Branch pile embankment reinforcing structure suitable for deep soft soil foundation

Abstract

The utility model discloses a branch pile embankment reinforcing structure suitable for a deep soft soil foundation, which comprises a road surface, embankment filling soil, a geogrid, a broken stone hardcore, a solidification layer and a squeezing branch pile which are sequentially arranged from top to bottom, the squeezing branch pile downwards extends into the soft soil foundation, the top end of the squeezing branch pile is embedded into the solidification layer, and the bottom end of the squeezing branch pile is embedded into the solidification layer. And a force bearing disc is extruded and expanded in the curing layer at the top end of the extruded and expanded branch pile. The bearing disc is extruded and expanded in the curing layer to play the role of the pile cap, the load of the embankment is conducted to the branch disc pile, the low embankment is prevented from having a mushroom pavement by coordinating deformation, in addition, the tedious steps of pile cap construction are avoided, and the bearing capacity of the curing layer is fully mobilized.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the field of ground treatment, especially relates to a branch disc pile embankment reinforcing structure suitable for deep thick soft soil foundation. BACKGROUND

[0002] Deep thick soft soil foundation not only has the characteristics of large water content and pore ratio, large compressibility, low strength and high sensitivity, but also has the characteristics of long settlement stability duration, slow dissipation of deep pore water pressure and difficult foundation treatment, so it is not suitable for filling embankment on it.

[0003] In recent years, rigid pile composite foundation has become a solution for soft foundation treatment due to its strong settlement control ability, short construction time, easy construction quality control and large foundation treatment depth. The patent application with publication number CN201109909Y discloses a branch disc pile, which comprises a main pile and a plurality of branch disc structures extending outward from the main pile. The branch disc structure is a protruding branch disc-shaped bearing structure. The branch disc pile is formed by rotating the branch disc pile machine by a certain angle and then extruding outward, which is performed multiple times or continuously. Finally, a branch disc-shaped cavity is formed, which is then filled with concrete. By adding branch disc structures on the main pile body using a special extrusion device, the contact area between the branch disc structure and the soil around the pile is increased to improve the bearing capacity of the pile foundation.

[0004] The branch disc pile was first developed in the field of traditional house building and has been widely used in bridge pile foundation construction in recent years. However, there are few design methods and structures for its application in soft soil foundation treatment in highway engineering, and as a type of rigid pile, the branch disc pile still has the following problems when applied to deep thick soft foundation treatment under embankment:

[0005] (1) High cost: The use of large-diameter branch disc piles for soft foundation treatment in linear highway construction will increase project expenditure.

[0006] (2) "Mushroom" road surface: In response to low filling embankment, local unevenness occurs due to differential settlement of pile and soil reflected to the surface layer.

[0007] (3) Risk of "progressive" damage: The pile group gradually damages from the slope foot to the inside of the road and causes the overall instability of the embankment due to the bending / shear yield of the rigid pile at the slope foot.

[0008] (4) Excessive bearing capacity: The vertical bearing capacity of the rigid pile can fully respond to the vertical load of the embankment. CONTENT OF THE UTILITY MODEL

[0009] The utility model aims to provide a branch disc pile embankment reinforcing structure suitable for deep thick soft soil foundation, which is simple to construct, low in cost, avoids the formation of "mushroom" road surface and fully utilizes the bearing capacity of the solidified layer.

[0010] The utility model discloses a kind of support disc pile embankment reinforcement structures suitable for deep soft soil foundation, it is characterized by, including from top to bottom sequentially arranged pavement, embankment fill, geogrid, crushed stone cushion, solidified layer and extruded support disc pile, the extruded support disc pile is inserted into soft soil foundation downwards, the top of the extruded support disc pile is embedded in the solidified layer, and extruded support disc pile top solidified layer extruded support disc.

[0011] The utility model extruded support disc pile in solidified layer plays the role of pile cap: ①conduction to support disc pile with embankment load, ②coordination deformation prevents low embankment from appearing "mushroom road surface", in addition, avoid the cumbersome steps of pile cap construction and fully mobilize the bearing capacity of solidified layer.

[0012] The utility model discloses the extruded support disc pile diameter selects "small diameter", and main pile diameter can select 500mm~700mm;And with relatively "big spacing" condition arrangement, and pile spacing can select 2~2.5 times the maximum outer diameter of extruded support disc.

[0013] The utility model discloses the solidified layer thickness changes with the change of embankment fill height, and the thickness of solidified layer is 0.2~0.4 times embankment fill height, and solidified layer thickness is not more than 4m.

