CN107237266B

CN107237266B - Open cut rock anchor combined foundation and reverse operation construction method thereof

Info

Publication number: CN107237266B
Application number: CN201710502333.8A
Authority: CN
Inventors: 柏华军; 毕玉琢; 吴斌; 王希
Original assignee: China Railway Siyuan Survey and Design Group Co Ltd
Current assignee: China Railway Siyuan Survey and Design Group Co Ltd
Priority date: 2017-06-27
Filing date: 2017-06-27
Publication date: 2023-02-28
Anticipated expiration: 2037-06-27
Also published as: CN107237266A

Abstract

The invention relates to the technical field of bridge construction, in particular to an open cut rock anchor combined foundation and a reverse operation construction method thereof. Removing exposed protruding rocks at the river bottom, and excavating a foundation pit; binding a reinforcing mesh in the foundation pit, embedding a positioning sleeve in the reinforcing mesh, and pouring an open-cut bearing platform on the bound reinforcing mesh; drilling holes in the bedrock at the bottom of the open cut bearing platform through a positioning sleeve on the open cut bearing platform to complete the construction of anchoring holes; inserting the anchor rod into each anchoring hole along the positioning sleeve, and pouring anchor rod mortar into the anchoring holes to realize anchoring of the anchor rod; welding the pier column stress main rib with the anchor rod at the corresponding position on the open cut bearing platform, binding a pier body reinforcement cage, and performing pier body concrete construction; and after the pier body construction is finished, backfilling concrete into the foundation pit to a ground line to finish the construction. Set up the position sleeve in open cut cushion cap, establish the anchor hole drilling through the position sleeve location back, it is easier to compare in directly drilling the pile on the basement rock, and is difficult for appearing phenomenons such as reaming.

Description

Open cut rock anchor combined foundation and reverse operation construction method thereof

Technical Field

The invention relates to the technical field of bridge construction, in particular to an open cut rock anchor combined foundation and a reverse operation construction method thereof.

Background

In bridge engineering, open cut foundations are the most common construction method when the geological bearing capacity is good and reaches over 350Kpa of foundation bearing capacity. Especially in the stratum with exposed bedrock, the open cut foundation shows larger economical efficiency than the pile foundation and is convenient to construct. When bedrock is exposed in water, the periphery of the open cut foundation in the water is disturbed by construction, and the foundation is particularly easy to be washed by water flow, so that the lower part of the foundation is empty, the stability is reduced, and the safety of the structure is threatened. Or when the hillside bedrock is exposed, the foundation is enlarged, the capability of resisting the water smooth slope thrust is weaker than that of a pile foundation, and the safety reserve of the structure is insufficient. To solve the safety problem, engineers often adopt a pile foundation scheme or bury the open cut foundation in deeper bedrock, increasing the safety of the structure. If adopt the pile foundation scheme, because it punches on the hard rock of texture directly, it is high to punch the degree of difficulty, and easy reaming, and the basis needs to regard as the support with the stake, and the intensity requirement to the stake is high, and the difficult construction of basis. The adoption of open cut foundations embedded in deeper bedrock is costly in cost and construction period.

Disclosure of Invention

In order to solve the technical problems, the invention provides an open cut rock anchor combined foundation and a reverse operation construction method thereof, wherein the open cut foundation can be adopted, the horizontal anti-pushing capability of the open cut foundation can be improved, the overturning stability is increased, and the foundation cannot be buried too deeply.

The invention relates to an open cut rock anchor combined foundation reverse operation construction method, which comprises the following steps:

step 1: removing exposed protruding rocks at the river bottom, and excavating a foundation pit;

step 2: binding a reinforcing mesh in the foundation pit, embedding a positioning sleeve in the reinforcing mesh, pouring an open cut bearing platform on the bound reinforcing mesh, and enabling the upper end surface of the open cut bearing platform to be not higher than the positioning sleeve;

and step 3: drilling holes in the open cut bearing platform through the positioning sleeves to the bedrock at the bottom of the open cut bearing platform to complete the construction of anchoring holes;

and 4, step 4: inserting the anchor rod into each anchoring hole along the positioning sleeve, and pouring anchor rod mortar into the anchoring holes to realize anchoring of the anchor rod;

and 5: welding the pier column stressed main reinforcement and the anchor rods at corresponding positions on the open-cut bearing platform, binding a pier body reinforcement cage, and performing pier body concrete construction;

step 6: and after the pier body construction is finished, backfilling concrete into the foundation pit to a ground line to finish the construction.

