Construction process of anchor rod for sand pebble stratum under water level of foundation pit engineering

Abstract

The application provides a construction process for an anchor rod in a sand pebble stratum below a water level of a foundation pit engineering, comprising the following steps: S10, installing a sealing device at an orifice; S20, advanced drilling of a sleeve; S30, injecting cement slurry through a drill rod until the cement slurry flows out of the orifice; S40, pulling out the drill rod section by section; S50, assembling a steel strand assembly; S60, inserting the steel strand assembly into the sleeve; S70, pulling out the sleeve and sealing grouting; S80, sealing the orifice with mastic; S90, after the cement slurry is finally cured, performing pressure grouting through a pressure grouting pipe; S100, after a preset number of days, tensioning the steel strand assembly; and S110, performing filling grouting through a filling grouting pipe. The technical scheme of the application solves the problem that water and sand are prone to gushing during the process of orifice opening, drilling, steel strand assembly installation and tensioning in the sand pebble stratum below the underground water level in the prior art.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of foundation pit engineering, in particular to a construction process of anchor rod in sand and pebble stratum below water level of foundation pit engineering. BACKGROUND

[0002] In the foundation pit engineering, a commonly used supporting method is continuous wall (pile) + anchor rod.

[0003] The construction process of the anchor rod includes the following steps: drilling by using double-pipe double-rotation process to a designed length, pulling out the drill rod, installing the steel strand, grouting, pulling out the sleeve pipe, maintenance and tensioning.

[0004] When the curtain water isolation method is used in the foundation pit engineering, the underground water level inside and outside the foundation pit is often quite different. In this case, if the anchor rod is constructed in the sand and pebble stratum below the underground water level, water and sand will easily gush out during the processes of hole opening, drilling, steel strand assembly installation and tensioning. SUMMARY

[0005] The main purpose of the present application is to provide a construction process of anchor rod in sand and pebble stratum below water level of foundation pit engineering, so as to solve the problem that water and sand will easily gush out when the anchor rod is constructed in the sand and pebble stratum below the underground water level.

[0006] To achieve the above object, the present application provides a construction process for anchor rod in sandy pebble stratum under water level of foundation pit engineering, comprising: step S10: drilling preparation step, comprising: step S11: setting a blocking device at the orifice of the embedded steel pipe on the underground continuous wall of the foundation pit; step S12: placing the casing and the drill rod located in the casing into the steel pipe, and the blocking device blocks the gap between the casing and the steel pipe; step S20: drilling, drilling into the multi-section drill rod and the multi-section casing until the drilling reaches the design length; step S30: injecting cement slurry through the drill rod until the cement slurry flows out of the orifice; step S40: pulling out the drill rod section by section; step S50: assembling the steel strand assembly, the step of assembling the steel strand assembly comprising connecting the blocking grouting pipe, the pressure grouting pipe and the filling grouting pipe to the plurality of steel strands, and threading the supplementary grouting pipe between the plurality of steel strands; step S60: inserting the steel strand assembly into the casing, wherein the distal end of the pressure grouting pipe comprises a plurality of grouting holes arranged along the length direction of the pressure grouting pipe, after the steel strand assembly is inserted into the casing, the distance between the end of the blocking grouting pipe and the soil-facing surface of the underground continuous wall is between 4m and 10m, the distance between the grouting hole of the pressure grouting pipe close to the orifice and the hole bottom of the drilling is between 4m and 6m, the distance between the end of the filling grouting pipe and the soil-facing surface of the underground continuous wall is between 1m and 3m, and the distance between the end of the supplementary grouting pipe and the hole bottom of the drilling is not more than 500mm; step S70: pulling out the casing section by section and performing blocking grouting; step S80: blocking the orifice using mastic; step S90: after the cement slurry is finally set, performing pressure grouting through the pressure grouting pipe; step S100: after a preset number of days, tensioning the steel strand assembly; and step S110: performing filling grouting through the filling grouting pipe, wherein the grouting liquid of the filling grouting pipe is double-liquid slurry.