[0014] The utility model discloses the solidified layer is relatively thin at road center and relatively thick at both sides slope foot.

[0015] The utility model discloses the extruded support disc pile along main pile arrangement support disc structure, and the minimum spacing of adjacent support disc structure is not less than 8 times the main pile diameter.

[0016] Compared with prior art, the utility model has following remarkable effects:

[0017] (1) the utility model extruded support disc pile in solidified layer plays the role of pile cap: ①conduction to support disc pile with embankment load, ②coordination deformation prevents low embankment from appearing "mushroom road surface", in addition, avoid the cumbersome steps of pile cap construction and fully mobilize the bearing capacity of solidified layer.

[0018] (2) the utility model effectively combines and uses solidified layer and extruded support disc pile, and with "small diameter, big spacing" pile arrangement form, the high bearing capacity of support disc pile is played, the purpose of saving material, reducing cost, shortening working hours is reached.

[0019] (3) the utility model makes full use of solidified layer: in early stage, solidified layer can be used as construction platform of early bridge pile foundation, support disc pile and other structures, and provide detour for heavy vehicle, which will increase construction efficiency; In construction stage, solidified layer provides embedded action for extruded support disc pile and its first disc, which is beneficial to the stability of single pile itself. In addition, solidified layer will improve the bearing capacity of foundation.

[0020] The in-situ solidification arrangement form of the utility model adopts "thin in the middle and thick on both sides", which on one hand improves the utilization rate of the solidification material in the middle, and on the other hand improves the strength and rigidity of the slope foot foundation and restrains the progressive damage caused by the bending damage of the side pile. BRIEF DESCRIPTION OF DRAWINGS

[0021] The utility model will be further explained in detail in combination with the drawings and specific embodiments.

[0022] Figure 1 It is a cross-sectional view of the utility model;

[0023] Figure 2 It is a top view of the utility model;

[0024] Figure 3 It is a single pile diagram of the squeezed supporting disc pile of the utility model;

[0025] Figure 4 It is a reinforcing diagram of the squeezed supporting disc pile of the utility model;

[0026] Figure 5 It is an elevation view of the bearing disc of the squeezed supporting disc pile of the utility model;

[0027] Figure 6 It is a bearing branch plane view of the squeezed supporting disc pile of the utility model;

[0028] Figure 7 It is a transition section diagram of the solidification layer under the shoulder of the utility model;

[0029] Figure 8 It is a flow chart of the settlement calculation method of the utility model;

[0030] Figure 9 It is an elevation diagram of the settlement calculation method of the utility model;

[0031] Figure 10 It is a plane diagram of the settlement calculation method of the utility model;

[0032] Figure 11 It is a parameter diagram of the settlement calculation method of the utility model.

[0033] In the drawings: 1-squeezed supporting disc pile; 2-bearing disc; 3-bearing branch; 4-solidification layer; 5-drainage ditch; 6-gravel cushion; 7-geogrid; 8-embankment fill; 9-pavement; 10-soft soil foundation; 11-pile spacing; 12-longitudinal reinforcement; 13-stirrup; 14-disc height; 15-disc ring width; 16-main pile diameter; 17-branch; 18-slope foot soft foundation treatment area; 19-internal soft foundation treatment area. DETAILED DESCRIPTION

[0034] The present invention will be further described below through specific embodiments, but this is not a limitation of the present invention. Those skilled in the art can make various modifications or improvements based on the basic idea of ​​the present invention, but as long as they do not depart from the basic idea of ​​the present invention, they are all within the protection scope of the present invention.

[0035] like Figures 1 to 7 As shown, this utility model discloses a pile-supported embankment reinforcement structure suitable for deep soft soil foundations. It includes, from top to bottom, a road surface 9, embankment fill 8, geogrid 7, crushed stone cushion layer 6, solidification layer 4, and extruded pile 1. The extruded pile 1 extends downward into the soft soil foundation 10. The top of the extruded pile 1 is embedded in the solidification layer 4, and the bearing plate 2 is extruded and expanded in the solidification layer 4 at the top of the extruded pile 1.

[0036] The solidification layer 4 is a soil layer with a certain strength and rigidity formed by mixing a solidifying agent into the surface soil using a special mixing machine; the extruded and expanded support pile 1 is formed by extruding and expanding the support structure along the pile body, and a steel cage is put in after the extrusion and expansion construction; the top of the extruded and expanded support pile 1 is located in the solidification layer 4, and the support structure is extruded and expanded in a soil layer with relatively good soil quality or in a deep soil layer; in the solidified structure, a geogrid 7 is laid at the top and middle of the cushion layer, and the strength of the geogrid 7 is determined according to the soft soil quality of the lower part and the embankment fill of the upper part; a drainage ditch 5 is set on the crushed stone cushion layer 6.

