S is the spacing between grouting holes, α is an empirical coefficient, R is the effective diffusion radius of a single grouting hole, and D(x, y) is the grouting density, which is the number of grouting holes per unit area in the grouting area.

[0009] Furthermore, for the precise control method of deep foundation pit micro-deformation provided by the present invention, it is determined that the diffusion range of the grouting hole after injecting the grouting slurry can cover the grouting area according to the constraint formula (6); S 2 ≤ R 2 (6); In formula (6), S is the spacing between grouting holes, and R is the effective diffusion radius of a single grouting hole.

[0010] Furthermore, for the precise control method of deep foundation pit micro-deformation provided by the present invention, the grouting volume expansion amount is calculated according to formula (7); (7); In formula (7), ΔV 1 is the actual grouting volume expansion amount, where ΔV = ΔV 1 , is the efficiency coefficient, ΔV 0 is the theoretical grouting volume expansion amount, V 0 is the grouting volume before expansion, R exp is the grouting volume expansion rate, Q1 is the injection flow rate of cement slurry per unit time, with the unit of m 3 / s, Q2 is the injection flow rate of water glass mixture per unit time, with the unit of m 3 / s, Q3 is the injection flow rate of expansion agent slurry per unit time, with the unit of m 3 / s, t is the total grouting time, k 1 , k 2 are material characteristic coefficients, and γ is the volume ratio of the expansion agent.

[0011] Furthermore, for the precise control method of deep foundation pit micro-deformation provided by the present invention, the grouting volume expansion rate is determined according to formula (8); (8); In formula (8), R expis the expansion rate, k 1 and k 2 are material characteristic coefficients, and γ is the volume ratio of the expansive agent.

[0012] Furthermore, in the deep foundation pit micro - deformation precise control method provided by the present invention, during the grouting maintenance period, the servo support force applied by the active servo control device is maintained at 50 - 70% of its designed axial force value; by real - time monitoring the displacement of the foundation pit retaining structure and the axial force value of the servo support force of the active servo control device, the axial force value of the servo support force of the active servo control device and the parameters of passive grouting compensation are dynamically adjusted to precisely control the micro - deformation amount generated by the foundation pit retaining structure during the foundation pit excavation process.

[0013] Furthermore, in the deep foundation pit micro - deformation precise control method provided by the present invention, when grouting and strengthening the unexcavated soil in the pit in each subsequent concrete support, the grouting depth is determined according to formula (3); When there is a next - stage concrete support below the current subsequent concrete support, the grouting depth of both ends of the current subsequent concrete support into the unexcavated soil in the pit is determined according to formula (3); When the current subsequent concrete support is the last subsequent concrete support, the grouting depth of both ends of the current subsequent concrete support into the unexcavated soil in the pit is at least 2 meters below the bottom of the pit.

[0014] Compared with the prior art, the beneficial effects of the deep foundation pit micro - deformation precise control method provided by the present invention are as follows: Through the active compensation of the servo support force applied by the active servo control device according to formula (1) and the passive compensation of grouting and strengthening the soil in the pit, the micro - deformation generated by the foundation pit retaining structure during the foundation pit excavation process is precisely controlled in a collaborative control manner, thereby precisely controlling the micro - deformation generated during the foundation pit excavation process, effectively ensuring the safety of foundation pit construction, achieving the effect of dynamic intelligent regulation of foundation pit micro - deformation, and avoiding the problem of poor accuracy in controlling foundation pit micro - deformation caused by the independent control of active compensation and passive compensation for foundation pit deformation.

[0015] By maintaining the servo support force during the grouting process through the collaborative control method of formula (1), the accuracy, effectiveness, and injection volume of passive compensation for foundation pit micro - deformation by grouting and strengthening the soil in the pit can be enhanced, avoiding the increase in cost and waste of materials caused by excessive grouting, and avoiding the problem of poor strengthening effect due to insufficient grouting volume for the soil in the pit. Specific embodiments

[0016] The embodiment of the present invention provides a deep foundation pit micro - deformation precise control method, including: Step 100, construct the first concrete support between the foundation pit retaining structures. The foundation pit retaining structures can be diaphragm walls or row piles. The cross-sectional size of the first concrete support is determined according to the design axial force value, and the typical value of the cross-sectional size of the first concrete support is 800mm×1000mm. The first concrete support is cured to the design strength (≥C30, curing time ≥7 days). After constructing the first concrete support, excavate the soil in the foundation pit to the design elevation of the second support.

