Anti-seepage treatment method for periphery of near-dike section pier foundation of dike-crossing bridge

Abstract

The invention relates to the technical field of embankment anti-seepage treatment of river regulation engineering, and discloses an anti-seepage treatment method for the periphery of a pier foundation of a near-embankment section of a cross-embankment bridge. And a circle of high-pressure rotary jet grouting cement soil piles are jetted on the periphery of the cast-in-place pile foundation within the dike management range to serve as a transition layer between the cast-in-place pile foundation and a soil body. The invention further discloses a construction method of the high-pressure rotary jet grouting cement soil pile. According to the anti-seepage treatment method for the periphery of the pier foundation of the near-dike section of the dike-crossing bridge, on the premise that an original dike body structure is not damaged, contact scouring between a dike foundation soil body and the pier cast-in-place pile foundation is effectively prevented, the possibility of seepage damage of the dike foundation in the flood season is reduced, and the flood prevention safety of the dike of the dike-crossing section of a newly-built bridge in the flood prevention season is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of dike seepage prevention treatment for river regulation projects, and particularly relates to a method for seepage prevention treatment around the pier foundation in the near-dike section of a cross-dike bridge. Background Art

[0002] The construction of the pier foundation of a cross-dike bridge has the following adverse effects on the seepage stability of the dike: When constructing the near-dike piers, since the bored pile foundation has a relatively deep hole formation, it is easy to break through the hydraulic connection between the sand layer and the ground surface inside the dike, resulting in water and sand gushing in the bored pile foundation; the equipment disturbance during the construction period is likely to further break through the seepage channels of the original dike body and dike foundation, and piping hazards may occur during the flood season.

[0003] Previous seepage prevention measures often adopt the form of a vertical impervious wall for the cross-dike section of the dike body and dike foundation to cut off or extend the seepage channel. This method has the following disadvantages:

[0004] ① The construction of the impervious wall needs to damage the original dike top road surface and the dike body protection structure;

[0005] ② It is difficult to form a closed interval in both the horizontal and vertical directions of the impervious wall.

[0006] Therefore, it is necessary to study and adopt more economical and effective seepage prevention measures to eliminate and reduce the adverse effects of the pier foundation on the dike seepage prevention and ensure the safety of the dike seepage prevention. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for seepage prevention treatment around the pier foundation in the near-dike section of a cross-dike bridge in view of the above deficiencies in the technology. Without damaging the original dike body structure, it can effectively prevent the contact scouring between the dike foundation soil and the pier bored pile foundation, reduce the possibility of seepage failure of the dike foundation during the flood season, and ensure the flood control safety of the cross-dike section of the newly built bridge during the flood season.

[0008] To achieve the above purpose, in the method for seepage prevention treatment around the pier foundation in the near-dike section of the cross-dike bridge designed by the present invention, the main structure of the pier includes a column, a bearing platform, and a bored pile foundation. While constructing the bored pile foundation, a circle of high-pressure jet grouting cement-soil piles is sprayed around the bored pile foundation within the scope of dike management as a transition layer between the bored pile foundation and the soil.

[0009] Preferably, the pile length, thickness, spacing, pile diameter, and arrangement method of the high-pressure jet grouting cement-soil piles are obtained through calculation.

[0010] Preferably, the pile length L of the high-pressure jet grouting cement-soil piles is obtained by calculating according to the following formula:

[0011]

[0012] In the formula, H is the water head difference before and after the dike, which can be approximately represented by the difference in elevation between the design flood level and the ground level inside the dike, G s is the specific gravity of the surface soil behind the dike, n is the porosity of the surface soil behind the dike, K is the safety factor, and the safety factor for piping can be taken as 1.5, and the safety factor for quicksand can be taken as 2.0.

[0013] Preferably, the thickness d of the high-pressure jet grouted soil-cement pile is obtained by calculating according to the following formula:

[0014]

[0015] In the formula: H is the water head difference before and after the dike, [J] is the maximum allowable hydraulic gradient of the high-pressure jet grouted soil-cement pile material, which specifically needs to be determined according to the material, construction method and curing age, and generally can be taken as 50 - 60.