Further, the process of excavating the foundation pit in the step 1 is as follows: and removing exposed convex rocks at the river bottom, excavating the foundation pit to be 0.3m above the open excavation bearing platform, and removing the last 0.3m to be fresh weakly weathered bedrock.

Furthermore, the positioning sleeves are arranged on the open cut cushion caps at positions corresponding to the stress main ribs of the pier columns and on the left side and the right side of the pier body.

Furthermore, after the pier body concrete construction, the positioning sleeves on two sides of the pier body are plugged by using durable concrete.

The invention relates to an open cut rock anchor combination foundation, which adopts the technical scheme that: including open-cut cushion cap and stock, open-cut cushion cap sets up on the basement rock, pre-buried location sleeve in the open-cut cushion cap, it is equipped with the communicating anchor hole with location sleeve to bore in the basement rock of open-cut cushion cap bottom, the stock passes location sleeve set up in the anchor hole, it has the stock mortar to fill between stock and location sleeve and the anchor hole inner wall.

Furthermore, the top of the positioning sleeve is not lower than the upper end surface of the open cut bearing platform.

Further, the anchor rod is a straight reinforcing steel bar with ribs, and the top of the anchor rod is welded and fixed with the pier stud stressed main rib.

Furthermore, durable concrete is plugged at the tops of the positioning sleeves on the left side and the right side of the pier body.

The invention has the beneficial effects that: according to the method, the open cut bearing platform is constructed preferentially, and other components are constructed based on the open cut bearing platform, so that the construction of a construction platform is facilitated. Set up the position sleeve in open cut cushion cap, establish the anchor hole drilling through the position sleeve location back, it is easier to compare in directly drilling the pile on the basement rock, and is difficult for appearing phenomenons such as reaming. Because the bedrock is adopted to support the open cut cushion cap, the open cut cushion cap can be used as the support of the anchor rod and the pier body, the anchor rod does not need to have higher strength, the anchor rod is only used for improving the horizontal thrust resistance of the structure and increasing the overturning stability, and the foundation structure is simpler compared with a rock anchor foundation structure. The anchor rod adopts a straight rod and is directly welded with the stressed main rib of the pier column, so that the stability is higher.

Drawings

FIG. 1 is a front view of a foundation of an open cut rock anchor assembly of the present invention;

fig. 2-7 are construction schematic diagrams of steps 1-6 of the open cut rock anchor combined foundation reverse operation construction method of the invention.

In the figure: the method comprises the following steps of 1-open excavation bearing platform, 2-anchor rod, 3-positioning sleeve, 4-anchor rod mortar, 5-anchoring hole, 6-pier column stress main rib, 7-bedrock, 8-pier body and 9-concrete.

Detailed Description

The invention is described in further detail below with reference to the following figures and specific examples:

as shown in fig. 1, the open cut rock anchor combined foundation comprises an open cut cushion cap 1 and an anchor rod 2, wherein the open cut cushion cap 1 is arranged on bedrock 7 and is of a reinforced concrete rectangular structure, and design check and calculation indexes such as compression resistance, thrust resistance, overturning resistance and the like all meet the design index requirements of a conventional open cut foundation. A positioning sleeve 3 is embedded in the open cut bearing platform 1, most of the positioning sleeve 3 is steel pipes and is used as a positioning guide hole for construction of the anchor rod drilling machine, and the diameter of the positioning guide hole is 0.5-2 cm larger than that of the anchor rod 2. The positioning sleeve 3 comprises three groups, wherein the middle group is annularly distributed, the middle group of positioning sleeve 3 corresponds to the pier body 8, and two rows of positioning sleeves 3 are respectively arranged on two sides of the pier body 8. The bed rock 7 of open cut cushion cap 1 bottom is bored in and is equipped with the communicating anchor hole 5 of locating sleeve 3, and stock 2 sets up in locating sleeve 3 and communicating anchor hole 5 to adopt stock mortar 4 fixed. The anchor rod mortar 4 has a hardening and expanding function and can enhance the anchoring property. And the top of the positioning sleeve 3 positioned at the two sides of the pier body 8 is injected with durable concrete to plug and protect the anchor rod mortar 4 inside. The anchor rod 2 is ordinary straight reinforcing bar with ribs, the anchor rod 2 is the safety storage measure that improves the anti horizontal thrust of structure and increase the stability of toppling, and anchor rod 2 is less than traditional rock anchor basis configuration a lot, according to the differentiation degree and the dangerous level of basic basement rock, disposes the reinforcing bar quantity according to engineering experience, and anchor length is no less than 35d. Preferably, the top end of the steel bar of the anchor rod 2 can extend out of the open-cut bearing platform 1 and is welded with the pier column stress main bar 6 at the root part of the pier body 8, so that the connection between the upper pier body 8 and the open-cut bearing platform 1 is enhanced.