[0017] Step 200, successively construct the subsequent concrete supports between the foundation pit retaining structures as the soil in the foundation pit is excavated. Install active servo control devices between each concrete support of the subsequent concrete supports and the foundation pit retaining structures. Grout and reinforce the soil in the unexcavated pit under both ends of each concrete support of the subsequent concrete supports. Precisely control the micro-deformation of the foundation pit retaining structure during the foundation pit excavation process through the collaborative control method of the active compensation of the servo support force applied by the active servo control device according to formula (1) and the passive compensation of the grouting and reinforcement of the soil in the pit. (1); In formula (1), ΔD is the foundation pit micro-deformation amount, k is the soil compression coefficient, ΔV is the grouting volume expansion amount, S is the grouting influence area, β is the servo support force sensitivity coefficient of the active servo control device, ΔF is the real-time adjustment amount of the servo support force of the active servo control device, with the unit of kN, F 0 is the initial servo support force of the active servo control device, with the unit of kN.

[0018] The cross-sectional size and design strength of the subsequent concrete supports can be set with reference to the first concrete support. The active servo control device includes a servo oil cylinder, whose rated axial force value can be 2000 - 5000kN, and pressure sensors such as strain gauges, with an induction accuracy of ±0.5%FS. Interfaces can be embedded at the ends of the concrete support to ensure the stability of the active servo control device installed on the subsequent concrete supports.

[0019] The precise control method for micro-deformation of deep foundation pits provided by the embodiments of the present invention precisely controls the micro-deformation generated by the foundation pit retaining structure during the excavation of the foundation pit through the active compensation of the servo support force applied by the active servo control device and the passive compensation of soil grouting reinforcement in the pit according to formula (1), thereby precisely controlling the micro-deformation generated during the excavation of the foundation pit, effectively ensuring the safety of foundation pit construction, and achieving the effect of dynamic intelligent regulation of the micro-deformation of the foundation pit. That is, while actively compensating the servo support force applied by the active servo control device, the collaborative control method for tracking the grouting construction of the passive compensation of soil grouting reinforcement in the pit is adopted, achieving the effect of dynamic intelligent regulation of the micro-deformation of the foundation pit, and avoiding the problem of poor accuracy in controlling the micro-deformation of the foundation pit caused by the independent control of the active compensation and the passive compensation for the deformation of the foundation pit.

[0020] The precise control method for micro-deformation of deep foundation pits provided by the embodiments of the present invention can maintain the servo support force during the grouting process through the collaborative control method of formula (1), which can enhance the accuracy, effectiveness, and injection volume of the passive compensation for the micro-deformation of the foundation pit by grouting and reinforcing the soil in the pit, avoid the increase in cost and waste of materials caused by excessive grouting, and avoid the problem of poor reinforcement effect due to insufficient reinforcement of the soil in the pit caused by too little grouting volume.

[0021] In order to determine the soil compression coefficient in formula (1), the precise control method for micro-deformation of deep foundation pits provided by the embodiments of the present invention records the micro-deformation amount of the foundation pit in formula (1) during the on-site grouting test stage. ΔD And the relationship with the grouting volume expansion amount ΔV The soil compression coefficient is calculated through a linear regression function k .

[0022] In order to determine the servo support force sensitivity coefficient in formula (1), the precise control method for micro-deformation of deep foundation pits provided by the embodiments of the present invention makes the grouting volume expansion amount ΔV = 0 during the activation stage of the active servo control device, records the real-time adjustment amount ΔF of the servo support force of the active servo control device and the corresponding relationship with the micro-deformation amount ΔD , and calculates the servo support force sensitivity coefficient β； according to formula (2); In formula (2), β is the servo support force sensitivity coefficient of the active servo control device, ΔD is the micro-deformation amount of the foundation pit, F 0 is the initial servo support force of the active servo control device, ΔF is the real-time adjustment amount of the servo support force of the active servo control device. Among them, formula (2) is derived from formula (1) when ΔVIt is derived when = 0.

