CN111321751A - Deep and thick soft foundation treatment structure suitable for thin holding layer and construction method - Google Patents
Deep and thick soft foundation treatment structure suitable for thin holding layer and construction method Download PDFInfo
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- CN111321751A CN111321751A CN202010195748.7A CN202010195748A CN111321751A CN 111321751 A CN111321751 A CN 111321751A CN 202010195748 A CN202010195748 A CN 202010195748A CN 111321751 A CN111321751 A CN 111321751A
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D27/00—Foundations as substructures
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D27/00—Foundations as substructures
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
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- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
- E02D5/22—Piles
- E02D5/34—Concrete or concrete-like piles cast in position ; Apparatus for making same
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Abstract
The invention belongs to the field of geotechnical engineering, and particularly relates to a deep and thick soft foundation treatment structure and a construction method suitable for a thin holding layer, wherein the foundation treatment structure comprises: a raft plate; the mattress layer is arranged at the bottom of the raft plate and is positioned at the top of the upper soft soil foundation layer; the tubular piles are arranged at intervals, the tubular piles are arranged at the bottom of the mattress layer, and the lower ends of the tubular piles are positioned in the middle bearing layer; stirring stake, the interval sets up, the stirring stake set up in mattress pad layer bottom, the stirring stake is located upper portion soft soil foundation layer. The deep and thick soft foundation treatment structure suitable for the thin holding layer is suitable for saving engineering investment; the settlement of the composite foundation is reduced, the bearing capacity of the composite foundation is improved, and the problems that the pile is located in the middle bearing layer, the settlement of the foundation is large, the bearing capacity of the foundation is low, and the pile easily pierces the middle bearing layer are solved.
Description
Technical Field
The invention belongs to the field of geotechnical engineering, and particularly relates to a deep and thick soft foundation treatment structure suitable for a thin holding layer and a construction method.
Background
At present, soft soil foundations are widely distributed in the southeast coast of China, the depth of the soft soil foundations is usually thick, and deep soft soil on the coast has the characteristics of high natural water content, large pore ratio, high compressibility, low strength, flow molding-plastic state and the like. In the actual design and construction process, a new stratum structure is discovered, namely a layer of fine clay or sandy soil is clamped between deep soft soil layers. The stratum has the characteristics of 'upper softness-middle hardness-lower softness', and specifically, as shown in fig. 1, the stratum is sequentially distributed from top to bottom into an upper soft soil foundation layer 7, a middle supporting layer 8 (non-soft soil layer), a lower soft soil foundation layer 9 and a lower supporting layer 10 (non-soft soil layer). The thickness of the middle supporting layer 8 is usually thick, but the middle supporting layer 8 is sometimes thin (the thickness is 1.5 to 4.0 m).
In engineering, soft soil foundations can be normally used after meeting the requirements of bearing capacity and settlement after foundation treatment. For the foundation treatment of the deep soft soil foundation with the middle supporting layer 8 (the thickness is 1.5-4.0 m), two foundation treatment modes can be adopted according to engineering experience, wherein one mode is to treat the middle supporting layer 8, and the other mode is to treat the middle thin supporting layer 10. The most common and effective method of treatment is if the treatment is to the lower support layer 10, but the required pile length is very long and the investment is often very large; if the treatment reaches the middle thin supporting layer 8, the lower soft soil foundation layer 9 still can subside under the effect of external load to cause the settlement of ground too big to the degree of depth that the pile tip got into the thin supporting layer 8 in middle part is very well controlled, and if too shallow can cause the ground bearing capacity to hang down, if too deep can probably exist: when the pile foundation is suddenly subjected to a large local stress, the pile foundation pierces the middle thin bearing layer 8 and falls into the lower soft soil foundation layer 9.
Disclosure of Invention
The invention aims to: aiming at the problems that the foundation treatment method for treating the deep and thick soft foundation to the lower supporting layer in the prior art is large in engineering investment, the foundation treatment method for treating the foundation to the middle thin supporting layer is too large in settlement, the depth of a pile end entering the supporting layer is difficult to control and the like in the deep and thick soft foundation treatment method for treating the thin supporting layer, the deep and thick soft foundation treatment structure and the construction method suitable for the thin supporting layer are provided, and the deep and thick soft foundation treatment structure and the construction method are particularly suitable for silt soft soil sections.
In order to achieve the purpose, the invention adopts the technical scheme that:
a deep and thick soft foundation treatment structure suitable for sandwiching a thin bearing layer, comprising:
a raft plate;
the mattress layer is arranged at the bottom of the raft plate and is positioned at the top of the upper soft soil foundation layer;
the tubular piles are arranged at intervals, the tubular piles are arranged at the bottom of the mattress layer, and the lower ends of the tubular piles are positioned in the middle bearing layer;
a plurality of stirring stake, the interval sets up, the stirring stake set up in mattress pad layer bottom, the stirring stake is located upper portion soft soil foundation layer.