[0016] Preferably, the spacing D of the high-pressure jet grouted soil-cement pile is obtained by calculating according to the following formula:

[0017] D ≤ 2d

[0018] In the formula, d is the thickness of the high-pressure jet grouted soil-cement pile, and the combined thickness a of the high-pressure jet grouted soil-cement pile and the cast-in-place pile foundation satisfies the following condition: a ≥ 0.25D, where D is the spacing of the high-pressure jet grouted soil-cement pile, to ensure the combined effect of the high-pressure jet grouted soil-cement pile and the cast-in-place pile foundation.

[0019] Preferably, the pile diameter of the high-pressure jet grouted soil-cement pile is obtained by calculating according to the following formula:

[0020]

[0021] In the formula, d is the thickness of the high-pressure jet grouted soil-cement pile, and D is the spacing of the high-pressure jet grouted soil-cement pile.

[0022] Preferably, the layout method of the high-pressure jet grouted soil-cement pile is to arrange it at equal angles around the center of the cast-in-place pile foundation, and its angle θ is:

[0023]

[0024] In the formula, D is the spacing of the high-pressure jet grouted soil-cement pile, R is the radius of the cast-in-place pile foundation, is the pile diameter of the high-pressure jet grouted soil-cement pile, and a is the combined thickness of the high-pressure jet grouted soil-cement pile and the cast-in-place pile foundation.

[0025] A construction method for high-pressure jet grouting cement-soil piles. First, determine the bridge piers to be treated, and then calculate the pile length, thickness, spacing, pile diameter, and layout method of the high-pressure jet grouting cement-soil piles. During construction, first complete the construction of the cast-in-place pile foundation. While constructing the cast-in-place pile foundation, spray a circle of high-pressure jet grouting cement-soil piles around the cast-in-place pile foundation within the scope of the dike management as a transition layer between the cast-in-place pile foundation and the soil mass. Then pour the bearing platform, and finally assemble the columns.

[0026] Preferably, when constructing the high-pressure jet grouting cement-soil piles, the following steps are included:

[0027] 1) First, implement the cast-in-place pile foundation and cure it to the preset strength.

[0028] 2) Conduct pile-forming tests on the high-pressure jet grouting cement-soil piles. The inspection indicators include the cement-soil mixing ratio, the unconfined compressive strength of the pile body, and the permeability coefficient of the impervious wall. The number of test points shall be no less than 3, and a wall with an axial length of 3 - 5 m shall be formed at each point.

[0029] 3) Arrange high-pressure jet grouting cement-soil piles around the cast-in-place pile foundation of a single bridge pier. The high-pressure jet grouting cement-soil piles start grouting from the ground, and ensure that the pile length is not less than the designed length L. The stop grouting surface of the high-pressure jet grouting cement-soil piles shall be higher than the bottom surface of the bearing platform. When constructing the bearing platform, then break the part of the high-pressure jet grouting cement-soil piles above the ground of the bearing platform to ensure that the newly poured concrete is closely connected with the high-pressure jet grouting cement-soil piles, thereby ensuring the anti-seepage effect.

[0030] 4) 28 days after the grouting of the high-pressure jet grouting cement-soil piles is completed, select key positions for on-site drilling and water injection tests. The test results shall ensure that the average value of the permeability coefficient of the high-pressure jet grouting cement-soil piles is less than 1.0×10 -6 cm / s.

[0031] Preferably, in the composition of the high-pressure jet grouting cement-soil piles, 2% - 4% of water glass and 10% - 50% by weight of bentonite are incorporated into the ordinary Portland cement slurry to enhance the pile-forming quality and anti-seepage effect of the high-pressure jet grouting cement-soil piles.

[0032] Compared with the prior art, the present invention has the following advantages:

[0033] 1. It is more targeted at preventing contact scouring between the bridge pier pile foundation and the dike foundation soil mass. A semi-rigid cement-soil mixture is used between the rigid bridge pier cast-in-place pile foundation and the flexible dike foundation soil, eliminating the conditions for contact scouring to occur, and having a better anti-seepage effect.

