A roadbed widening method

Abstract

The present invention discloses a roadbed widening method, which relates to the field of highway construction and addresses existing issues such as differential settlement between new and old roadbeds, poor durability, and significant environmental impacts of construction waste. The method comprises driving sheet piles to a certain embedding depth, excavating the existing roadbed, and driving reinforcing anchor rods; placing L-shaped panels and laying internal geocells; placing the topmost L-shaped panel; tensioning the prestressed anchor rods, and after tensioning is complete, locking the fixed ends of the prestressed anchor rods; and laying surface geocells to complete the construction of the widened roadbed structure. The present invention can be used for road widening construction.

Description

Technical Field

[0001] The present invention relates to the field of highway construction, and in particular to a roadbed widening method. Background Art

[0002] Compared with road network densification and construction of new roads at close distances, widening and reconstruction of old roads requires less land and demolition and requires relatively small project investment.

[0003] However, many existing widening projects have poor treatment effects, and the differential settlement of the new and old roadbeds is difficult to be effectively controlled. After construction, it is easy for the new roadbed to become unstable, the road surface to be damaged, and the overall performance to decline. Shortly after the road was opened to traffic, serious defects such as longitudinal cracks in the road surface appeared.

[0004] In addition, with the acceleration of urbanization, urban construction waste continues to increase. The stacking of these construction wastes not only occupies a large area and causes waste of land resources, but also has the problem of subsequent degradation and treatment, which has a great impact on the environment. Summary of the Invention

[0005] In view of the above analysis, the present invention aims to provide a roadbed widening method that solves at least one of the problems in the prior art of differential settlement between new and old roadbeds, poor durability, and significant environmental impact of construction waste.

[0006] The purpose of the present invention is mainly achieved through the following technical solutions:

[0007] The present invention provides a method for widening a roadbed, comprising the following steps:

[0008] Step 1: Drive sheet piles into the ground at the shoulder of the original roadbed to the embedding depth, excavate the original roadbed, and when the excavation reaches the designed position of the reinforcement anchor rod, drive the reinforcement anchor rod as required, and pour anchor mortar around the reinforcement anchor rod to form an anchor mortar layer. Excavate to the base of the original roadbed;

[0009] Step 2: Lay out the L-shaped panel, lay the internal geocell, and fix one end of the internal geocell to the L-shaped panel and the other end to the sheet pile. Carry out casting on the internal geocell to obtain an internal casting layer, and roughen the upper surface of the formed casting layer.

[0010] Step 3: Repeat step 2 until the topmost internal cast unit layer is cast.

[0011] Step 4: Place the top L-shaped panel, drill holes at the designed positions of the prestressed anchor rods, insert the prestressed anchor rods, and inject cement slurry into the holes to obtain the grouting layer;

[0012] Step 5: tension the prestressed anchor rod, and after tensioning is completed, lock the fixed end of the prestressed anchor rod;

[0013] Step 6: Lay the surface geocell, connect one end of the surface geocell to the L-shaped panel, and fix the other end to the sheet pile. Carry out casting construction on the surface geocell to obtain the surface casting layer, and complete the construction of the widened roadbed structure.

[0014] Furthermore, the following steps are included between step 1 and step 2:

[0015] A waterproof membrane is laid on the base of the original roadbed after excavation and the waterproof membrane is fixed.

[0016] Furthermore, in step 2, the casting thickness of the cast unit is flush with the top surface of the L-shaped panel.

[0017] Furthermore, in step 4, the drilling diameter is 80 mm to 110 mm.

[0018] Furthermore, in step 4, the distance between the center of the drilling hole and the inner side of the vertical panel of the L-shaped panel is 40 cm to 50 cm.

[0019] Furthermore, in step 4, the axis of the prestressed anchor rod coincides with the axis of the drill hole.

[0020] Furthermore, in step 5, when the strength of the cement slurry reaches more than 80% of the design strength, the prestressed anchor rods are tensioned.

[0021] Furthermore, before step 1, the following steps are also included:

[0022] Calculate the embedment depth of the sheet pile.

