阅读说明：本技术 利用被保护基础做锚体的深基坑无内支撑支护方法 (Deep foundation pit support method without inner support by using protected foundation as anchor body ) 是由 关英 于 2021-07-21 设计创作，主要内容包括：本发明涉及工业与民用建筑工程深基坑支护技术领域。利用被保护基础做锚体的深基坑无内支撑支护方法,首先判断被保护基础做深基坑无内支撑支护排桩的锚体是否适用,如果适用则进行设计施工,利用被保护基础建立锚拉式结构支护体系,支护排桩的锚体需同时满足五个条件则被保护基础做深基坑无内支撑支护排桩的锚体适用。通过被保护设备基础锚体的锚拉,支护排桩由悬臂受力变为锚拉式结构,支护结构变形大幅减小。(The invention relates to the technical field of deep foundation pit supporting of industrial and civil building engineering. The method for supporting the deep foundation pit without the inner support by using the protected foundation as the anchor body comprises the steps of firstly judging whether the anchor body of the protected foundation as the deep foundation pit supporting row pile without the inner support is suitable, if the anchor body is suitable, carrying out design construction, and building an anchor-pull type structure supporting system by using the protected foundation, wherein the anchor body of the supporting row pile is suitable for the anchor body of the protected foundation pit supporting row pile without the inner support when the anchor body of the supporting row pile needs to meet five conditions simultaneously. Through the anchor of the basic anchor body of the protected equipment, the supporting row piles are changed into anchor-pulling type structures from cantilever stress, and deformation of the supporting structures is greatly reduced.)

1. The deep foundation pit support method without inner support by using protected foundation as anchor body is characterized by comprising the following steps: firstly, judging whether the anchor body of the deep foundation pit supporting row pile without the inner support is suitable for the protected foundation, if so, carrying out design construction, building an anchor-pull type structure supporting system by utilizing the protected foundation, and if the anchor body of the supporting row pile simultaneously meets the following five conditions, then the anchor body of the deep foundation pit supporting row pile without the inner support is suitable for the protected foundation

The method is characterized in that the geology is silty soil and silty clay, and no soft soil layer exists; the foundation pit dewatering can reach 500mm below the foundation pit bottom elevation;

2, excavating earth and putting slope 1:1, wherein the influence line does not exceed 30% of the width of the anchor body foundation;

the condition 3 is that the influence line of the earthwork excavation slope release 1:2 is not more than 70% of the width of the anchor body foundation;

the ratio of the net height difference from the height of the bottom of the anchor body foundation to the height of the excavation bottom of the deep foundation pit to the net distance from the side of the supporting row pile to the side of the anchor body foundation is more than 1:0.4 under the condition 4;

and under the condition 5, the friction force between the anchor body foundation and the soil is greater than the designed tension force of the anchor rod steel bar.

Technical Field

The invention relates to the technical field of deep foundation pit supporting of industrial and civil building engineering.

Background

And a production line is newly built by utilizing a vacant site in the existing factory building, so that the construction cost can be reduced, and the process transformation progress is accelerated. The deep foundation pit construction is carried out in the existing factory building, and relates to the protection of the foundation of the original factory building and the foundation of peripheral equipment. Deep foundation pit supporting generally adopts a supporting structure or a cantilever type structure without an inner support, and anchor cables and anchor rods are in an anchor pulling type structure. Due to the influences of the depth, the position and the like of a protected building foundation and an equipment foundation, a cantilever type structure, an anchor cable and an anchor rod anchoring and pulling type structure cannot be used under many conditions, and only a supporting type structure can be adopted. When the deep foundation pit is in long and narrow construction environment, the influence of support in the foundation pit, the deep foundation pit construction of digging is extremely difficult, and supports should receive the equipment collision that digs, and construction safety is difficult to guarantee.

Disclosure of Invention

The technical problem to be solved by the invention is as follows: in a long and narrow closed construction environment, a protected foundation is used as a supporting row pile anchor body, and a deep foundation pit supporting structure adopts an anchor pulling type structure without an inner support, so that an efficient and safe construction method is provided for foundation pit earth excavation.

The technical scheme adopted by the invention is as follows: in long and narrow confined industrial factory building, the deep basal pit is strutted and is selected the pile type of proper strut row pile: h-shaped steel piles, steel pipe piles, concrete precast piles, cast-in-place piles and the like; and the equipment foundation and the plant foundation which need to be protected at the two sides outside the foundation pit are used as anchor bodies of the supporting row piles to form an anchoring system of the supporting row piles and the protected foundation.