[0034] 2. Compared with arranging vertical impervious walls along the dike body and dike foundation, the anti-seepage measure of the present invention is combined with the construction of the bridge pier foundation, and the original dike body structure does not need to be damaged.

[0035] 3. Reduce the possibility of seepage failure of the levee foundation during the flood season and ensure the flood control safety of the levee section across which the new bridge is built during the flood season;

[0036] 4. The construction technology is simple and easy to implement, and is applicable to various levee and bridge foundation projects;

[0037] 5. More economical and effective. Description of the Drawings

[0038] Figure 1 It is a schematic structural diagram of a high-pressure jet grouting cement-soil pile in the anti-seepage treatment method around the pier foundation of the near-dike section of the cross-dike bridge of the present invention;

[0039] Figure 2 It is Figure 1 the plan top view of;

[0040] Figure 3 It is a schematic detailed structural diagram of the combination of a single cast-in-place pile foundation and a high-pressure jet grouting cement-soil pile in the present invention.

[0041] The reference numerals of each component in the figure are as follows:

[0042] Column 1, bearing platform 2, cast-in-place pile foundation 3, high-pressure jet grouting cement-soil pile 4. Detailed Embodiment

[0043] Next, the technical solution of the present invention will be clearly and completely described in conjunction with the drawings. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of them. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without making creative efforts shall fall within the protection scope of the present invention.

[0044] As Figure 1 , Figure 2 and Figure 3 shown, a method for anti-seepage treatment around the pier foundation of the near-dike section of a cross-dike bridge. The main structure of the pier includes a column 1, a bearing platform 2, and a cast-in-place pile foundation 3. While the cast-in-place pile foundation 3 is being constructed, a circle of high-pressure jet grouting cement-soil piles 4 is sprayed around the cast-in-place pile foundation 3 within the scope of levee management as a transition layer between the cast-in-place pile foundation 3 and the soil mass.

[0045] Among them, the pile length, thickness, spacing, pile diameter, and layout method of the high-pressure jet grouting cement-soil pile 4 are obtained through calculation. Specifically, the pile length of the anti-seepage high-pressure jet grouting cement-soil pile 4 around the pier cast-in-place pile foundation 3 is calculated according to the physical and mechanical parameters of the surface soil layer behind the levee and the elevation difference between the designed flood level and the ground surface behind the levee. The minimum wall thickness of the high-pressure jet grouting cement-soil pile 4 is calculated according to the allowable seepage gradient of the high-pressure jet grouting cement-soil pile 4 material, and further the maximum pile spacing is calculated. According to the size requirements of the high-pressure jet grouting cement-soil pile 4 obtained by calculation, construction is carried out according to the construction technology.

[0046] Specifically, the pile length L of the high-pressure rotary jet grouted soil-cement pile 4 is obtained by calculating according to the following formula:

[0047]

[0048] In the formula, H is the water head difference before and after the dike, G s is the specific gravity of the surface soil behind the dike, n is the porosity of the surface soil behind the dike, K is the safety factor, the piping safety factor can be taken as 1.5, and the quicksand safety factor can be taken as 2.0.

[0049] The thickness d of the high-pressure rotary jet grouted soil-cement pile 4 is obtained by calculating according to the following formula:

[0050]

[0051] In the formula: H is the water head difference before and after the dike, [J] is the maximum allowable hydraulic gradient of the material of the high-pressure rotary jet grouted soil-cement pile 4, which specifically needs to be determined according to the material, construction method and curing age, and generally can be taken as 50-60.

[0052] The spacing D of the high-pressure rotary jet grouted soil-cement pile 4 is obtained by calculating according to the following formula:

[0053] D ≤ 2d

[0054] In the formula, d is the thickness of the high-pressure rotary jet grouted soil-cement pile 4, and the combined thickness a of the high-pressure rotary jet grouted soil-cement pile 4 and the cast-in-place pile foundation 3 satisfies the following condition: a ≥ 0.25D, where D is the spacing of the high-pressure rotary jet grouted soil-cement pile 4.

