Shield muck improvement method for water-rich coarse-grained formation

Abstract

The application provides a shield muck improvement method for water-rich coarse-grained stratum, and relates to the technical field of shield muck improvement, and comprises the following steps: calculating the cutting soil volume Vs of a shield machine cutter per unit time according to the excavation diameter D, the tunneling speed v and the loose coefficient K of the coarse-grained stratum of the shield machine; combining Vs with the injection ratio KIR to calculate the flow rate q of calcium-based clay mineral-sodium silicate mixed slurry per unit time; calculating the flow rate q of two raw materials in a single mixing container per unit time according to the preset volume ratio M of the calcium-based clay mineral slurry and the sodium silicate solution, the number N of mixing containers and q K , q G ; starting the shield machine, and pumping the two raw materials into the mixing container at q K , q G to prepare the mixed slurry, and then injecting the mixed slurry into the soil bin to mix with the shield muck. The mixed slurry can mix the shield muck and underground water by virtue of good bonding capacity, improve the plastic flow state of the muck and reduce the permeability, avoid gushing and muck lagging, and thus ensure the stability of the working face.

Description

TECHNICAL FIELD

[0001] The application relates to the field of shield muck improvement, and particularly to a method for improving shield muck in a water-rich coarse-grained stratum. BACKGROUND

[0002] The earth pressure balance shield method has rapidly become a main construction method for urban tunnel construction due to its safety, high efficiency and good economy, and in recent years, the earth pressure balance shield method has been successfully applied to various strata thanks to the rapid development of muck improvement technology. In the process of shield tunneling, the shield machine cuts the stratum through a cutter head, and a conventional muck improvement method usually mixes the excavated soil formed by the cutter head cutting the stratum with foam, bentonite slurry, polymer and other improvement materials to form improved muck, so as to resist the water and soil pressure in front of the working face as a supporting medium, and the improved muck can be transported to the belt conveyor in a controllable manner and then discharged out of the tunnel. However, the conventional muck improvement method is difficult to effectively reduce the permeability of the muck, and the plastic flow of the muck is very poor. When the shield machine passes through a water-rich coarse-grained stratum, the muck and water are in a state of "muck is muck and water is water", which leads to the problems of gushing and muck lagging, and further causes the instability of the working face and even the collapse of the ground surface.

[0003] To solve the above problems, the application provides a method for improving shield muck in a water-rich coarse-grained stratum to ensure the stability of the working face. SUMMARY

[0004] The application aims to provide a method for improving shield muck in a water-rich coarse-grained stratum.

[0005] The application provides a method for improving shield muck in a water-rich coarse-grained stratum, which comprises the following steps:

[0006] S1: calculating the volume Vs of the soil cut by the cutter head of the shield machine per unit time according to the excavation diameter D and the tunneling speed v of the shield machine and the loose coefficient K of the coarse-grained stratum;

[0007] S2: calculating the flow rate q of the calcium-based clay mineral-sodium silicate mixed slurry per unit time according to the volume Vs of the soil cut by the cutter head of the shield machine per unit time and the injection ratio KIR;

[0008] S3: calculating the flow rate q of the calcium-based clay mineral slurry per unit time in a single mixing container and the flow rate q of the sodium silicate solution per unit time in a single mixing container according to the preset volume ratio M of the calcium-based clay mineral slurry and the sodium silicate solution, the number N of the mixing containers and the flow rate q of the calcium-based clay mineral-sodium silicate mixed slurry per unit time. K G ​; the mixing container is used for mixing calcium-based clay mineral slurry input by the first raw material bin and sodium silicate solution input by the second raw material bin;

[0009] S4: starting the shield machine, the pumping device pumping the calcium-based clay mineral slurry and the sodium silicate solution into the mixing container according to the flow rate q K of the calcium-based clay mineral slurry and the flow rate q G of the sodium silicate solution per unit time, forming calcium-based clay mineral-sodium silicate mixed slurry, and injecting the calcium-based clay mineral-sodium silicate mixed slurry into the soil bin of the shield machine to mix with the shield slurry.

[0010] According to the technical scheme provided by some embodiments of the present application, before S1, the method further comprises:

[0011] According to a preset mass ratio of water and calcium-based clay mineral powder, the calcium-based clay mineral powder and water are added to the first raw material bin;

[0012] The calcium-based clay mineral powder and water in the first raw material bin are stirred until the calcium-based clay mineral slurry is formed;

[0013] The sodium silicate solution is added to the second raw material bin.

