CN113897998B - Root-hair type reinforced foundation structure and construction method - Google Patents

Abstract

The invention relates to a root-and-fibrous reinforced foundation structure and a construction method, including a plate foundation, a multi-layer geogrid, anchor hooks, backfill soil, and a capillary anti-seepage layer. The geogrid is connected with the plate foundation through the anchor hooks to form a plate foundation The roots of the backfill form a whole with the backfill to improve the compressive and pull-out bearing capacity of the foundation. The fibrous anchor hooks can coordinate with the backfill to deform, which is conducive to the compaction of the backfill. Capillary anti-seepage layer, the invention integrates the geogrid material with the plate foundation through anchor hooks and extends into the soil to form a space network root structure, and the root-fibrous geogrid can effectively distribute the foundation load and improve The load-bearing performance of the foundation ensures the reliability of the foundation's compressive and pull-out capabilities under saline-alkali geological conditions.

Description

Root and whisker reinforced foundation structure and its construction method

technical field

The invention relates to the technical field of transmission tower foundations, in particular to a root-and-fibrous reinforced foundation structure and a construction method.

Background technique

A large number of shallow foundations are used for the foundation of transmission lines in Northwest my country, and the construction method adopts the excavation method. The excavation construction will cause damage to the foundation soil, and the strength of the backfill soil may be greatly reduced. The backfill soil is reset due to the disturbance of the soil pore distribution. , the permeability may be higher than that of the undisturbed soil, and the infiltration of rainfall into the foundation soil may be greatly improved. Therefore, it will bury a safety hazard for the bearing capacity and pullout resistance of the tower foundation, and reduce the reliability of the long-term operation of the tower foundation for power transmission and transformation projects. , therefore, root-and-fibrous reinforcement and construction methods are needed to solve the above problems.

Contents of the invention

The purpose of the present invention is to overcome that the existing tower foundation construction method adopts the excavation method, and the excavation construction will cause damage to the foundation soil, and the strength of the backfill soil may be greatly reduced, which will greatly reduce the bearing capacity and pull-out resistance of the tower foundation. For potential safety hazards, provide root-and-fibrous reinforced infrastructure and construction methods.

The root-and-fibrous reinforced infrastructure provided by the present invention includes:

The slab foundation is set in the foundation pit, and its bottom is connected with the bottom of the foundation pit;

Multi-layer geogrids are evenly laid in the foundation pit from bottom to top, and the space between geogrids is filled with backfill;

An anchoring hook, the two ends of which are connected to the slab foundation, and the side away from the end is connected to the geogrid;

The capillary anti-seepage layer is laid on top of the backfill.

Preferably, the slab foundation includes a horizontal plate connected to the bottom of the foundation pit, a vertical plate connected to the horizontal plate, and two ends of the anchoring hook are fixedly connected to the sides of the vertical plate.

Preferably, the capillary anti-seepage layer includes a coarse aggregate layer and is laid on top of the backfill, and a fine aggregate layer is laid on top of the coarse aggregate layer.

Preferably, the anchoring hook is made of fibrous material.

Preferably, an organic soil layer is laid above the capillary anti-seepage layer.

Preferably, the following steps are included:

S1. Mark the excavation sideline, excavate the foundation pit along the excavation sideline, and lay the bottom geogrid at the bottom of the foundation pit;

S2. Bind the foundation reinforcement above the bottom geogrid and bury the anchor hook 3, fix the pouring formwork, and pour the slab foundation;

S3. After the slab foundation to be poured is solidified, lay geogrid layer by layer on both sides of the slab foundation and connect the geogrid to the corresponding anchor hooks, and at the same time backfill layer by layer and compact the backfill soil;

S4. Laying a coarse aggregate layer above the uppermost layer of backfill, and laying a first geotextile on the upper surface of the coarse aggregate layer;

S5. Laying a fine aggregate layer above the first geotextile, and laying a second geotextile on the upper surface of the fine aggregate layer;

S6. Laying an organic soil layer above the second geotextile.