[0037] The diameter of the expanded bearing plate pile 1 is selected as "small diameter", and the diameter of the main pile can be 500mm to 700mm; and it is arranged with a relatively "large spacing" condition, with the pile spacing being 2 to 2.5 times the maximum outer diameter of the bearing plate.

[0038] The thickness of the solidification layer 4 varies depending on the height of the embankment fill. The thickness of the solidification layer 4 is 0.2 to 0.4 times the height of the embankment fill, but the thickness of the solidification layer 4 should not exceed 4m.

[0039] The curing layer 4 is arranged in a pattern of "thin at the center of the road and thick at the toes of the slopes on both sides".

[0040] The expansion support pile 1 is arranged with support structure along the main pile. The vertical spacing of the support structure is support spacing 11, and the minimum vertical spacing should not be less than 8 times the main pile diameter.

[0041] The construction process of this utility model is as follows:

[0042] 1. Clean the topsoil and implement in-situ solidification: Before on-site construction, vegetation, tree roots, boulders and other obstacles should be removed from the site. In-situ solidification should be carried out using special solidification equipment such as PMX high-powered mixing heads. The solidification range should extend from the center of the road to 2-3m outside the toe of the embankment slope.

[0043] 2. Backfilling the working cushion layer with plain soil: This provides upper ballast for subsequent bored pile construction and the extruded bearing plate structure, ensuring the stability of the surface working platform. It is important to note that the extruded bearing plate pile construction can only proceed after the soil has cured in situ for a certain period; the compaction degree of the working cushion layer should reach 80%, and its top surface should also meet the basic requirements for flatness.

[0044] 3. Installation of Support Piles: The construction mode of the main piles is basically the same as that of traditional bored piles. After forming the main piles of equal diameter, the support is expanded at the corresponding elevation using a sizing device. After removing the sizing device, a precast steel cage is inserted. It should be noted that the construction of support piles has a certain soil displacement effect. Construction should proceed from the middle of the roadbed towards both sides of the road, from existing buildings and underground pipelines to distant locations, from existing ditches and slopes to distant locations, and from bridge abutments and culverts to distant locations. If necessary, continuous skip-driving and other construction methods should be used. Before subsequent construction, the quality of the support piles should be tested according to relevant specifications.

[0045] 4. Construct the crushed stone cushion layer and lay geogrid: The geogrid is laid on the top and middle of the crushed stone cushion layer; in the specific implementation case, the thickness of the crushed stone cushion layer is 0.4m to 0.5m, and the geogrid is a two-dimensional geogrid GSL / 500pp.

[0046] 5. Filling and unloading: Embankments should be filled and compacted in horizontal layers, with the maximum loose layer thickness not exceeding 30cm; the filling rate should be controlled during embankment construction to protect the support piles and solidified soil layers in the soft soil foundation; if conditions permit, equal load preloading should be maintained for more than 3 months.

[0047] Preferred specific implementation cases show the roadbed plan of the squeeze-expanded support pile treatment as follows: Figure 2 Preferably, the spacing S between the support piles can be determined based on the embankment fill height and foundation stiffness. In principle, due to the presence of the support structure, the spacing between the expanded support piles should be larger than that of conventional bored piles. In the engineering example, the length of the support pile is 35m, the diameter of the main pile is 16m and 0.5m, the width of the bearing plate is 15m and 1.5m, the spacing between the support piles on the inner side of the road is set to 4.0m, and the spacing between the piles at the toe of the road shoulder is set to 3.0m.

[0048] The arrangement of load-bearing plate 2 and load-bearing branch 3 can be referenced. Figure 3 In principle, for soft soil foundations with poor bearing conditions (10), bearing branches 3 should be attempted to be installed in the deep soft soil, while the bearing plate utilizes the solidified layer 5 as the bearing layer. In actual cases, the deep bearing branches and the top bearing plate are expanded sequentially from bottom to top. The bearing branches 3 are selected from 6 star branches arranged in the soft soil layer, with a branch width of 0.25m and a net distance of 4.0m between branches (8 times the main pile diameter 16). The bearing plate height 14 is 1.0m and is set in the solidified layer. The geometric center of the bearing plate should be located as close as possible to the middle and upper part of the solidified layer.