[0023] To ensure the precise control effect of the grouting reinforcement of the soil mass in the pit, in the deep foundation pit micro-deformation precise control method provided by the embodiment of the present invention, in step 200, the method for grouting and reinforcing the unexcavated soil mass in the pit includes: Step 201, drilling construction is carried out on the unexcavated soil mass under the two ends of each concrete support of the subsequent concrete supports on the inner side of the foundation pit retaining structure to form multiple rows of grouting holes, and the depth of the grouting holes is determined according to formula (3); D = 1.2L p + d (3); In formula (3), D is the depth of the grouting hole, L p is the excavation depth of the soil mass in the foundation pit, d is the allowable value of the deformation of the foundation pit retaining structure. Through formula (3), it can ensure that the slurry covers the weak area of the soil mass in the pit. Among them, multiple rows of grouting holes in the unexcavated soil mass under the two ends of each concrete support of the subsequent concrete supports can be arranged at the collar beam of the foundation pit retaining structure. Among them, multiple rows of grouting holes include but are not limited to two rows.

[0024] Step 202, calculate the grouting density according to formula (4); (4); In formula (4), D(x,y) is the grouting density, that is, the number of grouting holes per unit area, P p (x,y) is the value of the passive earth pressure after grouting, and k(x,y) is the permeability coefficient. The strength of the soil mass grouting reinforcement in the pit is ensured by the grouting density. To ensure the strength of the soil mass in the pit, the larger the value of D(x,y), the more the number of grouting holes needs to be arranged densely. Among them, D(x,y) is the plane layout relationship of the number of grouting holes per unit area of the grouting density. It can be seen from formula (4) that the number of grouting holes per unit area is affected by the passive earth pressure and the permeability coefficient, and the larger the grouting density, the smaller the spacing between grouting holes.

[0025] The spacing between grouting holes can be adjusted according to formula (5) to adjust the grouting density, that is, to adjust the number of grouting holes per unit area; (5); In formula (5), S is the spacing between grouting holes, α is an empirical coefficient, R is the effective diffusion radius of a single grouting hole, D(x,y) is the grouting density, and the number of grouting holes per unit area of the grouting area.

[0026] To ensure that the diffusion radius of the grouting holes is completely covered and improve the grouting effect, the diffusion range of the grouting holes after injecting the grout can be determined according to the constraint formula (6) to cover the grouting area; S 2 ≤ R 2 (6); In formula (6), S is the spacing of the grouting holes, and R is the effective diffusion radius of a single grouting hole.

[0027] Step 203: Insert a grouting pipe into each grouting hole and wrap geotextile around the periphery of the grouting pipe to prevent the grouting pipe from being blocked and affecting the grouting. The grouting pipe can be a steel pipe with a diameter of Φ42mm.

[0028] Step 204: Grout the soil in the pit through the grouting pipe wrapped with geotextile according to the predetermined slurry mix ratios of three kinds of slurries: cement slurry, sodium silicate mixture and slurry containing an expansion agent. The predetermined slurry mix ratios of the three kinds of slurries can be calculated through a large grouting reinforcement model based on the detection data of the soil reinforcement in the pit. The large grouting reinforcement model is an engineering analysis system constructed based on fluid mechanics, elastoplastic mechanics and numerical simulation technology, which is used to optimize the grouting reinforcement process parameters and predict the formation response. The injected cement slurry (water-cement ratio 0.6 - 0.8) is used to fill the pores of the soil in the pit, the injected sodium silicate mixture (dosage 3 - 5%) is used to control the initial setting time of the slurry ≤ 30 min; the injected slurry containing an expansion agent (dosage 8 - 12%) is used to generate an expansion rate of 3 - 5%. Grouting pressure control: initial pressure 0.5 MPa, final pressure ≤ 1.5 MPa; seal the hole after grouting is completed, and the curing time ≥ 48 hours.

[0029] To calculate the grouting volume expansion amount in formula (1), the precise control method for micro-deformation of deep foundation pits provided by the embodiments of the present invention calculates the grouting volume expansion amount according to formula (7); (7); In formula (7), ΔV 1 is the actual expansion amount of the grouting volume, where ΔV = ΔV 1 , is the efficiency coefficient, ΔV 0 is the theoretical expansion amount of the grouting volume, V 0 is the grouting volume before expansion, R exp is the grouting volume expansion rate, Q1 is the injection flow rate of the cement slurry per unit time, with the unit of m 3 / s, Q2 is the injection flow rate of the sodium silicate mixture per unit time, with the unit of m 3 / s, where Q3 is the injection flow rate of the expansive agent slurry per unit time, with the unit of m 3 / s, t is the total grouting time, which is determined by the setting time of the sodium silicate mixture, k 1 and k 2 is the material characteristic coefficient, and γ is the volume ratio of the expansive agent.

