Anti-streaming sliding sparse pile type highway composite soft soil foundation and design method thereof

Abstract

The invention discloses an anti-streaming sliding sparse pile type highway composite soft soil foundation and a design method thereof, and belongs to the technical field of soft foundation treatment, and the anti-streaming sliding sparse pile type highway composite soft soil foundation comprises a fill embankment, a reinforced drainage cushion layer, a plurality of prefabricated rigid piles, a soft soil foundation and a plurality of prefabricated insertion plates. A plurality of lateral reinforcement bodies are formed in the highway soft soil foundation by changing the shape of the section of the pile body and additionally arranging the vertical prefabricated insertion plates, the pile distance and the pile diameter do not need to be continuously increased under the condition that embankment filling meets the stable overall shear sliding condition, the restraining effect of lateral passive soil pressure of a soil body on streaming sliding is fully exerted, and the stability of the embankment filling is improved. The function requirement of resisting streaming sliding is met; and the structure prefabrication degree is high, construction is convenient, the design method is simple and reliable in principle, and operation is convenient.

Description

Technical Field

[0001] The invention relates to the technical field of soft foundation treatment, and in particular to an anti-circumvention sliding sparse pile type highway composite soft soil foundation and a design method thereof. Background Art

[0002] In traditional soft foundation treatment, compared with replacement, grouting, flexible piles, and semi-rigid mixing piles, the composite foundation structure with prefabricated rigid piles as the main and various pile types as the auxiliary has become a more commonly used soft soil foundation treatment method in highway engineering due to its advantages such as large treatment depth, low construction difficulty, high degree of industrialization, controllable construction quality, and small post-construction settlement.

[0003] For embankments with rigid pile composite foundations, the shear strength of the rigid piles is very high, and the safety factor surplus of the sliding surface through the foundation is often very large, so the rigid piles and the soil between the piles will not be sheared along the sliding surface at the same time. However, the results of landslide engineering case investigations and centrifugal model tests over the years have shown that the soil between the piles will slide around or have a tendency to slide around, which will cause the rigid piles to break or tilt due to bending, and ultimately lead to the overall landslide of the roadbed. In order to avoid roadbed landslides, it is necessary to prevent the soil between the piles from sliding around, that is, it is necessary to verify the stability of the roadbed sliding around.

[0004] In the flow sliding analysis, the foundation soil between piles and embankment are generally used as the analysis objects, and the resistance of the rigid pile to the foundation and embankment: the vertical force p of the pile top on the embankment p , the friction force between the pile and the soil between the piles t, the horizontal anti-sliding resistance of the pile to the soil between the piles q h As an external force, the stability of the foundation soil and embankment is analyzed according to conventional stability analysis methods such as arc strip method. In engineering practice in soft soil areas, because the horizontal bearing capacity of the soil layer is small and the displacement of the soil between piles is significantly greater than that of the rigid piles, the horizontal anti-sliding resistance q of the pile to the soil between piles is h It is difficult to play a role and is generally ignored in calculations. In order to meet the requirements of flow-around sliding stability, it is necessary to reduce the pile spacing and increase the pile length so that the vertical bearing capacity is far greater than the actual demand, which increases the cost investment and construction difficulty.

[0005] The above problems need to be solved urgently. Therefore, a sparse pile type highway composite soft soil foundation with anti-circumvention sliding and its design method are proposed. Summary of the invention

[0006] The technical problem to be solved by the present invention is: how to solve the problem of how to fully exert the inhibitory effect of the lateral passive earth pressure of the soil on the flow-around sliding without further increasing the pile spacing and the pile diameter under the condition that the embankment fill meets the overall shear slip stability, meet the functional requirements of anti-flow-around sliding, and provide a sparse-pile type highway composite soft soil foundation that is anti-flow-around sliding.

[0007] The present invention solves the above technical problems through the following technical scheme, which includes an embankment, a reinforced drainage cushion layer, a plurality of prefabricated rigid piles, a soft soil foundation, and a plurality of prefabricated plug plates; the embankment is located above the reinforced drainage cushion layer, the reinforced drainage cushion layer is located on the top of a pile group formed by a plurality of prefabricated rigid piles, the plurality of prefabricated rigid piles are arranged in a plum blossom shape or in a square in the soft soil foundation, and the plurality of prefabricated rigid piles form a plurality of longitudinal columns, each longitudinal column is arranged in parallel along the road axis direction, and two adjacent prefabricated rigid piles in each longitudinal column are connected by a prefabricated plug plate, so that the single piles are connected to each other, and a number of parallel lateral reinforcements are formed in the soft soil foundation.