According to the deep and thick soft foundation treatment structure suitable for the thin holding layer, the arrangement of the raft plates can redistribute the filling load and the external load, so that the loads transmitted to the tubular piles and the stirring piles of the mattress layer are more uniform, and the situation that part of the tubular piles pierce the middle holding layer due to overlarge local stress is avoided;
in order to avoid the problem that the pile top of the tubular pile is a raft plate, and the pile bottom of the tubular pile forms a rigid supporting condition for a middle holding layer, so that most of external load can be transmitted to the tubular pile, and the tubular pile punctures the middle holding layer due to overlarge stress, a mattress layer is arranged, so that the stress distribution of the tubular pile and the stirring pile can be well adjusted, the stress share of the stirring pile is increased, the average stress of each tubular pile is reduced, and the situation that the middle holding layer is punctured due to overlarge stress of part of the tubular pile due to uneven stress of each tubular pile is avoided;
the lower ends of the pipe piles arranged at intervals are positioned in the middle holding layer and are used for supporting the upper load together with the stirring piles; the middle holding layer is adopted instead of the lower holding layer as the holding layer of the tubular pile, so that the engineering investment can be effectively reduced.
The pile end of the stirring pile is arranged in the upper soft foundation, the stirring pile is located in the upper soft foundation layer, the composite foundation formed by the stirring pile and the upper soft foundation layer forms a hard shell layer with a certain thickness relative to all soft soil below the pile end of the stirring pile, namely a foundation structure with a hard top and a soft bottom, the hard shell layer can change the stress diffusion of the filled load and the external load, the depth of the stress diffusion is reduced, the deformation of the lower soft foundation layer under the action of the filled load and the external load can be reduced, and the purpose of controlling the total settlement of the foundation is achieved. The composite foundation formed by the tubular piles and the stirring piles has better bearing capacity of the composite foundation of shallow soil compared with the foundation which is processed to the middle bearing layer by only adopting the tubular piles. Compared with a foundation treatment mode of only adopting a pipe pile to treat the foundation to the middle bearing layer, the settlement of the composite foundation is reduced and the bearing capacity of the composite foundation is improved after the suspended stirring piles are arranged.
In summary, the deep and thick soft foundation treatment structure suitable for the thin holding layer is characterized in that by means of the composite foundation treatment mode of the tubular pile and the stirring pile, compared with the mode of treating the tubular pile to the lower holding layer, the foundation treatment structure saves engineering investment due to reduction of the length of the tubular pile; compared with a foundation treatment mode of only adopting the pipe piles to treat the middle bearing layer, the foundation treatment structure reduces the settlement of the composite foundation and improves the bearing capacity of the composite foundation, and solves the problems that the settlement of the foundation of the pipe pile located on the middle bearing layer is large, the bearing capacity of the foundation is low, and the pipe pile easily penetrates through the middle bearing layer.
Preferably, the tubular pile buries the degree of depth on middle part holding power layer does 0.3 ~ 0.5 times of middle part holding power layer thickness, just the tubular pile buries the degree of depth on middle part holding power layer is greater than or equal to the tubular pile diameter.
The pile end of the tubular pile is located in the middle holding layer, and the depth of the tubular pile entering the middle holding layer is 0.3-0.5 times of the thickness of the middle holding layer and is not less than 1 time of the diameter of the tubular pile. On one hand, the bearing capacity of the pile end can be fully exerted (if the depth of the pile end entering the bearing layer is too small, the bearing capacity of the tubular pile is reduced), and on the other hand, the middle bearing layer is reserved below the pile end by 0.5-0.7 times, so that the tubular pile can be ensured not to pierce the middle bearing layer in the construction and use processes.
Preferably, the depth of the tubular pile embedded in the middle supporting layer is one third of the thickness of the middle supporting layer.
Preferably, the stirring piles are arranged between the adjacent pipe piles.
Tubular pile and stirring stake interval arrangement, stirring stake are arranged at the tubular pile periphery for tubular pile and stirring stake atress are reasonable, have reduced the local condition that takes place stress concentration and impale middle part holding force layer of tubular pile.
Preferably, all the tubular piles are arranged in a grid shape, and the stirring piles are arranged between the diagonal tubular piles.
Tubular pile and stirring stake interval arrangement, the tubular pile adopts the square arrangement of net, and the stirring stake is arranged at the tubular pile periphery for tubular pile and stirring stake atress are more reasonable, have reduced the local condition that takes place stress concentration and impale middle part holding force layer of tubular pile.
Preferably, the thickness of the mattress layer is 0.3 m-0.6 m, and the effect of adjusting the stress is the best.
Preferably, the thickness of the raft is 0.4-0.6 m.
Preferably, the length of the stirring pile is 4-8 m.