[0007] In one embodiment, the length of the first section of casing is greater than the length of the first section of drill rod, so that the end of the first section of casing is located in front of the end of the first section of drill rod.

[0008] In one embodiment, the distance between the end of the first section of casing and the end of the first section of drill rod is between 50mm and 500mm.

[0009] In one embodiment, when the drilling reaches the design length, the casing is forwardly abutted, so that the end of the first section of casing is inserted into the undisturbed sandy layer.

[0010] In one embodiment, step S40 further comprises: supplementing the cement slurry into the drilling through the drill rod while pulling out the drill rod.

[0011] In one embodiment, step S70 further comprises: supplementing the cement slurry into the drilling through the supplementary grouting pipe while pulling out the casing.

[0012] In one embodiment, step S70 further comprises: when the first grouting opportunity occurs, injecting the double liquid slurry into the borehole through the blocking grouting pipe, the first grouting opportunity comprising: when the casing is pulled outwards, the cement slurry is squeezed out of the orifice; or the length of the casing in the borehole is shorter than the length of the blocking grouting pipe.

[0013] In one embodiment, step S70 further comprises: after the first grouting through the blocking grouting pipe is completed, pulling out the casing while injecting the cement slurry through the blocking grouting pipe until the casing is pulled out completely.

[0014] In one embodiment, step S70 further comprises: after the casing is pulled out completely, pulling out the supplementary grouting pipe.

[0015] In one embodiment, when the supplementary grouting pipe is pulled outwards, the cement slurry is supplemented into the borehole while the supplementary grouting pipe is pulled out.

[0016] In one embodiment, the step of assembling the steel strand assembly further comprises: installing the plurality of steel strands on a bracket, the bracket having a through hole, and the supplementary grouting pipe is inserted between the plurality of steel strands through the through hole.

[0017] By applying the technical solution of the present application, before drilling, the blocking device is installed at the orifice, and the blocking device can block the gap between the casing and the steel pipe, so that after the anchor rod drilling machine opens the hole, the sand soil behind the underground continuous wall cannot flow out of the orifice along the gap between the casing and the steel pipe, thereby avoiding the phenomenon of "water and sand gushing during the opening and drilling process" mentioned in the background art, and solving the problem of water and sand gushing during the opening and drilling process in the construction of the anchor rod in the sand and gravel stratum below the groundwater level in the prior art.

[0018] In addition to the purposes, features and advantages described above, the present application has other purposes, features and advantages. The present application will be further described below with reference to the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0019] The drawings accompanying the specification of the present application serve to provide further understanding of the present application, and the illustrative embodiments of the present application and their descriptions serve to explain the present application, and do not constitute an improper limitation on the present application. In the drawings:

[0020] Figure 1 A flowchart showing an embodiment of the construction process for the anchor rod in the sand and gravel stratum below the water level of the foundation pit engineering according to the present application is shown;

[0021] Figure 2 A schematic diagram of the working condition corresponding to step S20 of the construction process of Figure 1 is shown;

[0022] Figure 3 A schematic diagram of the working condition corresponding to step S30 of the construction process ofFigure 2 A partial enlarged diagram of the working condition schematic diagram;

[0023] Figure 4 Shown Figure 1 A schematic diagram of the main view of the blocking device used in the construction process;

[0024] Figure 5 Shown Figure 1 Schematic diagram of the working condition corresponding to the completion of step S30 of the construction process;

[0025] Figure 6 Shown Figure 1 Schematic diagram of the working condition corresponding to the completion of step S60 of the construction process;

[0026] Figure 7 Shown Figure 1 Schematic diagram of the working condition during the first grouting in step S70 of the construction process;

[0027] Figure 8 Shown Figure 1 A schematic diagram of the working condition during subsequent grouting in step S70 of the construction process;

[0028] Figure 9 Shown Figure 1 Schematic diagram of the working condition corresponding to the completion of step S80 of the construction process;

[0029] Figure 10 Shown Figure 1 Schematic diagram of the working condition corresponding to the completion of step S90 of the construction process;

[0030] Figure 11 Shown Figure 1 A schematic diagram of the working condition corresponding to the completion of step S110 of the construction process; and

[0031] Figure 12 Shown Figure 1 Cross-section of the steel strand assembly used in the construction process.

