阅读说明：本技术 深基坑中的局部加深区域的支护方法 (Supporting method for local deepened area in deep foundation pit ) 是由 李治军 梁犇 宋大琴 于 2020-03-31 设计创作，主要内容包括：本发明具体是一种深基坑中的局部加深区域的支护方法；其特征是：深基坑按照设计要求逐层开挖至基坑基底设计标高,土方整理后浇筑第一开挖面承台底垫层,绑扎承台钢筋,在适当标高位置预留穿预应力锚索的钢管,浇筑承台混凝土；继续向下开挖加深区域土方并施打钢板桩,钢板桩顶下返0.2m处设置有一排预留孔洞,在钢板桩内侧与预留孔洞相同标高处满焊钢冠梁,其上设置预应力锚索端头,通过钢板桩上的预留洞将锚索穿入承台内预埋的钢管内,承台侧张拉预应力锚索到设计拉力；开挖钢板桩合围范围内的土方至加深区域设计标高,待加深区域结构施工完毕后拔出钢板桩。工艺原理简单,易于操作实施,且成本低见效快的优点。(The invention relates to a supporting method of a local deepened area in a deep foundation pit; the method is characterized in that: excavating the deep foundation pit layer by layer to the designed elevation of the foundation pit base according to the design requirement, pouring a bottom cushion layer of a bearing platform of a first excavation surface after earthwork arrangement, binding reinforcing steel bars of the bearing platform, reserving a steel pipe penetrating through a prestressed anchor cable at the position of the proper elevation, and pouring concrete of the bearing platform; continuously excavating deepened area earthwork downwards and driving steel sheet piles, arranging a row of reserved holes at a position which returns 0.2m below the top of each steel sheet pile, fully welding steel crown beams at the same elevation as the reserved holes on the inner sides of the steel sheet piles, arranging prestressed anchor cable ends on the steel sheet piles, penetrating anchor cables into steel pipes pre-buried in a bearing platform through the reserved holes in the steel sheet piles, and tensioning the prestressed anchor cables to a design tension on the side of the bearing platform; and excavating earthwork in the steel sheet pile surrounding range to the design elevation of the deepened area, and pulling out the steel sheet pile after the construction of the deepened area structure is finished. Simple process principle, easy operation and implementation, low cost and quick effect.)

1. A supporting method for a local deepened area in a deep foundation pit is characterized by comprising the following steps: the method comprises the following steps:

step 1, integrally excavating a foundation pit to a first layer of base designed elevation, and pouring bearing platform bottom cushion layer concrete;

step 2, binding reinforcing steel bars in the bearing platform, embedding a steel pipe for penetrating a prestressed anchor cable to a design position, and pouring bearing platform concrete;

step 3, driving the steel sheet piles into a soil layer with a designed depth on the excavation surface of the first layer of the substrate according to the designed position of the local deepened area by a steel sheet pile hammering method;

step 4, after the construction of the steel sheet pile is finished, a row of reserved holes are formed in the position, returning to 0.2m below the top of the steel sheet pile, steel crown beams are fully welded at the same elevation as the reserved holes on the inner side of the steel sheet pile, and prestressed anchor cable fixing end heads are arranged on the steel crown beams; adjusting the angle of the fixed end of the anchor cable to ensure that the axis of the prestressed anchor cable is vertical to the anchor backing plate;

step 5, penetrating a prestressed anchor cable from a pre-buried steel pipe in a bearing platform through a steel sheet pile reserved hole, locking a steel sheet pile side anchor cable fixing end, arranging an anchor backing plate on the bearing platform side, adjusting the angle, tensioning the prestressed anchor cable, and locking the prestressed anchor cable to a design tensioning value;

and 6, excavating earthwork within the surrounding range of the steel sheet pile layer by adopting machinery to the bottom elevation of the deepened area, backfilling the earthwork between the steel sheet pile and the structure after constructing the structure at the part, pulling out the steel sheet pile after unloading the prestressed anchor cable, and grouting reserved steel pipe holes in the bearing platform.

Technical Field

The invention relates to the field of foundation pit construction, in particular to a supporting method for a local deepened area in a deep foundation pit.

Background

With the rapid development of urban construction and economy in China, landmark type super high-rise buildings are built in more and more cities, which is an important measure for urban development and reasonable land development and utilization. However, the deep foundation pit construction and supporting problems of the super high-rise building are the most important and difficult parts in the super high-rise construction all the time, and particularly the supporting problem of the local deepened area at the bottom of the deep foundation pit is the most important. How to safely, economically and quickly finish the excavation and supporting problems of the area, at present, a structure which can be designed according to the original project needs to be found to improve the safety and the economical efficiency of the local excavation area.

