Construction method of double-wheel slot milling machine for building underground diaphragm wall

Abstract

The invention relates to the technical field of continuous wall construction, in particular to a construction method of a double-wheel slot milling machine for building an underground continuous wall, which comprises the following steps of: digging an initial continuous slot; collecting a humidity distribution diagram; respectively determining a high-permeability soil layer area and a low-permeability soil layer area of the initial continuous groove according to the average humidity; a grouting pipe is placed in the initial continuous groove, and zoned grouting is conducted on the high-permeability soil layer area and the low-permeability soil layer area sequentially and correspondingly in a partial pressure grouting mode or a low-air-pressure auxiliary stable pressure grouting mode from bottom to top; the number of cavities in the side wall of the initial continuous groove is detected; the vertical moving track of the grouting pipe is adjusted when the grouting mode of the partition grouting is switched next time; grouting the initial continuous groove to form a reinforced continuous groove; and a prefabricated reinforcement cage is inserted into the reinforced continuous groove, and concrete is poured to form the underground continuous wall. According to the invention, the stability and the bearing capacity of the groove wall are improved.

Description

Technical Field

[0001] The invention relates to the technical field of continuous wall construction, in particular to a construction method of a double-wheel slot milling machine for building an underground continuous wall. Background Art

[0002] In existing technology, the entire underground continuous wall is divided into several trench sections according to design requirements. To ensure the verticality and stability of the trench sections, guide walls, typically made of reinforced concrete, are constructed on the surface. A dedicated grab bucket or trench milling machine is used to form the trench. This process requires slurry protection, which primarily stabilizes the trench walls, prevents collapse, and carries drill cuttings. Verticality must be strictly controlled during trenching to ensure wall quality and accuracy.

[0003] Chinese Patent Publication No.: CN113279415B discloses a high-pressure slurry wall construction method for underground continuous wall trenching, comprising the following steps: A. forming a guide wall; before the underground continuous wall trenching construction, the guide wall is first constructed in accordance with the specification requirements; B. installing a trench milling machine; the suspension line and slurry outlet pipe of the trench milling machine are passed through the reserved holes of the sealing device and placed on the upper part of the trench milling machine guide frame; the sealing device includes a sealing cover plate and a sealing airbag, the sealing cover plate includes a top plate and a side plate arranged on the lower side of the top plate edge, the cross section of the sealing cover plate matches the surface of a single excavated trench section; the sealing airbag is arranged around the outer side of the side plate; the top plate The plate is provided with slurry inlet holes and perforations for the milling machine suspension line; C. Slot milling; the milling machine begins to sink along the guide wall into a slot, and slurry is used to protect the wall in the slot; when the guide frame of the slot milling machine completely enters the soil at the bottom of the guide wall, a number of ring-shaped sealing air bags that match the size of the sealing device are sequentially set from top to bottom on the outside of the sealing device, and the sealing device is placed in the excavated slot. The sealing device should fit tightly with the soil around the slot; D. Excavation slot sealing; the sealing air bag is inflated by an air pressure pump, so that the sealing air bag expands and squeezes the sealing device and the outer soil to complete the sealing of the excavation slot; E. High-pressure deep excavation; the slurry pump is used to pump in the mud Pressurize to form high-pressure wall protection conditions in the hole, the slot milling machine continues to slot downward, and the drill cuttings are discharged out of the slot through the slurry outlet channel at the bottom of the slot milling machine, maintaining the high-pressure conditions in the hole, and the mud pressure state in the slot is monitored and recorded by the pressure gauge at the slurry inlet; F. Pressure relief: When the slot milling machine slots to the preset depth, the drill cuttings in the slot are first discharged out of the slot through mud circulation, and then the mud concentration in the hole is increased through the slurry inlet. After the mud concentration in the hole reaches the predetermined standard, the mud pressure in the hole is released, and then the air pressure in the sealing airbag is released; G. Final slot milling: Lift the slot milling machine together with the sealing device from the slot and rotate it 180 degrees After the degree, repeat the above steps C to F, and continue to excavate the other half of the soil in the trench section until the entire trench section is completed; in the step B, the outer side of the suspension line and the slurry outlet pipe passing through the sealing device is provided with a telescopic sealing sleeve, and the two ends of the telescopic sealing sleeve are sealed. The end of the telescopic sealing sleeve is provided with an annular connecting protrusion, and the annular connecting protrusion includes an annular folding surface that is integrated with the upper end of the telescopic sealing sleeve. The outer end of the annular folding surface is provided with a sealing edge arranged around the outer end of the annular folding surface, and the cross-section of the sealing edge is "S"-shaped; the outer end of the sealing edge is provided with a sealing lip that abuts against the plane where the upper end of the telescopic sealing sleeve is located. It can be seen from this that the high-pressure mud wall protection construction method for the underground continuous wall trenching has the problem that due to the difference in permeability of the stratum, the soil layer in the high permeability soil layer area is strong, which leads to mud loss, poor trench wall stability, and weak soil layer permeability in the low permeability soil layer area. Excessive pressure during grouting may cause uneven pressure on the trench wall or damage. Summary of the Invention

[0004] To this end, the present invention provides a double-wheel milling machine construction method for building underground continuous walls, which is used to overcome the problem in the prior art that due to the difference in permeability of the strata, the soil layer in the high permeability soil layer area has strong permeability, which in turn leads to mud loss and poor trench wall stability, and the soil layer in the low permeability soil layer area has weak permeability, and excessive pressure during grouting may cause uneven pressure on the trench wall or damage.