The invention also discloses a construction method for forming the deep and thick soft foundation treatment structure suitable for the thin holding layer, which comprises the following steps:
s1: performing construction of all mixing piles;
s2: performing construction of all tubular piles;
s3, filling a mattress layer above the mixing piles and the pipe piles and compacting;
s4: and (5) performing raft construction.
According to the construction method for the deep and thick soft foundation treatment structure suitable for the thin holding layer, due to the fact that the construction mixing pile has a certain soil squeezing effect (particularly near the pile top) and the construction machinery of the tubular pile is larger and heavier than the mixing pile, the construction sequence of constructing the mixing pile first and then constructing the tubular pile is adopted, a hard shell layer can be formed on the ground surface before the tubular pile is constructed, movement of the tubular pile machinery and construction of the tubular pile are facilitated, and meanwhile, the situation that the tubular pile is squeezed and deviated to influence the foundation treatment effect of the tubular pile when the mixing pile is constructed in the construction method of constructing the tubular pile first and then constructing the mixing pile can be avoided.
Preferably, the tubular piles are arranged in a grid shape, and step S2 specifically includes:
s21, carrying out ith row of pipe pile construction, wherein i is more than or equal to 1;
s22, carrying out the i +1 th row of pipe piles construction, and dynamically monitoring the floating, inclining and breaking conditions of the 1 st to i th rows of pipe piles;
s23, circulating the steps S21-S22 to finish the construction of all the tubular piles;
preferably, when the constructed tubular pile floats upwards, inclines or fractures, the pile floating upwards, inclines or fractures is subjected to re-pressing or pile repairing construction, the construction progress is slowed down, and finally construction of all the tubular piles is finished.
By controlling the construction sequence of the tubular piles and carrying out dynamic monitoring, the soil squeezing effect of the tubular piles can be effectively reduced and the construction progress can be controlled; even if the soil squeezing effect of the tubular pile causes the constructed tubular pile to float, incline and break, the problems can be found in time and remedied by adopting the monitoring of the constructed tubular pile, the effect of treating the whole foundation is ensured, and the bearing capacity and the settlement of the composite foundation can meet the use requirements.
Preferably, the tubular pile construction specifically comprises:
A1. determining the position, the length and the depth of the tubular pile entering the middle bearing stratum;
A2. carrying out pile pressing construction, when the distance between the pile end and the middle bearing layer is equal to or less than 2.0m, reducing the pile feeding length, reducing the pile sinking speed, and continuously pressing the pile until the depth of the pile end entering the middle bearing layer reaches the design requirement;
A3. processing the upper end of the tubular pile to enable the upper end of the tubular pile to meet the design requirement;
A4. and pouring micro-expansion concrete into the pile top of the tubular pile to seal the tubular pile, and finishing the construction of the single tubular pile.
When the distance between the pile end and the middle bearing layer is not more than 2.0m, the pile feeding length is reduced, the pile pressing speed is reduced, the depth of the pile entering the middle bearing layer can be better controlled, and the middle bearing layer is prevented from being pierced. When the geological conditions are not accordant with the design, the upper end of the tubular pile is processed, and although a small part of engineering investment is increased by the processing method, the bearing capacity of the pile end can be fully exerted, and the pile end does not pierce through the middle bearing layer. The construction of each tubular pile is controlled by the construction method, so that the aim of strictly controlling the depth of the pile end entering the middle bearing stratum can be fulfilled.
Preferably, the step a3 is specifically:
when the top end of the tubular pile extends out of the theoretical design position of the top end of the tubular pile, performing pile cutting construction on the tubular pile until the top end of the tubular pile reaches the theoretical design position of the top end of the tubular pile;
and when the top end of the tubular pile does not reach the theoretical design position of the upper end of the tubular pile, pile splicing construction is carried out on the tubular pile until the top end of the tubular pile reaches the theoretical design position of the top end of the tubular pile.
Due to the reasons of non-uniformity, uncertainty and insufficient exploration precision of geological distribution, the burial depth and the thickness of the middle bearing stratum have certain differences relative to a design drawing, and the pile is too long or too short.
If the pile tip has reached the design depth into the middle bearing layer but the pile top is still partially above ground (i.e. the pile is too long), then the too long part of the pile top is chiseled off and the too long pile is strictly prohibited from being pressed into the middle bearing layer.
If the pipe pile completely enters the upper soft soil foundation layer, but the pile end does not enter the middle bearing layer (i.e. the pile is too short), pile pressing is required to continue on the pile top until the depth of the pile end entering the middle bearing layer reaches the design depth.