[0023] Furthermore, the embedment depth of the sheet pile is calculated using the following method:

[0024] Step a: Based on the principle that the active earth pressure and passive earth pressure are equal, calculate the vertical distance between the point where the active earth pressure and passive earth pressure in the first layer of anchor are equal and the excavation bottom surface:

[0025]

[0026] Where: y1 - the vertical distance between the point where the active earth pressure and the passive earth pressure in the first layer of anchor are equal and the bottom surface of the excavation, m;

[0027] e a1 - Active earth pressure strength at the excavation surface in the first layer of anchors, kN / m 2 ;

[0028] K a - active earth pressure coefficient;

[0029] K p - passive earth pressure coefficient;

[0030] γ-average density of original roadbed filler, kN / m 3 ;

[0031] q-ground load, kPa;

[0032] The sheet pile AB1 of unit width between the point where the active earth pressure and the passive earth pressure are equal in the first layer of anchor and the design position of the reinforcement anchor is regarded as a simply supported beam. The moment of the point B1 where the active earth pressure and the passive earth pressure are equal in the first layer of anchor is taken, and the bending moment of point B1 is set to

[0033] ∑M B1 =0, calculate the anchor force required to strengthen the anchor in the first layer of anchor:

[0034]

[0035] Where: T1-anchor force required to strengthen the anchor in the first layer of anchor, kN;

[0036] z a1 -The height between the active earth pressure action point in the first layer of anchor and the original roadbed surface, m;

[0037] E a1 - The active earth pressure above point B1 of the original roadbed base corresponding to the first layer of anchors, kN / m;

[0038] h1-the excavation depth required for the first layer of anchoring, m;

[0039] h2-the excavation depth required for the second layer of anchoring, m;

[0040] Step b: Based on the principle that the active earth pressure and passive earth pressure are equal, calculate the vertical distance between the point where the active earth pressure and passive earth pressure in the second layer of anchor are equal and the excavation bottom surface:

[0041]

[0042] Where: y2 - the vertical distance between the point where the active earth pressure and the passive earth pressure in the second layer of anchor are equal and the bottom surface of the excavation, m;

[0043] e a2 - Active earth pressure strength at the excavation surface in the second layer of anchors, kN / m 2 ;

[0044] K a - active earth pressure coefficient;

[0045] K p - passive earth pressure coefficient;

[0046] γ-average density of original roadbed filler, kN / m 3 ;

[0047] q-ground load, kPa;

[0048] The sheet pile AB2 of unit width between the point where the active earth pressure and the passive earth pressure are equal in the second layer of anchor and the design position of the reinforcement anchor is regarded as a simply supported beam. The moment of the point B2 where the active earth pressure and the passive earth pressure are equal in the second layer of anchor is taken, and the bending moment of point B2 is set to

[0049] ∑M B2 =0, at this time, T1 is used as a known point force to calculate the anchor force required to strengthen the anchor in the second layer of anchoring:

[0050]

[0051] Where: T2-anchor force required to strengthen the anchor in the second layer of anchor, kN;

[0052] T1-anchor force required to strengthen the anchor in the first layer of anchor, kN;

[0053] E a2 - The active earth pressure above point B2 on the original roadbed base corresponding to the second layer of anchors, kN / m;

[0054] H-total excavation depth, m;

[0055] h1-the excavation depth required for the first layer of anchoring, m;

[0056] h2-the excavation depth required for the second layer of anchoring, m;

[0057] h3-excavation depth required for the third layer of anchoring, m;

[0058] Step c: According to the method of step b, calculate to the k-1th layer anchoring stage and obtain T1, T2, ..., T k-1 ;

[0059] Step d: Dig to the designed excavation depth of the original roadbed. Based on the principle that the active earth pressure and passive earth pressure are equal, calculate the vertical distance between the point where the active earth pressure and passive earth pressure in the k-th anchor layer are equal and the excavation bottom surface:

[0060]

[0061] Where: y k -The vertical distance between the point where the active earth pressure and the passive earth pressure in the k-th anchor layer are equal and the bottom surface of the excavation, m;

[0062] e ak- Active earth pressure strength at the excavation surface in the kth layer of anchor, kN / m 2 ;

[0063] K a - active earth pressure coefficient;

[0064] K p - passive earth pressure coefficient;

[0065] γ-average density of original roadbed filler, kN / m 3 ;

[0066] q-ground load, kPa;

[0067] The sheet pile AB of unit width between the point where the active earth pressure and the passive earth pressure are equal in the kth layer anchor and the design position of the reinforcement anchor is k As a simply supported beam, the point B corresponding to the equal active earth pressure and passive earth pressure in the k-th anchor layer is k Take the moment and let B k Bending moment at point

