Deep foundation pit survey lofting method

Abstract

The invention belongs to the technical field of foundation pit survey lofting, and relates to a deep foundation pit survey lofting method which comprises the steps that four reference points are determined on the bottom face of a deep foundation pit, the plane positions of the four reference points are consistent with the plane positions of sideline angular points formed after a theoretical sideline of a to-be-constructed bearing platform is externally expanded by a preset width, and a liftable measuring pier is placed on each reference point; a prism is erected at the top end of each liftable measuring pier, the pier core is lifted to the highest position, the plane positions of the four measuring piers are measured, and the measuring piers are fixed in the deep foundation pit after being checked to be qualified; descending the pier core until the height of the top surface is above the middle of the height of the bearing platform to be constructed, and connecting a stay wire between the centers of every two adjacent measuring piers; and the bearing platform formwork is hung into the deep foundation pit and corresponds to the stay wire, the distance between the bearing platform formwork and the stay wire is measured through the pull ruler, and the bearing platform formwork is moved to enable the distance to reach the preset distance and then located in the deep foundation pit. According to the invention, the problem that the lofting precision is difficult to guarantee in the current deep foundation pit large-angle measurement mode is solved, and the measurement lofting precision in the deep foundation pit is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of foundation pit measurement and setting out, and in particular relates to a deep foundation pit measurement and setting out method. Background Art

[0002] Some large-scale cross-sea channel projects, such as the Shenzhen-Zhongshan Channel, feature a 200m-long non-navigable span with a 5x40m span. The entire bridge's box girder is a single unit, divided into two left and right spans, constructed as cast-in-place prestressed concrete continuous beams. Construction primarily involves the non-navigable span pile foundation, cap, pier, upper cast-in-place beam, and bridge deck. The cap is constructed using a combined steel sheet pile cofferdam to form a waterstop structure. The cap's bottom elevation is -10.5m, while the top of the steel sheet pile cofferdam is +4.5m. The height difference from the top of the steel sheet pile cofferdam to the cap's bottom is 15m, indicating that the excavation depth of the cap pit will far exceed 5m, representing a deep foundation pit. Understandably, the entire cap is located within the deep foundation pit, as is the lower portion of the pier.

[0003] At present, when measuring and staking out a pedestal in an excavated foundation pit, a total station is usually set up outside the top of the foundation pit, and a prism is set up on the bottom of the foundation pit. The total station is aimed at the prism in a depression measurement posture to directly lay out the edge line of the pedestal on the bottom of the foundation pit; then four pedestal templates are hung in the deep foundation pit, and the pedestal templates are positioned in the deep foundation pit with reference to the pedestal edge line after layout, and then the pedestal is poured in the pedestal templates.

[0004] However, for deep foundation pits, this conventional measurement method involves large-angle measurement. Due to the depth of the deep foundation pit, the angle of depression during measurement is large, making it difficult to ensure measurement and layout accuracy. This also makes it difficult for the constructed foundation pile to meet the high-precision requirements of ±10mm for the acceptance of the foundation pile plane position. This also affects the subsequent pier construction accuracy. Therefore, it is urgent to develop a deep foundation pit measurement and layout method to improve the measurement and layout accuracy within deep foundation pits. Summary of the Invention

[0005] In response to the shortcomings in the relevant technologies, the present invention provides a deep foundation pit measurement and layout method, which aims to solve the drawbacks of the current large-angle measurement method of deep foundation pits, improve the measurement and layout accuracy in deep foundation pits, and further improve the construction accuracy of subsequent foundation piles, etc.

[0006] The present invention provides a deep foundation pit surveying and setting out method, comprising the following steps:

[0007] S1. Fabricate multiple liftable measuring piers. The liftable measuring piers include a coaxially arranged pier tube and a pier core. The pier tube has an axially extending central channel. The pier core is inserted into the central channel and can move up and down. A forced centering plate is provided at the top of the pier core. The height of the forced centering plate is adjusted by the up and down movement of the pier core.