Preferably, in step S3, the calculation method of the anchorage length of the geogrid is as follows:

S31. Measure the depth H of the foundation pit, and calculate the laying layers N of the geogrid according to the following formula ①:

In the formula, N is the number of laying layers of geogrid, N is an integer, H is the depth of the foundation pit, S is the distance between adjacent geogrids, 1m≤S≤1.5m;

S32. Knowing the compressive bearing capacity F of the slab foundation to be achieved after strengthening, _{and strengthening} , calculate the total anchoring force F _anchor of the geogrid according to the following formula ②:

In the formula, F _{pressure, reinforcement} is the compression bearing capacity of the reinforced slab foundation, F _pressure is the original design compression bearing capacity of the slab foundation, and η _pressure is the compression correction coefficient;

S33. According to the number of laying layers N of geogrid calculated by formula ① and the total anchoring force F _anchor of geogrid calculated by formula ②, the anchoring force F of single-layer geogrid is calculated by the following formula ③:

In the formula, F _anchor is the total anchoring force of geogrid, and N is the number of laying layers of geogrid;

S34. Determine the failure surface according to the shearing method for the calculation of the uplift stability of the tower foundation. The total length of the geogrid is L, the free length is L ₁ , and the anchorage length is L ₂ . Calculate the anchorage length L ₂ of the geogrid by the following formula ④ :

In the formula, F is the anchoring force of the single-layer geogrid, c′ is the effective cohesion of the soil where the geogrid is located, σ′ _v is the vertical effective stress of the soil where the geogrid is located, and δ is the effective stress of the soil where the geogrid is located. _The friction angle between the soil and the geogrid, L2 is the anchorage length of the geogrid.

Preferably, in step S4, the particle size of the coarse aggregate layer 4 is 10mm-25mm.

Preferably, in step S5, the particle size of the fine aggregate layer 5 is 0.1mm-2mm.

Compared with the prior art, the root and whisker type reinforced foundation structure and construction method provided by the present invention have the beneficial effects of:

1. In the present invention, the geogrid material is integrated with the slab foundation through anchor hooks and extended into the soil to form a space network root-fibrous structure. The root-fibrous geogrid can effectively distribute the foundation load and improve the bearing capacity of the foundation. Performance, to ensure the reliability of the foundation's ability to resist compression and pullout under saline-alkali geological conditions.

2. The fiber anchoring hook used in the present invention is a kind of flexible material, which can cooperate with the backfill soil to deform, ensuring the compactness of the backfill soil. It can bear normal stress under the condition of saline-alkali geological conditions, which effectively guarantees the reliability of the foundation's compressive and pull-out bearing capacity under saline-alkali geological conditions.

3. The present invention calculates and designs the particle size and thickness of the coarse and fine aggregate layer according to the principle of unsaturated soil mechanics and the historical maximum rainfall of the engineering project location. The coarse aggregate layer will form a water-stop curtain to effectively prevent the rainfall from affecting the foundation soil. The infiltration and softening effect of the foundation can effectively strengthen the foundation's ability to resist complex and harsh natural environments, and effectively improve the durability of the foundation's compression and pull-out bearing capacity under complex natural conditions.

Description of drawings

Fig. 1 is the overall structure schematic diagram of the present invention;

Fig. 2 is a reference diagram for the calculation and design method of the anchorage length of the geogrid 2 in the present invention.

Explanation of reference signs:

1. Plate foundation; 2. Geogrid; 3. Anchor hook; 4. Coarse aggregate layer; 5. Fine aggregate layer; 6. Organic soil layer; 7. Foundation pit; 8. Backfill soil.

detailed description

A specific embodiment of the present invention will be described in detail below with reference to accompanying drawings 1 and 2 , but it should be understood that the protection scope of the present invention is not limited by the specific embodiment.

As shown in Figure 1, the root-and-fibrous reinforced foundation structure provided by the present invention includes a plate foundation 1, a multi-layer geogrid 2, an anchor hook 3, backfill soil 8, and a capillary anti-seepage layer. The plate foundation 1 is arranged in the foundation pit 7, the bottom of which is connected to the bottom of the foundation pit 7, and multi-layer geogrids 2 are evenly laid in the foundation pit 7 from bottom to top, and backfill soil 8 is filled between two adjacent geogrids 2, and the anchoring hooks The two ends of 3 are pre-buried in the slab foundation 1, and the side of the anchor hook 3 away from the end is connected with the geogrid 2; a capillary anti-seepage layer is laid on the uppermost layer of backfill 8.

Among them, the anchorage length and laying layers of geogrid 2 are calculated according to the bearing capacity of the foundation and geological conditions to determine the specific size and laying quantity. During construction, the geogrid material is first laid and then backfilled and compacted. Under the anti-seepage layer, each layer of geogrid is integrated into a whole through multiple anchor hooks and slab foundations and extends into the soil to form a spatial network of roots and fibrous structures. The root and fibrous geogrids can effectively distribute the foundation load , improve the bearing capacity of the foundation.