In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:
1. according to the deep and thick soft foundation treatment structure suitable for the thin holding layer, the tubular pile and the stirring pile are compounded to treat the foundation, and compared with the method of treating the foundation to the lower holding layer by adopting the tubular pile, the foundation treatment structure saves the engineering investment due to the reduction of the length of the tubular pile; compared with a foundation treatment mode of only adopting the pipe piles to treat the middle bearing layer, the foundation treatment structure reduces the settlement of the composite foundation and improves the bearing capacity of the composite foundation, and solves the problems that the settlement of the foundation of the pipe pile located on the middle bearing layer is large, the bearing capacity of the foundation is low, and the pipe pile easily penetrates through the middle bearing layer.
2. According to the deep and thick soft foundation treatment structure suitable for the thin holding layer, the pile end of the pipe pile is located on the middle holding layer, and the depth of the pipe pile entering the middle holding layer is 0.3-0.5 times of the thickness of the middle holding layer and not less than 1 time of the diameter of the pile. On one hand, the bearing capacity of the pile end can be fully exerted (if the depth of the pile end entering the bearing layer is too small, the bearing capacity of the tubular pile is reduced), and on the other hand, the middle bearing layer is reserved below the pile end by 0.5-0.7 times, so that the tubular pile can be ensured not to pierce the middle bearing layer in the construction and use processes.
3. According to the deep and thick soft foundation treatment structure suitable for the thin holding layer, the tubular piles and the stirring piles are arranged at intervals, and the stirring piles are arranged on the periphery of the tubular piles, so that the tubular piles and the stirring piles are stressed reasonably, and the situation that the central holding layer is pierced due to the local stress concentration of the tubular piles is reduced.
4. According to the construction method for forming the deep and thick soft foundation treatment structure suitable for the thin holding layer, due to the fact that the construction mixing pile has a certain soil squeezing effect (particularly near the pile top) and the construction machinery of the tubular pile is larger and heavier than the mixing pile, the construction sequence of constructing the mixing pile first and then constructing the tubular pile is adopted, a hard shell layer can be formed on the ground surface before the tubular pile is constructed, movement of the tubular pile machinery and construction of the tubular pile are facilitated, and meanwhile, the situation that the tubular pile is squeezed and deviated to influence the foundation treatment effect of the tubular pile when the mixing pile is constructed in the construction method of constructing the tubular pile first and then constructing the mixing pile can be avoided.
5. According to the construction method for forming the deep and thick soft foundation treatment structure suitable for the thin holding layer, the depth of the tubular pile entering the middle holding layer can be strictly controlled, the bearing capacity of the tubular pile can be fully exerted without piercing the holding layer, the soil squeezing effect of the tubular pile can be reduced, the construction sequence and the construction progress of the tubular pile can be controlled, the treatment effect of the composite foundation is ensured, and the bearing capacity and the settlement of the composite foundation can meet the use requirements.
6. The construction method for forming the deep soft foundation treatment structure suitable for the thin and thick holding layer is safe and reliable for the deep soft foundation with the thin and thick holding layer, strong in implementability, capable of ensuring construction quality and foundation treatment effect, and capable of avoiding the problems of insufficient bearing capacity of the foundation, penetration of tubular piles into the lower holding layer and the like in the later period.
7. According to the construction method for forming the deep and thick soft foundation treatment structure suitable for the thin and firm bearing layer, the soil squeezing effect of the pipe pile can be effectively reduced and the construction progress can be controlled by controlling the construction sequence of the pipe pile and carrying out dynamic monitoring; even if the soil squeezing effect of the tubular pile causes the constructed tubular pile to float, incline and break, the problems can be found in time and remedied by adopting the monitoring of the constructed tubular pile, the effect of treating the whole foundation is ensured, and the bearing capacity and the settlement of the composite foundation can meet the use requirements.
8. According to the construction method for forming the deep and thick soft foundation treatment structure suitable for the thin holding layer, when the distance between the pile end and the middle holding layer is not more than 2.0m, the pile feeding length is reduced, the pile pressing speed is reduced, the depth of the pile entering the middle holding layer can be better controlled, and the middle holding layer is prevented from being punctured. When the geological conditions are not accordant with the design, the upper end of the tubular pile is processed, and although a small part of engineering investment is increased by the processing method, the bearing capacity of the pile end can be fully exerted, and the pile end does not pierce through the middle bearing layer. The construction of each tubular pile is controlled by the construction method, so that the aim of strictly controlling the depth of the pile end entering the middle bearing stratum can be fulfilled.
9. According to the construction method for forming the deep and thick soft foundation treatment structure suitable for the thin and thick bearing stratum, due to the reasons of non-uniformity, uncertainty and insufficient exploration precision of geological distribution, the burial depth and the thickness of the middle bearing stratum have certain differences relative to a design drawing, and the pile is too long or too short. If the pile tip has reached the design depth into the middle bearing layer but the pile top is still partially above ground (i.e. the pile is too long), then the too long part of the pile top is chiseled off and the too long pile is strictly prohibited from being pressed into the middle bearing layer. If the pipe pile completely enters the upper soft soil foundation layer, but the pile end does not enter the middle bearing layer (i.e. the pile is too short), pile pressing is required to continue on the pile top until the depth of the pile end entering the middle bearing layer reaches the design depth. Thereby guarantee that the tubular pile can satisfy the position requirement that the lower extreme stretched into in the middle part holding force layer, can satisfy the position requirement of upper end and mattress bed course matched with again.