[0055] The pile diameter of the high-pressure rotary jet grouted soil-cement pile 4 is obtained by calculating according to the following formula:

[0056]

[0057] In the formula, d is the thickness of the high-pressure rotary jet grouted soil-cement pile 4, and D is the spacing of the high-pressure rotary jet grouted soil-cement pile 4.

[0058] The layout method of the high-pressure rotary jet grouted soil-cement pile 4 is to arrange it at equal angles around the center of the cast-in-place pile foundation 3, and its angle θ is:

[0059]

[0060] In the formula, D is the spacing of the high-pressure rotary jet grouted soil-cement pile 4, R is the radius of the cast-in-place pile foundation 3, is the pile diameter of the high-pressure rotary jet grouted soil-cement pile 4, and a is the combined thickness of the high-pressure rotary jet grouted soil-cement pile 4 and the cast-in-place pile foundation 3.

[0061] Taking a certain cross-dike bridge as an example, there are 5 bridge piers arranged within the embankment management scope. The foundation structure of each bridge pier is the same. The cap 2 is 6m wide, 8m long, and 2m thick. There are 5 bored cast-in-place pile foundations 3 under each cap 2. The diameter of each bored cast-in-place pile foundation 3 is 1.32m. The surface soil behind the embankment is silty clay, and its physical and mechanical parameters of the soil mass are as follows: porosity n = 0.426, specific gravity of soil mass G s = 2.72, the elevation difference between the design flood level and the ground inside the embankment is 7m. The safety factor K is considered according to the flow failure and taken as 2.0. According to the above steps, the layout of the high-pressure jet grouting cement-soil piles is calculated as follows:

[0062] According to the pile length calculation formula, the pile length L of the high-pressure jet grouting cement-soil pile 4 can be calculated to be L≥4.67m. Taking the allowable seepage gradient [J] of the high-pressure jet grouting cement-soil pile 4 material as 60, then according to the aforementioned cut-off wall thickness calculation formula, the cut-off wall thickness d of the high-pressure jet grouting cement-soil pile 4 can be calculated to be d≥0.12m, the corresponding pile spacing D≤0.24m, the combined thickness a between the high-pressure jet grouting cement-soil pile 4 and the bored cast-in-place pile foundation 3≥0.06m, and the pile diameter of the high-pressure jet grouting cement-soil pile 4 The layout angle θ of the high-pressure jet grouting cement-soil pile 4 around the center of the bored cast-in-place pile foundation 3 is 0.388rad.

[0063] In this embodiment, during the construction of the high-pressure jet grouting cement-soil pile 4, first, the bridge piers to be treated are determined, and then the pile length, thickness, spacing, pile diameter, and layout method of the high-pressure jet grouting cement-soil pile 4 are calculated. During construction, first, the bored cast-in-place pile foundation 3 is constructed. While the bored cast-in-place pile foundation 3 is being constructed, a circle of high-pressure jet grouting cement-soil piles 4 is sprayed around the bored cast-in-place pile foundation 3 within the embankment management scope as a transition layer between the bored cast-in-place pile foundation 3 and the soil mass. Then, the cap 2 is poured, and finally, the column 1 is assembled.

[0064] Specifically, the construction of the high-pressure jet grouting cement-soil pile 4 includes the following steps:

[0065] 1) First, implement the bored cast-in-place pile foundation 3 and cure it to the preset strength;

[0066] 2) Conduct pile-forming tests on the high-pressure jet grouting cement-soil pile 4. The inspection indicators include the cement-soil mixing ratio, the unconfined compressive strength of the pile body, and the permeability coefficient of the cut-off wall. The number of test points is not less than 3, and a wall with an axial length of 3 - 5m should be formed at each point;