[0032] The above drawings include the following reference numerals:

[0033] 1. Underground continuous wall; 2. Drilling; 10. Drill rod; 20. Casing; 30. Steel pipe; 40. Sealing device; 41. Rubber ring; 42. Steel ring plate; 43. Expansion bolt; 50. Steel strand assembly; 51. Grouting pipe; 52. Sealing grouting pipe; 53. Pressure grouting pipe; 54. Filling grouting pipe; 55. Steel strand; 56. Bracket; 561. Perforation; 60. Cement. DETAILED DESCRIPTION

[0034] It should be noted that the embodiments and features of the present application can be combined with each other, if there is no conflict. The present application will be described in detail below with reference to the accompanying drawings and embodiments.

[0035] In order to make the technical personnel of the present technology better understand the present application scheme, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor should belong to the scope of protection of the present application.

[0036] It should be noted that the terms "first", "second" and the like in the specification and claims of the present application and the above-described drawings are used to distinguish similar objects, and do not necessarily have to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged under appropriate circumstances, so that the embodiments of the application described herein can be implemented. 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 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.

[0037] It should be noted that the terms used herein are only for the purpose of describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form unless the context clearly indicates otherwise, and furthermore, it should be understood that when the terms "comprise" and / or "include" are used in the specification, there is a feature, step, operation, device, component and / or combination thereof.

[0038] As Figures 1 to 12As shown, the anchor rod construction process for the sand and pebble stratum below the water level of the foundation pit engineering of the embodiment comprises: step S10: a drilling preparation step, the drilling preparation step comprises: step S11: setting a plugging device 40 at the orifice of a steel pipe 30 pre-buried on the underground continuous wall 1 of the foundation pit; step S12: placing a casing pipe 20 and a drill rod 10 located in the casing pipe 20 into the steel pipe 30, and the plugging device 40 plugs the gap between the casing pipe 20 and the steel pipe 30; step S20: drilling, drilling into the multi-section drill rod 10 and the multi-section casing pipe 20 until the drilling 2 reaches the designed length; step S30: injecting cement slurry through the drill rod 10 until the cement slurry flows out of the orifice; step S40: pulling out the drill rod 10 section by section; step S50: assembling a steel strand assembly 50, the step of assembling the steel strand assembly 50 comprises connecting a pressure grouting pipe 53 and a filling grouting pipe 54 to the plurality of steel strands 55; step S60: inserting the steel strand assembly 50 into the casing pipe 20, wherein the distal end of the pressure grouting pipe 53 comprises a plurality of grouting holes arranged along the length direction thereof, and the distance between the grouting hole of the pressure grouting pipe 53 close to the orifice and the hole bottom of the drilling 2 is between 4m and 6m (position requirement, preferably, the above distance is 5m) after the steel strand assembly 50 is inserted into the casing pipe 20, and the distance between the end of the filling grouting pipe 54 and the earth-facing surface of the underground continuous wall 1 is between 1m and 3m (position requirement, preferably 2m); step S70: pulling out the casing pipe 20 section by section; step S80: using mastic 60 to plug the orifice; step S90: after the cement slurry is finally set, pressure grouting is performed through the pressure grouting pipe 53; step S100: after a preset number of days, the steel strand assembly 50 is tensioned; step S110: filling grouting is performed through the filling grouting pipe 54, wherein the grouting liquid of the filling grouting pipe 54 is double liquid slurry (cement and water glass slurry, the double liquid slurry forms paste-like slurry after being injected).