[0008] Furthermore, the prefabricated rigid piles are provided with two mortises along the road axis, the mortises between two adjacent prefabricated rigid piles in each longitudinal row are arranged opposite to each other, and the prefabricated plug plate is longitudinally inserted from the top along the mortises on the opposite sides of the two adjacent prefabricated rigid piles.

[0009] Furthermore, both ends of the prefabricated plug board are provided with the same T-shaped tenon structure, the cross-sectional shape of the mortise groove is T-shaped matching the T-shaped tenon structure, and the T-shaped tenon structure is inserted into the pile body along the mortise groove.

[0010] Furthermore, the prefabricated plug board is prefabricated in one piece through a polymer material, and its height is the same as the depth of the mortise.

[0011] Furthermore, in the same longitudinal column, the lengths of the precast rigid piles are the same, and the lengths of the precast rigid piles in each longitudinal column gradually increase from the road axis outward.

[0012] Furthermore, the precast rigid piles are precast concrete piles.

[0013] The present invention also provides a design method for a composite soft soil foundation of a road with sparse piles and an anti-circumferential flow and sliding resistance, which is used to design the vertical height and thickness of a prefabricated plug plate in the composite soft soil foundation, and comprises the following steps:

[0014] S1: Considering the effect of prefabricated plugs, based on the modified arc strip method, the safety factor F of the flow sliding stability is s The vertical height z of the prefabricated plug plate is determined by satisfying the sliding stability condition of the embankment flow. b scope;

[0015] S2: According to the thickness b of the prefabricated plug board c , tensile strength of the plate material [σ t ], the relationship between shear strength [τ] and pile spacing s, and then determine the thickness b of the prefabricated plug c scope.

[0016] Furthermore, in step S1, the embankment flow sliding stability condition expression is as follows:

[0017]

[0018] Among them, M Rs，j represents the soil anti-sliding moment on the jth sliding surface; M Rh，j M represents the anti-sliding moment of the lateral reinforcement on the jth sliding surface; D，j represents the sliding moment on the jth sliding surface;

[0019] M Rs，j 、M Rh，j 、M D，j The calculation formula is as follows:

[0020]

[0021] Among them, T i represents the sliding resistance of the i-th soil strip on the sliding interface; is the equivalent cohesion of the fill at the bottom of the i-th soil strip, m p is the pile body replacement rate; b i represents the width of the i-th soil strip; θ i represents the angle between the normal line at the midpoint of the sliding arc surface of the i-th soil strip and the vertical plane; represents the equivalent self-weight load of the i-th soil strip; represents the internal friction angle of the fill at the bottom of the i-th soil strip; R j represents the sliding radius of the jth sliding surface; c0, K p They represent the initial cohesion and passive earth pressure coefficient of soft soil foundation respectively; s0 Indicates the initial natural weight of soft soil foundation; b It is the vertical height of the prefabricated plug board.

[0022] Furthermore, the equivalent self-weight load of the i-th soil strip is The calculation formula is as follows:

[0023]

[0024] in, represents the load reduction effect coefficient; γ f Indicates the original natural weight of the fill embankment material; represents the equivalent fill height in the i-th soil strip; represents the equivalent weight of soil between piles after considering the friction effect on the pile side; i represents the height of the soil between piles in the i-th soil strip; h m Indicates the thickness of the reinforced drainage cushion layer, m c is the area coverage of the pile cap, n c is the pile-soil stress ratio at the pile cap elevation, Q sk With Quk They represent the ultimate lateral resistance and ultimate bearing capacity of the pile body respectively. It represents the average length of two adjacent piles in the i-th soil strip.