[0049] As described in the previous construction process, the precast steel cage is put into the support pile after the expansion is completed; Figure 4 The elevation view of the reinforcing cage of the pile is shown. The top of the pile is arranged with small-spacing stirrups 13 and longitudinal bars 12, and the bottom 2m below the pile top is arranged with large-spacing stirrups 13. In this case, the length of the longitudinal bars is about 70% of the pile length.

[0050] Preferably, this utility model provides a foundation transition section below the road shoulder, the form of which is as follows: Figure 7 As shown. The area outside the shoulder is designated as the soft soil treatment zone 18 at the toe of the slope (hereinafter referred to as the "toe treatment zone"), and the area inside is designated as the inner soft soil treatment zone 19 (hereinafter referred to as the "inner treatment zone"). During implementation, the thickness of the solidified layer in the inner treatment zone 19 should be greater than 2.0m, and the thickness of the solidified layer in the toe treatment zone 18 should be greater than 3.0m. The transition of the solidified layer thickness in both areas is achieved by controlling the mixing depth of the on-site solidification equipment, and the spacing of the expansion piles 1 changes from sparse to dense. To suppress the progressive damage of the embankment system in the deep soft soil, in addition to adjusting the pile spacing and the thickness of the solidified layer, the amount or specification of the longitudinal reinforcement 12 in the toe treatment zone 18 will be increased. In the actual case, the toe treatment zone 18 uses 8@14mm longitudinal reinforcement, while the inner treatment zone uses 6@12mm longitudinal reinforcement.

[0051] like Figure 8 As shown, a settlement calculation method for the above-mentioned pile-supported embankment reinforcement structure applicable to deep soft soil foundations includes the following steps:

[0052] 1. Based on the structural form and soil characteristics of the embankment reinforcement structure with pile supports, select the ground settlement calculation point and determine the vertical load on the top of the expanded pile supports.

[0053] The vertical load borne by the top of the pile is determined based on the geometric dimensions and pavement type of the embankment with expanded and enlarged support piles; the height of each soil layer and the soil mechanical properties are determined based on the distribution of soil in the foundation; the ground settlement calculation point to be calculated can be selected within the settlement control range in the middle of the roadbed or within the slope sliding stability control range, and the pile top load at different settlement calculation points may be different.

[0054] In this step, the expanded and spurred pile embankment reinforcement structure includes the embankment fill and the expanded and spurred pile structure arranged below the ground line. Selecting the settlement calculation point determines the specific location of the ground settlement to be calculated; based on the construction form and geometry of the embankment fill and pavement structure, the self-weight of the embankment structure borne by the pile top and the equivalent pavement load can be determined; based on the distribution of the foundation soil below the ground line, the thickness of each soil layer can be reasonably divided, and its soil mechanical parameters can be clarified, which facilitates the calculations in subsequent steps two and three.

[0055] In practice, the load distribution above the ground line and the characteristics of the foundation soil below the ground line have a significant impact on the final settlement deformation of the ground. The load on the top of the pile can be included in the overfill load of the embankment soil. The piles in the middle of the roadbed settlement control range can be considered to bear the self-weight of the embankment structure uniformly, while the piles in the slope sliding stability control range can be considered to bear the self-weight of the embankment structure according to the gradient distribution. Each soil layer of the foundation should be divided according to the same type of soil characteristics, and the soil layer thickness should be subdivided as much as possible, but the workload of calculation should also be considered. The depth of foundation settlement calculation should be determined by trial calculation.

[0056] 2. For the selected ground settlement calculation point, calculate the bearing length of the expanded support pile at the settlement calculation point based on the vertical load at the pile top, and determine the bearing surface of the expanded support pile in the soil layer; the vertical load at the pile top includes the self-weight of the embankment fill, the converted load of the pavement, etc.; the bearing surface of the expanded support pile in the soil layer is the position where the axial force of the support pile body is 0, and the calculation of the axial force of the support pile body should take into account the pile side friction and the bearing capacity provided by the bearing support structure.

[0057] In this step, once the ground settlement calculation point is identified, the pile top load at the settlement calculation point can be determined according to Step 1. Based on the pile top load of the expanded support pile, the structural form of the bearing support and disc, and the soil characteristics of the pile body, the axial force distribution of the pile body can be calculated, and the actual bearing length of the support pile can be determined. The location where the pile axial force is 0 corresponds to the bearing surface. The location where the pile axial force is 0 is the bearing surface. At the bearing surface, the pile body does not provide reaction force. The bearing force of the pile body is provided by the surface reaction force transmitted to the bearing surface after the pile side friction and the end resistance of the disc are diffused.

