CN116084427A - Construction method of raft inner foundation pit for water-rich foundation in quicksand layer - Google Patents

Abstract

The invention provides a foundation pit construction method in a quicksand layer water-rich foundation raft, which comprises the following steps: step 1), driving Larson steel sheet piles; step 2) vertically excavating earthwork in Larson steel sheet piles, excavating to the bottom of a foundation pit in a raft, and pouring a concrete cushion layer on the bottom of the foundation pit in the raft by adopting C20 concrete; step 3) placing a precast concrete module on the concrete cushion layer, so that the top elevation of the precast concrete module is equal to the bottom elevation of the raft cushion layer, and filling gaps between the precast concrete module and the Larson steel sheet piles by adopting C20 concrete pouring; and 4) pulling out the Larson steel sheet pile, binding steel bar casting concrete in a groove of the Larson steel sheet pile to serve as a wall of a foundation pit in the raft, and anchoring 90-degree bent anchor steel bars on the precast concrete module, wherein the concrete casting forms a raft cushion layer, so that the construction of the foundation pit in the raft is completed. The invention utilizes Larson steel sheet piles and precast concrete modules to effectively block water and flow sand, and has good blocking effect on the water-rich geological condition of the flow sand.

Description

Construction method of raft inner foundation pit for water-rich foundation in quicksand layer

technical field

The invention relates to the technical field of building construction, in particular to a method for constructing a foundation pit in a water-rich foundation raft in a quicksand layer.

Background technique

Under normal circumstances, the engineering elevator foundation pit and sump pit are located under the foundation trench, and the sump pit and elevator pit are excavated with slopes (45° to 60°). Forming, the conventional method is to carry out slope protection construction in the form of brick guide wall and soil nail wall spray anchor, but when encountering fine sand (layer or sandy silt layer) geology, if the water level is too high, the slope will not be formed. And the formation of quicksand and piping phenomenon.

When the elevator foundation pit and sump pit are excavated, there will be a lot of water gushing in the pit. Because the soil of this layer is silt and fine sand layer, the self-stability is poor, and it is easy to cause quicksand and collapse at the edge of the pit due to the influence of seepage, which will affect the safety of the foundation pit. During the construction period, if it is the rainy season, a large amount of rainwater infiltrates and scours seriously affects the stability of the slope. Especially in the foundation treatment area, the sump pit and the elevator foundation pit are connected into one piece, and there are a large number of cement fly ash gravel piles inside. If they are not handled properly, the cement fly ash gravel piles may even break and deviate. structure is adversely affected.

Contents of the invention

In order to overcome the problems existing in the prior art, the present invention provides a method for constructing a raft inner foundation pit in a water-rich foundation in a quicksand layer, which can block water and quicksand in excavating the raft inner foundation pit in a water-rich foundation in a quicksand layer effect.

A method for constructing a foundation pit in a water-rich foundation raft in a quicksand layer, comprising the following steps:

Step 1) According to the layout design of the foundation pit in the raft slab on the drawing, drive Larsen steel sheet piles at the first distance from the outer wall of the foundation pit in the raft slab;

Step 2) Excavate the earthwork vertically in the Larsen steel sheet pile, excavate to the bottom of the foundation pit in the raft, at the second distance from the inner wall of the Larsen steel sheet pile, and use C20 concrete to pour concrete pads on the bottom of the foundation pit in the raft layer;

Step 3) Put the precast concrete module on the concrete cushion, so that the top elevation of the precast concrete module is the same as the bottom elevation of the raft cushion, and the gap between the precast concrete module and the Larsen steel sheet pile is filled with C20 concrete;

Step 4) After the Larsen steel sheet piles are poured and the concrete is initially set, the Larsen steel sheet piles are pulled out, and the upper mouth of the precast concrete module is poured with the same grade of concrete as the raft foundation cushion, and the Larsen steel sheet piles are pulled out and bound in the groove Reinforcement, concrete is poured as the wall of the foundation pit in the raft slab, anchored by 90° bent anchor steel bars on the prefabricated concrete module, and concrete is poured to form the cushion of the raft slab to complete the construction of the foundation pit in the raft slab.