Further, the slab foundation 1 includes a horizontal plate, which is connected to the bottom surface of the foundation pit, and the vertical plate is connected to the horizontal plate, and the two ends of the anchoring hook 3 are fixedly connected to the sides of the vertical slab, and the slab foundation 1 is poured, and at the same time The ends of the anchor hooks 3 are poured into the risers.

Further, the capillary anti-seepage layer includes a coarse aggregate layer 4, which is laid on the top of the backfill soil 8, and a fine aggregate layer 5 is laid on the top of the coarse aggregate layer 4, and the middle of the coarse aggregate layer 4 and the fine aggregate layer 5 uses The geotextile is used to isolate the particle size and thickness of the coarse aggregate layer 4 and the fine aggregate layer 5, which are designed and confirmed according to the principle of unsaturated soil mechanics and the highest rainfall in local history. According to the principle of unsaturated soil mechanics, the coarse aggregate The layer will form a water-stop curtain, which can effectively prevent the infiltration and softening of the foundation soil by rainfall, effectively strengthen the foundation's ability to resist complex and harsh natural environments, and effectively improve the foundation's ability to resist compression and pullout under complex natural conditions. Durability.

Further, the anchoring hook 3 is made of fibrous material, and the fibrous anchoring hook is a kind of flexible material that can cooperate with the soil body to deform, which is beneficial to the compaction of the backfill 8. At the same time, the fibrous anchoring hook and the geogrid The grid material has strong corrosion resistance and can bear normal force in saline-alkali environment, which can effectively enhance the corrosion resistance of the root structure under saline-alkali geological conditions, and ensure the reliability of the foundation's compressive and pull-out resistance under saline-alkali geological conditions.

Further, an organic soil layer 6 is laid above the capillary anti-seepage layer, and the type of vegetation planted on the organic soil layer 6 is selected from survivable vegetation according to the local environment, and the thickness of the organic soil layer 6 is designed according to the selected vegetation type.

Corresponding to the above-mentioned root-and-fibrous reinforced foundation structure, the embodiment of the present invention also provides a construction method for the root-and-fibrosis-type reinforced foundation structure, including the following steps:

S1, mark the excavation sideline, excavate the foundation pit 7 along the excavation sideline, and lay the bottom geogrid 2 at the bottom of the foundation pit 7;

S2. Bind the foundation steel bars above the bottom geogrid 2 and bury the anchor hook 3, fix the pouring formwork, and pour the slab foundation 1;

S3. After the slab foundation 1 to be poured is solidified, lay the geogrid 2 layer by layer on both sides of the slab foundation 1 and connect the geogrid 2 with the corresponding anchor hook 3, and backfill and tamp the backfill soil 8 layer by layer at the same time;

S4, laying the coarse aggregate layer 4 above the uppermost layer of backfill soil 8, and laying the first geotextile on the upper surface of the coarse aggregate layer 4;

S5. Laying a fine aggregate layer 5 above the first geotextile, and laying a second geotextile on the upper surface of the fine aggregate layer 5;

S6. The organic soil layer 6 is laid on the second geotextile.

Specifically, in step S3, the anchorage length and laying layers of the geogrid 2 are calculated and determined according to the bearing capacity of the slab foundation 1, and the calculation and design method is as follows:

Referring to attached drawing 2, the dotted line in attached drawing 2 is the failure surface determined by the calculation and shearing method of the uplift stability of the tower foundation in reference to DL/T 5219-2005 "Technical Regulations for the Design of Overhead Power Transmission Line Foundation", where L is the geogrid The total length of , L ₁ is the free length, L ₂ is the anchor length, L=L ₁ +L ₂ ;

S31. Measure the depth H of the foundation pit 7, and calculate the number of laying layers N of the geogrid 2 by the following formula ①:

In the formula, N is the number of laying layers of geogrid 2, N is an integer, H is the depth of foundation pit 7, S is the distance between adjacent geogrids 2, 1m≤S≤1.5m;

S32. Knowing the compressive bearing capacity F to be achieved of the slab foundation 1 after strengthening, _{and strengthening} , calculate the total _anchoring force F of the geogrid 2 according to the following formula ②:

In the formula, F _{pressure, reinforcement} is the compression bearing capacity of slab foundation 1 after strengthening, F _pressure is the original design compression bearing capacity of slab foundation 1, and η _pressure is the compression correction coefficient;

S33, according to the number of laying layers N of geogrid 2 calculated by formula 1 and the total anchorage force F _anchor of geogrid 2 calculated by formula 2, the anchorage force F of single-layer geogrid 2 is calculated by the following formula 3:

In the formula, F _anchor is the total anchoring force of geogrid 2, and N is the number of laying layers of geogrid 2;

S34. Determine the failure surface according to the calculation and shearing method of the uplift stability of the tower foundation. The total length of the geogrid 2 is L, the free length is L ₁ , and the anchorage length is L ₂ . Calculate the anchorage length of the geogrid 2 by the following formula ④ L2 _:

In the formula, F is the anchoring force of the single-layer geogrid 2, c′ is the effective cohesion of the soil where the geogrid 2 is located, σ′ _v is the vertical effective stress of the soil where the geogrid 2 is located, and δ is the geotechnical The friction angle between the soil where the grid 2 is located and the geogrid 2, L ₂ is the anchorage length of the geogrid 2.

Further, in step S32, the total _anchoring force F of the geogrid 2 can also be calculated by the following formula ⑤:

In the formula, F _{, reinforcement} is the tensile bearing capacity of slab foundation 1 after reinforcement, F _, originally designed slab foundation 1’s tensile bearing capacity, and _η , is the tension correction coefficient.

Further, it also includes a method of optimizing the laying layers N of the geogrid 2 and the anchorage length L _{i, 2} of each layer of geogrid 2, where i represents the i-th layer of geogrid, and _{Li, 2} is The anchorage length of the i-th layer of geogrid after optimization design, the anchoring force F _i of the i-th layer of geogrid after optimization design is calculated by the following formula ⑥:

F _i ＝(c _i '+σ' _v,i tanδ _i )L _i,2 ⑥

In the formula, c′ _i is the effective cohesion of the soil where the i-th layer of geogrid is located, δ _i is the friction angle between the soil where the i-th layer of geogrid is located and the geogrid, σ′ _v,i is The vertical effective stress of the soil where the i-th layer of geogrid is located, L _i,2 is the anchorage length of the i-th layer of geogrid after optimized design;

The anchoring force F _anchor produced by all geogrids after the optimized design is calculated by the following formula ⑦:

In the formula, F _anchor is the total anchoring force of all geogrids, N is the total number of layers of geogrids laid, F _i is the anchoring force of the i-th layer of geogrids.

Under the condition that the reinforced compressive capacity F _{, reinforcement} and _uplift capacity F are sufficient, the anchorage length L _i,2 of the geogrid 2 and the number of laying layers N are optimized according to the above calculation method design.

Specifically, in step S4, the particle size and thickness of the coarse aggregate layer 4 are determined according to the principle of unsaturated soil mechanics and the historical maximum rainfall design of the project site, and the particle size of the fine aggregate layer is initially selected as 0.1mm -2mm, the optimization of the selection scheme of the specific particle size can be determined by numerical simulation with finite elements.

Specifically, in step S5, the particle size and thickness of the fine aggregate layer 5 are determined according to the principles of unsaturated soil mechanics and the historical maximum rainfall design of the project location, and the particle size of the coarse aggregate layer is initially selected as 10mm-25mm , the optimization of the specific particle size selection scheme can be determined by numerical simulation with finite elements. The selection of the particle size of the coarse and fine particle layers depends on the rainfall conditions. As a water-stop layer, it mainly undertakes the function of a water-stop curtain.

In summary, the present invention integrates the geogrid material with the slab foundation through anchor hooks and extends it into the soil to form a spatial network of roots and fibrous structures. The root and fibrous geogrids can effectively distribute the foundation load and improve The load-bearing performance of the foundation ensures the reliability of the foundation’s compression and pull-out resistance under saline-alkali geological conditions. The fiber anchor hook is a flexible material that can be deformed together with the backfill to ensure the compactness of the backfill. At the same time Fiber anchor hooks and geogrid materials have strong corrosion resistance, and can bear normal stress under saline-alkali geological conditions, effectively ensuring the reliability of the foundation's compressive and pull-out bearing capacity under saline-alkali geological conditions. According to the principle of unsaturated soil mechanics The calculation and design of the historical maximum rainfall at the location of the project determine the particle size and thickness of the coarse and fine aggregate layer. The coarse aggregate layer will form a water-stop curtain, which can effectively prevent the infiltration and softening of rainfall on the foundation soil, and can effectively strengthen The ability of the foundation to resist complex and harsh natural environments can effectively improve the durability of the foundation's resistance to compression and pullout under complex natural conditions, and eliminate or reduce the safety of power transmission and transformation project tower foundations during the operation period with minimal construction costs Hidden danger.