[0005] To achieve the above object, the present invention provides a construction method of a double-wheel slot milling machine for constructing an underground continuous wall, comprising: Use a double-wheel slot milling machine to dig an initial continuous slot in the target area; Collecting a moisture distribution diagram of the side wall of the initial continuous groove in the vertical direction, wherein the side wall is the side wall close to the preset outer wall direction of the continuous wall; Analyzing the humidity distribution map to obtain the average humidity of a plurality of sampling points on each horizontal height sampling line; Determining the high permeability soil layer area and the low permeability soil layer area of the initial continuous groove respectively according to the average moisture; Putting a grouting pipe into the initial continuous groove, and sequentially adopting the divided pressure grouting method / low-pressure assisted stable pressure grouting method to perform zone grouting on the high permeability soil layer area and the low permeability soil layer area from bottom to top; emitting ultrasonic waves to the slurry during the grouting process and detecting the propagation velocity of the echoes to determine the number of cavities on the sidewalls of the initial continuous grooves; Adjusting the up and down movement trajectory of the grouting pipe when switching the grouting mode of the partitioned grouting next time according to the number of cavities; Grouting the initial continuous groove according to the up-and-down movement trajectory, and extracting all the grout after a predetermined interval after the grouting is completed to form a reinforced continuous groove; A prefabricated steel cage is inserted into the reinforced continuous groove and concrete is poured to form an underground continuous wall.

[0006] Furthermore, the high permeability soil layer and the low permeability soil layer are grouted in different zones using the divided pressure grouting method, including: Obtaining the average humidity of a plurality of sampling points on a plurality of horizontal height sampling lines in the humidity distribution diagram; The area where the average humidity is greater than or equal to the preset second humidity is marked as a high permeability soil layer area, and the high permeability soil layer area is subjected to a partial pressure grouting method.

[0007] Furthermore, the average humidity is the ratio of the sum of the humidity of the plurality of sampling points to the number of the sampling points.

[0008] Furthermore, the partial pressure grouting method includes: The grouting pressure is applied to the high permeability soil layer according to the first pressure; After the infiltration, the grouting pressure is increased to a third pressure and the grouting is continued until the preset depth of the high permeability soil layer is reached; reducing the grouting pressure to a second pressure and continuing grouting until the high permeability soil layer is covered; The first pressure is lower than the second pressure, and the second pressure is lower than the third pressure.

[0009] Furthermore, low-pressure assisted stable pressure grouting is used to carry out zonal grouting in the low-permeability soil layer, including: Marking the area where the average humidity is less than or equal to the preset first humidity as a low permeability soil layer area, and adopting a low-pressure assisted stable pressure grouting method for the low permeability soil layer area; The low-pressure assisted stable pressure grouting is to reduce the air pressure in the low-permeability soil layer before grouting and to use a constant pressure for continuous grouting, wherein the constant pressure is lower than the first pressure.

[0010] Furthermore, if the average humidity is greater than the preset first humidity and less than the preset second humidity, grouting is performed according to the initial grouting pressure.

[0011] Furthermore, the initial grouting pressure is greater than the constant pressure, and the initial grouting pressure is less than the first pressure.

[0012] Furthermore, adjusting the up and down movement trajectory of the grouting pipe when switching the grouting mode of the partitioned grouting next time according to the number of the cavities includes: Obtaining the number of cavities; comparing the number of cavities with a preset number; If the number of the cavities is greater than or equal to the preset number, the up and down movement trajectory of the grouting pipe is adjusted when the grouting mode of the partitioned grouting is switched next time.

[0013] Furthermore, the number of cavities is the total number of cavities on the side walls of the initial continuous grooves in the corresponding high permeability soil layer area or low permeability soil layer area.

[0014] Furthermore, adjusting the up and down movement trajectory of the grouting pipe when switching the grouting mode of the partitioned grouting next time includes: If the next time the zoned grouting mode is switched from the partial pressure grouting to the low-pressure assisted stable pressure grouting, the low-pressure assisted stable pressure grouting is performed after the grouting pipe is raised; If the next time the zoned grouting mode is switched from the low-pressure assisted stable pressure grouting to the partial pressure grouting, the grouting pipe is lowered when the grouting pressure is increased to the third pressure; If the next time the partition grouting mode is switched, the output end of the grouting pipe is lowered below the liquid level of the slurry and the up and down movement frequency of the grouting pipe is increased.