[0067] 3) Arrange the high-pressure jet grouting cement-soil pile 4 around the bored cast-in-place pile foundation 3 of a single bridge pier. The high-pressure jet grouting cement-soil pile 4 starts grouting construction from the ground and ensures that the pile length is not less than the designed length L. The stop grouting surface of the high-pressure jet grouting cement-soil pile 4 should be higher than the bottom surface of the cap 2. In this embodiment, it is 50cm. When the cap 2 is constructed, the part of the high-pressure jet grouting cement-soil pile 4 above the ground of the cap 2 is broken to ensure the dense connection between the newly poured concrete and the high-pressure jet grouting cement-soil pile 4, thus ensuring the anti-seepage effect;

[0068] 4) After 28 days of the grouting completion of the high-pressure jet grouting cement-soil pile 4, on-site borehole water injection tests are carried out at key positions, and the test results shall ensure that the average value of the permeability coefficient of the high-pressure jet grouting cement-soil pile 4 is less than 1.0×10 -6 cm / s.

[0069] Among them, in the composition of the high-pressure jet grouting cement-soil pile 4, 2% - 4% of water glass and 10% - 50% by weight of bentonite are incorporated into the ordinary Portland cement slurry to enhance the pile-forming quality and anti-seepage effect of the high-pressure jet grouting cement-soil pile 4.

[0070] The anti-seepage treatment method for the pier foundation in the near-dike section of the cross-dike bridge of the present invention is more targeted at preventing the contact scouring along the pier pile foundation. A semi-rigid cement-soil mixture is used between the rigid pier cast-in-place pile foundation 3 and the flexible dike foundation soil, eliminating the conditions for the occurrence of contact scouring and having a better anti-seepage effect; compared with arranging a vertical anti-seepage wall along the dike body and dike foundation of the dike, the anti-seepage measure of the present invention is combined with the construction of the pier foundation and does not need to damage the original dike body structure; it reduces the possibility of the occurrence of seepage failure of the dike foundation during the flood season, ensuring the flood control safety of the cross-dike section of the newly built bridge during the flood season; the construction process is simple and easy to implement, applicable to various dike and bridge foundation projects; it is more economical and effective.

[0071] Meanwhile, it should be noted that the description of the above technical solutions is exemplary. This specification can be embodied in different forms and should not be construed as limited to the technical solutions described herein. On the contrary, providing these descriptions will make the disclosure of the present invention thorough and complete, and will fully convey the scope disclosed in this specification to those skilled in the art. In addition, the technical solutions of the present invention are only limited by the scope of the claims. The features of various embodiments of the present invention can be combined or spliced partially or wholly with each other, and can be implemented in various different configurations as can be fully understood by those skilled in the art. The embodiments of the present invention can be implemented independently of each other, or can be implemented in a mutually dependent relationship.

[0072] For those of ordinary skill in the art to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can still be made, and the above structures should all be regarded as belonging to the protection scope of the present invention.

Claims

1. A method for anti-seepage treatment around the pier foundation of a cross-embankment bridge near the embankment, characterized in that: The main structure of the bridge pier includes a column (1), a cap (2) and a bored pile foundation (3). While the bored pile foundation (3) is being constructed, a circle of high-pressure rotary jet cement soil piles (4) is sprayed around the bored pile foundation (3) within the embankment management range to serve as a transition layer between the bored pile foundation (3) and the soil.

2. The anti-seepage treatment method around the pier foundation of the cross-embankment bridge near the embankment section according to claim 1 is characterized by: The pile length, thickness, spacing, pile diameter and arrangement of the high-pressure rotary jet cement soil piles (4) are obtained through calculation.

3. The anti-seepage treatment method around the pier foundation of the cross-embankment bridge near the embankment section as claimed in claim 2, characterized in that: The pile length L of the high-pressure rotary jet cement soil pile (4) is calculated according to the following formula: In the formula, H is the water head difference before and after the dike, G s is the specific gravity of the surface soil behind the embankment, n is the porosity of the surface soil behind the embankment, and K is the safety factor.