Drawings
FIG. 1 is a schematic cross-sectional view of a deep soft foundation formation structure of the prior art.
Fig. 2 is a schematic cross-sectional view of a deep soft foundation treatment structure suitable for sandwiching a thin bearing layer according to the present invention.
Fig. 3 is a schematic plan view of a deep soft foundation treatment structure suitable for sandwiching a thin bearing layer according to the present invention.
Fig. 4 is a flow chart of a construction method for forming the deep and thick soft foundation treatment structure suitable for sandwiching a thin bearing layer according to the present invention.
Fig. 5 is a flow chart of the single tubular pile construction of the invention.
Icon: 1-pipe pile; 2-stirring piles; 3-a mattress layer; 4-raft plates; 5-filling soil; 6-field flat surface; 7-upper soft soil foundation layer; 8-middle holding layer; 9-lower soft soil foundation layer; 10-lower support layer.
Detailed Description
The present invention will be described in detail below with reference to the accompanying drawings.
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
As shown in fig. 2-3, the deep and thick soft foundation treatment structure for a thin bearing layer according to the present embodiment has the following foundation conditions: the upper soft soil foundation layer is 20m thick silt, the middle supporting layer is 3m thick silty clay, the upper soft soil foundation layer is 27m thick silt sand inclusion, the lower supporting layer is coarse sand, and the upper filling is 3m thick silty clay.
A deep and thick soft foundation treatment structure suitable for a thin holding layer comprises a raft 4, a mattress layer 3, a tubular pile 1 and a stirring pile 2. Raft 4 sets up and fills in 5 below, and mattress layer 3 sets up near the natural ground of raft 4 below, and tubular pile 1 and stirring stake 2 interval arrange in mattress layer below and with mattress layer 3's bottom surface in close contact with, and the stake end of tubular pile 1 passes upper portion soft soil foundation 7 and is arranged in middle part bearing layer 8, and the stake end of stirring stake 2 is arranged in upper portion soft foundation 1.
Specifically, the raft 4 is of a reinforced concrete structure with the thickness of 0.5 m; the mattress layer 3 adopts a gravel cushion layer with the thickness of 0.3 m; the PHC tubular pile has the advantages that the pile diameter of the tubular pile 1 is 0.5m, the depth of the tubular pile 1 with the pile length of 21m entering the middle holding layer 8 is 1m (just 1/3 of the thickness of the middle holding layer 8), and the distance between the centers of the piles is 2.2 m; the mixing pile 2 is a cement mixing pile with the pile diameter of 0.5m, the pile length is 6m, and the pile center distance is 1.1 m.
If the tubular pile 1 and the stirring pile 2 are directly contacted with the raft 4 without the mattress layer 3, the pile top of the tubular pile 1 is the rigid supporting condition of the raft 4 and the pile bottom is the middle holding layer 8, and the external load is transmitted to the tubular pile 1 mostly. After the mattress layer 3 is arranged, the stress of the tubular pile 1 and the stirring pile 2 can be well adjusted to share, the stress of the stirring pile 2 is increased to share, and the stress of the tubular pile 1 is reduced.
The pile end of the tubular pile 1 is positioned on the middle holding layer 8, the depth of the tubular pile entering the middle holding layer 8 is 1m, the depth is just 1/3, the thickness of the middle holding layer 8 is not less than 1 time of the diameter of the pile, and the diameter is 0.5 m. Therefore, on one hand, the bearing capacity of the pile end of the tubular pile can be fully exerted (if the depth of the tubular pile entering the bearing layer is too small, the bearing capacity of the tubular pile is reduced), and on the other hand, the middle bearing layer 8 of 2/3 is reserved below the pile end, so that the tubular pile 1 can not penetrate through the middle bearing layer 8 in the construction and use processes.
The pile end of the stirring pile 2 is arranged in the upper soft soil foundation layer 7, the pile length is 6m, and the pile end is positioned in the upper soft soil foundation layer 7. The composite foundation formed by the mixing pile 2 and the upper soft soil foundation layer 7 forms a hard shell layer with a certain thickness relative to all soft soil below the pile end of the mixing pile 2, namely a foundation structure with a hard top and a soft bottom, the hard shell layer can change the stress diffusion of the filling load and the external load, reduce the depth of the stress diffusion, and reduce the deformation of the lower soft soil layer under the effects of the filling load and the external load, thereby achieving the purpose of controlling the total settlement of the foundation. The composite foundation formed by the tubular piles 1 and the stirring piles 2 has better bearing capacity of the composite foundation of shallow soil compared with the foundation which is processed to a middle thin bearing layer by only adopting the tubular piles 1. Therefore, compared with a foundation treatment mode of only adopting the tubular pile 1 to treat the middle thin bearing layer, the settlement of the composite foundation is reduced and the bearing capacity of the composite foundation is improved after the suspended stirring piles 2 are arranged.