[0058] In practice, the axial force state of the expanded bearing plate pile is mainly affected by the pile side friction and the bearing capacity of the soil at the bearing plate end. Domestic standards such as the *Code for Design of Highway Bridge and Culvert Foundations* (JTG 3363-2019), *Expanded Bearing Plate Pile for Bridges* (JT / T 855-2013), and *Technical Specification for Expanded Bearing Plate Pile for Guangdong Highway Bridges* (T / GDHS 002-2020) all provide calculation formulas for the pile side friction and the bearing capacity of the soil at the bearing plate end. It should be noted that the friction provided by the bearing plate side is usually considered as a safety reserve and not included. It is important to note that when the pile tip force is not zero, the bearing surface should be at the pile tip location.

[0059] 3. Based on the location of the support surface of the extruded and expanded bearing pile, calculate the ground settlement caused by soil deformation above and below the support surface. The ground settlement above the support surface is calculated based on the pile compression, and the ground settlement below the support surface is calculated based on the soil compression.

[0060] To calculate the ground settlement caused by soil deformation above the bearing surface, considering the constraint of the expanded support piles on the soil above the bearing surface, the settlement should be indirectly calculated through the vertical compression of the pile body, and obtained using the following formula:

[0061]

[0062] Among them, s 上 L0 represents the final ground settlement caused by soil deformation above the support surface; EA represents the axial compressive stiffness of the expanded support pile; and F(x) represents the axial force distribution along the pile body, which should be calculated based on soil characteristics, support size, spacing, and quantity.

[0063] The ground settlement caused by soil deformation below the bearing surface should be calculated based on the sum of the compression of each soil layer below the bearing surface, and obtained using the following formula:

[0064]

[0065] Where, ψ c The empirical coefficient for pile foundation settlement calculation should be determined by statistical comparison based on local engineering measurement data in each region; l is the number of adjacent piles (including the same pile) that affect the foundation settlement calculation point; m is the number of soil layers within the foundation deformation calculation depth range; n is the number of bearing plates (branches) above the bearing surface; p i,k E represents the additional pressure on the bearing surface of the i-th bearing plate (branch) of the k-th pile near the foundation settlement calculation point; sj To calculate the compression modulus of the j-th soil layer below the support surface, the pressure range from the soil's self-weight pressure to the sum of its self-weight pressure and the additional pressure should be taken; j z j-1 It is the distance from the supporting surface to the bottom surface of the j-th and (j-1)-th soil layers below; The average additional stress coefficient is the average additional stress coefficient within the range from the calculation point of the foundation settlement on the bearing surface caused by the kth pile to the bottom surface of the jth and j-1th soil layers. It is adopted according to the average additional stress coefficient of the internal and external points under the uniformly distributed circular load surface.

[0066] In this step, the settlement calculation method should differ depending on the mechanism of soil deformation above and below the bearing surface. Above the bearing surface, the vertical load at the pile top is mainly transmitted through the pile shaft. As the load at the pile top is transmitted downwards along the pile shaft, it is gradually distributed to each soil layer through the pile side friction and the end resistance of the bearing support. In any soil layer above the bearing surface, there is a load transmitted to both the pile shaft and the soil layer simultaneously, making the pile-soil system more complex. Therefore, the settlement should be indirectly obtained by calculating the pile shaft compression. Below the bearing surface, there is no load transmission within the pile shaft; the pile top load is completely transmitted to the bearing surface. The settlement deformation should be obtained by calculating the compression of each soil layer below the bearing surface.

[0067] In practice, the axial force distribution along the pile body direction of the support pile is a variable. The axial force function of the pile body should be obtained according to the standard method, and the compression of the pile body should be obtained by integration. The thickness of the soil layer below the support surface should be reasonably divided, and the total compression of the soil layer should be calculated by the unidirectional compression layer summation method.

[0068] Fourth, calculate the sum of the pile compression and the soil compression to obtain the final ground settlement deformation of the embankment reinforcement structure with pile support.

[0069] In this step, the final ground settlement deformation of the embankment reinforcement structure with expanded and reinforced piles is the sum of the soil (pile body) deformation above and below the support surface, including pile compression and soil compression.

[0070] In practice, based on the calculated results of pile compression above the bearing surface and soil compression below the bearing surface obtained in step three, the final total settlement deformation can be obtained by superimposing the two results. It should be noted that when calculating the soil compression below the bearing surface using the uniaxial compression layered summation method, the empirical coefficient ψ for pile foundation settlement calculation should be considered. c The value of this coefficient should be determined based on statistical comparison of local engineering measurement data in each region.