[0025] Furthermore, in step S2, the relationship is as follows:

[0026]

[0027] Compared with the prior art, the present invention has the following advantages: the sparse pile type highway composite soft soil foundation for resisting bypass sliding and the design method thereof form several lateral reinforcement bodies in the highway soft soil foundation by changing the cross-sectional shape of the pile body and adding vertical prefabricated plug plates. Under the condition that the embankment fill meets the overall shear sliding stability, there is no need to further increase the pile spacing and the pile diameter, and the lateral passive earth pressure of the soil body can be fully utilized to inhibit bypass sliding, thereby meeting the functional requirements of resisting bypass sliding; and the structure has a high degree of prefabrication, is convenient to construct, and the design method principle is concise and reliable, and is easy to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic diagram of a cross-sectional structure of a composite foundation in an embodiment of the present invention;

[0029] Figure 2 is a schematic diagram of a longitudinal section structure of a composite foundation in an embodiment of the present invention;

[0030] Figure 3 is a schematic diagram of a top view of a plurality of prefabricated rigid piles in an embodiment of the present invention;

[0031] Figure 4 Schematic diagram of the coordination between the prefabricated rigid pile and the prefabricated plug plate in the embodiment of the present invention;

[0032] Figure 5 It is a schematic diagram of calculating the safety factor of flow-sliding stability in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiment.

[0034] Embodiment 1

[0035] like Figure 1 to Figure 4 As shown in the figure, due to the small horizontal bearing capacity of the soft soil foundation and the large relative displacement, the horizontal anti-sliding resistance q of the pile to the soil between the piles is hIt is difficult to play a role, so this embodiment provides a technical solution: a sparse pile type highway composite soft soil foundation with anti-circumvention sliding, comprising a fill embankment 1, a reinforced drainage cushion layer 2, a plurality of prefabricated rigid piles 3, a soft soil foundation 4, and a plurality of prefabricated plug plates 5;

[0036] In this embodiment, the fill embankment 1 is located above the reinforced drainage cushion layer 2, and the top of the pile group formed by multiple prefabricated rigid piles 3 is located below the reinforced drainage cushion layer 2. The multiple prefabricated rigid piles 3 are arranged in a plum blossom shape or a square in the soft soil foundation 4, and the multiple prefabricated rigid piles 3 form a plurality of vertical columns, each of which is arranged parallel to the road axis direction. Two adjacent prefabricated rigid piles 3 in each vertical column are connected by a prefabricated plug plate 5, so that the single piles are connected to each other, forming several parallel lateral reinforcements in the soft soil foundation 4.

[0037] In this embodiment, the precast rigid piles 3 are high-strength concrete precast piles.

[0038] In this embodiment, the reinforced drainage cushion layer 2 is used to achieve drainage and coordinated deformation.

[0039] In this embodiment, the prefabricated rigid piles 3 are provided with two mortises 31 along the direction of the road axis, the mortises 31 between two adjacent prefabricated rigid piles 3 in each longitudinal row are arranged opposite to each other, and the prefabricated plug plate 5 is inserted longitudinally from the top along the mortises 31 on the opposite sides of the two adjacent prefabricated rigid piles 3.

[0040] In this embodiment, the prefabricated plug plate 5 is prefabricated in one piece by polymer material, and its height is the same as the depth of the mortise groove 31 .

[0041] In this embodiment, both ends of the prefabricated plug plate 5 are provided with the same T-shaped tenon structure, the cross-sectional shape of the mortise groove 31 is a T-shape matching the T-shaped tenon structure, and the T-shaped tenon structure is smoothly inserted into the pile body along the mortise groove 31; two adjacent prefabricated rigid piles 3 are connected to form a lateral reinforcement body, and the lateral reinforcement body refers to a combination of a longitudinal row of prefabricated plug plates 5 and prefabricated rigid piles 3.

[0042] In this embodiment, in the same longitudinal column, the lengths of the precast rigid piles 3 are the same. According to the sliding stability theory, the closer to the outside of the road axis, the greater the sliding moment. From the road axis outward, the lengths of the precast rigid piles 3 in each longitudinal column will gradually increase.

[0043] like Figure 5 As shown, in order to give full play to the anti-sliding effect of the prefabricated rigid piles 3 and the prefabricated plug plates 5, the calculation should be performed based on the arc strip method and in the following steps after considering the anti-sliding effect of the lateral reinforcement on the soil strip. The specific design method is as follows:

[0044] Step 1: Considering the effect of the plug plate, based on the modified arc strip method, the safety factor F of the flow sliding stability iss To meet the embankment sliding stability conditions, determine the vertical height z of the prefabricated plug plate 5 b range; (Compared with the ordinary arc strip division method, the modified arc strip division method in this embodiment specifically includes: considering the correction of the sliding soil strip gravity by the pile cap resistance and the lateral friction resistance of the composite pile foundation, see formula (5); the lateral anti-sliding moment provided by the plug plate, see formula (3))