If the lower supporting layer 10 is adopted as the foundation treatment scheme of the pile end supporting layer of the tubular pile 1, compared with the scheme, only the stirring pile 2 needs to be cancelled, the pile length of the tubular pile 1 is increased to 51m, and the comparison is 1000m2Investment difference under foundation treatment area: when the foundation treatment scheme is adopted, the total length of the tubular pile 1 is 4339m, the total length of the stirring pile 2 is 3719m, the unit price of the tubular pile 1 is 200 yuan/m, the unit price of the stirring pile 2 is 250 yuan/m, and the total investment is 1053750 yuan; when the scheme of treating the foundation from the tubular pile 1 to the lower bearing stratum 10 is adopted, the total length of the tubular pile 1 is 10537m, and the total investment is 2107438 yuan; comparing the two, it can be found that the engineering investment is reduced by 1053688 yuan (about 50%) by adopting the foundation treatment scheme of the invention compared with the foundation treatment scheme of the pipe pile 1 to the lower supporting layer 10.
Therefore, by adopting the mode of treating the composite foundation by the tubular pile 1 and the stirring pile 2, compared with the mode of treating the lower bearing layer 10 by adopting the tubular pile 1, the foundation treatment structure saves the engineering investment due to the reduction of the pile length of the tubular pile 1; compared with a foundation treatment mode that only the tubular pile 1 is used for treating the composite foundation to the middle supporting layer 8, the foundation treatment structure reduces the settlement of the composite foundation and improves the bearing capacity of the composite foundation, and solves the problems that the tubular pile 1 is positioned on the middle supporting layer 8, the foundation settlement is large, the foundation bearing capacity is low, and the tubular pile 1 easily penetrates through the middle supporting layer 8.
Example 2
As shown in fig. 2 to 5, the present embodiment describes a deep and thick soft foundation treatment structure suitable for sandwiching a thin bearing layer,
1: leveling, measuring and paying off the field, and determining the positions of each tubular pile 1 and each stirring pile 2;
2: and (3) completing the construction of all the mixing piles 2 in sequence, and standing for a period of time to ensure that the mixing piles 2 have certain strength.
3: completing the construction of all the construction tubular piles 1, performing quality detection, and detecting to be qualified;
4, filling and compacting the mattress layer 3 in a layered manner, and carrying out quality detection, wherein the detection is qualified;
5: binding a raft 4 steel reinforcement cage, erecting a mould, and casting the raft 4 concrete in situ to complete the construction of the raft 4;
6: filling soil 5 in layers and compacting, and constructing an upper structure.
Because the construction mixing pile 2 has certain soil squeezing effect (particularly near the pile top) and the construction machinery of the tubular pile 1 is larger and heavier than the mixing pile, a layer of hard shell layer can be formed on the earth surface before the tubular pile 1 is constructed by adopting the construction sequence of constructing the mixing pile 2 firstly and then constructing the tubular pile 1, so that the movement of the tubular pile machinery and the construction of the tubular pile are convenient, and meanwhile, under the construction method of constructing the mixing pile 2 after constructing the tubular pile 1 firstly, the tubular pile 1 is squeezed and deviated when the mixing pile 2 is constructed, so that the foundation treatment effect of the tubular pile 1 is influenced.
The construction sequence of all tubular piles specifically is as follows:
1: firstly, constructing a1 st row of tubular piles 1 from left to right;
2: constructing a2 nd row of tubular piles 1 according to the construction direction (from left to right) of the 1 st row of tubular piles 1, and dynamically monitoring the floating, inclining and breaking conditions of the constructed 1 st row of tubular piles 1;
3: constructing a3 rd row of tubular piles 1 according to the construction direction (from left to right) of the 2 nd row of tubular piles 1, and dynamically monitoring the floating, inclination and fracture conditions of the constructed 1 st and 2 nd rows of tubular piles 1;
4: the first construction of all the tubular piles 1 is completed by the circulation;
5: if the constructed tubular pile 1 is found to have the conditions of floating, inclination, fracture and the like in the construction process, re-pressing or pile repairing is carried out according to specific conditions, the construction progress is slowed down, the soil squeezing effect of the tubular pile 1 is reduced, and finally the construction of all the tubular piles 1 is finished.