[0008] S2. After the bottom concrete of the deep foundation pit is poured and reaches the designed strength, four reference points are preliminarily determined on the bottom surface of the deep foundation pit. The plane positions of the four reference points are aligned with the plane positions of the corner points of the theoretical edge of the foundation pile to be constructed, which is expanded by a preset width D1. A liftable measuring pier is placed at each reference point.

[0009] S3. Install a prism on each forced centering plate and raise the four pier cores to their highest position. Set up a total station outside the top of the deep foundation pit and aim at the prisms on each of the four pier cores to measure the planar positions of the four liftable measuring piers. Verify the measurement results with the planar positions of the corner points of the theoretical edge of the foundation to be constructed, expanded by a preset width D1. Once the verification is qualified, secure the liftable measuring piers to the bottom concrete.

[0010] S4. Lower the four pier cores until the height of the forced centering plates on them is above the middle of the height of the pier to be constructed; remove all prisms on the forced centering plates, and insert a positioning stud at the center of each forced centering plate; connect a tension wire between every two adjacent positioning studs;

[0011] S5. Hang a pedestal template into the deep foundation pit and align it with a tension line. Use a ruler to measure the distance between the pedestal template and the tension line. Move the pedestal template until the distance reaches the preset distance d1. Position the pedestal template on the bottom concrete, where d1 = D1 - W1, and W1 is the thickness of the pedestal template. Position other pedestal templates in the deep foundation pit according to this process, and then complete the measurement and layout of the pedestal to be constructed in the deep foundation pit.

[0012] In some embodiments, step S5 also includes, when measuring the distance between the foundation template and the tension wire with a ruler, also using a plumb bob to detect the verticality of the foundation template.

[0013] In some embodiments, the deep foundation pit surveying and setting out method further includes the following steps:

[0014] S6. Carry out pouring construction of the pedestal within the enclosed area of ​​all pedestal formwork, and ensure that the pedestal reaches the designed strength after construction;

[0015] S7. Raise the four pier cores until the height of the forced centering plate on them is higher than the top surface height of the pedestal; hang a pier body template on the pedestal and align it with a guy line, measure the distance between the pier body template and the guy line with a ruler, move the pier body template until the distance reaches the preset distance d2, and then position the pier body template on the pedestal, wherein d2 = D1 + D2 - W2, D2 is the width between the theoretical pedestal edge line of the pedestal to be constructed and the theoretical pier body side line of the pier to be constructed, and W2 is the thickness of the pier body template; follow this process to position other pier body templates on the pedestal, and then complete the measurement and layout of the pier body to be constructed on the pedestal.

[0016] In some embodiments, step S7 further includes, when measuring the distance between the pier body formwork and the guy wire with a ruler, also using a plumb bob to detect the verticality of the pier body formwork.

[0017] In some embodiments, a plurality of threaded holes are circumferentially arranged on the wall of the pier tube at at least two height positions; the liftable measuring pier also includes a plurality of locking bolts, which are screwed into the threaded holes one by one; when the pier core is moved into position, the locking bolts are tightened to fix the pier core in the pier tube.

[0018] In some embodiments, the liftable measuring pier further includes a base, the top surface of the base is connected to the bottom end of the pier tube, and the bottom surface of the base is used to be connected to the bottom sealing concrete; a plurality of bolt through holes are opened on the base.

[0019] In some embodiments, the minimum height of the liftable measuring pier is greater than half the height of the cap to be constructed, and the maximum height of the liftable measuring pier is greater than the height of the cap to be constructed.

[0020] In some embodiments, a positioning screw hole is provided at the center of the forced centering disk for connection with a prism or a positioning stud.