[0015] Compared with the prior art, the beneficial effect of the present invention is that the method of the present invention determines the high permeability soil layer area and the low permeability soil layer area by collecting the moisture distribution diagram of the inner wall of the initial continuous groove in the vertical direction. Since the soil layers with different moisture levels represent different differences in their permeability to liquids, by adopting the method of divided pressure grouting in the high permeability soil layer area and the method of low air pressure assisted stable pressure grouting in the low permeability soil layer area, the problems of mud loss caused by the difference in soil layer permeability, poor groove wall stability and excessive pressure during grouting that may damage the groove wall are reduced. In the high permeability soil layer area, low-pressure infiltration is used to avoid soil disturbance caused by initial impact, high-pressure covering is used to make the slurry spread evenly and radially penetrate the soil layer, and medium-pressure strengthening is used to make the slurry deeply fill the pores. The low permeability soil layer has a low porosity, which makes it difficult for traditional grouting methods to fully fill the slurry. Penetrating into the soil, by reducing the air pressure in the soil layer and expanding the pore space, the slurry's permeability is improved, making it easier for the slurry to enter the soil's micropores. Low-pressure assisted grouting can form a more uniform pressure distribution in the soil, avoiding the problem of uneven slurry distribution caused by local pressure being too high or too low, and achieving more consistent overall strength and stability of the soil after grouting; in the process of grouting on the surfaces of different soil layers, the slurry's infiltration effect on different soil layers will be affected by the characteristics of the soil layer. Therefore, the sound velocity change rate during the grouting process is collected to determine whether there is a cavity, and the movement trajectory of the grouting pipe is adjusted during the next partition grouting, thereby optimizing the slurry distribution and filling effect; after the grouting is completed, the slurry is air-dried and solidified to form a reinforced continuous groove, which enhances the stability and bearing capacity of the groove wall.

[0016] Furthermore, the method of the present invention adopts divided pressure grouting. In the first stage, low-pressure grouting is used to quickly form a closed shell on the surface of the soil layer in the high seepage area, thereby preventing the mud from further flowing into the high seepage area, stabilizing the trough wall, avoiding the risk of trough wall collapse due to mud loss, providing a preliminary barrier, creating conditions for subsequent high-pressure grouting, and reducing direct leakage of slurry; in the second stage, the grouting pressure is increased to increase the radial penetration distance of the slurry into the soil layer. High-pressure grouting can break through the pore limitations of the soil and push the slurry to a farther area, ensuring that the soil in the high seepage area is fully filled. The reinforcement is carried out in stages, so that the slurry penetrates into the larger pores and cracks in the soil, combines with soil particles to form a consolidated body, improves the overall strength and anti-seepage performance of the soil, and effectively blocks the groundwater flow channel by expanding the penetration range, reducing the groundwater reverse seepage damage that may occur during the construction process and later use; in the third stage, it is used to fill the tiny cracks in the soil. Under medium pressure, the slurry can more evenly fill the tiny pores and cracks in the soil, reduce local overpressure or crack expansion caused by high pressure, and reduce potential weak points inside the soil by filling microcracks, thereby improving the stability of the reinforced soil.

[0017] Furthermore, the method of the present invention adopts a low-pressure assisted stable pressure grouting method. In low-permeability areas, the close arrangement of soil particles will increase the resistance to slurry flow. By reducing the air pressure, the friction and adsorption between soil particles can be effectively reduced, and the resistance during the slurry advancement process can be reduced, thereby making grouting smoother. By keeping the grouting pressure stable, the slurry has enough residence time to fully contact the soil and undergo physical and chemical reactions to form a stable consolidated body, thereby improving the compressive strength, shear strength and overall stiffness of the soil, thereby enhancing the foundation bearing capacity and anti-seepage performance of the underground continuous wall. Direct high-pressure grouting in low-permeability soil layers may cause excessive local stress on the soil, causing deformation or even damage. The use of low-pressure assistance combined with moderate pressure can meet the grouting needs without causing excessive impact force on the trench wall, thereby effectively preventing the occurrence of trench wall instability and achieving improved stability of the continuous trench structure.

[0018] Furthermore, the method of the present invention determines whether there are cavities. Since the heterogeneity of the soil layer increases the complexity of the slurry flow, for example, the local presence of large particles, cracks or weak interlayers makes it difficult for the slurry to fully fill the gaps between large particles, or the slurry preferentially flows along the cracks, while ignoring the filling needs in other directions, resulting in cavities formed around the cracks, or displacement or deformation occurs during the grouting process, resulting in the slurry being unable to completely fill the target area. When a cavity is formed inside the slurry, the sound propagation in the slurry is accelerated, and the propagation path of the sound wave will change, which manifests as an abnormally accelerated propagation speed or an enhanced reflection signal. By detecting the grouting effect, the accuracy of the grouting effect is improved.

[0019] Furthermore, the method of the present invention adjusts the up and down movement trajectory of the grouting pipe when the partitioned grouting mode is switched next time, and raises the grouting pipe when the partial pressure grouting is switched to the low-pressure assisted stable pressure grouting. Since the grouting pressure of the low-pressure assisted stable pressure grouting is less than the end pressure of the partial pressure grouting, the fluidity of the slurry is reduced during the switching process. By raising the grouting pipe, the gravitational potential energy of the grouting pipe and the slurry in the continuous groove is increased, so that there is a greater impact force during the falling process of the slurry to effectively disturb the slurry in the continuous groove, thereby improving the filling effect of the slurry, compensating for the problem of reduced fluidity caused by pressure changes, and avoiding local cavities or insufficient filling caused by uneven slurry flow.

[0020] Furthermore, the method of the present invention adjusts the up and down movement trajectory of the grouting pipe when the zoned grouting mode is switched next time. When the low-pressure assisted stable pressure grouting is switched to the partial pressure grouting, since the grouting pressure of the partial pressure grouting is higher than the grouting pressure of the low-pressure assisted stable pressure grouting, the high-pressure impact will cause the slurry to splash and adhere to the inner wall of the continuous groove above the grouting area, causing the slurry to solidify in the continuous groove in advance, and then cause the subsequent slurry infiltration to be in an unfused state, resulting in the formation of cavities. By lowering the grouting pipe, excessive accumulation or splashing in local areas due to a sudden increase in pressure is avoided, the risk of slurry adhesion and premature solidification is reduced, and at the same time, the increased grouting pressure is directly applied to the slurry below to increase the flow effect of the slurry and the impact on the continuous groove wall to reduce the formation of cavities.