[0045] In this step, the flow sliding stability safety factor F s The sliding stability condition of embankment flow is expressed as follows:

[0046]

[0047] Among them, M Rs，j represents the soil anti-sliding moment on the jth sliding surface; M Rh，j M represents the anti-sliding moment of the lateral reinforcement on the jth sliding surface; D，j represents the sliding moment on the jth sliding surface; according to equations (2) to (4), solve them respectively:

[0048]

[0049] In the above formulas:

[0050] T i represents the sliding resistance of the i-th soil strip on the sliding interface;

[0051] is the equivalent cohesion of the bottom fill of the i-th soil strip (kPa), m p is the pile replacement rate;

[0052] b i represents the width of the i-th soil strip (m);

[0053] θ i represents the angle between the normal line at the midpoint of the sliding arc surface of the i-th soil strip and the vertical plane (°);

[0054] represents the equivalent self-weight load of the i-th soil strip (kN), which is calculated and solved according to equations (5) to (7);

[0055] represents the internal friction angle of the fill at the bottom of the i-th soil strip (°);

[0056] R j represents the sliding radius of the jth sliding surface (m);

[0057] c0, K p represent the initial cohesion (kPa) and passive earth pressure coefficient of soft soil foundation 4 respectively;

[0058] z b Indicates the vertical height of the prefabricated plugboard 5 (m);

[0059] γ s0 Indicates the initial natural weight of soft soil foundation 4 (kN / m 3 );

[0060] In this step, The determination of the pile should take into account the effect of the pile on the pile top embankment, the embankment between piles, and the foundation soil between piles:

[0061]

[0062] In the formula, μ represents the load reduction effect coefficient, which is calculated according to formula (6);

[0063] γ f Indicates the original natural weight of the fill embankment 1 material (kN / m 3 );

[0064] It represents the equivalent fill height (m) in the i-th soil strip, including the vehicle load, road surface, and working cushion layer, which is related to the slope of both sides of the embankment and the road surface grade;

[0065] = represents the equivalent weight of the soil between piles after considering the friction effect on the pile side (kN / m 3 );

[0066] z i represents the height of soil between piles in the i-th soil strip;

[0067] h m Indicates the thickness of the reinforced drainage cushion layer 2 (m);

[0068] m c is the area coverage of the pile cap;

[0069] n c is the pile-soil stress ratio at the pile cap elevation;

[0070] Q sk With Q uk They represent the ultimate lateral resistance (kN) and ultimate bearing capacity (kN) of the pile respectively;

[0071] It represents the average length of two adjacent piles in the i-th soil strip.

[0072] m c 、n c , Q sk , Q uk These are all relatively common calculation parameters in the current technical specification system, and the methods for obtaining their values ​​will not be repeated here.

[0073] Step 2: According to the thickness b of the prefabricated plug board 5 c , tensile strength of the plate material [σ t ], the relationship between shear strength [τ] and pile spacing s, and then determine the thickness b of the prefabricated plug board 5 c scope.

[0074] In this step, the relationship is as follows:

[0075]

[0076] In summary, the anti-flow-sliding sparse pile highway composite soft soil foundation and its design method of the above-mentioned embodiment form several lateral reinforcement bodies in the highway soft soil foundation by changing the cross-sectional shape of the pile body and adding vertical prefabricated plug plates. Under the condition that the embankment fill meets the overall shear sliding stability, there is no need to further increase the pile spacing and the pile diameter, and the lateral passive earth pressure of the soil body can give full play to the inhibitory effect of the flow-sliding, thereby meeting the functional requirements of anti-flow-sliding. In addition, the structure has a high degree of prefabrication, the construction is convenient, the design method principle is concise and reliable, and it is easy to operate.

[0077] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A sparse pile type highway composite soft soil foundation with anti-circumvention sliding, It is characterized in that It includes an embankment, a reinforced drainage cushion layer, a plurality of prefabricated rigid piles, a soft soil foundation, and a plurality of prefabricated plug plates; the embankment is located above the reinforced drainage cushion layer, the reinforced drainage cushion layer is located on the top of a pile group formed by a plurality of prefabricated rigid piles, the plurality of prefabricated rigid piles are arranged in a plum blossom shape or in a square in the soft soil foundation, and the plurality of prefabricated rigid piles form a plurality of longitudinal columns, each longitudinal column is arranged parallel to the road axis, two adjacent prefabricated rigid piles in each longitudinal column are connected by a prefabricated plug plate, so that the single piles are connected to each other, and a number of parallel lateral reinforcements are formed in the soft soil foundation.