[0014] According to the technical scheme provided by some embodiments of the present application, after S4, the method further comprises:

[0015] S5: every other preset time period, the mixture of the calcium-based clay mineral-sodium silicate mixed slurry and the shield slurry is taken from the belt conveyor of the shield machine to perform a field slump test, and the injection ratio KIR is adjusted according to the slump value so that the slump value is greater than or equal to 15 cm and less than or equal to 20 cm.

[0016] According to the technical scheme provided by some embodiments of the present application, the injection ratio KIR is adjusted according to the slump value so that the slump value is greater than or equal to 15 cm and less than or equal to 20 cm, which comprises:

[0017] If the slump value is less than 15 cm, the injection ratio KIR is increased by 5% and S2-S5 are repeated until the slump value is greater than or equal to 15 cm and less than or equal to 20 cm;

[0018] If the slump value is greater than 20 cm, the injection ratio KIR is reduced by 5% and S2-S5 are repeated until the slump value is greater than or equal to 15 cm and less than or equal to 20 cm.

[0019] According to the technical scheme provided by some embodiments of the present application, the preset mass ratio of water and calcium-based clay mineral powder is 3:1.

[0020] According to the technical scheme provided by some embodiments of the present application, the preset volume ratio M of the calcium-based clay mineral slurry and the sodium silicate solution is 10:1-7:1.

[0021] According to the technical scheme provided by some embodiments of the present application, the injection ratio KIR is 10%-20%.

[0022] According to the technical scheme provided by some embodiments of the present application, the number N of the mixing containers is 1-4.

[0023] According to the technical scheme provided by some embodiments of the present application, the preset time period is 1-5 minutes.

[0024] According to the technical scheme provided by some embodiments of the present application, the pumping pressure of the calcium-based clay mineral slurry in the first raw material bin and the sodium silicate solution in the second raw material bin into the mixing container is equal, and is greater than the pressure inside the soil bin of the shield machine.

[0025] The present application provides a shield slurry improvement method for water-rich coarse-grained stratum, comprising: S1: calculating the volume Vs of the soil body cut by the cutter head of the shield machine per unit time according to the excavation diameter D and the tunneling speed v of the shield machine and the loose coefficient K of the coarse-grained stratum; S2: calculating the flow rate q of the calcium-based clay mineral-sodium silicate mixed slurry per unit time according to the volume Vs of the soil body cut by the cutter head of the shield machine per unit time and the injection ratio KIR; S3: calculating the flow rate q of the calcium-based clay mineral slurry per unit time in a single mixing container and the flow rate q of the sodium silicate solution per unit time in a single mixing container according to the preset volume ratio M of the calcium-based clay mineral slurry and the sodium silicate solution, the number N of the mixing containers, and the flow rate q of the calcium-based clay mineral-sodium silicate mixed slurry per unit time; the mixing container is used for mixing the calcium-based clay mineral slurry input by the first raw material bin and the sodium silicate solution input by the second raw material bin; S4: starting the shield machine, and the pumping device pumps the calcium-based clay mineral slurry and the sodium silicate solution into the mixing container according to the flow rate q of the calcium-based clay mineral slurry per unit time and the flow rate q of the sodium silicate solution per unit time. K G ; the mixing container is used for mixing the calcium-based clay mineral slurry input by the first raw material bin and the sodium silicate solution input by the second raw material bin; S4: starting the shield machine, and the pumping device pumps the calcium-based clay mineral slurry and the sodium silicate solution into the mixing container according to the flow rate q of the calcium-based clay mineral slurry per unit time and the flow rate q of the sodium silicate solution per unit time. K G ​​Meanwhile, the calcium-based clay mineral slurry in the first raw material bin and the sodium silicate solution in the second raw material bin are pumped into the mixing container to form a calcium-based clay mineral-sodium silicate mixed slurry, and the calcium-based clay mineral-sodium silicate mixed slurry is injected into the soil bin of the shield machine to be mixed with the shield muck. By virtue of the good binding capacity of the calcium-based clay mineral-sodium silicate mixed slurry, the shield muck and underground water can be mixed into one, so that the large muck can be wrapped in the inside, the large-particle muck which is originally dispersed and easy to be stuck can form a slurry with good overall fluidity, the slurry can be conveniently discharged through the screw machine, and the screw machine is prevented from being blocked due to the accumulation of the muck at the bottom of the soil bin; meanwhile, the fine-particle muck does not flow away, and can be well filled between the pores of the large muck, so that the permeability coefficient of the muck is reduced, the gushing accident is avoided, and the stability of the tunnel face is ensured.