[0021] Furthermore, the method of the present invention can fully mix the newly injected slurry with the already filled slurry by increasing the frequency of the up and down movement of the grouting pipe, reduce the stratification phenomenon caused by pressure fluctuations or soil heterogeneity during the grouting process, and thus reduce the risk of cavity formation; by moving the grouting pipe at high frequency, the problem of local pressure being too high or too low caused by grouting at the same position for a long time is avoided, thereby improving the stability of the overall grouting effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is an overall flow chart of a construction method of a double-wheel slot milling machine for constructing an underground continuous wall according to an embodiment of the present invention; Figure 2 This is a flow chart of the divided pressure grouting of a construction method of a double-wheel slot milling machine for building an underground continuous wall according to an embodiment of the present invention; Figure 3 A flowchart of the up and down movement trajectory of the grouting pipe when the grouting mode of the partitioned grouting is switched next time in the construction method of the double-wheel slot milling machine for constructing an underground continuous wall according to an embodiment of the present invention; Figure 4 Schematic diagram of the grouting process of the double-wheel slot milling machine construction method for building an underground continuous wall according to an embodiment of the present invention; Explanation of the accompanying numbers: 1-electric reel, 2-preset outer wall, 3-humidity sensor, 4-grouting pipe, 5-initial continuous groove, 6-slurry. DETAILED DESCRIPTION

[0023] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention.

[0024] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0025] Furthermore, it should be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0026] See also Figure 1 、 Figure 2 、 Figure 3 as well as Figure 4 The figures are as follows, which respectively show the overall flow chart of the double-wheel slot milling machine construction method for constructing an underground continuous wall according to an embodiment of the present invention, the pressure-dividing grouting flow chart, the flow chart of the up and down movement trajectory of the grouting pipe when adjusting the grouting method for the next switching of the partitioned grouting, and the schematic diagram of the grouting process. The double-wheel slot milling machine construction method for constructing an underground continuous wall according to an embodiment of the present invention includes: Step S1, using a double-wheel slot milling machine to dig an initial continuous slot 5 in the target area; Step S2, collecting a humidity distribution diagram of the side wall of the initial continuous groove in the vertical direction, wherein the side wall is the side wall close to the preset outer wall direction of the continuous wall; Step S3, analyzing the humidity distribution diagram to obtain the average humidity of several sampling points on each horizontal height sampling line; Step S4, determining the high permeability soil layer area and the low permeability soil layer area of the initial continuous groove 5 according to the average humidity; Step S5: placing a grouting pipe 4 into the initial continuous groove 5, and performing zone grouting on the high permeability soil layer area and the low permeability soil layer area using a divided pressure grouting method and a low pressure assisted stable pressure grouting method in order from bottom to top; Step S6, emitting ultrasonic waves to the slurry during the grouting process and detecting the propagation velocity of the echo to determine the number of cavities on the sidewall of the initial continuous groove; Step S7, adjusting the up and down movement trajectory of the grouting pipe 4 when switching to the grouting mode of the partitioned grouting next time according to the number of the cavities; Step S8, grouting the initial continuous groove 5 according to the up-and-down movement trajectory, and extracting all the slurry 6 after a predetermined interval after the grouting is completed to form a reinforced continuous groove; Step S9: inserting a prefabricated steel cage into the reinforced continuous groove and pouring concrete to form an underground continuous wall.

[0027] Specifically, an embodiment of the slurry 6 includes one of silicate-nanoclay composite slurry, epoxy resin-silica powder infiltration slurry, and magnesium phosphate cement slurry.

[0028] Specifically, the cavity is a gas gap formed between the solidified slurry 6 and the inner wall of the initial continuous groove 5 .

[0029] Specifically, the technical means for determining the number of cavities on the sidewalls of the initial continuous groove according to the propagation speed of the echo in step S6 is well known to those skilled in the art and will not be described in detail here.

[0030] Specifically, in step S6, the device for emitting ultrasonic waves to the pulp 6 in the pulping process is an ultrasonic detector.

[0031] Specifically, the preset outer wall 2 of the continuous wall is the side wall of the continuous wall that contacts the external soil after being built.

[0032] Specifically, the grouting pressure is adjusted by a liquid pump connected to the input end of the grouting pipe 4 .

[0033] Specifically, the interval between executing step S1 and executing step S2 is 2 hours.

[0034] Specifically, the humidity distribution map is obtained by setting up an array of humidity sensors 3 on the outer wall of the initial continuous groove 5 in the long axis direction to obtain the soil moisture at the corresponding position. The array of humidity sensors 3 has several rows of humidity sensors 3 set at equal intervals along the horizontal height sampling lines, and the vertical spacing between every two adjacent rows of horizontal height sampling lines is equal.

[0035] Specifically, the output end of the grouting pipe 4 is provided with a rotation controller for adjusting the output angle of the slurry 6 .

[0036] Specifically, in step S8, under the condition that the depth of the continuous groove is 12m and the width is 0.8m, the general value range of the predetermined interval time is [120min, 300min], and the preferred embodiment of the predetermined interval time is 180min.