The construction sequence of the tubular pile 1 is controlled and dynamically monitored by the construction method, so that the soil squeezing effect of the tubular pile 1 can be effectively reduced and the construction progress is controlled; even if the soil squeezing effect of the tubular pile 1 causes the upward floating, the inclination and the fracture of the constructed tubular pile 1, due to the adoption of the monitoring of the constructed tubular pile 1, the problems can be discovered in time and remedied, the treatment effect of the whole foundation is ensured, and the bearing capacity and the settlement of the composite foundation can meet the use requirements.
The construction of the single tubular pile is as follows:
1: determining the position of the tubular pile 1, the pile length to be 21m and the depth to enter the middle supporting layer 8 to be 1m according to design data and field construction conditions;
2: the pile pressing machine is adopted to carry out normal pile pressing construction, the pile feeding length is 2 m/time, the pile pressing speed is 0.8m/min, when the pile pressing depth reaches 18m (the distance between the pile end and the middle holding layer 8 is 2.0m), the pile feeding length is changed to 0.5 m/time, the pile pressing speed is 0.5m/min, and pile pressing is carried out until the depth of the pile end entering the middle holding layer 8 reaches 1 m. Wherein, when the stake end gets into middle part bearing force layer 8 from upper portion soft soil foundation layer 7, the reading of pressure instrument table can take place the sudden change, just can judge this moment that the stake end just gets into middle part bearing force layer 8.
3: when the depth of burial and the thickness of the middle support layer 8 are different from the design drawing, the pile is too long or too short. For example, when the buried depth is 18m, after the depth of the pile end entering the middle holding layer 8 reaches 1m, but the pile top still has 2m and remains above the ground flat surface 6 (i.e. the pile is too long), the part 2m above the pile top is chiseled off to strictly prohibit the overlong pile from being pressed into the middle holding layer 8; if the buried depth is 22m, after the pipe pile has completely entered the upper soft soil foundation layer 7, but the pile end has not entered the middle holding force layer 8 (i.e. the pile is too short), then pile pressing is continued until the depth of the pile end entering the middle holding force layer 8 reaches 1m after pile-splicing 2m at the pile top.
4: and after the pile pressing is finished, pouring micro-expansion concrete to seal the tubular pile within 2m of the pile top, and finishing the construction of the single pipe 1.
Whether the middle bearing layer 8 is entered or not is judged through a pressure instrument meter of the pile pressing machine, and the method is simple and practical. When the distance between the pile end and the middle supporting layer 8 is not more than 2.0m, the depth of the pile end entering the middle supporting layer 8 can be better controlled by reducing the pile feeding length and reducing the pile pressing speed, and the middle supporting layer 8 is prevented from being pierced. When the geological conditions are not consistent with the design, the pile cutting or pile splicing mode is adopted, and although the construction method can increase some engineering investment, the bearing capacity of the pile end can be fully exerted, and the pile end does not pierce the middle bearing layer 8. The construction of each tubular pile 1 is controlled by the construction method, so that the aim of strictly controlling the depth of the pile end entering the middle bearing stratum 8 can be achieved.
In conclusion, the construction method can strictly control the depth of the tubular pile 1 entering the middle bearing layer 8, ensure that the bearing capacity of the tubular pile 1 can be fully exerted without piercing the bearing layer, reduce the soil squeezing effect of the tubular pile 1, control the construction sequence and the construction progress of the tubular pile 1, ensure the treatment effect of the composite foundation and ensure that the bearing capacity and the settlement of the foundation can meet the use requirements. For the deep and thick soft foundation with the thin bearing layer, the construction method is safe and reliable, has strong practicability, can ensure the construction quality and the foundation treatment effect, and can avoid the problems of insufficient bearing capacity of the foundation, penetration of tubular piles into the lower bearing layer and the like in the later period.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (10)
1. The utility model provides a structure is handled to soft base foundation of deep thickness suitable for press from both sides thin holding power layer which characterized in that: the method comprises the following steps:
a raft plate (4);
the mattress layer (3) is arranged at the bottom of the raft plate (4), and the mattress layer (3) is positioned at the top of the upper soft soil foundation layer (7);
the pile-type mattress comprises a plurality of tubular piles (1) which are arranged at intervals, wherein the tubular piles (1) are arranged at the bottom of a mattress layer (3), and the lower ends of the tubular piles (1) are positioned in a middle supporting layer (8);
a plurality of stirring stake (2), the interval sets up, stirring stake (2), set up in mattress pad layer (3) bottom, stirring stake (2) are located upper portion soft soil foundation layer (7).
2. The structure is handled to soft base foundation of a depth suitable for press from both sides thin holding power layer according to claim 1, characterized in that, the degree of depth that tubular pile (1) buries middle part holding power layer (8) is 0.3 ~ 0.5 times of middle part holding power layer (8) thickness, just tubular pile (1) buries the degree of depth that middle part held power layer (8) is greater than or equal to tubular pile (1) diameter.