[0021] Based on the above technical solution, the deep foundation pit measurement and layout method in the embodiment of the present invention provides a new method for measurement and layout in deep foundation pits through the application of four liftable measuring piers and the specific step design of the deep foundation pit measurement and layout method. It can solve the problem that the current large-angle measurement method of deep foundation pits is difficult to ensure the layout accuracy, significantly improve the measurement and layout accuracy in deep foundation pits, and thus improve the construction accuracy of subsequent foundation bearing platforms, pier bodies, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of this application. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0023] Figure 1 This is a flow chart of the deep foundation pit surveying and setting out method of the present invention;

[0024] Figure 2 It is a structural schematic diagram of the liftable measuring pier in the present invention;

[0025] Figure 3 Schematic diagram of the arrangement of the liftable measuring pier in the deep foundation pit of the present invention;

[0026] Figure 4 It is a top view schematic diagram of the deep foundation pit measurement and layout method of the present invention when supporting the foundation plate formwork;

[0027] Figure 5 Schematic side view of the deep foundation pit measurement and layout method of the present invention when supporting the foundation plate formwork (the guy wire is not shown);

[0028] Figure 6 It is a top view schematic diagram of the deep foundation pit measurement and layout method of the present invention when supporting the pier body formwork;

[0029] Figure 7 It is a side view schematic diagram of the deep foundation pit measurement and layout method of the present invention when supporting the pier body formwork (the guy wire is not shown).

[0030] In the figure: 1. Deep foundation pit; 11. Bottom sealing concrete; 2. Liftable measuring pier; 21. Pier tube; 22. Pier core; 23. Base; 231. Bolt hole; 24. Locking bolt; 25. Forced centering plate; 251. Centering groove; 26. Positioning stud; 3. Cap formwork; 4. Cap; 5. Pier body formwork; 6. Guy wire. DETAILED DESCRIPTION

[0031] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0032] In the description of the present invention, it should be understood that the terms "center", "lateral", "longitudinal", "up", "down", "top", "bottom", "inside", "outside", "left", "right", "front", "back", "vertical", "horizontal", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0033] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood broadly. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to direct connections, indirect connections through an intermediary, or 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 the specific circumstances.

[0034] refer to Figure 1-Figure 5 As shown, the present invention provides a deep foundation pit measurement and layout method, which is at least used to achieve high-precision measurement and layout of the foundation cap 4 to be constructed in the deep foundation pit 1. The method includes the following steps:

[0035] S1. Produce multiple elevating measuring piers 2. Each elevating measuring pier 2 includes a coaxially arranged pier tube 21 and a pier core 22. The pier tube 21 has an axially extending central channel, and the pier core 22 is inserted into the central channel and can move up and down relative to the pier tube 21, thereby adjusting the overall height of the elevating measuring pier 2. A forced centering plate 25 is installed at the top center of the pier core 22. The height of the forced centering plate 25 is adjusted by the up and down movement of the pier core 22. It is understood that the forced centering plate 25 has a centering groove 251. The centering groove 251 can be a three-slot positioning type or a cross-slot positioning type, which is not limited here.

[0036] S2. After the excavation is completed, the bottom concrete 11 is poured in the deep foundation pit 1 to make the bottom surface of the deep foundation pit 1 horizontal; after the bottom concrete 11 in the deep foundation pit 1 is poured and reaches the design strength, four reference points are preliminarily determined on the bottom surface of the deep foundation pit 1, i.e., on the bottom concrete 11, so that the plane positions of the four reference points are consistent with the plane positions of the corner points of the edge line of the theoretical foundation pile 4 to be constructed after it is expanded by a preset width D1; a liftable measuring pier 2 is placed on each reference point, and the center position of the liftable measuring pier 2 is aligned with the reference point.

[0037] It should be noted that the method for preliminarily determining the four reference points is specifically to set up a total station outside the top of the deep foundation pit 1, and set up prisms near the four corners of the bottom of the deep foundation pit 1. The total station aims at the prism in a depression measurement posture, and refers to the calculated plane positions of the corner points of the edge line of the theoretical foundation pedestal 4 to be constructed after expanding a preset width D1. The plane positions of the four reference points are preliminarily determined; the specific measurement and positioning method is well known to those skilled in the art and will not be elaborated here; it can be understood that the plane positions of the four reference points are determined under the large-angle measurement method of the deep foundation pit, and there will be certain positioning deviations or errors. The purpose of this step is to preliminarily determine the plane positions of the four reference points to achieve the initial positioning of the four liftable measuring piers 2 in the deep foundation pit 1.