[0030] The actual expansion volume of the grouting volume calculated by formula (7) ΔV 1 is the expansion volume of the grouting volume in formula (1) ΔV , so that through the expansion volume of the grouting volume in formula (1) ΔV the influence of the passive compensation of the in-pit grouting on the micro-deformation of the foundation pit can be controlled.

[0031] The grouting volume expansion rate can be determined according to formula (8); (8); In formula (8), R exp is the expansion rate, k 1 and k 2 are the material characteristic coefficients, and γ is the volume ratio of the expansive agent.

[0032] Furthermore, for the precise control method of the micro-deformation of the deep foundation pit provided by the embodiments of the present invention, during the grouting maintenance period, the servo support force applied by the active servo control device is maintained at 50 - 70% of its designed axial force value; the displacement of the foundation pit retaining structure can be monitored in real time by a total station, and the axial force value of the servo support force of the active servo control device can be monitored by a strain gauge. According to formula (1), the axial force value of the servo support force of the active servo control device and the parameters of the passive grouting compensation are dynamically adjusted to precisely control the micro-deformation generated by the foundation pit retaining structure during the foundation pit excavation process.

[0033] In order to ensure the precise control of the passive compensation, for the precise control method of the micro-deformation of the deep foundation pit provided by the embodiments of the present invention, when grouting and reinforcing the unexcavated soil in the pit in the subsequent concrete supports, the grouting depth is determined according to the method of formula (3); When there is a next concrete support below the current subsequent concrete support, according to formula (3), the two ends of the current subsequent concrete support are grouted into the unexcavated soil in the pit; When the subsequent concrete support of the current lane is the last subsequent concrete support, the two ends of the subsequent concrete support of the current lane are grouted into the soil body in the unexcavated pit to a depth of at least 2 meters below the bottom of the pit. Among them, the grouting depth at least 2 meters below the bottom of the pit of the last subsequent concrete support can prevent the micro-deformation of the foundation pit retaining structure caused by the uplift of the bottom of the pit.

[0034] The present invention is not limited to the above specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art belong to the scope of protection of the present invention. Those skilled in the art can make other levels of modifications and changes to the present invention. Thus, if these modifications and changes of the present invention fall within the scope of the claims of the present invention, the present invention also intends to include these modifications and changes.

Claims

1. A precise control method for micro-deformation of deep foundation pits, characterized in that, Including: Construct the first concrete support between the foundation pit retaining structures; Construct the subsequent concrete supports in sequence as the soil in the foundation pit is excavated between the foundation pit retaining structures. Install active servo control devices between each concrete support of the subsequent concrete supports and the foundation pit retaining structures. Grout and reinforce the unexcavated soil in the pit under both ends of each concrete support of the subsequent concrete supports. Accurately control the micro-deformation of the foundation pit retaining structure during the foundation pit excavation process through the collaborative control method of the active compensation of the servo support force applied by the active servo control device according to formula (1) and the passive compensation of the grouting and reinforcement of the soil in the pit. （1）； In formula (1), ΔD is the micro-deformation amount of the foundation pit, k is the soil compression coefficient, ΔV is the grouting volume expansion amount, S is the area of the grouting influence zone, β is the servo support force sensitivity coefficient of the active servo control device, ΔF is the real-time adjustment amount of the servo support force of the active servo control device, F 0 is the initial servo support force of the active servo control device.

2. The precise control method for micro-deformation of deep foundation pits according to claim 1, characterized in that, During the grouting test stage at the construction site, record the micro-deformation of the foundation pit in formula (1) ΔD and the volume expansion of grouting ΔV relationship, and calculate the soil compression coefficient through a linear regression function k .

3. The precise control method for micro-deformation of deep foundation pits according to claim 1, characterized in that, During the activation stage of the active servo control device, the grouting volume expansion ΔV = 0, and record the real-time adjustment amount of the servo support force of the active servo control device Δ F and the micro-deformation amount ΔD corresponding relationship, and calculate the servo support force sensitivity coefficient according to formula (2) β； （2）； In formula (2), β is the servo support force sensitivity coefficient of the active servo control device, ΔD is the micro deformation amount of the foundation pit, F 0 is the initial servo support force of the active servo control device, ΔF is the real-time adjustment amount of the servo support force of the active servo control device.