Further, in step 1, the embedding depth of the Larsen steel sheet pile driven into the foundation pit in the raft is twice the depth of the foundation pit in the raft, and the top elevation of the Larsen steel sheet pile is at least higher than that of the raft pad The elevation of the bottom of the layer is 300mm, and the first distance is greater than or equal to 350mm.

Further, in step 2, the second distance is greater than or equal to 50 mm, and the thickness of the concrete cushion is 100 mm to 150 mm.

Further, in step 3, the thickness of the precast concrete module is 200mm, and the precast concrete module is made of Ø8@200 double-layer two-way steel mesh and C20 concrete pouring, and the inner corner of the precast concrete module is an arc corner.

Further, in step 4, the thickness of the raft cushion layer is 100mm-150mm.

The beneficial effects of the present invention are: the Larsen steel sheet pile adopted in the present invention effectively prevents quicksand from rushing to the sump and the elevator foundation pit, prevents the side slope from collapsing, avoids the disturbance of the surrounding foundation soil caused by the collapsed part, and increases the foundation treatment measures and costs, Compared with the traditional brick membrane, the prefabricated concrete module has faster construction, effectively blocks water and quicksand, and has a good barrier effect on quicksand and water-rich geological conditions, and the surface layer is smooth and flat, ensuring the smooth and effective waterproof base.

Description of drawings

Fig. 1 is the top view of the foundation pit in the quicksand layer water-rich foundation raft of the present invention;

Fig. 2 is a sectional view of the foundation pit in the raft of the quicksand layer water-rich foundation of the present invention.

Explanation of symbols in the accompanying drawings:

1. Inner diameter of the foundation pit in the raft, 2. Waterproof layer, 3. Precast concrete module layer, 4. C20 concrete pouring to fill the gap,

5. Larsen steel sheet pile, 6. Precast concrete module arc inner corner, 7. Concrete cushion, 8. Original soil, 9. Reserved original soil.

Detailed ways

In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

Wherein, the accompanying drawings are only for illustrative purposes, showing only schematic diagrams, rather than physical drawings, and should not be construed as limitations on this patent; in order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings will be omitted, Enlargement or reduction does not represent the size of the actual product; for those skilled in the art, it is understandable that certain known structures and their descriptions in the drawings may be omitted.

In the drawings of the embodiments of the present invention, the same or similar symbols correspond to the same or similar components; , "inner", "outer" and other indicated orientations or positional relationships are based on the orientations or positional relationships shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred devices or elements must It has a specific orientation, is constructed and operated in a specific orientation, so the terms describing the positional relationship in the drawings are for illustrative purposes only, and should not be understood as limitations on this patent. For those of ordinary skill in the art, the specific understanding of the specific meaning of the above terms.

In the description of this patent, unless otherwise clearly stipulated and limited, if the term "connection" appears to indicate the connection relationship between parts, the term should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection. Connection, or integration; it can be mechanical connection or electrical connection; it can be direct connection or indirect connection through an intermediary, and it can be the internal communication of two parts or the interaction relationship between two parts. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention in specific situations.

A method for constructing a foundation pit in a water-rich foundation raft in a quicksand layer, comprising the following steps:

Step 1) According to the layout design of the foundation pit in the raft slab on the drawing, drive Larsen steel sheet piles at the first distance from the outer wall of the foundation pit in the raft slab;

Further, in step 1, the embedding depth of the Larsen steel sheet pile driven into the foundation pit in the raft is twice the depth of the foundation pit in the raft, and the top elevation of the Larsen steel sheet pile is at least higher than that of the raft pad The elevation of the bottom of the layer is 300mm, and the first distance is greater than or equal to 350mm.