[0071] This step determines the specific location of the pile bottom support surface by calculating the actual stress length of the expanded and spurred pile embankment reinforcement structure based on its structural form and stress characteristics. Different methods for calculating vertical settlement are selected based on the soil deformation characteristics of the upper and lower parts of the support surface.

[0072] This utility model relates to a reinforced embankment structure using expanded and spur-piled piles. Because the foundation structure is reinforced with spur-piled piles, the pile-soil system within the foundation experiences complex stresses. While the finite element method (FEM) is commonly used to simulate and analyze ground settlement, this method is cumbersome and time-consuming in the design process. The ground settlement calculation method for this embankment reinforced structure proposed in this utility model is conceptually clear, highly operable, and reflects the actual stress characteristics of the structure.

[0073] In one embodiment, step one above, which involves obtaining the structural form and soil characteristics of the expanded and spurred pile embankment reinforcement structure, selecting the ground settlement calculation point to be calculated, and determining the pile top load of the expanded and spurred pile, further includes: determining the vertical load borne by the pile top based on the geometric dimensions and pavement form of the expanded and spurred pile embankment; determining the height and soil mechanical properties of each soil layer based on the soil distribution within the foundation; the ground settlement calculation point to be calculated can be within the settlement control range in the middle of the roadbed or within the slope sliding stability control range, and the pile top load at different settlement calculation points may be different.

[0074] In this embodiment, as Figure 9 As shown, the pile top load of the extruded and expanded support piles is determined based on the embankment fill height and the unit weight of the fill and pavement structure materials; the soil layer thickness is divided according to the soil layer distribution characteristics below the ground line and the calculation parameters required in steps two and three.

[0075] In practice, since the ground settlement is greatest in the central part of the roadbed, the ground settlement calculation points are usually selected in the central part of the roadbed. Within this range, it is approximately assumed that the self-weight of the embankment fill and the equivalent pavement load are evenly distributed on the tops of each pile, thus allowing for a rapid determination of the load conditions at the pile tops; for example... Figure 10 As shown, the distances between the support piles and adjacent piles are S1 and S2, respectively. First, clarify the pressure surface load values ​​of the embankment fill, pavement structure, and equivalent pavement load transferred to the ground line. Then, the pressure surface load shared by each pile is S1S2. Divide soils with similar soil mechanical properties into the same soil layer. The thickness of the soil layer below the support surface should be moderate to avoid excessive calculation in step three.

[0076] This embodiment provides the parameters required for the calculations in steps two and three by clarifying the values ​​of the pile top load and the principles for dividing the soil layer thickness.

[0077] In one embodiment, step two above, calculating the bearing length of the expanded support pile at the selected ground settlement calculation point and determining the bearing surface of the expanded support pile in the soil layer, includes: for the selected ground settlement calculation point, the bearing length of the expanded support pile at the settlement calculation point should be calculated based on the vertical load at the pile top. The vertical load at the pile top includes the self-weight of the embankment fill, the converted load of the pavement, etc.; the bearing surface of the expanded support pile in the soil layer is the position where the axial force of the support pile is 0, and the calculation of the axial force of the support pile should consider the pile side friction and the bearing capacity provided by the bearing support structure.

[0078] In this embodiment, the pile top load is determined in step one, and the pile axial force distribution is calculated according to the pile top load and soil layer distribution characteristics in accordance with the standard method. For example, the "Design Code for Highway Bridge and Culvert Foundations" (JTG 3363-2019) specifies the calculation method for pile side friction and bearing capacity of the soil at the bearing plate end; the end of the pile bottom axial force distribution is taken as the bearing surface.

[0079] In practice, the axial force distribution of the pile body is determined according to the pile top load and the calculation methods for the pile side friction and bearing capacity of the support plate end soil specified in the code; the position where the pile top load is completely offset by the pile side friction and the bearing capacity of the support plate end soil is the support surface.

[0080] This embodiment determines the location of the bearing surface of the support pile in the soil by calculating and analyzing the axial force distribution state of the expanded support pile, and provides the parameters required for the calculation in step three.

[0081] In one embodiment, in step two above, the pile side friction of the support pile is calculated in the following manner:

[0082]

[0083] Where R1 is the characteristic value of the axial compressive bearing capacity of a single pile provided by the pile side skin friction; u is the pile perimeter; n is the number of soil layers; q ik To be with l i The corresponding standard values ​​of skin friction between each soil layer and the pile side; i The thickness of the i-th layer of soil below the bottom surface of the foundation or the local scour line. When there are supports or plates in this layer of soil, 1.5 times the height of each support and plate should be deducted.