4. The precise control method for micro-deformation of deep foundation pits according to claim 1, characterized in that, The method for grouting and reinforcing the unexcavated soil in the pit includes: Drill holes in the unexcavated soil in the pit under both ends of each concrete support of the subsequent concrete supports on the inner side of the foundation pit retaining structure to form multiple rows of grouting holes, and determine the grouting hole depth according to formula (3); D = 1.2L p + d （3）； In formula (3), D is the depth of the grouting hole, L p is the excavation depth of the soil in the foundation pit, d is the allowable value of the deformation of the foundation pit retaining structure; Calculate the grouting density according to formula (4); （4）； In formula (4), D(x, y) is the grouting density, which is the number of grouting holes per unit area, and P p (x, y) is the value of the passive earth pressure after grouting, and k(x, y) is the permeability coefficient; Insert grouting pipes into each grouting hole, and wrap geotextiles around the periphery of the grouting pipes; Grout the soil in the pit through the grouting pipes wrapped with geotextiles according to the predetermined slurry mix ratio of three slurries: cement slurry, water glass mixture and slurry containing expansion agent.

5. The precise control method for micro-deformation of deep foundation pits according to claim 4, characterized in that, Adjust the grouting density by adjusting the spacing between grouting holes according to formula (5); （5）； In formula (5), S is the spacing between grouting holes, α is the empirical coefficient, R is the effective diffusion radius of a single grouting hole, D(x,y) is the grouting density, and the number of grouting holes per unit area of the grouting area.

6. The precise control method for micro-deformation of deep foundation pits according to claim 5, characterized in that, Determine that the diffusion range of the grouting hole after grouting can cover the grouting area according to constraint formula (6); S 2 ≤ R 2 (6); In formula (6), S is the spacing between grouting holes, and R is the effective diffusion radius of a single grouting hole.

7. The precise control method for micro-deformation of deep foundation pits according to claim 1, characterized in that, Calculate the grouting volume expansion amount according to formula (7); （7）； In formula (7), ΔV 1 is the actual expansion volume of the grouting volume, where ΔV=ΔV 1 , is the efficiency coefficient, ΔV 0 is the theoretical expansion volume of the grouting volume, V 0 is the grouting volume before expansion, R exp is the grouting volume expansion rate, Q1 is the injection flow rate of the cement slurry per unit time, with the unit of m 3 / s, Q2 is the injection flow rate of the sodium silicate mixture per unit time, with the unit of m 3 / s, Q3 is the injection flow rate of the expansion agent slurry per unit time, with the unit of m 3 / s, t is the total grouting time, k 1 、 k 2 are the material characteristic coefficients, and γ is the volume ratio of the expansion agent.

8. The precise control method for micro-deformation of deep foundation pits according to claim 7, characterized in that, Determine the grouting volume expansion rate according to formula (8); （8）； In formula (8), R exp is the expansion rate, k 1 , k 2 are the material characteristic coefficients, and γ is the volume ratio of the expansion agent.

9. The precise control method for micro-deformation of deep foundation pits according to claim 1, characterized in that During the grouting curing period, keep the servo support force applied by the active servo control device at 50 - 70% of its designed axial force value; Dynamically adjust the axial force value of the servo support force of the active servo control device and the parameters of the passive grouting compensation by real-time monitoring the displacement of the foundation pit retaining structure and the axial force value of the servo support force of the active servo control device to accurately control the micro-deformation amount of the foundation pit retaining structure during the foundation pit excavation process.

10. The precise control method for micro-deformation of deep foundation pits according to claim 4, characterized in that When grouting and reinforcing the unexcavated soil in the pit in each of the subsequent concrete supports, determine the grouting depth according to formula (3); When there is a next concrete support under the current subsequent concrete support, determine the grouting depth of both ends of the current subsequent concrete support into the unexcavated soil in the pit according to formula (3); When the current subsequent concrete support is the last subsequent concrete support, the grouting depth of both ends of the current subsequent concrete support into the unexcavated soil in the pit is at least 2 meters below the pit bottom.

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