[0037] During implementation, the method of the present invention collects the moisture distribution diagram of the inner wall of the initial continuous groove 5 in the vertical direction, and then determines the high permeability soil layer area and the low permeability soil layer area. Since soil layers with different moisture levels represent different differences in their permeability to liquids, the method of divided pressure grouting is adopted in the high permeability soil layer area, and the method of low air pressure assisted stable pressure grouting is adopted in the low permeability soil layer area, thereby reducing the problems of mud loss caused by the difference in soil layer permeability, poor groove wall stability, and excessive pressure during grouting that may damage the groove wall. In the high permeability soil layer area, low-pressure infiltration is used to avoid soil disturbance caused by initial impact, high-pressure covering is used to make the slurry spread evenly and radially penetrate the soil layer, and medium-pressure strengthening is used to make the slurry 6 deeply fill the pores. The low permeability soil layer has a low porosity, which makes it difficult for the traditional grouting method to make the slurry fully penetrate into the soil. By reducing the air pressure in the soil layer and expanding the pore space, the permeability of the slurry is improved, making it easier for the slurry to enter the fine pores of the soil. Low-pressure assisted grouting can form a more uniform pressure distribution in the soil, avoiding the problem of uneven slurry distribution caused by local pressure being too high or too low, and achieving more consistent overall strength and stability of the soil after grouting; since the infiltration effect of the slurry 6 on different soil layers will be affected by the characteristics of the soil layer during grouting on the surface of different soil layers, the sound velocity change rate during the grouting process is collected to determine whether there is a cavity, and the movement trajectory of the grouting pipe 4 is adjusted during the next zone grouting, thereby optimizing the distribution and filling effect of the slurry 6; after the grouting is completed, the slurry 6 is air-dried and solidified to form a reinforced continuous groove, which enhances the stability and bearing capacity of the groove wall.

[0038] Specifically, the divided pressure grouting method is used to carry out grouting in the high permeability soil layer and the low permeability soil layer, including: Obtaining the average humidity of a plurality of sampling points on a plurality of horizontal height sampling lines in the humidity distribution diagram; The area where the average humidity is greater than or equal to the preset second humidity is marked as a high permeability soil layer area, and the high permeability soil layer area is subjected to a partial pressure grouting method.

[0039] Specifically, the average humidity is the ratio of the sum of the humidity of the plurality of sampling points to the number of the sampling points.

[0040] Specifically, under the conditions that the depth of the continuous groove is 12m and the width is 0.8m, the general value range of the preset first humidity is [18%, 25%], the general value range of the preset second humidity is [32%, 40%], the preferred embodiment of the preset first humidity is 20%, and the preferred embodiment of the preset second humidity is 35%.

[0041] Those skilled in the art can understand that the optional range of the preset first humidity and the preset second humidity provided in this embodiment and the preferred embodiment are the values selected under the conditions of the continuous groove having a depth of 12m and a width of 0.8m in this embodiment to achieve the best effect on the technical problem solved by the technical solution of the present invention. In actual applications or experiments, those skilled in the art can adaptively adjust the preset first humidity and the preset second humidity according to the actual application environment and application scenarios.

[0042] Specifically, the partial pressure grouting method includes: The grouting pressure is applied to the high permeability soil layer according to the first pressure; After the infiltration, the grouting pressure is increased to a third pressure and the grouting is continued until the preset depth of the high permeability soil layer is reached; reducing the grouting pressure to a second pressure and continuing grouting until the high permeability soil layer is covered; The first pressure is lower than the second pressure, and the second pressure is lower than the third pressure.

[0043] Specifically, the process of infiltrating the high permeability soil layer is that the rotary controller drives the output end of the grouting pipe 4 to rotate so that the slurry 6 flows downward along the side wall of the initial continuous groove 5 so that the surrounding side walls of the high permeability soil layer are infiltrated with the slurry 6.

[0044] Specifically, under the conditions that the depth of the continuous groove is 12m, the width is 0.8m, and the viscosity of the slurry 6 is 180Pa·s, the general value range of the first pressure is [1.5MPa, 2.5MPa], the general value range of the second pressure is [3MPa, 4.5MPa], and the general value range of the third pressure is [6MPa, 9MPa]. The preferred embodiment of the first pressure is 2MPa, the preferred embodiment of the second pressure is 4MPa, and the preferred embodiment of the third pressure is 8MPa.

[0045] Those skilled in the art can understand that the optional ranges of the first pressure, the second pressure and the third pressure provided in this embodiment and the preferred embodiment are the values selected to achieve the best effect on the technical problem solved by the technical solution of the present invention under the conditions that the depth of the continuous groove is 12m, the width is 0.8m, and the viscosity of the slurry 6 is 180Pa·s. In actual applications or experiments, those skilled in the art can adaptively adjust the first pressure, the second pressure and the third pressure according to the actual application environment and application scenario.

[0046] Specifically, the preset depth of the high permeability soil layer area = the depth of the high permeability soil layer area × 0.7.