[0026] It should be understood that the description of technical features, technical solutions, beneficial effects or similar language in this application does not imply that all features and advantages can be realized in any single embodiment. On the contrary, it can be understood that the description of a feature or a beneficial effect means that the specific technical feature, technical solution or beneficial effect is included in at least one embodiment. Therefore, the description of technical features, technical solutions or beneficial effects in this specification does not necessarily refer to the same embodiment. Furthermore, the technical features, technical solutions and beneficial effects described in this embodiment can be combined in any appropriate manner. Those skilled in the art will understand that the embodiments can be implemented without one or more specific technical features, technical solutions or beneficial effects of a specific embodiment. In other embodiments, additional technical features and beneficial effects can be identified in specific embodiments that do not embody all embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can obtain other drawings from these drawings without creating any creative labor.

[0028] Figure 1 A schematic diagram of the instability of the shield tunnel face under the conventional muck improvement method provided by the embodiments of the present application;

[0029] Figure 2 A flowchart of the shield muck improvement method for water-rich coarse-grained strata provided by the embodiments of the present application;

[0030] Figure 3 A process schematic diagram of the shield muck improvement based on the calcium-based clay mineral-sodium silicate mixed slurry provided by the embodiments of the present application.

[0031] The text annotations in the figure are shown as:

[0032] 1, mixing container; 2, first raw material bin; 3, second raw material bin; 4, pumping device; 5, soil bin; 6, screw machine; 7, water-rich coarse-grained stratum; 8, slurry; 9, collapse cavity. DETAILED DESCRIPTION

[0033] In order for those skilled in the art to better understand the technical solutions of the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings, and the description in this part is only exemplary and explanatory, and should not have any limiting effect on the protection scope of the present application. Specifically, the described embodiments are only a part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor should belong to the protection scope of the present application.

[0034] It should be noted that similar reference numerals and letters represent similar items in the following drawings, so once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a series of steps or units does not have to be limited to only those steps or units clearly listed, but can include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0035] When the shield machine is excavating in the water-rich coarse-grained stratum 7, the shield muck is required to be able to resist the water and soil pressure in front of the working face and be discharged through the screw machine 6 in a controllable manner, which requires the shield muck to have low permeability and appropriate plastic flow. However, conventional muck improvement methods are difficult to effectively improve the water-rich coarse-grained stratum 7, as shown in the figure, the shield muck shows a "muck is muck, water is water" state, large pieces of shield muck are discharged at the bottom of the soil bin 5, and the stratum water together with part of the fine particles of the shield muck becomes slurry 8 filling the upper part of the soil bin 5. Under the action of water pressure, the slurry 8 will be sprayed out of the outlet of the screw machine 6 through the gaps of the lower large pieces of shield muck, causing a gushing accident, further inducing instability of the working face, and causing the stratum to produce a collapse cavity 9. Figure 1

[0036] In view of this, in order to solve the above problems, as shown in Figure 2 and Figure 3 The present embodiment provides a shield muck improvement method for a water-rich coarse-grained stratum, comprising:

[0037] ​S1: According to the excavation diameter D of the shield machine, the tunneling speed v and the loose coefficient K of the coarse-grained stratum, the volume Vs of the soil cut by the cutter head of the shield machine per unit time is calculated;

[0038] Specifically, the calculation method of the volume Vs of the soil cut by the cutter head of the shield machine per unit time is shown in the following formula (1):

[0039] Formula (1)

[0040] Wherein, Vs is the volume of the soil cut by the cutter head of the shield machine per unit time, K is the loose coefficient of the coarse-grained stratum, D is the excavation diameter of the shield machine, and v is the tunneling speed of the shield machine.

[0041] The loose coefficient K of the coarse-grained stratum refers to the volume ratio of the soil after excavation or blasting to the original state, and the loose coefficient K of different types of soil is different, which needs to be determined according to the field test.

[0042] S2: According to the volume Vs of the soil cut by the cutter head of the shield machine per unit time and the injection ratio KIR, the flow rate q of the calcium-based clay mineral-sodium silicate mixed slurry per unit time is calculated;

[0043] Specifically, the calculation method of the flow rate q of the calcium-based clay mineral-sodium silicate mixed slurry per unit time is shown in the following formula (2):

[0044] Formula (2)

[0045] Wherein, q is the flow rate of the calcium-based clay mineral-sodium silicate mixed slurry per unit time, Vs is the volume of the soil cut by the cutter head of the shield machine per unit time, and KIR is the injection ratio.