[0038] S3. A prism is set up on the forced centering plate 25 of each liftable measuring pier 2, and the four pier cores 22 are raised to the highest position. Specifically, the excavation depth of the deep foundation pit 1 is usually more than 5m. Considering the structural strength of the liftable measuring pier 2 itself and the need for overall coaxiality and verticality control, the maximum height of the liftable measuring pier 2 when the pier core 22 is raised to the highest position will not exceed the depth of the deep foundation pit 1. Furthermore, a total station is set up outside the top of the deep foundation pit 1 to aim at the prisms on the four pier cores 22 raised to the highest position, so as to measure the plane positions of the four liftable measuring piers 2, and the measurement results are checked with the plane positions of the corner points of the edge line after the theoretical edge line of the pedestal 4 to be constructed is expanded by a preset width D1. If the check fails, the placement position of the liftable measuring pier 2 is adjusted and measured and checked again, until the liftable measuring pier 2 is fixed on the bottom concrete 11 in the deep foundation pit 1 after the check passes. Thus, the final positioning of the plane positions of the four liftable measuring piers 2 is achieved.

[0039] To further illustrate, when the core 22 of the liftable measuring pier 2 is raised or lowered, the planar position of the center of the forced centering plate 25 thereon remains unchanged, with only a change in height. Compared to the prior art method of measuring with a total station at a large depression angle, in which a prism is mounted on the bottom surface of the deep foundation pit 1, this step significantly reduces the height difference between the total station outside the top of the deep foundation pit 1 and the prism on the liftable measuring pier 2 by raising the core 22 to its highest position, thereby driving the prism on the forced centering plate 25 to its highest position simultaneously. This significantly reduces the depression angle during total station measurement, thereby enabling more accurate measurement of the planar position of the liftable measuring pier 2, thereby achieving accurate deviation correction of the planar position of each liftable measuring pier 2, and thus ensuring the precise installation and positioning of the four liftable measuring piers 2 within the deep foundation pit 1.

[0040] S4. Lower the four pier cores 22 until the height of the forced centering plates 25 on them is above the middle of the height of the pedestal 4 to be constructed; remove all prisms on the forced centering plates 25, and insert a positioning stud 26 at the center of each forced centering plate 25; connect a tension wire 6 between every two adjacent positioning studs 26, and the tension wire 6 is in a horizontal state and is securely tightened.

[0041] S5. Hang a cap template 3 into the deep foundation pit 1 and align it with one of the tension wires 6. Use a ruler (not shown) to measure the distance between the cap template 3 and the tension wire 6. Move the cap template 3 until the distance between the cap template 3 and the tension wire 6 reaches the preset distance d1. Then, support and position the cap template 3 on the bottom concrete 11 in the deep foundation pit 1. The preset distance d1 = D1 - W1, where W1 is the thickness of the cap template 3. It is understandable that when measuring the distance between the cap template 3 and the tension wire 6 with a ruler, Take tape measurements at at least three different positions along the length direction of the pedestal template 3 to ensure that the length direction of the pedestal template 3 is parallel to the direction of the tension wire 6 and the spacing between the two is uniform; follow this process to support and position other pedestal templates 3 in the deep foundation pit 1; when all pedestal templates 3 are positioned, all pedestal templates 3 are connected and reinforced, and the outline formed by the enclosed area of ​​all pedestal templates 3 is the pedestal edge line of the pedestal 4 to be constructed, thereby completing the measurement and layout of the pedestal 4 to be constructed in the deep foundation pit 1.