[0047] In practice, the method of the present invention adopts divided pressure grouting. In the first stage, low pressure grouting is used to quickly form a closed shell on the surface of the soil layer in the high seepage area, preventing the mud from further flowing into the high seepage area, stabilizing the groove wall, avoiding the risk of groove wall collapse due to mud loss, providing a preliminary barrier, creating conditions for subsequent high-pressure grouting, and reducing direct leakage of slurry; in the second stage, the grouting pressure is increased to increase the radial penetration distance of the slurry 6 to the soil layer. High-pressure grouting can break through the pore limitations of the soil and push the slurry to a farther area, ensuring that the soil in the high seepage area is fully filled. The reinforcement is carried out in stages, so that the slurry penetrates into the larger pores and cracks in the soil, combines with soil particles to form a consolidated body, improves the overall strength and anti-seepage performance of the soil, and effectively blocks the groundwater flow channel by expanding the penetration range, reducing the groundwater reverse seepage damage that may occur during the construction process and later use; in the third stage, it is used to fill the tiny cracks in the soil. Under medium pressure, the slurry can more evenly fill the tiny pores and cracks in the soil, reduce local overpressure or crack expansion caused by high pressure, and reduce potential weak points inside the soil by filling microcracks, thereby improving the stability of the reinforced soil.

[0048] Specifically, low-pressure assisted stable pressure grouting is used to carry out zonal grouting in low-permeability soil areas, including: Marking the area where the average humidity is less than or equal to the preset first humidity as a low permeability soil layer area, and adopting a low-pressure assisted stable pressure grouting method for the low permeability soil layer area; The low-pressure assisted stable pressure grouting is to reduce the air pressure in the low-permeability soil layer before grouting and to use a constant pressure for continuous grouting, wherein the constant pressure is lower than the first pressure.

[0049] Specifically, the air pressure in the low permeability soil layer area is adjusted by a vacuum pump lowered into the initial continuous tank 5 .

[0050] Specifically, under the conditions that the depth of the continuous tank is 12 m, the width is 0.8 m, and the viscosity of the slurry 6 is 180 Pa·s, the general value range of the constant pressure is [0.8 MPa, 1 MPa], and the preferred embodiment of the constant pressure is 0.5 MPa.

[0051] Those skilled in the art will understand that the optional range of constant pressure provided in this embodiment and the preferred embodiment are the values selected to achieve the best effect on the technical problem solved by the technical solution of the present invention under the conditions that the depth of the continuous groove is 12m, the width is 0.8m, and the viscosity of the slurry 6 is 180Pa·s. In actual applications or experiments, those skilled in the art can adaptively adjust the constant pressure according to the actual application environment and application scenarios.

[0052] During implementation, if the difference between the preset first humidity and the average humidity is within 1%, the air pressure in the low permeability soil layer area will be reduced by 1000Pa. If the difference between the preset first humidity and the average humidity exceeds 1%, the air pressure will be reduced by 800Pa for every 1% increase. For example, the current air pressure in the low permeability soil layer area is 100,000Pa, and the difference between the preset first humidity and the average humidity is 3%, then the air pressure will be reduced to 100,000Pa-1000Pa-800Pa×2=97,400Pa.

[0053] In implementation, the method of the present invention adopts a low-pressure assisted stable pressure grouting method. In low-permeability areas, the close arrangement of soil particles will increase the resistance to slurry flow. By reducing the air pressure, the friction and adsorption between soil particles can be effectively reduced, and the resistance during the slurry advancement process can be reduced, thereby making grouting smoother. By keeping the grouting pressure stable, the slurry has sufficient residence time to fully contact the soil and undergo physical and chemical reactions to form a stable consolidated body, thereby improving the compressive strength, shear strength and overall stiffness of the soil, thereby enhancing the foundation bearing capacity and anti-seepage performance of the underground continuous wall. Direct high-pressure grouting in low-permeability soil layers may cause excessive local stress on the soil, causing deformation or even damage. The use of low-pressure assistance combined with moderate pressure can meet the grouting needs without causing excessive impact on the trench wall, thereby effectively preventing the occurrence of trench wall instability and achieving improved stability of the continuous trench structure.

[0054] Specifically, if the average humidity is greater than the preset first humidity and less than the preset second humidity, grouting is performed according to the initial grouting pressure.

[0055] Specifically, under the conditions that the depth of the continuous groove is 12m, the width is 0.8m, and the viscosity of the slurry 6 is 180Pa·s, the general value range of the initial grouting pressure is [1MPa, 2MPa], and the preferred embodiment of the initial grouting pressure is 1.6MPa.

[0056] Those skilled in the art will understand that the optional range of the initial grouting pressure provided in this embodiment and the preferred embodiment are the values selected to best achieve the technical problem solved by the technical solution of the present invention under the conditions that the depth of the continuous groove is 12 m, the width is 0.8 m, and the viscosity of the slurry 6 is 180 Pa·s. In actual applications or experiments, those skilled in the art can adaptively adjust the initial grouting pressure according to the actual application environment and application scenarios.

[0057] Specifically, the initial grouting pressure is greater than the constant pressure, and the initial grouting pressure is less than the first pressure.

[0058] Specifically, adjusting the up and down movement trajectory of the grouting pipe 4 when switching the grouting mode of the partitioned grouting next time according to the number of cavities includes: Obtaining the number of cavities; comparing the number of cavities with a preset number; If the number of the cavities is greater than or equal to the preset number, the up and down movement trajectory of the grouting pipe 4 is adjusted when the grouting mode of the partitioned grouting is switched next time.

[0059] Specifically, if the number of cavities is less than a preset number, the position of the grouting pipe 4 is not adjusted.

[0060] Specifically, under the conditions that the depth of the continuous tank is 12 m, the width is 0.8 m, and the viscosity of the slurry 6 is 180 Pa·s, the general value range of the preset number is [20, 30], and the preferred embodiment of the preset number is 24.