[0046] S3: According to the preset volume ratio M of the calcium-based clay mineral slurry and the sodium silicate solution, the number N of the mixing containers 1 and the flow rate q of the calcium-based clay mineral-sodium silicate mixed slurry per unit time, the flow rate q of the calcium-based clay mineral slurry per unit time in a single mixing container 1 K , and the flow rate q of the sodium silicate solution per unit time in a single mixing container 1 G ; the mixing container 1 is used to mix the calcium-based clay mineral slurry input by the first raw material bin 2 and the sodium silicate solution input by the second raw material bin 3;

[0047] Specifically, the mixing container 1 is 1, which can perform the related operation of improving the shield spoil, but when the number of the mixing containers 1 is multiple, the injection efficiency of the calcium-based clay mineral-sodium silicate mixed slurry can be improved, therefore, the calculation method of the flow rate q of the calcium-based clay mineral slurry per unit time in a single mixing container 1 K is shown in the following formula (3):

[0048] Formula (3)

[0049] Where, q K q represents the flow rate of the calcium-based clay mineral slurry per unit time, M represents the preset volume ratio of the calcium-based clay mineral slurry to the sodium silicate solution, N represents the number of mixing containers 1, and q represents the flow rate of the calcium-based clay mineral-sodium silicate mixed slurry per unit time.

[0050] The flow rate q of the sodium silicate solution per unit time in a single mixing container 1 G The calculation method is shown in the following formula (4):

[0051] Formula (4)

[0052] Where, q G q represents the flow rate of the calcium-based clay mineral slurry per unit time, M represents the preset volume ratio of the calcium-based clay mineral slurry to the sodium silicate solution, N represents the number of mixing containers 1, and q represents the flow rate of the calcium-based clay mineral-sodium silicate mixed slurry per unit time.

[0053] S4: Start the tunnel boring machine. Pumping device 4 operates according to the flow rate q of the calcium-based clay mineral slurry per unit time. K And the flow rate q of sodium silicate solution per unit time G Simultaneously, the calcium-based clay mineral slurry in the first raw material silo 2 and the sodium silicate solution in the second raw material silo 3 are pumped into the mixing container 1 to form a calcium-based clay mineral-sodium silicate mixed slurry. The calcium-based clay mineral-sodium silicate mixed slurry is then injected into the soil chamber 5 of the tunnel boring machine to mix with the tunnel boring machine's excavated soil.

[0054] Specifically, such as Figure 3 As shown, the tunnel boring machine is started, and the pumping device 4 operates according to the flow rate q of the calcium-based clay mineral slurry per unit time. K And the flow rate q of sodium silicate solution per unit time GMeanwhile, the calcium-based clay mineral slurry in the first raw material bin 2 and the sodium silicate solution in the second raw material bin 3 are pumped into the mixing container 1, and the calcium-based clay mineral slurry and the sodium silicate solution are pumped at the same time so that the pumping time of the two is equal, thereby ensuring that the flow ratio of the two is the volume ratio, and the two form a calcium-based clay mineral-sodium silicate mixed slurry according to the preset volume ratio M, and the calcium-based clay mineral-sodium silicate mixed slurry is injected into the soil bin 5 of the shield machine to mix with the shield muck, forming a mixture of the calcium-based clay mineral-sodium silicate mixed slurry and the shield muck. The shield muck generated by the shield machine during tunneling can directly enter the soil bin 5 of the shield machine; and the pumping device 4 first pumps the calcium-based clay mineral slurry and the sodium silicate solution into the mixing container 1 for mixing, and then delivers the mixed slurry to the soil bin 5 to mix with the shield muck in the soil bin 5. The pumping device 4 can be an electric pressure pump, or other devices capable of achieving the above functions, which are not limited here.

[0055] According to the present application, the calcium-based clay mineral slurry and the sodium silicate solution are mixed according to the preset ratio to form a calcium-based clay mineral-sodium silicate mixed slurry, which is then injected into the soil bin of the shield machine to mix with the muck in the soil bin of the shield machine. The calcium-based clay mineral-sodium silicate mixed slurry has good binding ability, which can mix the shield muck and underground water into one, so that the large pieces of muck can be wrapped inside, and the originally dispersed and easily jammed large particles of muck form a slurry with good overall fluidity, which is convenient to discharge through the screw machine, avoiding the accumulation of these mucks at the bottom of the soil bin and causing the screw machine to be blocked. At the same time, the fine particles of muck do not flow away, and can fill well between the pores of the large pieces of muck, reducing the permeability coefficient of the muck and avoiding the occurrence of gushing accidents, thereby ensuring the stability of the working face.