According to the layout design of the inner foundation pit of the raft, determine the position of the inner foundation pit of the raft and the position of the outer wall of the inner foundation pit of the raft. , drive into the Larsen steel plate, excavate the area enclosed by the Larsen steel sheet pile, and excavate the foundation pit in the raft. Excavating the foundation pit in the raft on the water-rich foundation of the quicksand layer is prone to a large amount of water gushing, because the soil in this layer is silt and fine sand layer, which has poor self-stability, and is easily affected by seepage to cause quicksand and collapse at the side of the pit, affecting the foundation. To ensure the safety of the pit, Larsen steel plates are installed to prevent quicksand and water from collecting into the area enclosed by Larsen steel sheet piles, which is the foundation pit inside the raft. The purpose of setting the first spacing is to put the precast concrete modules in later. The depth of the Larsen steel sheet pile driven into the foundation pit in the raft is twice the depth of the foundation pit in the raft. In this embodiment, the design depth of the foundation pit in the raft is 4 meters, and the depth of the Larsen steel sheet piles driven into the foundation of the foundation pit in the raft is 9 meters. The top elevation of the Larsen steel sheet pile is at least 300mm higher than the bottom elevation of the raft cushion. The top elevation of the Larsen steel sheet pile is set at least 300mm higher than the bottom elevation of the raft cushion, so that there will be a place to add force when the Larsen steel sheet pile is pulled out later. Considering the actual situation and cost, the height of the top elevation of the Larsen steel sheet pile above the bottom elevation of the raft cushion cannot be greater than 1m.

Step 2) Excavate the earthwork vertically in the Larsen steel sheet pile, excavate to the bottom of the foundation pit in the raft, at the second distance from the inner wall of the Larsen steel sheet pile, and use C20 concrete to pour concrete pads on the bottom of the foundation pit in the raft layer;

Further, in step 2, the second distance is greater than or equal to 50 mm, and the thickness of the concrete cushion is 100 mm to 150 mm.

After the Larsen steel sheet piles are driven into the foundation pit foundation in the raft slab, the earthwork is excavated vertically in the Larsen steel sheet piles. At the second interval of the inner wall of the steel sheet pile, the original soil at the bottom of the pit is made of C20 concrete to pour the concrete cushion. The second distance is set to prevent the concrete cushion from contacting the Larsen steel sheet piles, and the concrete will fix the Larsen steel sheet piles, making it difficult to pull out the Larsen steel sheet piles. According to the engineering regulations, the thickness setting range of the concrete cushion at the bottom of the foundation pit in the raft is 100mm to 150mm. In this embodiment, the thickness of the concrete cushion is 150mm.

Step 3) Put the precast concrete module on the concrete cushion, so that the top elevation of the precast concrete module is the same as the bottom elevation of the raft cushion, and the gap between the precast concrete module and the Larsen steel sheet pile is filled with C20 concrete;

Further, in step 3, the thickness of the precast concrete module is 200mm, and the precast concrete module is made of Ø8@200 double-layer two-way steel mesh and C20 concrete pouring, and the inner corner of the precast concrete module is an arc corner.

In the prior art, the inner foundation pit of the raft needs to be built with brick tire molds, and the brick mold in the inner foundation pit of the raft on the water-rich foundation of the quicksand layer cannot stop the quicksand. Therefore, in the present invention, Larsen steel sheet piles are first arranged outside the foundation pit in the raft to stop the interlayer water in the foundation, so that quicksand will not form, and then put into the prefabricated concrete module, which effectively blocks water and quicksand It has a good barrier effect on the quicksand and water-rich geological conditions. Moreover, the prefabricated concrete module can be pre-cast with concrete at the construction site, or processed to be pre-cast outside the site, and can be directly hoisted and placed on the concrete cushion when in use. The construction period is shortened, and the natural foundation around the sump is not disturbed at the same time, so as to ensure the construction quality. In this embodiment, the prefabricated concrete modules are pre-prepared on site and poured with C20 concrete and Ø8@200 double-layer two-way steel mesh. According to the depth of the foundation pit in the raft, the thickness of the prefabricated concrete module is calculated to be 200mm, which can meet the requirements of mechanical force and engineering size. The internal corners of the precast concrete modules are arc corners, which are used to make the waterproof membranes stick together and form a smooth waterproof layer when the waterproof membrane is pasted. The precast concrete module is a block with a thickness of 200mm, so it is placed on the concrete cushion, and there must be gaps between the Larsen steel sheet piles. These gaps are filled with C20 concrete that is consistent with the concrete strength of the precast concrete module. , forming precast concrete module layers.