[0039] By applying the technical solution of the embodiment, before drilling, the plugging device is installed at the orifice, which can plug the gap between the casing pipe 20 and the steel pipe 30, so that after the anchor rod drilling machine opens the hole, the sand behind the underground continuous wall 1 cannot flow out of the orifice along the gap between the casing pipe 20 and the steel pipe 30, thereby avoiding the phenomenon of “extremely easy to appear water and sand gushing during the hole opening and drilling process” mentioned in the background art, and solving the problem of “extremely easy to appear water and sand gushing during the hole opening and drilling process” in the prior art when the anchor rod is constructed in the sand and pebble stratum below the groundwater level. In addition, by applying the technical solution of the embodiment, at least the following three effects are achieved: first, after the cement slurry is finally set (usually after 24 hours of grouting), the grouting is performed again through the pressure grouting pipe 53, which can compact the disturbed sand layer and improve the pullout resistance of the anchor rod, and the pullout resistance can be improved by about 30% ( Figure 10C in the figure represents the working condition after pressure grouting. Second, due to the anchor rod after coagulation, cracks may be formed after tensioning, and water and sand near the orifice may flow out through the cracks under pressure. Therefore, by applying the technical solution of the embodiment, filling grouting pipe 54 is used for filling grouting after tensioning, which can fill the cracks formed by cracking, thereby preventing water and sand near the orifice from flowing out of the gap formed after the steel strand is tensioned. Figure 11 D in the figure represents the working condition after filling grouting. Third, after the casing 20 is pulled out and the double-liquid slurry grouting is completed, the orifice is blocked using the mastic 60, which can prevent slurry loss and water and sand leakage.

[0040] It should be noted that in the embodiment, the drill rod 10 and the casing 20 are driven by an anchor rod drill, and the anchor rod drill uses a double-tube double-rotation process. Figure 2 L in the figure is the excavation surface.

[0041] It should also be noted that, as shown in Figure 3 and Figure 4 In the embodiment, the sealing device 40 includes a rubber ring 41, a steel ring plate 42, and an expansion bolt 43, and the rubber ring 41 and the steel ring plate 42 are provided with corresponding mounting holes. The expansion bolt 43 is arranged in the mounting hole and is driven into the underground continuous wall 1, so that the steel ring plate 42 presses the rubber ring 41 on the underground continuous wall 1. The middle part of the rubber ring 41 and the steel ring plate 42 are provided with avoiding holes for avoiding the casing 20, and the hole diameter of the avoiding hole of the rubber ring 41 is smaller than the hole diameter of the avoiding hole of the steel ring plate 42 and the outer diameter of the casing 20. The rubber ring 41 is slightly pressed on the casing 20, which plays a sealing role while not affecting the movement of the casing 20.

[0042] Since the embodiment is for constructing an anchor rod in a sandy pebble stratum, the stratum soil is not dense, and after the drill rod 10 is pulled out, the end of the casing 20 is easy to be filled with sandy pebbles, which causes the subsequent steel strand to be unable to be installed in place, thereby finally affecting the locking force of the anchor rod. In order to solve the above problem, as shown in Figure 2 In the embodiment, the length of the first section of the casing 20 is greater than the length of the first section of the drill rod 10, so that the end of the first section of the casing 20 is located in front of the end of the first section of the drill rod 10. The above arrangement makes the front end of the casing have a casing advance section, that is, the end of the drill rod 10 is located behind the casing advance section. In this way, during the drilling process, the disturbed soil around the end of the drill rod 10 will impact the inner wall of the casing advance section, thereby greatly reducing the impact on the stratum during drilling, thereby avoiding reaming or hole collapse (avoiding the inflow of sandy pebbles into the hole), ensuring that the subsequent steel strand can be installed in place, and finally ensuring the locking force of the anchor rod.

[0043] In the embodiment, the distance between the end of the first section of casing 20 and the end of the first section of drill rod 10 is between 50mm and 500mm. The distance of the casing advance section needs to be determined according to the geological conditions and the equipment capacity. Specifically, the looser the geology, the longer the distance of the casing advance section can be, and the denser the geology, the shorter the distance of the casing advance section needs to be. The stronger the equipment capacity, the longer the distance of the casing advance section can be, and the weaker the equipment capacity, the shorter the distance of the casing advance section needs to be.