[0056] In a preferred embodiment, before S1, the method further comprises:

[0057] The calcium-based clay mineral powder and water are added to the first raw material bin 2 according to the preset mass ratio of water to calcium-based clay mineral powder;

[0058] The calcium-based clay mineral powder and water in the first raw material bin 2 are stirred until a calcium-based clay mineral slurry is formed;

[0059] The second raw material bin 3 is added with a sodium silicate solution.

[0060] Specifically, as Figure 3As shown, before mixing the calcium-based clay mineral slurry and the sodium silicate solution in the mixing container 1, the calcium-based clay mineral slurry and the sodium silicate solution should also be prepared. According to the preset mass ratio of water and calcium-based clay mineral powder, the calcium-based clay mineral powder and water are added to the first raw material bin 2, and the calcium-based clay mineral powder and water in the first raw material bin 2 are stirred until the calcium-based clay mineral slurry is formed. The calcium-based clay mineral powder and water should be fully stirred to ensure the uniformity of the calcium-based clay mineral slurry, and the stirring time can be controlled within 5-10 minutes. The sodium silicate solution is added to the second raw material bin 3, and the calcium-based clay mineral slurry and the sodium silicate solution are placed in separate bins to avoid premature contact and reaction of the two substances, and to facilitate subsequent pumping as needed.

[0061] In a preferred embodiment, after S4, the method further comprises:

[0062] S5: every preset time interval, a mixture of the calcium-based clay mineral-sodium silicate mixed slurry and the shield muck is taken from the belt conveyor of the shield machine for a field slump test, and the injection ratio KIR is adjusted according to the slump value to make the slump value greater than or equal to 15 cm and less than or equal to 20 cm.

[0063] Specifically, the mixture of the calcium-based clay mineral-sodium silicate mixed slurry and the shield muck is taken every preset time interval for detection to give the calcium-based clay mineral-sodium silicate mixed slurry and the shield muck a certain reaction time, so that the calcium-based clay mineral-sodium silicate mixed slurry and the shield muck are fully reacted before the test, to improve the accuracy of the test; at the same time, the stability of the mixture can be monitored in real time to avoid construction failures caused by fluctuations in material ratios. The slump value is limited to greater than or equal to 15 cm and less than or equal to 20 cm, which is a commonly used standard for judging the fluidity of substances through slump tests. A slump value that is too small (<15 cm) indicates that the fluidity of the mixture is too poor, which can cause the muck to be dry and hard, blocking the belt conveyor transport channel or the screw machine, causing construction to stop. A slump value that is too large (>20 cm) indicates that the fluidity of the mixture is too strong, making it difficult to effectively resist the water and soil pressure in the forward direction of the shield machine, resulting in instability of the working face. The belt conveyor (not shown in the figure) of the shield machine is usually connected to the screw machine 6 at one end and has a muck transport vehicle at the other end, which is used to transport the muck delivered by the screw machine 6 to the outside of the tunnel for long distances and high efficiency, completing the muck removal process.

[0064] In a preferred embodiment, the injection ratio KIR is adjusted according to the slump value to make the slump value greater than or equal to 15 cm and less than or equal to 20 cm, which comprises:

[0065] If the slump value is less than 15 cm, the injection ratio KIR is increased by 5% and the steps S2-S5 are repeated until the slump value is greater than or equal to 15 cm and less than or equal to 20 cm.

[0066] If the slump value is greater than 20 cm, the injection ratio KIR is reduced by 5% and S2-S5 are repeated until the slump value is greater than or equal to 15 cm and less than or equal to 20 cm.

[0067] Specifically, if the slump value is less than 15 cm, it indicates that the mixture has poor fluidity, and the calcium-based clay mineral-sodium silicate mixed slurry does not bond the shield muck well, so that the shield muck is still loose. Therefore, the injection ratio KIR is increased by 5% and S2-S5 are repeated until the slump value is greater than or equal to 15 cm and less than or equal to 20 cm. If the slump value is greater than 20 cm, it indicates that the mixture has too strong fluidity. Therefore, the injection ratio KIR is reduced by 5% and S2-S5 are repeated until the slump value is greater than or equal to 15 cm and less than or equal to 20 cm.

[0068] In a preferred embodiment, the preset mass ratio of the water and the calcium-based clay mineral powder is 3:1.