As shown in fig. 2-7, the reverse operation construction method of the open cut rock anchor combined foundation comprises the following steps:

step 1: removing exposed protruding rocks at the river bottom, excavating a foundation pit to be 0.3m above the bottom of the open-cut bearing platform, preparing before construction, and removing the last 0.3m to be fresh weakly weathered bedrock before the open-cut bearing platform 1 is constructed;

step 2: binding a reinforcing mesh in the foundation pit, embedding a positioning sleeve in the reinforcing mesh, pouring an open cut cushion cap (requiring full pouring) on the bound reinforcing mesh, and enabling the upper end surface of the open cut cushion cap not to be higher than the positioning sleeve;

and step 3: and drilling holes in the open cut bearing platform through the positioning sleeves to the bedrock at the bottom of the open cut bearing platform to complete the construction of the anchoring holes. In order to ensure that the anchoring holes are not damaged, power impact type drilling equipment is strictly forbidden. Preferentially adopting construction equipment matched with an anchoring product or a static water drilling machine;

and 4, step 4: and removing impurities such as dust and the like in the anchoring holes 5, inserting the anchor rod into each anchoring hole along the positioning sleeve, and pouring anchor rod mortar into the anchoring holes to realize anchoring of the anchor rod. The construction requirements meet the operation specifications of the product and relevant industrial standards, and the construction is carried out under the guidance of professional engineers of the product. In order to ensure the construction quality, an in-situ drawing test is carried out before construction, and the bearing capacity of the anchoring part is not lower than the tensile bearing capacity of the steel bar;

and 5: welding the pier column stress main rib with the anchor rod at the corresponding position on the open cut bearing platform, binding a pier body reinforcement cage, and performing pier body concrete construction;

The above description is only an embodiment of the present invention, and it should be noted that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the protection scope of the present invention.

Claims

1. An open cut rock anchor combined foundation reverse operation construction method is characterized by comprising the following steps:

step 2: binding a reinforcing mesh in the foundation pit, embedding a positioning sleeve (3) in the reinforcing mesh, pouring an open cut bearing platform (1) on the bound reinforcing mesh, and enabling the upper end surface of the open cut bearing platform (1) to be not higher than the positioning sleeve (3);

and 3, step 3: drilling holes in bedrock at the bottom of the open cut bearing platform (1) through a positioning sleeve (3) on the open cut bearing platform (1) to complete construction of anchoring holes (5);

and 4, step 4: inserting the anchor rods (2) into the anchoring holes (5) along the positioning sleeves (3), and pouring anchor rod mortar (4) into the anchoring holes (5) to realize the anchoring of the anchor rods (2);

and 5: welding the pier column stress main rib (6) with the anchor rod (2) at the corresponding position on the open cut bearing platform (1), binding a pier body reinforcement cage, and performing pier body concrete construction;

step 6: and after the pier body (8) is constructed, backfilling concrete (9) into the foundation pit to a ground line to finish construction.

2. The open cut rock anchor combined foundation reverse operation construction method as claimed in claim 1, wherein the process of excavating the foundation pit in the step 1 is as follows: and removing exposed convex rocks at the river bottom, excavating the foundation pit to be 0.3m above the open excavation bearing platform, and removing the final 0.3m to be fresh weakly weathered bedrock (7).

3. The open cut rock anchor combined foundation reverse operation construction method as claimed in claim 1, characterized in that: the positioning sleeves (3) are arranged on the open-cut bearing platform (1) and at positions corresponding to the pier column stress main ribs (6) and on the left side and the right side of the pier body (8).

4. The open cut rock anchor combined foundation reverse operation construction method as claimed in claim 3, characterized in that: after the pier body concrete construction, the positioning sleeves (3) on the two sides of the pier body (8) are plugged by using durable concrete.