[0044] In the embodiment, when the borehole 2 reaches the designed length, the casing 20 is advanced to insert the end of the first section of casing 20 into the undisturbed sand layer. Specifically, when the borehole 2 reaches the designed length, the casing 20 can be advanced by the anchor drill machine, and as the casing 20 advances, a part of the sand will enter the front end of the casing 20 to form a structure similar to a plug, which makes the borehole 2 less likely to collapse, thus ensuring that the subsequent steel strand can be installed in place and ultimately ensuring the locking force of the anchor rod.

[0045] Since the drill rod 10 occupies a certain volume in the borehole 2, when the multiple sections of drill rod 10 are completely pulled out of the borehole, the slurry cannot fill the borehole 2, resulting in poor quality of the set anchor rod. To solve the above problem, as shown in Figure 5 In the embodiment, the step S40 further includes supplementing the cement slurry into the borehole 2 through the drill rod 10 while pulling out the drill rod 10. The above step can timely fill the slurry, ensuring that the borehole 2 can be filled with the cement slurry when the multiple sections of drill rod 10 are completely pulled out of the borehole, thereby ensuring the quality of the anchor rod.

[0046] Similarly, since the casing 20 occupies a certain volume in the borehole 2, as the casing 20 is pulled out, the liquid level in the borehole 2 drops, and the slurry cannot fill the borehole, resulting in poor quality of the set anchor rod. To solve the above problem, in the embodiment, the step of assembling the steel strand assembly 50 further includes inserting the slurry supplementing pipe 51 between the multiple steel strands 55, and after the steel strand assembly 50 is inserted into the casing 20, the end of the slurry supplementing pipe 51 is not more than 500mm from the bottom of the borehole 2; and the step S70 further includes supplementing the cement slurry into the borehole 2 through the slurry supplementing pipe 51 while pulling out the casing 20. The above steps enable the cement slurry to be supplemented into the borehole 2 in time as the casing 20 is pulled out, so as to fill the volume occupied by the casing 20, thereby ensuring the quality of the set anchor rod.

[0047] As shown in Figures 6 to 8 and Figure 12As shown, in the present embodiment, the step of assembling the steel strand assembly 50 further comprises connecting the blocking grouting pipe 52 to the plurality of steel strands 55, and the distance between the end of the blocking grouting pipe 52 and the soil-facing surface of the underground continuous wall 1 is between 4m and 10m after the steel strand assembly 50 is inserted into the casing 20; the step S70 further comprises: determining whether the first grouting opportunity occurs, and when the first grouting opportunity occurs, injecting the double-liquid slurry (cement-water glass slurry, the double-liquid slurry forms a paste-like slurry after being injected, which is equivalent to a liquid soft plug) into the borehole 2 through the blocking grouting pipe 52; the first grouting opportunity includes: when the casing 20 is pulled out, the cement slurry is squeezed out of the orifice; or, the length of the casing 20 in the borehole 2 is shorter than the length of the blocking grouting pipe 52. The above steps serve to inject the slurry through the blocking grouting pipe 52 when the cement slurry is squeezed out of the orifice by water pressure during the pulling-out process of the casing 20 or when the casing 20 is pulled out by a predetermined length, which is equivalent to injecting a liquid soft plug at the position of the borehole close to the orifice, thereby achieving the blocking effect and preventing the cement slurry and water and sand in the formation from flowing out of the casing orifice. Figure 7 A in the above figure indicates the working condition after the first grouting. It should be noted that the length of the blocking grouting pipe 52 is not longer than the length of the non-anchoring section.

[0048] In the present embodiment, after the first grouting through the blocking grouting pipe 52 is completed, the casing 20 is pulled out while continuously grouting through the blocking grouting pipe 52 until the casing 20 is completely pulled out. The above steps enable the double-liquid slurry to fill the volume occupied by the casing 20, thereby ensuring the quality of the set anchor rod. Figure 8 B in the above figure indicates the working condition of subsequent grouting

[0049] It should be noted that when the blocking grouting pipe 52 is activated, the grouting through the grouting pipe 51 is stopped. If subsequent grouting is required, the grouting pipe 51 can be used for grouting.