[0042] The above-mentioned schematic embodiment significantly reduces the depression angle during total station measurement through the application of four liftable measuring piers 2 and the specific step design of the deep foundation pit measurement and layout method, and realizes the precise installation and positioning of the four liftable measuring piers 2 in the deep foundation pit 1. On this basis, there is no need to set up measuring instruments in the deep foundation pit 1 in the future. Referring to the preset relationship between the edge line of the pedestal to be constructed and the four liftable measuring piers 2, the support and positioning of the pedestal template 3 in the deep foundation pit 1 can be carried out by measuring with a ruler, thereby completing the layout of the edge line of the pedestal to be constructed, thereby avoiding the problem of limited measurement line of sight in the current deep foundation pit large-angle measurement method, solving the problem that the current deep foundation pit large-depression angle measurement method is difficult to ensure the layout accuracy, significantly improving the measurement and layout accuracy in the deep foundation pit 1, and thereby improving the subsequent construction accuracy of the pedestal 4, etc.

[0043] In some embodiments, step S5 also includes, when measuring the distance between the foundation template 3 and the tension wire 6 with a ruler, also using a plumb bob to detect the verticality of the foundation template 3 to ensure that the verticality of the foundation template 3 meets the construction requirements, thereby improving the construction accuracy of the subsequent foundation 4.

[0044] refer to Figure 1-Figure 7 As shown, in some embodiments, the deep foundation pit surveying and setting out method further includes the following steps:

[0045] S6. Cast the cap 4 in the enclosed area of ​​all the cap formworks 3, and make the cap 4 reach the designed strength after construction; then remove all the cap formworks 3.

[0046] S7, raise the four pier cores 22 to a height that the forced centering plate 25 thereon is higher than the top surface height of the pedestal 4; hang a pier body template 5 on the top surface of the pedestal 4 and correspond to one of the guy wires 6, measure the distance between the pier body template 5 and the guy wire 6 by a ruler (not shown), move the pier body template 5 until the distance between the pier body template 5 and the guy wire 6 reaches the preset distance d2, and then support and position the pier body template 5 on the top surface of the pedestal 4, wherein the preset distance d2 = D1 + D2 - W2, D2 is the width between the theoretical pedestal edge line of the pedestal 4 to be constructed and the theoretical pier side line of the pier body to be constructed, and W2 is the thickness of the pier body template 5; it can be understood that When measuring the distance between the pier body formwork 5 and the guy wire 6 with a ruler, the ruler measurement should be performed at at least three different positions in the length direction of the pier body formwork 5 to ensure that the length direction of the pier body formwork 5 is parallel to the direction of the guy wire 6 and the distance between the two is uniform; according to this process, other pier body formworks 5 are supported and positioned on the top surface of the pedestal 4; when all pier body formworks 5 are positioned, all pier body formworks 5 are connected and reinforced, and the contour line formed by the enclosed area of ​​all pier body formworks 5 is the pier body side line of the pier body to be constructed, thereby completing the measurement and layout of the pier body to be constructed on the pedestal 4; and then the pier body is cast in the enclosed area of ​​all pier body formworks 5.

[0047] In the above-mentioned schematic embodiment, by using four liftable measuring piers 2, there is no need to set up measuring instruments. By referring to the preset relationship between the side line of the pier to be constructed and the four liftable measuring piers 2, the support and positioning of the pier body formwork 5 on the base 4 can be carried out by measuring with a ruler, thereby completing the layout of the side line of the pier to be constructed.

[0048] In some embodiments, step S7 also includes, when measuring the distance between the pier body formwork 5 and the tension wire 6 with a ruler, also using a plumb bob to detect the verticality of the pier body formwork 5 to ensure that the verticality of the pier body formwork 5 meets the construction requirements, thereby improving the subsequent pier body construction accuracy.

[0049] refer to Figure 2 As shown, in some embodiments, a plurality of threaded holes are arranged circumferentially on the wall of the pier tube 21 at at least two height positions, and the threaded holes all penetrate the wall of the pier tube 21 radially. The liftable measuring pier 2 also includes a plurality of locking bolts 24, and the plurality of locking bolts 24 are screwed into the threaded holes one by one. When the pier core 22 is moved up and down relative to the pier tube 21, the pier core 22 can be fixed in the pier tube 21 by tightening the locking bolts 24; correspondingly, the positioning between the pier core 22 and the pier tube 21 can be released by loosening the locking bolts 24, and the pier core 22 can be lifted or lowered; thereby achieving the convenience and reliability of the height adjustment of the liftable measuring pier 2, that is, the convenience and reliability of the height adjustment of the forced centering plate 25 at the top of the pier core 22.