[0069] Specifically, the preset mass ratio of the water and the calcium-based clay mineral powder is 3:1. This ratio allows the calcium-based clay mineral powder to be fully dispersed in the water without clumping or uneven dispersion, laying a foundation for subsequent steps. Meanwhile, the calcium-based clay mineral-sodium silicate mixed slurry formed under this ratio has the best improvement effect on the permeability and plasticity of the muck. The preset mass ratio of the water and the calcium-based clay mineral powder is obtained through field tests, and can be adjusted according to the actual situation on site during actual operation.

[0070] In a preferred embodiment, the preset volume ratio M of the calcium-based clay mineral slurry and the sodium silicate solution is 10:1-7:1.

[0071] Specifically, the preset volume ratio M of the calcium-based clay mineral slurry and the sodium silicate solution is 10:1-7:1. The calcium-based clay mineral-sodium silicate mixed slurry formed within this ratio range has the best improvement effect on the permeability and plasticity of the shield muck. The preset volume ratio M of the calcium-based clay mineral slurry and the sodium silicate solution is obtained through field tests, and can be adjusted according to the actual situation on site during actual operation.

[0072] In a preferred embodiment, the injection ratio KIR is 10%-20%.

[0073] Specifically, setting the injection ratio KIR can clearly define the starting point of the test, and setting the injection ratio KIR provides a basis for subsequent calculation of the flow rate of the calcium-based clay mineral slurry and the sodium silicate solution per unit time. Based on industry experience, setting the injection ratio KIR to 10%-20% can reduce the number of invalid tests and avoid entering an obviously incorrect range at the beginning. Only fine tuning within a certain range is needed, which saves time, material, and labor costs compared to trial and error from zero.

[0074] In a preferred embodiment, the number N of the mixing containers 1 is 1-4.

[0075] Specifically, the number of the mixing containers 1 is 1, which can perform the related operation of the shield muck improvement. When the number of the mixing containers 1 is multiple, the injection efficiency of the calcium-based clay mineral-sodium silicate mixed slurry can be improved. However, the limitation of the actual operation space should also be considered. Therefore, the number N of the mixing containers 1 is determined to be 1-4. When the number of the mixing containers 1 is multiple, the mixing containers 1 are dispersed to different positions of the soil bin 5, so as to facilitate the uniform mixing of the calcium-based clay mineral-sodium silicate mixed slurry and the shield muck in the soil bin 5.

[0076] In a preferred embodiment, the preset time period is 1-5 minutes.

[0077] Specifically, the preset time period is set to 1-5 minutes, which is mainly determined according to the initial setting time of the calcium-based clay mineral-sodium silicate mixed slurry and the pumping time of the mixed slurry. According to this time interval, the sample (the mixture of the calcium-based clay mineral-sodium silicate mixed slurry and the shield muck) is taken from the belt conveyor of the shield machine every 1-5 minutes, which can not only ensure that the pumping device 4 has successfully delivered the calcium-based clay mineral-sodium silicate mixed slurry into the soil bin 5, but also ensure that the initial setting process of the calcium-based clay mineral-sodium silicate mixed slurry occurs in the soil bin 5, rather than in the mixing container 1 in advance, thereby avoiding the problem of blockage of the mixing container 1.

[0078] In a preferred embodiment, the pumping pressure of the calcium-based clay mineral slurry in the first raw material bin 2 and the sodium silicate solution in the second raw material bin 3 into the mixing container 1 is equal, and both are greater than the pressure inside the soil bin 5 of the shield machine.

[0079] Specifically, the pumping pressure of the calcium-based clay mineral slurry in the first raw material bin 2 and the sodium silicate solution in the second raw material bin 3 into the mixing container 1 is equal, which can ensure that the flow of the two raw materials is stable and the ratio is accurate during entering the mixing container 1, thereby avoiding that one kind of raw material is delivered too fast or too slow due to the pressure difference, and further affecting the final performance of the mixed slurry, and providing protection for the subsequent muck improvement effect. The pumping pressure of both is greater than the pressure inside the soil bin 5 of the shield machine, so that the calcium-based clay mineral slurry and the sodium silicate solution can enter the soil bin 5 and mix with the shield muck under the action of the pressure, and at the same time, the backflow of the muck or gas in the soil bin 5 to the mixing container 1 can be prevented, which can not only ensure the stability of the delivery process of the calcium-based clay mineral slurry and the sodium silicate solution, but also avoid the pollution and blockage of the raw materials to the delivery pipeline, thereby ensuring the normal progress of the shield construction.