[0050] In the present embodiment, after the casing 20 is completely pulled out, the grouting pipe 51 is pulled out. The above steps enable the grouting pipe 51 to be reused, thereby reducing costs.

[0051] Similarly, since the grouting pipe 51 occupies a certain volume in the borehole 2, as the grouting pipe 51 is pulled out, the liquid level in the borehole 2 drops, and the slurry will not be able to fill the borehole, resulting in poor quality of the set anchor rod. In the present embodiment, as the grouting pipe 51 is pulled out, the cement slurry is supplemented into the borehole 2. The above steps enable the cement slurry to be supplemented into the borehole 2 in a timely manner as the grouting pipe 51 is pulled out, so that the cement slurry fills the volume occupied by the grouting pipe 51, thereby ensuring the quality of the set anchor rod.

[0052] In the embodiment, the step of assembling the steel strand assembly 50 further comprises: installing the plurality of steel strands 55 on the bracket 56, the bracket 56 having a through hole 561, the grouting pipe 51 being inserted between the plurality of steel strands 55 through the through hole 561. The above structure makes the grouting pipe 51 convenient to pull out, and facilitates the operation of the construction personnel.

[0053] It should be noted that, in the embodiment, the plugging grouting pipe 52, the pressure grouting pipe 53 and the filling grouting pipe 54 are actually connected (such as bundled connection and the like) on the plurality of steel strands 55, and then the grouting pipe 51 is inserted between the plurality of steel strands 55 through the through hole 561 of the bracket to form the steel strand assembly 50. Wherein, after the steel strand assembly 50 is inserted into the casing 20, the end of the filling grouting pipe 54, the end of the plugging grouting pipe 52 and the end of the pressure grouting pipe 53 are arranged from front to back in order, and meet the above position requirements.

[0054] From the above description, it can be seen that the above-mentioned embodiments of the present application achieve the following technical effects:

[0055] Ensure the safe and smooth construction of the anchor rod in the complex and adverse stratum such as high water head difference, soft sand and the like, and ensure the construction quality of the anchor rod.

[0056] Unless specifically stated otherwise, the relative arrangements of parts and steps, numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the application. At the same time, it should be understood that the sizes of the various parts shown in the drawings are not drawn in accordance with the actual proportional relationship. The technology, methods and equipment known to those skilled in the relevant art can not be discussed in detail, but in appropriate cases, the technology, methods and equipment should be considered as part of the authorized specification. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, and not as a limitation. Therefore, other examples of exemplary embodiments can have different values. It should be noted that similar reference numbers 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 discussed in subsequent drawings.

[0057] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used herein to describe the spatial positional relationship of a device or feature to other devices or features as shown in the figures. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figures. For example, if the device in the drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0058] In the description of the present invention, it should be understood that the directions or positional relationships indicated by directional words such as "front, back, up, down, left, right", "horizontal, vertical, perpendicular, horizontal" and "top, bottom" are usually based on the directions or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description. Unless otherwise specified, these directional words do not indicate or imply that the device or element referred to must have a specific direction or be constructed and operated in a specific direction. Therefore, they cannot be understood as limiting the scope of protection of the present invention; the directional words "inside and outside" refer to the inside and outside relative to the outline of each component itself.