[0050] refer to Figure 2 、 Figure 3 As shown, in some embodiments, the liftable measuring pier 2 further includes a base 23. The top surface of the base 23 is connected to the bottom end of the pier tube 21, and the bottom surface of the base 23 is used to connect to the bottom concrete 11 in the deep foundation pit 1. The base 23 is provided with a plurality of bolt holes 231, so that expansion bolts can be passed through the bolt holes 231 to connect and secure the base 23 to the bottom concrete 11.

[0051] refer to Figure 2 、 Figure 5 、 Figure 7 As shown, in some embodiments, the minimum height of the liftable measuring pier 2 when the pier core 22 is lowered to the lowest position is greater than half the height of the pedestal 4 to be constructed, but not greater than the height of the pedestal 4 to be constructed; this facilitates the measurement of the distance between the pedestal formwork 3 and the guy wire 6 by a ruler in step S5, and also facilitates the rapid erection and positioning of the pedestal formwork 3. The maximum height of the liftable measuring pier 2 when the pier core 22 is raised to the highest position is greater than the height of the pedestal 4 to be constructed; it should be noted that the specific difference between the maximum height of the liftable measuring pier 2 and the height of the pedestal 4 to be constructed is set on the basis of ensuring good coaxiality and verticality between the pier core 22 and the pier tube 21 when the pier core 22 is raised and lowered, and preferably the liftable measuring pier 2 is higher than the top surface of the pedestal 4 to be constructed, thereby facilitating the measurement of the distance between the pier body formwork 5 and the guy wire 6 by a ruler in step S7, and also facilitates the rapid erection and positioning of the pier body formwork 5.

[0052] refer to Figure 2 As shown, in some embodiments, a positioning screw hole is opened at the center of the forced centering disk 25 for connecting with the prism or the positioning stud 26.

[0053] To sum up, the deep foundation pit measurement and layout method of the present invention provides a new method for measurement and layout in a deep foundation pit 1 through the application of four liftable measuring piers 2 and the specific step design of the deep foundation pit measurement and layout method. It can significantly reduce the depression angle during total station measurement, and realize the precise installation and positioning of the four liftable measuring piers 2 in the deep foundation pit 1. On this basis, there is no need to set up measuring instruments in the deep foundation pit 1 in the future. The support and positioning of the pedestal template 3 in the deep foundation pit 1 and the support and positioning of the pier body template 5 on the pedestal 4 can be carried out by measuring with a ruler, thereby completing the layout of the edge line of the pedestal to be constructed and the edge line of the pier to be constructed, solving the problem that the current deep foundation pit large depression angle measurement method is difficult to ensure the layout accuracy, significantly improving the measurement and layout accuracy in the deep foundation pit 1, and thus improving the subsequent construction accuracy of the pedestal 4, pier body, etc.

[0054] Finally, it should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0055] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the same. Although the present invention has been described in detail with reference to preferred embodiments, persons skilled in the art should understand that the specific implementation methods of the present invention may still be modified or some technical features may be replaced by equivalents without departing from the spirit of the technical solutions of the present invention, and all of these should fall within the scope of the technical solutions claimed for protection by the present invention.