[0061] Specifically, the number of cavities is the total number of cavities on the side walls of the initial continuous groove 5 in the corresponding high permeability soil layer area or low permeability soil layer area.

[0062] In implementation, the method of the present invention determines whether there is a cavity. Since the heterogeneity of the soil layer increases the complexity of the slurry flow, for example, the local presence of large particles, cracks or weak interlayers makes it difficult for the slurry to fully fill the gaps between large particles, or it preferentially flows along the cracks, while ignoring the filling needs in other directions, causing cavities to form around the cracks, or displacement or deformation occurs during the grouting process, resulting in the slurry being unable to completely fill the target area. When a cavity is formed inside the slurry 6, the sound propagation in the slurry 6 is accelerated, and the propagation path of the sound wave will change, which is manifested as an abnormal acceleration of the propagation speed or an enhancement of the reflected signal. By detecting the grouting effect, the accuracy of the grouting effect is improved.

[0063] Specifically, adjusting the up and down movement trajectory of the grouting pipe 4 when switching the grouting mode of the partitioned grouting next time includes: If the next time the zoned grouting mode is switched from the partial pressure grouting to the low-pressure assisted stable pressure grouting, the low-pressure assisted stable pressure grouting is performed after the grouting pipe 4 is raised; If the next time the zoned grouting mode is switched from the low-pressure assisted stable pressure grouting to the partial pressure grouting, the grouting pipe 4 is lowered when the grouting pressure is increased to the third pressure; If the next time the partition grouting mode is switched, the output end of the grouting pipe 4 is lowered below the liquid level of the slurry 6 and the up and down movement frequency of the grouting pipe 4 is increased.

[0064] Specifically, after the grouting pipe 4 is raised and then low-pressure assisted stable pressure grouting is performed, the raising distance of the grouting pipe 4 is positively correlated with the number of cavities; When the grouting pressure is increased to the third pressure, the grouting pipe 4 is lowered, and the lowering distance of the grouting pipe 4 is positively correlated with the number of cavities; When the output end of the grouting pipe 4 is lowered below the liquid level of the slurry and the up and down movement frequency of the grouting pipe 4 is increased, the vertical distance between the output end of the grouting pipe 4 and the liquid level of the slurry is positively correlated with the number of cavities, and the up and down movement frequency is positively correlated with the number of cavities.

[0065] Specifically, the grouting pipe 4 moves up and down once each time, and the up and down movement frequency is the ratio of the up and down movement times to the unit grouting time, wherein the unit grouting time is 1 minute.

[0066] Specifically, the up and down movement trajectory of the grouting pipe 4 is adjusted by the electric reel 1 set on the ground.

[0067] During implementation, if the difference between the number of cavities and the preset number increases by 5 for every time, the rising distance of the grouting pipe 4 increases by 15 cm, the lowering distance of the grouting pipe 4 increases by 6 cm, the vertical distance between the output end of the grouting pipe 4 and the liquid surface of the slurry increases by 4 cm, and the up and down movement frequency increases by 1 time / min; if the difference between the number of cavities and the preset number and the remainder of 5 are greater than or equal to 3, the above-mentioned adjustment method of the grouting pipe 4 is executed; if the difference between the number of cavities and the preset number and the remainder of 5 are less than 3, the above-mentioned adjustment method of the grouting pipe 4 is not executed.

[0068] In implementation, the method of the present invention adjusts the up and down movement trajectory of the grouting pipe 4 when the partitioned grouting mode is switched next time, and raises the grouting pipe 4 when the partial pressure grouting is switched to the low-pressure assisted stable pressure grouting. Since the grouting pressure of the low-pressure assisted stable pressure grouting is less than the end pressure of the partial pressure grouting, the fluidity of the slurry 6 is reduced during the switching process. By raising the grouting pipe 4, the gravitational potential energy of the grouting pipe 4 and the slurry 6 in the continuous groove is increased, so that the slurry 6 has a greater impact force during the falling process to effectively disturb the slurry 6 in the continuous groove, thereby improving the filling effect of the slurry 6, compensating for the problem of reduced fluidity caused by pressure changes, and avoiding local cavities or insufficient filling caused by uneven flow of the slurry 6.

[0069] In implementation, the method of the present invention adjusts the up and down movement trajectory of the grouting pipe 4 when the partitioned grouting mode is switched next time. When the low-pressure assisted stable pressure grouting is switched to the partial pressure grouting, since the grouting pressure of the partial pressure grouting is higher than the grouting pressure of the low-pressure assisted stable pressure grouting, the high-pressure impact will cause the slurry 6 to splash and adhere to the inner wall of the continuous groove above the grouting area, causing the slurry 6 to solidify in the continuous groove in advance, and then cause the subsequent slurry 6 to be infiltrated in an unfused state, resulting in the formation of cavities. By lowering the grouting pipe 4, excessive accumulation or splashing in local areas due to a sudden increase in pressure is avoided, reducing the risk of slurry adhesion and premature solidification, and at the same time, the increased grouting pressure directly acts on the slurry 6 below to increase the flow effect of the slurry 6 and the impact on the continuous groove wall to reduce the formation of cavities.