[0084] In one embodiment, in step two above, the bearing capacity of the soil at the bearing end of the bearing pile is calculated in the following manner:

[0085]

[0086] Where R2 is the characteristic value of the axial compressive bearing capacity of a single pile provided by the bearing capacity of the soil at the support end; m is the total number of supports and supports; A pj Let q be the area of ​​the j-th support or plate (excluding the area of ​​the main pile); rj is the characteristic value of the bearing capacity of the soil at the j-th support or end plate; m0 is the cleaning coefficient; λ is the correction coefficient; f aj γ1 is the characteristic value of the bearing capacity of the soil at the support; k2 is the depth correction coefficient for the characteristic value of the bearing capacity; γ2 is the weighted average unit weight of the soil layers above the pile tip, the support, and the bearing capacity of the soil at ... bearing capacity of the soil at the bearing capacity of the soil at the support; h2 is the characteristic value of j This refers to the embedment depth of the support plate.

[0087] In one embodiment, step three above, which calculates the ground settlement caused by soil deformation above and below the support surface based on the support surface location of the expanded support pile, includes: determining the support surface location based on calculation; calculating the settlement above the support surface based on the pile compression; and calculating the settlement below the support surface based on the soil layer compression.

[0088] In this embodiment, as Figure 11 As shown, a calculation model for the settlement deformation of a single pile with a bearing plate is established; in the calculation model diagram: L i d is the distance from the i-th bearing plate (branch) above the bearing surface to the bearing surface; D is the diameter of the bearing plate (branch); d is the diameter of the main pile; F 0,k The vertical load borne by the top of the kth pile includes the self-weight of the embankment fill and the converted load of the pavement; F i,k E represents the axial force on the pile body below the i-th bearing plate (branch) of the k-th pile; sj For the compression modulus of the j-th soil layer below the bearing surface, the pressure range from the soil's self-weight pressure to the sum of its self-weight pressure and additional pressure should be used for calculation; m is the number of soil layers within the foundation deformation calculation depth range; n is the number of bearing plates (branches) above the bearing surface; z j z j-1 It is the distance from the supporting surface to the bottom surface of the j-th and (j-1)-th soil layers below; The internal friction angle is the soil layer where the i-th bearing plate (branch) of the k-th pile is located. Since there are many parameters involved in the calculation of the settlement deformation of the bearing plate pile, and the relationship between each parameter affects each other, the calculation model diagram can better identify the relationship between each parameter, and also make the calculation process clearer.

[0089] In practice, the soil settlement above the bearing surface is indirectly obtained by calculating the pile compression, which is based on the pile axial force distribution obtained in step two. The soil settlement below the bearing surface is the sum of the soil layer compressions, calculated using the unidirectional compression layered summation method. In addition to this pile, the influence of adjacent piles on the settlement calculation point should be considered.

[0090] Based on the stress characteristics of the embankment reinforcement structure with pile bearing, this embodiment uses different methods to calculate the foundation settlement, with the bearing surface as the dividing line.

[0091] In one embodiment, in step three above, the soil settlement within the area above the support surface is calculated in the following manner:

[0092]

[0093] Among them, s 上L0 represents the final ground settlement caused by soil deformation above the support surface; EA represents the axial compressive stiffness of the expanded support pile; and F(x) represents the axial force distribution along the pile body, which should be calculated based on soil characteristics, support size, spacing, and quantity.

[0094] In this embodiment, F(x) is the axial force distribution along the pile body, which is obtained according to step two.

[0095] In one embodiment, in step three above, the soil settlement within the area below the support surface is calculated in the following manner:

[0096]

[0097] Among them, s 下 ψ represents the final ground settlement caused by soil deformation below the support surface. c The empirical coefficient for pile foundation settlement calculation should be determined by statistical comparison based on local engineering measurement data in each region; l is the number of adjacent piles (including the same pile) that affect the foundation settlement calculation point; m is the number of soil layers within the foundation deformation calculation depth range; n is the number of bearing plates (branches) above the bearing surface; p i,k E represents the additional pressure on the bearing surface of the i-th bearing plate (branch) of the k-th pile near the foundation settlement calculation point; sj To calculate the compression modulus of the j-th soil layer below the support surface, the pressure range from the soil's self-weight pressure to the sum of its self-weight pressure and the additional pressure should be taken; j z j-1 It is the distance from the supporting surface to the bottom surface of the j-th and (j-1)-th soil layers below; is the average additional stress coefficient within the range from the calculation point of the foundation settlement on the bearing surface caused by the k-th pile to the bottom surface of the j-th and j-1-th soil layers.