The above disclosures are only preferred specific embodiments of the present invention, however, the embodiments of the present invention are not limited thereto, and any changes conceivable by those skilled in the art shall fall within the protection scope of the present invention.

Claims (4)

1. A construction method of root-and-fibrous type reinforced foundation structure, characterized in that, the structure comprises: The slab foundation (1) is arranged in the foundation pit (7), and its bottom is connected with the bottom of the foundation pit (7); Multi-layer geogrids (2) are evenly laid in the foundation pit (7) from bottom to top, and backfill soil (8) is filled between the geogrids (2); An anchoring hook (3), the two ends of which are connected to the slab foundation (1), and the side away from the end is connected to the geogrid (2); The capillary anti-seepage layer is laid on the top of the backfill (8); The capillary anti-seepage layer includes a coarse aggregate layer (4), which is laid above the backfill soil (8), and a fine aggregate layer (5) is laid above the coarse aggregate layer (4); The plate foundation (1) includes a horizontal plate connected to the bottom surface of the foundation pit, a vertical plate is connected to the horizontal plate, and both ends of the anchoring hook (3) are fixedly connected to the sides of the vertical plate ; The construction method of the structure includes the following steps: S1, mark the excavation sideline, excavate the foundation pit (7) along the excavation sideline, and lay the bottom geogrid (2) at the bottom of the foundation pit (7); S2. Bind the foundation reinforcement above the bottom geogrid (2) and bury the anchor hook (3), fix the pouring formwork, and pour the slab foundation (1); S3. After the slab foundation (1) to be poured is solidified, lay geogrids (2) layer by layer on both sides of the slab foundation (1) and connect the geogrids (2) with the corresponding anchor hooks (3), at the same time Backfill and tamp the backfill soil (8) layer by layer; the calculation method for the anchorage length of the geogrid (2) is as follows: S31, measure the depth H of the foundation pit (7), and calculate the number of laying layers N of the geogrid (2) by the following formula 1.:

In the formula, N is the number of laying layers of the geogrid (2), N is an integer, H is the depth of the foundation pit (7), S is the distance between adjacent geogrids (2), 1m≤S≤1.5 m; S32. Knowing the compressive bearing capacity F of the slab foundation (1) to be achieved after _{reinforcement} , and strengthening, calculate the total anchoring force F _anchor of the geogrid (2) according to the following formula ②:

In the formula, F _{pressure, reinforcement} is the compressive bearing capacity of the slab foundation (1) after reinforcement, F _pressure is the original design slab foundation (1) compressive bearing capacity, and η _pressure is the compression correction coefficient; S33, according to the number of laying layers N of the geogrid (2) calculated by formula 1 and the total anchoring force F _anchor of the geogrid (2) calculated by formula 2, the single-layer geogrid (2) is calculated by the following formula 3 ) anchoring force F:

In the formula, the F _anchor is the total anchoring force of the geogrid (2), and N is the number of laying layers of the geogrid (2); S34. Determine the failure surface according to the shearing method for calculating the stability of the tower foundation. The total length of the geogrid (2) is L, the free length is L ₁ , and the anchorage length is L ₂ . Calculate the geogrid (2) by the following formula ④ ) anchorage length L ₂ :

In the formula, F is the anchoring force of the single-layer geogrid (2), c′ is the effective cohesion of the soil where the geogrid (2) is located, and σ′ _v is the vertical direction of the soil where the geogrid (2) is located. Effective stress, δ is the friction angle between the soil of the geogrid (2) and the geogrid (2), and L ₂ is the anchorage length of the geogrid (2); S4. Laying a coarse aggregate layer (4) above the uppermost layer of backfill soil (8), and laying a first geotextile on the upper surface of the coarse aggregate layer (4); S5, laying a fine aggregate layer (5) above the first geotextile, and laying a second geotextile on the upper surface of the fine aggregate layer (5); S6. Laying an organic soil layer (6) above the second geotextile. 2. The construction method of the root and whisker type reinforced foundation structure according to claim 1, characterized in that, the anchoring hook (3) is made of fibrous material. 3. The construction method of root-and-fibrous reinforced foundation structure according to claim 1, characterized in that, in step S4, the particle size of the coarse aggregate layer (4) is 10mm-25mm. 4. The construction method of root-and-fibrous reinforced foundation structure according to claim 1, characterized in that, in step S5, the particle size of the fine aggregate layer (5) is 0.1mm-2mm.

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