[0080] The application mixes the calcium-based clay mineral slurry and the sodium silicate solution according to a preset volume ratio to prepare a calcium-based clay mineral-sodium silicate mixed slurry, injects the mixed slurry into the soil chamber of the shield machine and mixes the mixed slurry with the shield muck in the soil chamber, and the good bonding characteristics of the mixed slurry can tightly mix the shield muck and the underground water, wrap the large shield muck in the slurry, and aggregate the large and dispersed shield muck into a slurry with better overall flowability, so that the shield muck can be smoothly discharged through the screw conveyor, and the problem of screw machine blockage caused by the accumulation of shield muck at the bottom of the soil chamber is avoided. At the same time, the fine shield muck will not be lost and can fully fill the pores of the large shield muck, effectively reducing the permeability coefficient of the shield muck, thereby preventing gushing accidents and ultimately ensuring the stability of the working face. The unimproved coarse shield muck is dispersed and hard, and the rotation of the cutter head of the shield machine needs to overcome the extrusion, friction and large muck blockage during tunneling. The improved shield muck is paste-like and has uniform stress, so that the friction and resistance that the cutter head needs to overcome are reduced, thereby prolonging the service life of the cutter head of the shield machine.

[0081] For the convenience of those skilled in the art, further, the working process of the shield muck improvement method for water-rich coarse granular stratum provided by the application is as follows:

[0082] The water and the calcium-based clay mineral powder are added to the first raw material bin 2 according to a preset mass ratio of 3:1 and stirred to form a calcium-based clay mineral slurry, and a sodium silicate solution is added to the second raw material bin 3; the cutter head cutting soil volume Vs per unit time is calculated according to the shield machine excavation diameter D, the tunneling speed v and the coarse granular stratum loose coefficient K; the calcium-based clay mineral-sodium silicate mixed slurry unit time flow q is determined according to the cutter head cutting soil volume Vs per unit time and the injection ratio KIR of 10% to 20%; the clay slurry unit time flow q is calculated according to the volume ratio M of 10:1 to 7:1 of the clay slurry and the sodium silicate solution, the number N of the mixing containers 1 and the calcium-based clay mineral-sodium silicate mixed slurry unit time flow q K and the sodium silicate solution unit time flow q G ; the shield machine is started, and the pumping device 4 pumps the clay slurry unit time flow q K and the sodium silicate solution unit time flow q GThe raw materials of the first raw material bin 2 and the second raw material bin 3 are simultaneously pumped into the mixing container 1 to form a calcium-based clay mineral-sodium silicate mixed slurry at a pumping pressure equal to and greater than the internal pressure of the soil bin 5, and then the calcium-based clay mineral-sodium silicate mixed slurry is injected into the soil bin 5 to mix with the spoil; the mixture of the calcium-based clay mineral-sodium silicate mixed slurry and the shield spoil on the belt conveyor of the shield machine is subjected to a field slump test, and the injection ratio KIR is adjusted according to the slump value (if the slump is less than 15 cm, the injection ratio KIR is increased by 5%, and if the slump is greater than 20 cm, the injection ratio KIR is decreased by 5%, and the test is repeated), so that the slump value is greater than or equal to 15 cm and less than or equal to 20 cm.

[0083] The calcium-based clay mineral slurry and the sodium silicate solution are mixed at a predetermined volume ratio to prepare a calcium-based clay mineral-sodium silicate mixed slurry, which is injected into the soil bin of the shield machine and mixed with the shield spoil in the bin. Through the good bonding performance of the mixed slurry, the shield spoil can be closely combined with groundwater, not only wrapping large pieces of shield spoil inside the slurry, but also making the originally dispersed and easily jammed large-particle shield spoil aggregate into a better-slipping slurry, which is then smoothly discharged through the screw conveyor, solving the problem of screw jamming caused by the accumulation of shield spoil at the bottom of the soil bin. At the same time, fine-particle shield spoil does not flow away and can fully fill the pores between large pieces of shield spoil, effectively reducing the permeability coefficient of shield spoil, thereby avoiding gushing accidents and ultimately ensuring the stability of the working face. In addition, unimproved coarse-particle shield spoil is dispersed and hard, and the cutter head rotation needs to overcome the extrusion, friction between particles, and blockage of large pieces of spoil during shield tunneling. After improvement, the shield spoil is in a paste-like state, with uniform internal stress distribution, and the friction and resistance required to be overcome during cutter head rotation are greatly reduced, which also prolongs the service life of the cutter head of the shield machine.