The method for supporting the deep foundation pit without the inner support by using the protected foundation as the anchor body comprises the steps of firstly judging whether the anchor body of the protected foundation as the deep foundation pit supporting row pile without the inner support is suitable, if the anchor body is suitable, carrying out design construction, and establishing an anchor-pull type structure supporting system by using the protected foundation, wherein the anchor body of the supporting row pile is suitable for the anchor body of the protected foundation as the deep foundation pit supporting row pile without the inner support if the anchor body of the protected foundation needs to meet the following five conditions simultaneously

The method is characterized in that the geology is silty soil and silty clay, and no soft soil layer exists; the foundation pit dewatering can reach 500mm below the foundation pit bottom elevation;

2, excavating earth and putting slope 1:1, wherein the influence line does not exceed 30% of the width of the anchor body foundation;

the condition 3 is that the influence line of the earthwork excavation slope release 1:2 is not more than 70% of the width of the anchor body foundation;

the ratio of the net height difference from the height of the bottom of the anchor body foundation to the height of the excavation bottom of the deep foundation pit to the net distance from the side of the supporting row pile to the side of the anchor body foundation is more than 1:0.4 under the condition 4;

and under the condition 5, the friction force between the anchor body foundation and the soil is greater than the designed tension force of the anchor rod steel bar.

The invention has the beneficial effects that: the foundation pit supporting row pile adopts a supporting structure process of inserting the cement mixing pile into the H-shaped steel, utilizes a protected foundation as an anchor body, and has an anchor pulling type structure without an inner foundation pit support, thereby solving the construction problem that the deep foundation pit is extremely difficult to dig due to the influence of the inner foundation pit support.

The anchor pulling relation is formed among the supporting row piles, the top beams and the anchor body equipment foundations through anchor rod reinforcing steel bars, the supporting row piles are changed into anchor pulling structures through cantilever stress through anchor pulling of the anchor bodies of the protected equipment foundations, and deformation of the supporting structures is greatly reduced. Because the deformation of the supporting structure is greatly reduced, the settlement deformation of the protected equipment foundation is also greatly reduced, the supporting row piles and the protected foundation are supplemented, and the safety coefficient of foundation pit supporting is obviously improved.

Drawings

FIG. 1 is a schematic cross-sectional view of the present invention;

FIG. 2 is a diagram showing data in mm in the example;

wherein: 1. the method comprises the following steps of foundation pit, 2 supporting row piles, 3 waterproof curtain, 4 excavating influence line, 5 protected equipment foundation which is also used as an anchor body, 6 production equipment, 7 clear height difference, 8 crown beam, 9 anchor rod reinforcing steel bar and 10 clear distance.

Detailed Description

Deep foundation pit support method without inner support by using protected foundation as anchor body

The method comprises the following specific steps: firstly, field investigation; secondly, selecting the type of the deep foundation pit supporting row piles; (III) judging whether the anchor body of the protected foundation for supporting the row piles is applicable or not; (IV) anchor rod reinforcing steel bar requirements; (V) designing and constructing a crown beam;

the method comprises the following steps of (I) field investigation:

1. investigating the positions, sizes, embedding depths and distances between the existing building foundation and the equipment foundation and the deep foundation pit;

2. investigating the hydrogeology condition of the existing site: underground water level depth and technical parameters of soil quality of each layer;

3. and calculating the net distance from the existing equipment foundation edge to the edge of the to-be-newly-built structure foundation, and determining the position range of the support row piles which can be designed and arranged.

And (II) deep foundation pit supporting pile arrangement type selection:

1. deep foundation pit support row pile selection, commonly used pile type: h-shaped steel piles, steel pipe piles, concrete precast piles, cast-in-place piles and the like;

2. the selection of the pile type of the deep foundation pit supporting row piles needs to consider the water interception, water stop and precipitation of the foundation pit; the supporting row piles and the waterproof curtain are designed in a unified mode and have the same requirements as those of the prior art.

(III) judging whether the anchor body of the protected foundation for supporting the row piles is applicable or not;

the application range of the anchor body of the row pile for supporting by utilizing the protected foundation is as follows:

the method is characterized in that the geology is silty soil and silty clay, and no soft soil layer exists; the foundation pit dewatering can reach 500mm below the foundation pit bottom elevation;

2, excavating earth and putting slope 1:1, wherein the influence line does not exceed 30% of the width of the anchor body foundation;

the condition 3 is that the influence line of the earthwork excavation slope release 1:2 is not more than 70% of the width of the anchor body foundation;

and 4, the ratio of the net height difference between the height of the bottom of the anchor body foundation and the height of the excavated bottom of the deep foundation pit to the net distance between the side of the supporting row pile and the side of the anchor body foundation is more than 1: 0.4.

And under the condition 5, the friction force between the anchor body foundation and the soil is greater than the designed tension force of the anchor rod steel bar.

The protected foundation can be used as an anchor body when the above 5 conditions are met;

(IV) anchor rod reinforcing steel bar requirements;

1. the diameter of the anchor rod steel bar is not smaller than 25 mm; one end of the anchor body is embedded into the anchor body foundation, and the other end of the anchor body foundation is anchored into the crown beam; the embedded steel bars are threaded steel bars HRB 400; the steel bar is deeply embedded into the anchor body foundation according to the yield strength.