[0059] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A process for anchoring in sand and gravel strata below the water level in foundation pit engineering, characterized in that: Comprising: Step S10: a pre-drilling preparation step, the pre-drilling preparation step comprising: Step S11: providing a blocking device (40) at an orifice of a steel pipe (30) pre-buried on a diaphragm wall (1) of a foundation pit; Step S12: placing a casing pipe (20) and a drill pipe (10) located inside the casing pipe (20) into the steel pipe (30), the blocking device (40) blocking a gap between the casing pipe (20) and the steel pipe (30); Step S20: drilling, drilling into multiple sections of the drill pipe (10) and multiple sections of the casing pipe (20) until the drill hole (2) reaches a designed length; Step S30: injecting cement slurry through the drill pipe (10) until the cement slurry flows out of the orifice; Step S40: pulling out the drill pipe (10) section by section; Step S50: assembling a steel strand assembly (50), the step of assembling the steel strand assembly (50) comprising connecting a blocking grouting pipe (52), a pressure grouting pipe (53), and a filling grouting pipe (54) to a plurality of steel strands (55), and threading a grout supplement pipe (51) between the plurality of steel strands (55); Step S60: inserting the steel strand assembly (50) into the casing pipe (20), wherein a distal end of the pressure grouting pipe (53) comprises a plurality of grouting holes spaced along a length direction of the pressure grouting pipe (53), after the steel strand assembly (50) is inserted into the casing pipe (20), a distance between an end of the blocking grouting pipe (52) and a soil-facing surface of the diaphragm wall (1) is between 4m and 10m, a distance between a grouting hole of the pressure grouting pipe (53) close to the orifice and a hole bottom of the drill hole (2) is between 4m and 6m, a distance between an end of the filling grouting pipe (54) and the soil-facing surface of the diaphragm wall (1) is between 1m and 3m, and a distance between an end of the grout supplement pipe (51) and the hole bottom of the drill hole (2) is not more than 500mm; Step S70: pulling out the casing pipe (20) section by section, supplementing cement slurry into the drill hole (2) through the grout supplement pipe (51) while the casing pipe (20) is being pulled out, and pulling out the grout supplement pipe (51) after the casing pipe (20) is completely pulled out; When a first grouting opportunity occurs, injecting double-liquid slurry into the drill hole (2) through the blocking grouting pipe (52), the first grouting opportunity comprising: When the casing pipe (20) is pulled outwards, cement slurry is squeezed out of the orifice; or, A length of the casing pipe (20) in the drill hole (2) is shorter than a length of the blocking grouting pipe (52); Step S80: blocking the orifice using mastic (60); Step S90: after the cement slurry is finally set, performing pressure grouting through the pressure grouting pipe (53); Step S100: after a preset number of days, tensioning the steel strand assembly (50); Step S110: performing filling grouting through the filling grouting pipe (54), wherein a grouting liquid of the filling grouting pipe (54) is double-liquid slurry.

2. The construction process for the anchor rod in the sand-pebble stratum below the water level of the foundation pit engineering according to claim 1, characterized in that, The length of the first section of the casing (20) is greater than the length of the first section of the drill pipe (10) so that the end of the first section of the casing (20) is located in front of the end of the first section of the drill pipe (10).

3. The construction process for the anchor rod in the sand-pebble stratum below the water level of the foundation pit engineering according to claim 2, characterized in that, The distance between the end of the first section of the casing (20) and the end of the first section of the drill pipe (10) is between 50mm and 500mm.

4. The construction process for the anchor rod in the sand-pebble stratum below the water level of the foundation pit engineering according to claim 2, characterized in that, When the borehole (2) reaches the design length, the casing (20) is advanced to insert the end of the first section of the casing (20) into the undisturbed sand layer.

5. The construction process for the anchor rod in the sand-pebble stratum below the water level of the foundation pit engineering according to claim 1, characterized in that, The step S40 further comprises: The cement slurry is supplemented into the borehole (2) through the drill pipe (10) as the drill pipe (10) is pulled out.

6. The construction process for the anchor rod in the sand-pebble stratum below the water level of the foundation pit engineering according to claim 1, characterized in that, The step S70 further comprises: after the first time of grouting through the grouting pipe (52) is completed, the casing (20) is pulled out while grouting through the grouting pipe (52) until the casing (20) is completely pulled out.

7. The process for construction of anchor in sand-pebble stratum under water level of foundation pit engineering according to claim 1, characterized in that, When the grouting pipe (51) is pulled out, the cement slurry is supplemented into the borehole (2) as the grouting pipe (51) is pulled out.

8. The process for construction of anchor in sand-pebble stratum under water level of foundation pit engineering according to claim 1, characterized in that, The step of assembling the steel strand assembly (50) further comprises: a plurality of the steel strands (55) are installed on a support (56) having a perforation (561) through which the grouting pipe (51) penetrates between the plurality of the steel strands (55).

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