[0084] The principles and implementation modes of the present application are described by applying specific examples in this paper, and the above examples are only used to help understand the method and its core idea. The above description is only the preferred embodiment of the present application. It should be noted that due to the limitation of language expression, there are infinite specific structures, and for ordinary skilled persons in the technical field, some improvements, refinements or changes can be made without departing from the principles of the present application, and the above technical features can be combined in an appropriate manner; these improvements, refinements, changes or combinations, or the direct application of the inventive concept and technical solution to other occasions without improvement, shall be regarded as the protection scope of the present application.

Claims

1. A method for improving shield tunnel excavated soil in water-rich, coarse-grained strata, characterized in that, include: S1: Calculate the volume of soil Vs cut by the tunnel boring machine cutterhead per unit time based on the tunneling diameter D, tunneling speed v, and loosening coefficient K of the coarse-grained stratum. S2: Calculate the flow rate q of the calcium-based clay mineral-sodium silicate mixed slurry per unit time based on the volume of soil cut by the tunnel boring machine cutterhead Vs and the injection ratio KIR per unit time. S3: Based on the preset volume ratio M of calcium-based clay mineral slurry to sodium silicate solution, the number of mixing containers (1) N, and the flow rate q of the calcium-based clay mineral-sodium silicate mixed slurry per unit time, calculate the flow rate q of the calcium-based clay mineral slurry per unit time in a single mixing container (1). K And the flow rate q of the sodium silicate solution per unit time in a single mixing container (1). G The mixing container (1) is used to mix the calcium-based clay mineral slurry input from the first raw material silo (2) and the sodium silicate solution input from the second raw material silo (3); S4: Start the tunnel boring machine, pumping device (4) according to the flow rate q of the calcium-based clay mineral slurry per unit time K And the flow rate q of sodium silicate solution per unit time G At the same time, the calcium-based clay mineral slurry in the first raw material bin (2) and the sodium silicate solution in the second raw material bin (3) are pumped into the mixing container (1) to form a calcium-based clay mineral-sodium silicate mixed slurry, and the calcium-based clay mineral-sodium silicate mixed slurry is injected into the soil bin (5) of the shield machine to mix with the shield slag. S5: Every preset time interval, take a mixture of calcium-based clay mineral-sodium silicate slurry and shield excavated soil from the conveyor belt of the tunnel boring machine and conduct an on-site slump test. Adjust the injection ratio KIR according to the slump value so that the slump value is greater than or equal to 15cm and less than or equal to 20cm. The step of adjusting the injection ratio KIR according to the slump value to make the slump value greater than or equal to 15 cm and less than or equal to 20 cm includes: If the slump value is less than 15 cm, then increase the injection ratio by 5% and repeat S2-S5 until the slump value is greater than or equal to 15 cm and less than or equal to 20 cm. If the slump value is greater than 20 cm, reduce the injection ratio by 5% and repeat S2-S5 until the slump value is greater than or equal to 15 cm and less than or equal to 20 cm.

2. The method for improving shield tunnel excavation soil in water-rich, coarse-grained strata according to claim 1, characterized in that, Prior to S1, the method further includes: According to the preset mass ratio of water to calcium-based clay mineral powder, calcium-based clay mineral powder and water are added to the first raw material silo (2). Stir the calcium-based clay mineral powder and water in the first raw material silo (2) until a calcium-based clay mineral slurry is formed; Add sodium silicate solution to the second raw material silo (3).

3. The method for improving shield tunnel excavation soil in water-rich, coarse-grained strata according to claim 2, characterized in that, The preset mass ratio of water to calcium-based clay mineral powder is 3:

1.

4. The method for improving shield tunnel excavated soil in water-rich, coarse-grained strata according to claim 1, characterized in that, The preset volume ratio M of the calcium-based clay mineral slurry to the sodium silicate solution is 10:1 to 7:

1.

5. The method for improving shield tunnel excavated soil in water-rich, coarse-grained strata according to claim 1, characterized in that, The injection ratio KIR is 10%~20%.

6. The method for improving shield tunnel excavated soil in water-rich, coarse-grained strata according to claim 1, characterized in that, The number N of the mixing containers (1) is 1 to 4.

7. The method for improving shield tunnel excavated soil in water-rich, coarse-grained strata according to claim 1, characterized in that, The preset time period is 1 to 5 minutes.

8. The method for improving shield tunnel excavated soil in water-rich, coarse-grained strata according to claim 1, characterized in that, The pumping pressures of the calcium-based clay mineral slurry in the first raw material silo (2) and the sodium silicate solution in the second raw material silo (3) into the mixing container (1) are equal and both are greater than the pressure inside the soil chamber (5) of the tunnel boring machine.

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