4. The anti-seepage treatment method around the pier foundation of the cross-embankment bridge near the embankment section as claimed in claim 2, characterized in that: The thickness d of the high-pressure rotary jet cement soil pile (4) is calculated according to the following formula: Where: H is the water head difference before and after the embankment, [J] is the maximum allowable permeability gradient of the high-pressure rotary jet cement soil pile (4).

5. The anti-seepage treatment method around the pier foundation of the cross-embankment bridge near the embankment section as claimed in claim 2, characterized in that: The spacing D of the high-pressure rotary jet cement soil piles (4) is calculated according to the following formula: D≤2d In the formula, d is the thickness of the high-pressure rotary jet cement soil pile (4), and the combined thickness a of the high-pressure rotary jet cement soil pile (4) and the cast-in-place pile foundation (3) satisfies the following condition: a≥0.25D, and D is the spacing between the high-pressure rotary jet cement soil piles (4).

6. The anti-seepage treatment method around the pier foundation of the cross-embankment bridge near the embankment section as claimed in claim 2, characterized in that: The pile diameter of the high-pressure rotary jet cement soil pile (4) Calculated according to the following formula: In the formula, d is the thickness of the high-pressure rotary grouting cement soil pile (4), and D is the spacing between the high-pressure rotary grouting cement soil piles (4).

7. The anti-seepage treatment method around the pier foundation of the cross-embankment bridge near the embankment section as claimed in claim 2, characterized in that: The high-pressure rotary jet cement soil piles (4) are arranged at equal angles around the center of the cast-in-place pile foundation (3), and the angle θ is: Wherein, D is the spacing between the high-pressure rotary grouting cement soil piles (4), R is the radius of the cast-in-place pile foundation (3), is the pile diameter of the high-pressure rotary grouting cement soil pile (4), and a is the combined thickness of the high-pressure rotary grouting cement soil pile (4) and the cast-in-place pile foundation (3).

8. A high-pressure rotary grouting cement soil pile construction method, characterized in that: Firstly, the bridge piers to be treated are determined, and then the pile length, thickness, spacing, pile diameter and arrangement of the high-pressure rotary jet cement soil piles (4) are calculated. During construction, the bored pile foundation (3) is first constructed. While the bored pile foundation (3) is being constructed, a circle of high-pressure rotary jet cement soil piles (4) is sprayed around the bored pile foundation (3) within the embankment management range as a transition layer between the bored pile foundation (3) and the soil. Then the cap (2) is poured, and finally the columns (1) are assembled.

9. The high-pressure rotary grouting cement soil pile construction method according to claim 9, characterized in that: The construction of high-pressure rotary grouting cement soil pile (4) includes the following steps: 1) first implement the cast-in-place pile foundation (3), and maintain the cast-in-place pile foundation (3) to a preset strength; 2) Conduct a pile test on the high-pressure rotary jet cement soil pile (4), with the test indicators including cement soil mixing ratio, unconfined compressive strength of the pile body, and permeability coefficient of the anti-seepage wall. The test points shall be no less than 3, and each point shall form a wall with an axial length of 3 to 5 meters; 3) high-pressure rotary jet cement soil piles (4) are arranged around the cast-in-place pile foundation (3) of a single bridge pier. The high-pressure rotary jet cement soil piles (4) are sprayed from the ground and the pile length is not less than the designed length L. The stop surface of the high-pressure rotary jet cement soil piles (4) should be higher than the bottom surface of the cap (2). When the cap (2) is constructed, the part of the high-pressure rotary jet cement soil piles (4) that is higher than the ground of the cap (2) is removed; 4) 28 days after the grouting of high-pressure rotary jet cement soil pile (4) is completed, select key locations for on-site drilling and water injection tests. The test results should ensure that the average permeability coefficient of the high-pressure rotary jet cement soil pile (4) is less than 1.0×10 -6 cm / s.

10. The high-pressure rotary grouting cement soil pile construction method according to claim 9, characterized in that: The high-pressure rotary jet cement soil pile (4) comprises ordinary silicate cement slurry mixed with 2% to 4% water glass and 10% to 50% bentonite in a weight ratio.

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