[0070] During implementation, the method of the present invention can fully mix the newly injected slurry with the already filled slurry by increasing the up and down movement frequency of the grouting pipe 4, reducing the stratification phenomenon caused by pressure fluctuations or soil heterogeneity during the grouting process, thereby reducing the risk of cavity formation; by moving the grouting pipe 4 at high frequency, the problem of local pressure being too high or too low caused by grouting at the same position for a long time is avoided, thereby improving the stability of the overall grouting effect.

[0071] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

Claims

1. A double-wheel slot milling machine construction method for building an underground continuous wall, characterized in that: include: Use a double-wheel slot milling machine to dig an initial continuous slot in the target area; Collecting a moisture distribution diagram of the side wall of the initial continuous groove in the vertical direction, wherein the side wall is the side wall close to the preset outer wall direction of the continuous wall; Analyzing the humidity distribution map to obtain the average humidity of a plurality of sampling points on each horizontal height sampling line; Determining the high permeability soil layer area and the low permeability soil layer area of the initial continuous groove respectively according to the average moisture; Putting a grouting pipe into the initial continuous groove, and sequentially adopting the divided pressure grouting method / low-pressure assisted stable pressure grouting method to perform zone grouting on the high permeability soil layer area and the low permeability soil layer area from bottom to top; emitting ultrasonic waves to the slurry during the grouting process and detecting the propagation velocity of the echoes to determine the number of cavities on the sidewalls of the initial continuous grooves; Adjusting the up and down movement trajectory of the grouting pipe when switching the grouting mode of the partitioned grouting next time according to the number of cavities; Grouting the initial continuous groove according to the up-and-down movement trajectory, and extracting all the grout after a predetermined interval after the grouting is completed to form a reinforced continuous groove; A prefabricated steel cage is inserted into the reinforced continuous groove and concrete is poured to form an underground continuous wall.

2. The double-wheel slot milling machine construction method for building an underground continuous wall according to claim 1, characterized in that: The divided pressure grouting method is used to carry out grouting in the high permeability soil layer and the low permeability soil layer, including: Obtaining the average humidity of a plurality of sampling points on a plurality of horizontal height sampling lines in the humidity distribution diagram; The area where the average humidity is greater than or equal to the preset second humidity is marked as a high permeability soil layer area, and the high permeability soil layer area is subjected to a partial pressure grouting method.

3. The double-wheel slot milling machine construction method for building an underground continuous wall according to claim 2, characterized in that: The average humidity is the ratio of the sum of the humidity of the plurality of sampling points to the number of the sampling points.

4. The double-wheel slot milling machine construction method for building an underground continuous wall according to claim 3, characterized in that: The method of partial pressure grouting includes: The grouting pressure is applied to the high permeability soil layer according to the first pressure; After the infiltration, the grouting pressure is increased to a third pressure and the grouting is continued until the preset depth of the high permeability soil layer is reached; reducing the grouting pressure to a second pressure and continuing grouting until the high permeability soil layer is covered; The first pressure is lower than the second pressure, and the second pressure is lower than the third pressure.

5. The double-wheel slot milling machine construction method for building an underground continuous wall according to claim 4, characterized in that: Use low-pressure assisted stable pressure grouting to carry out zoning grouting in low-permeability soil areas, including: Marking the area where the average humidity is less than or equal to the preset first humidity as a low permeability soil layer area, and adopting a low-pressure assisted stable pressure grouting method for the low permeability soil layer area; The low-pressure assisted stable pressure grouting is to reduce the air pressure in the low-permeability soil layer before grouting and to use a constant pressure for continuous grouting, wherein the constant pressure is lower than the first pressure.

6. The double-wheel slot milling machine construction method for building an underground continuous wall according to claim 5, characterized in that: If the average humidity is greater than the preset first humidity and less than the preset second humidity, grouting is performed according to the initial grouting pressure.

7. The double-wheel slot milling machine construction method for building an underground continuous wall according to claim 6, characterized in that: The initial grouting pressure is greater than the constant pressure, and the initial grouting pressure is less than the first pressure.

8. The double-wheel slot milling machine construction method for building an underground continuous wall according to claim 7, characterized in that: Adjusting the up and down movement trajectory of the grouting pipe when switching the grouting mode of the partitioned grouting next time according to the number of cavities includes: Obtaining the number of cavities; comparing the number of cavities with a preset number; If the number of the cavities is greater than or equal to the preset number, the up and down movement trajectory of the grouting pipe is adjusted when the grouting mode of the partitioned grouting is switched next time.

9. The double-wheel slot milling machine construction method for building an underground continuous wall according to claim 8, characterized in that: The number of cavities is the total number of cavities on the side walls of the initial continuous grooves in the corresponding high permeability soil layer area or low permeability soil layer area.

10. The double-wheel slot milling machine construction method for building an underground continuous wall according to claim 9, characterized in that: Adjusting the up and down movement trajectory of the grouting pipe when switching the grouting mode of the partitioned grouting next time includes: If the next time the zoned grouting mode is switched from the partial pressure grouting to the low-pressure assisted stable pressure grouting, the low-pressure assisted stable pressure grouting is performed after the grouting pipe is raised; If the next time the zoned grouting mode is switched from the low-pressure assisted stable pressure grouting to the partial pressure grouting, the grouting pipe is lowered when the grouting pressure is increased to the third pressure; If the next time the partition grouting mode is switched, the output end of the grouting pipe is lowered below the liquid level of the slurry and the up and down movement frequency of the grouting pipe is increased.

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