The design tension of anchor rod steel bar is taken according to Fh

The anchor bar spacing is calculated as follows: Fh/N.fy.As

Fh: the horizontal counter force of the elastic fulcrum in the width range is calculated by the soil retaining structure; and calculating according to JGJ120 technical Specification for supporting foundation pits of buildings.

N: number of reinforcing bars

Fy: the design value of the tensile strength of the common steel bar;

as: the cross-sectional area of the tensioned reinforcement;

(V) designing and constructing the crown beam:

the design and construction of the crown beam are designed and constructed according to the JGJ120 of the existing building foundation pit supporting technology, the anchor rod reinforcing steel bar pulling resistance test is carried out, and the foundation pit earthwork excavation is carried out after the foundation pit reinforcing steel bar pulling resistance test is qualified.

Examples

Stainless steel pickling line: a Cr steel special pickling line project is newly built in a Tai-Gai stainless cold rolling plant and is positioned on the west side of a 3# mixed line of an old factory building of the cold rolling plant, and an E-F span the axis of 40-57. The width of a foundation bottom opening of the special pickling line equipment for newly-built Cr steel is 10.2 meters, the length of the foundation bottom opening is about 205.5 meters, and the foundation excavation elevation is-7.70 meters. The buildings and structures parallel to the full length of the 205.5 m deep foundation pit of the project are as follows: the east side is the 3# mixed line equipment foundation of normal production, and the west side is 18 factory building column foundations, all need take protective measures in foundation ditch excavation 45 spread angle influence scope. And the owner requires that two 75-ton crown blocks normally operate and a 3# mixed line normally produces during the construction of the deep foundation pit.

The east 3# mixed line is adjacent to the through length of the deep foundation pit, if the mixed line foundation deforms too much, the inestimable influence is caused on the production line, and the consequences are extremely serious; the loss of the bottom soil of the east mixed line is prevented, and the control of the sedimentation deformation is important.

The construction environment is long and narrow, no construction channel exists, the excavation is extremely difficult and the construction period is tight after the deep foundation pit is conventionally supported by opposite tops, the foundation pit is exposed for a long time and is not beneficial to safe production, and the excavation becomes a key factor for restricting the progress of the construction period.

The engineering supporting row pile adopts a supporting structure type that a cement mixing pile is inserted into H-shaped steel, and a protected equipment foundation is used as an anchor body. An anchor-pull type structure is formed among the supporting row piles, the crown beams and the equipment foundation through anchor rod reinforcing steel bars, and the protected foundation is used as an anchor body, so that the anchor-pull type structure supporting process without the inner support of the deep foundation pit is realized. During the construction of the deep foundation pit, the Tai-Gai stainless 3# mixed line is normally produced, the deformation of the equipment foundation of the production line meets the standard requirement, and the supporting process is successful.

Judging whether an anchor body for supporting the row piles by the protected foundation is applicable or not;

as shown in fig. 2: the 3# mixed wire furnace section equipment base is 12.0 meters wide and 2.5 meters thick, the upper part is a steel coil heating equipment furnace body, the base bottom is 2.5 meters high, the distance between the base bottom and the foundation pit is 2.1 meters, and the height difference is 5.2 meters. Under the condition of good precipitation of a normal foundation pit, the coefficient of slope setting of an earth excavation side slope of a deep foundation pit with the depth of-7.7 m is 1:1, and if the precipitation effect is poor, the influence width of the side slope excavation is at least 1: 2.

The stratum soil texture is shown in the following table, and the stratum soil texture accords with the conditions that the geology is better silt and silty clay, and no soft soil layer exists; the foundation pit dewatering can meet the requirement that the elevation of the foundation bottom is 500 mm;

the influence line of 1:1 of the earthwork excavation slope release reaches 3.1 meters of the foundation, and accounts for 25.4 percent and less than 30 percent of the width of the foundation of 12.2 m;

the influence line of 1:2 of the earthwork excavation slope release reaches 8.3 meters of the foundation, and accounts for 68.0 percent and less than 70 percent of the width of the foundation of 12.2 m;

the ratio of the net height difference from the elevation of the bottom of the anchor body foundation to the excavation bottom elevation of the deep foundation pit to the net distance from the side of the supporting row pile to the side of the anchor body foundation: 5200: 2100=1: 0.404; 0.404 > 0.4.

The calculated value of the friction force between the anchor body foundation and the soil is greater than the designed tension of the anchor rod steel bar.

The requirements of 5 conditions for supporting the row pile anchor body by the protected foundation are met.

Through calculation, the displacement of the supporting row piles is about 9mm, and the ground settlement is carried out by three algorithms: 16mm by trigonometry, 24mm by exponential method and 12mm by parabolic method. The settlement value meets the requirement of the first-grade foundation pit support of JGJ120 of the Specification of building foundation pit support technology.

The construction is started in 6 months in 2012, and the construction is finished in 12 months in 2012, and the settlement observation is carried out on the mixed line foundation and the plant room column foundation in the period, wherein the settlement values are less than 10mm, and the settlement does not have adverse effect on the normal production of the 3# mixed line, so that the invention is proved to be safe and reliable.