Disclosure of Invention

The invention aims to provide a construction method, which utilizes an original structure as a part of a supporting structure to form an integral structure with a foundation cap of a first excavation surface through an anchor rope under the condition of not disturbing a soil body below the first excavation surface. The lateral stiffness of the steel sheet pile is improved, the deformation of a supporting structure of a local deepened area is controlled, and meanwhile the steel sheet pile can provide a certain water stopping effect for the deepened area.

In order to achieve the above object, the present invention is realized by:

a supporting method for a local deepened area in a deep foundation pit comprises the following steps:

step 1, integrally excavating a foundation pit to a first layer of base designed elevation, and pouring bearing platform bottom cushion layer concrete;

step 2, binding reinforcing steel bars in the bearing platform, embedding a steel pipe for penetrating a prestressed anchor cable to a design position, and pouring bearing platform concrete;

step 3, driving the steel sheet piles into a soil layer with a designed depth on the excavation surface of the first layer of the substrate according to the designed position of the local deepened area by a steel sheet pile hammering method;

step 4, after the construction of the steel sheet pile is finished, a row of reserved holes are formed in the position, returning to 0.2m below the top of the steel sheet pile, steel crown beams are fully welded at the same elevation as the reserved holes on the inner side of the steel sheet pile, and prestressed anchor cable fixing end heads are arranged on the steel crown beams; adjusting the angle of the fixed end of the anchor cable to ensure that the axis of the prestressed anchor cable is vertical to the anchor backing plate;

step 5, penetrating a prestressed anchor cable from a pre-buried steel pipe in a bearing platform through a steel sheet pile reserved hole, locking a steel sheet pile side anchor cable fixing end, arranging an anchor backing plate on the bearing platform side, adjusting the angle, tensioning the prestressed anchor cable, and locking the prestressed anchor cable to a design tensioning value;

and 6, excavating earthwork within the surrounding range of the steel sheet pile layer by adopting machinery to the bottom elevation of the deepened area, backfilling the earthwork between the steel sheet pile and the structure after constructing the structure at the part, pulling out the steel sheet pile after unloading the prestressed anchor cable, and grouting reserved steel pipe holes in the bearing platform.

The method is suitable for the situation that the height difference of the bottom elevation of the foundation pit is large, and under the condition that soil mass below a first excavation surface is not disturbed, the original structure is used as one part of a supporting structure, so that convenience is provided for accelerating the construction of the deep foundation pit of the super high-rise building.

Drawings

Fig. 1 is a plan view and a sectional view of a supporting structure when the construction method is used.

Detailed Description

The invention is further illustrated by the following specific examples.

As shown in fig. 1, a method for supporting a local deepened area in a deep foundation pit includes the following steps:

step 1, integrally excavating a foundation pit to a first layer of base designed elevation, and pouring bearing platform bottom cushion layer concrete;

step 2, binding reinforcing steel bars in the bearing platform, embedding a steel pipe for penetrating a prestressed anchor cable to a design position, and pouring bearing platform concrete;

step 3, driving the steel sheet piles into a soil layer with a designed depth on the excavation surface of the first layer of the substrate according to the designed position of the local deepened area by a steel sheet pile hammering method;

step 4, after the construction of the steel sheet pile is finished, a row of reserved holes are formed in the position, returning to 0.2m below the top of the steel sheet pile, steel crown beams are fully welded at the same elevation as the reserved holes on the inner side of the steel sheet pile, and prestressed anchor cable fixing end heads are arranged on the steel crown beams; adjusting the angle of the fixed end of the anchor cable to ensure that the axis of the prestressed anchor cable is vertical to the anchor backing plate;

step 5, penetrating a prestressed anchor cable from a pre-buried steel pipe in a bearing platform through a steel sheet pile reserved hole, locking a steel sheet pile side anchor cable fixing end, arranging an anchor backing plate on the bearing platform side, adjusting the angle, tensioning the prestressed anchor cable, and locking the prestressed anchor cable to a design tensioning value;

and 6, excavating earthwork within the surrounding range of the steel sheet pile layer by adopting machinery to the bottom elevation of the deepened area, backfilling the earthwork between the steel sheet pile and the structure after constructing the structure at the part, pulling out the steel sheet pile after unloading the prestressed anchor cable, and grouting reserved steel pipe holes in the bearing platform.

The method is suitable for the situation that the height difference of the bottom elevation of the foundation pit is large, and under the condition that soil mass below a first excavation surface is not disturbed, the original structure is used as one part of a supporting structure, so that convenience is provided for accelerating the construction of the deep foundation pit of the super high-rise building.