[0098] In this embodiment, p i,k The additional pressure on the bearing plate (branch) of the k-th pile near the foundation settlement calculation point is the pressure on the bearing surface. The additional pressure on the bearing surface is a hollow annular region, which is calculated in the following way. If the pile end of the bearing plate is under stress, the bearing surface should be selected at the bottom surface of the pile end, and the additional pressure transmitted from the pile end to the bearing surface should be considered.

[0099]

[0100] Where, p i,k F represents the additional pressure on the bearing surface of the i-th bearing plate (branch) of the k-th pile near the foundation settlement calculation point; i,k denoted as , where is the axial force of the pile body below the i-th bearing plate (branch) of the k-th pile; D is the diameter of the bearing plate (branch); d is the diameter of the main pile. It is the internal friction angle of the soil layer where the i-th bearing plate (branch) of the k-th pile is located.

[0101] In this embodiment, The average additional stress coefficient is defined as the average additional stress coefficient of the internal and external points under a uniformly distributed circular load surface, within the range from the calculation point of the foundation settlement on the bearing surface caused by the k-th pile to the bottom surface of the j-th and (j-1)-th soil layers. It can be indirectly obtained using a similar corner point method, based on the average additional stress coefficient of the internal and external points under a uniformly distributed circular load surface, and is calculated as follows:

[0102]

[0103] in, The average additional stress coefficient at the outer points under a uniformly distributed circular load surface; θ is the average additional stress coefficient of the internal points under a uniformly distributed circular load surface; θ0 is the angle between the line connecting the external point and the tangent point of the circle and the horizontal line; ρ1(θ) and ρ2(θ) are the distances from the external point (pole) to the intersection of the line passing through the external point and the circle, ρ1(θ)>ρ2(θ); ρ3(θ) is the distance from the internal point (pole) to the circle, ρ1(θ)>ρ2(θ).

[0104] In one embodiment, step four above, the final ground settlement deformation of the embankment reinforcement structure with expanded and expanded piles is the sum of the pile compression and the soil compression, including: the final total ground settlement deformation should be the settlement calculated above the support surface plus the settlement calculated below the support surface.

[0105] In this embodiment, the final ground settlement of the embankment reinforcement structure with expanded and reinforced piles is obtained through step four.

[0106] In practice, the final ground settlement of the embankment reinforcement structure with expanded and reinforced piles is obtained by adding the soil deformation above and below the support surface.

[0107] This embodiment obtains the final ground settlement of the embankment reinforcement structure with expanded and reinforced piles.

[0108] In one embodiment, the final ground settlement deformation in step four above is calculated in the following manner:

[0109] s = s 上 +s 下

[0110] Where s is the final settlement at the foundation settlement calculation point; s 上 The final ground settlement caused by soil deformation above the support surface; s 下 This refers to the final ground settlement caused by soil deformation below the support surface.

[0111] The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit this utility model. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model should still be covered by the claims of this utility model.

Claims

1. A pile-supported embankment reinforcement structure suitable for deep soft soil foundations, characterized in that: The structure includes, from top to bottom, a road surface, embankment fill, geogrid, crushed stone cushion layer, solidification layer, and extrusion bearing piles. The extrusion bearing piles extend downward into the soft soil foundation, and the top of the extrusion bearing piles is embedded in the solidification layer, thereby extruding and expanding the bearing plate in the solidification layer at the top of the extrusion bearing piles.

2. The embankment reinforcement structure with pile supports suitable for deep soft soil foundations according to claim 1, characterized in that: The main pile diameter of the expanded bearing plate pile is 500mm to 700mm, and the pile spacing of the expanded bearing plate pile is 2 to 2.5 times the maximum outer diameter of the expanded bearing plate.

3. The embankment reinforcement structure with pile supports suitable for deep soft soil foundations according to claim 2, characterized in that: The cured layer is thinner at the center of the road and thicker at the toes of the slopes on both sides.

4. The embankment reinforcement structure with pile supports suitable for deep soft soil foundations according to claim 3, characterized in that: The expansion bearing piles are arranged along the main pile with bearing structures, and the minimum spacing between adjacent bearing structures is not less than 8 times the diameter of the main pile.

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