Step 4) After the Larsen steel sheet piles are poured and the concrete is initially set, the Larsen steel sheet piles are pulled out, and the upper mouth of the precast concrete module is poured with the same grade of concrete as the raft foundation cushion, and the Larsen steel sheet piles are pulled out and bound in the groove Reinforcement, concrete is poured as the wall of the foundation pit in the raft slab, anchored by 90° bent anchor steel bars on the prefabricated concrete module, and concrete is poured to form the cushion of the raft slab to complete the construction of the foundation pit in the raft slab. Further, the thickness of the raft cushion layer is 100mm-150mm.

The high-quality clay foundation design is stipulated, the slope is set at 60 degrees, and the steel bars are also installed along the 60-degree slope. In the present invention, the precast concrete module is placed vertically on the concrete cushion of the foundation pit, and the corresponding steel bars are also bent at 60 degrees. 90 degrees from vertical. After binding the steel bars, use C20 concrete to pour the raft cushion to complete the construction of the foundation pit in the raft. According to engineering regulations, the thickness of the raft cushion is between 100 mm and 150 mm. In this embodiment, the thickness of the raft cushion is 150 mm.

It should be declared that the above specific implementation manners are only preferred embodiments of the present invention and applied technical principles. Those skilled in the art should understand that various modifications, equivalent replacements, changes and the like can be made to the present invention. However, as long as these changes do not deviate from the spirit of the present invention, they should all be within the protection scope of the present invention. In addition, some terms used in the specification and claims of this application are not limiting, but are only for convenience of description.

Claims (5)

1. A foundation pit construction method in the water-rich foundation raft of quicksand layer, is characterized in that, comprises the following steps: Step 1) According to the layout design of the foundation pit in the raft slab on the drawing, drive Larsen steel sheet piles at the first distance from the outer wall of the foundation pit in the raft slab; Step 2) Excavate the earthwork vertically in the Larsen steel sheet pile, excavate to the bottom of the foundation pit in the raft, at the second distance from the inner wall of the Larsen steel sheet pile, and use C20 concrete to pour concrete pads on the bottom of the foundation pit in the raft layer; Step 3) Put the precast concrete module on the concrete cushion, so that the top elevation of the precast concrete module is the same as the bottom elevation of the raft cushion, and the gap between the precast concrete module and the Larsen steel sheet pile is filled with C20 concrete; Step 4) After the Larsen steel sheet piles are poured and the concrete is initially set, the Larsen steel sheet piles are pulled out, and the upper mouth of the precast concrete module is poured with the same grade of concrete as the raft foundation cushion, and the Larsen steel sheet piles are pulled out and bound in the groove Reinforcement, concrete is poured as the wall of the foundation pit in the raft slab, anchored by 90° bent anchor steel bars on the prefabricated concrete module, and concrete is poured to form the cushion of the raft slab to complete the construction of the foundation pit in the raft slab. 2. the foundation pit construction method in the quicksand layer water-rich foundation raft slab according to claim 1, is characterized in that, in step 1, the embedding depth of the foundation pit foundation in the raft slab of the Larsen steel sheet pile is driven into Twice the depth of the foundation pit in the raft, the top elevation of the Larsen steel sheet pile is at least 300mm higher than the bottom elevation of the raft cushion, and the first distance is greater than or equal to 350mm. 3. The method for constructing an inner foundation pit in a water-rich ground raft in quicksand layer according to claim 1, characterized in that, in step 2, the second distance is greater than or equal to 50 mm, and the thickness of the concrete cushion is 100 mm to 150 mm . 4. The method for constructing a foundation pit in a water-rich ground raft in quicksand layer according to claim 1, characterized in that, in step 3, the thickness of the precast concrete module is 200 mm, and the precast concrete module adopts Ø8@200 double-layer bidirectional It is made of reinforced mesh and C20 concrete, and the internal corners of the precast concrete modules are arc corners. 5 . The method for constructing an inner raft foundation pit on a water-rich foundation in a quicksand layer according to claim 1 , wherein, in step 4, the thickness of the raft cushion layer is 100 mm to 150 mm. 5 .

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