2. The anti-circumvention sliding sparse pile type composite soft soil foundation for highway according to claim 1, Features: The prefabricated rigid piles are provided with two mortises along the road axis, the mortises between two adjacent prefabricated rigid piles in each longitudinal row are arranged opposite to each other, and the prefabricated plug plate is longitudinally inserted from the top along the mortises on the opposite sides of the two adjacent prefabricated rigid piles.

3. The anti-circumvention sliding sparse pile type composite soft soil foundation for highway according to claim 2, Features: Both ends of the prefabricated plug board are provided with the same T-shaped tenon structure, the cross-sectional shape of the mortise groove is T-shaped matching the T-shaped tenon structure, and the T-shaped tenon structure is inserted into the pile body along the mortise groove.

4. The anti-circumvention sliding sparse pile type composite soft soil foundation for highway according to claim 1, Features: The prefabricated plug board is prefabricated in one piece through a polymer material, and its height is the same as the depth of the mortise.

5. The anti-circumvention-sliding sparse-pile type composite soft soil foundation for highway according to claim 1, Features: In the same longitudinal column, the lengths of the precast rigid piles are the same, and the lengths of the precast rigid piles in each longitudinal column gradually increase from the road axis outward.

6. The anti-circumvention-sliding sparse-pile type composite soft soil foundation for highway according to claim 1, Features: The prefabricated rigid piles are prefabricated concrete piles.

7. A design method for a composite soft soil foundation of a highway with sparse piles and anti-slip flow. It is characterized in that The method for designing the vertical height and thickness of the prefabricated plug-in plate in the composite soft soil foundation as claimed in claim 3 comprises the following steps: S1: Considering the effect of prefabricated plugs, based on the modified arc strip method, the safety factor F of the flow sliding stability is s The vertical height z of the prefabricated plug plate is determined by satisfying the sliding stability condition of the embankment flow. b scope; S2: According to the thickness b of the prefabricated plug board c , tensile strength of the plate material [σ t ], the relationship between shear strength [τ] and pile spacing s, and then determine the thickness b of the prefabricated plug c scope.

8. The design method of a sparse pile type composite soft soil foundation for highway with anti-circumvention sliding according to claim 7, Features: In step S1, the sliding stability condition expression of the embankment flow is as follows: Among them, M Rs，j represents the soil anti-sliding moment on the jth sliding surface; M Rh，j M represents the anti-sliding moment of the lateral reinforcement on the jth sliding surface; D，j represents the sliding moment on the jth sliding surface; M Rs，j 、M Rh，j 、M D，j The calculation formula is as follows: Among them, T i represents the sliding resistance of the i-th soil strip on the sliding interface; is the equivalent cohesion of the fill at the bottom of the i-th soil strip, mp is the pile replacement rate; b i represents the width of the i-th soil strip; θ i represents the angle between the normal line at the midpoint of the sliding arc surface of the i-th soil strip and the vertical plane; represents the equivalent self-weight load of the i-th soil strip; represents the internal friction angle of the fill at the bottom of the i-th soil strip; R j represents the sliding radius of the jth sliding surface; c 0 , K p They represent the initial cohesion and passive earth pressure coefficient of soft soil foundation respectively; s0 Indicates the initial natural weight of soft soil foundation; b It is the vertical height of the prefabricated plug board.

9. The design method of a sparse pile type composite soft soil foundation for highway with anti-circumvention sliding according to claim 8, Features: Equivalent self-weight load of the i-th soil strip The calculation formula is as follows: in, represents the load reduction effect coefficient; γ f Indicates the original natural weight of the fill embankment material; represents the equivalent fill height in the i-th soil strip; represents the equivalent weight of soil between piles after considering the friction effect on the pile side; i represents the height of the soil between piles in the i-th soil strip; h m Indicates the thickness of the reinforced drainage cushion layer, m c is the area coverage of the pile cap, n c is the pile-soil stress ratio at the pile cap elevation, Q sk With Q uk They represent the ultimate lateral resistance and ultimate bearing capacity of the pile body respectively. It represents the average length of two adjacent piles in the i-th soil strip.

10. The design method of a sparse pile type composite soft soil foundation for highway with anti-circumvention sliding according to claim 9, Features: In step S2, the relationship is as follows:

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