3. The structure for treating deep and thick soft foundation suitable for clamping thin bearing layer according to claim 1, wherein said mixing pile (2) is arranged between adjacent said tubular piles (1).
4. The structure of claim 3, wherein all the tubular piles (1) are arranged in a grid pattern, and the mixing piles (2) are arranged between the diagonal tubular piles (1).
5. A deep soft foundation treatment structure suitable for sandwiching thin bearing layers according to any one of claims 1 to 4, wherein the thickness of the mattress layer (3) is 0.3 to 0.6 m; the thickness of the raft plate (4) is 0.4-0.6 m; the length of the stirring pile (2) is 4-8 m.
6. A construction method for forming a deep soft foundation treatment structure suitable for sandwiching a thin bearing layer according to any one of claims 1 to 5, comprising the steps of:
s1: constructing all the mixing piles (2);
s2: constructing all the tubular piles (1);
s3, filling a mattress layer (3) above the mixing pile (2) and the pipe pile (1) and compacting;
s4: and (5) constructing the raft (4).
7. The construction method according to claim 6, wherein the tubular piles (1) are arranged in a grid shape, and the step S2 is specifically as follows:
s21, constructing the pipe pile (1) in the ith row, wherein i is more than or equal to 1;
s22, constructing the (i + 1) th row of tubular piles, and dynamically monitoring the floating, inclining and breaking conditions of the 1-i th row of tubular piles (1);
s23, circulating the steps S21-S22 to finish the construction of all the tubular piles (1).
8. A construction method according to claim 7, characterized in that when the constructed tubular pile (1) floats upwards, inclines or breaks, the pile (1) which floats upwards, inclines or breaks is subjected to re-pressing or pile repairing construction, the construction progress is slowed down, and finally the construction of all tubular piles is completed.
9. The construction method according to any one of claims 6 to 8, wherein the construction of the tubular pile (1) is specifically as follows:
A1. determining the position, the pile length and the depth of the tubular pile (1) entering a middle bearing stratum;
A2. carrying out pile pressing construction, when the distance between the pile end and the middle bearing layer is equal to or less than 2.0m, reducing the pile feeding length, reducing the pile sinking speed, and continuously pressing the pile until the depth of the pile end entering the middle bearing layer reaches the design requirement;
A3. processing the upper end of the tubular pile (1) to enable the upper end of the tubular pile (1) to meet the design requirement;
A4. pouring micro-expansion concrete at the pile top of the tubular pile (1) to seal the tubular pile (1) and completing the construction of the single tubular pile (1).
10. The construction method according to claim 9, wherein the step a3 is specifically:
when the top end of the tubular pile (1) extends out of the theoretical design position of the top end of the tubular pile (1), pile cutting construction is carried out on the tubular pile (1) until the top end of the tubular pile (1) reaches the theoretical design position of the top end of the tubular pile (1);
and when the top end of the tubular pile (1) does not reach the theoretical design position of the upper end of the tubular pile (1), pile splicing construction is carried out on the tubular pile (1) until the top end of the tubular pile (1) reaches the theoretical design position of the top end of the tubular pile (1).
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| CN202010195748.7A CN111321751A (en) | 2020-03-19 | 2020-03-19 | Deep and thick soft foundation treatment structure suitable for thin holding layer and construction method |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112257166A (en) * | 2020-10-30 | 2021-01-22 | 同济大学建筑设计研究院(集团)有限公司 | Raft plate load guiding processing method and device, computer equipment and storage medium |
| CN113338267A (en) * | 2021-05-31 | 2021-09-03 | 中南大学 | Pile-bin combined supporting structure for building large-area high-field ground |
| CN114969889A (en) * | 2022-04-18 | 2022-08-30 | 甘肃省公路交通建设集团有限公司 | Method for calculating stress of overhanging raft plate of piled raft foundation |
-
2020
- 2020-03-19 CN CN202010195748.7A patent/CN111321751A/en active Pending
Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112257166A (en) * | 2020-10-30 | 2021-01-22 | 同济大学建筑设计研究院(集团)有限公司 | Raft plate load guiding processing method and device, computer equipment and storage medium |
| CN112257166B (en) * | 2020-10-30 | 2023-04-07 | 同济大学建筑设计研究院(集团)有限公司 | Raft plate load guiding processing method and device, computer equipment and storage medium |
| CN113338267A (en) * | 2021-05-31 | 2021-09-03 | 中南大学 | Pile-bin combined supporting structure for building large-area high-field ground |
| CN113338267B (en) * | 2021-05-31 | 2022-11-22 | 中南大学 | Pile-bin combined supporting structure for building large-area high-field ground |
| CN114969889A (en) * | 2022-04-18 | 2022-08-30 | 甘肃省公路交通建设集团有限公司 | Method for calculating stress of overhanging raft plate of piled raft foundation |
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