Claims

1. A deep foundation pit surveying and setting out method, characterized in that: The following steps are involved: S1. Fabricate multiple liftable measuring piers; the liftable measuring piers include a coaxially arranged pier tube and a pier core. The pier tube has an axially extending central channel, and the pier core is inserted into the central channel and can move up and down. The top of the pier core is provided with a forced centering plate, and the height of the forced centering plate is adjusted by the up and down movement of the pier core. S2. After the bottom concrete in the deep foundation pit is poured and reaches the designed strength, four reference points are preliminarily determined on the bottom surface of the deep foundation pit, so that the plane positions of the four reference points are consistent with the plane positions of the corner points of the theoretical edge of the foundation pile to be constructed after it is expanded by a preset width D1; a liftable measuring pier is placed at each reference point; S3. Install a prism on each of the forced centering plates and raise the four pier cores to their highest position. Set up a total station outside the top of the deep foundation pit and aim at the prisms on the four pier cores to measure the planar positions of the four liftable measuring piers. Verify the measurement results with the planar positions of the corner points of the theoretical edge of the foundation pile to be constructed, which is expanded by a preset width D1. After passing the verification, secure the liftable measuring piers to the bottom concrete. S4. Lower the four pier cores until the height of the forced centering plates on them is above the middle of the height of the pier to be constructed; remove the prisms on all the forced centering plates, and insert a positioning stud at the center of each forced centering plate; connect a tension wire between each of the two adjacent positioning studs; S5. Hang a cap template into the deep foundation pit and align it with one of the tension lines. Use a ruler to measure the distance between the cap template and the tension line. Move the cap template until the distance reaches the preset distance d1. Position the cap template on the bottom concrete, where d1 = D1 - W1, and W1 is the thickness of the cap template. Position other cap templates in the deep foundation pit according to this process, and then complete the measurement and layout of the cap to be constructed in the deep foundation pit.

2. The deep foundation pit surveying and setting out method according to claim 1, characterized in that: Step S5 also includes, when measuring the distance between the foundation template and the tension wire with a ruler, also using a plumb bob to detect the verticality of the foundation template.

3. The deep foundation pit surveying and setting out method according to claim 2, characterized in that: The deep foundation pit surveying and setting out method further comprises the following steps: S6. Casting the cap within the enclosed area of ​​all the cap templates, and ensuring that the cap reaches the designed strength after construction; S7. Raise the four pier cores until the height of the forced centering plate thereon is higher than the top surface height of the pedestal; hang a pier body template on the pedestal and align it with one of the guy wires, measure the distance between the pier body template and the guy wire with a ruler, move the pier body template until the distance reaches a preset distance d2, and then position the pier body template on the pedestal, wherein d2 = D1 + D2 - W2, D2 is the width between the theoretical pedestal edge line of the pedestal to be constructed and the theoretical pier body edge line of the pier body to be constructed, and W2 is the thickness of the pier body template; position other pier body templates on the pedestal according to this process, and then complete the measurement and layout of the pier body to be constructed on the pedestal.

4. The deep foundation pit surveying and setting out method according to claim 3, characterized in that: Step S7 also includes, when measuring the distance between the pier body formwork and the guy wire with a ruler, simultaneously detecting the verticality of the pier body formwork by hanging a plumb bob.

5. The deep foundation pit surveying and setting out method according to claim 1, characterized in that: The pier tube is provided with a plurality of threaded holes along the circumferential direction on the tube wall at at least two height positions; the liftable measuring pier also includes a plurality of locking bolts, and the plurality of locking bolts are screwed into the threaded holes one by one; when the pier core is moved into position, the locking bolts are tightened to fix the pier core in the pier tube.

6. The deep foundation pit surveying and setting out method according to claim 1, characterized in that: The liftable measuring pier further comprises a base, the top surface of the base is connected to the bottom end of the pier tube, and the bottom surface of the base is used to be connected to the bottom sealing concrete; a plurality of bolt through holes are opened on the base.

7. The deep foundation pit surveying and setting out method according to claim 1, characterized in that: The minimum height of the liftable measuring pier is greater than half the height of the pedestal to be constructed, and the maximum height of the liftable measuring pier is greater than the height of the pedestal to be constructed.

8. The deep foundation pit surveying and setting out method according to claim 1, characterized in that: A positioning screw hole is provided at the center of the forced centering disk for connecting with the prism or the positioning stud.

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