[0068] ∑M Bk =0, T1, T2, T3, ..., T k-1 The anchor force and B required to strengthen the anchor in the kth layer are calculated by taking the known point force into account. k The support reaction force of the point:

[0069]

[0070] P Bk =E ak -∑T k

[0071] Where: T k - Anchor force required to strengthen the anchor in the kth layer of anchor, kN;

[0072] P Bk -Support reaction force at the point where the active earth pressure is equal to the passive earth pressure in the k-th anchor layer, kN;

[0073] E ak - The original roadbed base B corresponding to the kth layer of anchor k Resultant active earth pressure above the point, kN / m;

[0074] Step e: Calculate the point B corresponding to the equalization of active earth pressure and passive earth pressure in the kth layer anchor k Height to bottom of sheet pile:

[0075]

[0076] Where: x is the point B where the active earth pressure is equal to the passive earth pressure in the k-th anchor layerk Height to the bottom of the sheet pile, m;

[0077] P Bk -Support reaction force at the point where the active earth pressure is equal to the passive earth pressure in the k-th anchor layer, kN;

[0078] K a - active earth pressure coefficient;

[0079] K p - passive earth pressure coefficient;

[0080] γ-average density of original roadbed filler, kN / m 3 ;

[0081] Step f: Calculate the embedment depth of the sheet pile;

[0082] t0=x+y k

[0083] Where: t0-embedding depth of sheet pile.

[0084] Furthermore, after step f, the following steps are further included: performing a stress analysis based on the stress conditions of the sheet piles, and calculating the maximum bending moment borne by the sheet piles:

[0085]

[0086] Where: σ-stress of the sheet pile when it is subjected to the maximum bending moment, MPa,

[0087] M-maximum bending moment supported by the sheet pile, kN·m;

[0088] W x -Sectional modulus of sheet pile, cm 3 ;

[0089] [σ] - Strength of sheet pile, MPa.

[0090] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0091] A) The roadbed widening method provided by the present invention, on the one hand, can widen the roadbed under conditions of limited land occupation, reduce the land use area and damage to the surrounding environment, reduce project costs, and shorten the construction period; on the other hand, sheet piles and reinforced anchor rods are set in the original roadbed, and the two form a tension anchor support system, forming a whole with the original roadbed that is jointly stressed, which can maximize the original roadbed's own strength and improve the overall bending stiffness; on the other hand, surface geocells, internal geocells, prestressed anchor rods, vertical panels and transverse panels are set in the cast body, and the vertical panels and transverse panels together constitute the retaining panels of the cast body, which have strong anti-overturning ability, high overall stiffness, high stability, durability and strong bending and shear resistance, can form a whole with the original roadbed, effectively solve problems such as uneven settlement between the new and old roadbeds, and extend its service life.

[0092] B) The roadbed widening method provided by the present invention first completes the pouring of the internal casting body layer, then carries out the construction of the prestressed anchor rods, and finally completes the pouring of the surface casting body layer. This can effectively ensure the construction quality of the prestressed anchor rods and better play the anchoring role. The addition of the prestressed anchor rods can improve the overall anti-overturning ability and bending and shearing ability of the new roadbed, thereby extending the service life of the new roadbed; the part within the overlapping range of the original roadbed and the new roadbed (usually the slope and / or shoulder) is excavated, and the excavated soil can be backfilled for the construction of the new roadbed, which is conducive to rapid construction and reduced project costs.

[0093] Other features and advantages of the present invention will be described in the following description, and part of them will become obvious from the description, or will be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained by the structures particularly pointed out in the written description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0094] The accompanying drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like parts throughout the drawings.

[0095] Figure 1 A schematic structural diagram of a widened roadbed structure in a roadbed widening method according to a first embodiment of the present invention is provided;

[0096] Figure 2 for Figure 1 A magnified view of;

[0097] Figure 3 A schematic diagram of the end portion of a reinforcement anchor rod in the roadbed widening method provided in the first embodiment of the present invention;

[0098] Figure 4a This is a front view of an L-shaped panel in the roadbed widening method provided in Example 1 of the present invention;

[0099] Figure 4b A side view of an L-shaped panel in the roadbed widening method provided in Example 1 of the present invention;

[0100] Figure 4c A top view of an L-shaped panel in the roadbed widening method provided in Example 1 of the present invention;

[0101] Figure 5a A front view of a panel connection assembly in the roadbed widening method provided in the first embodiment of the present invention;

[0102] Figure 5b A side view of a panel connection assembly in the roadbed widening method provided in the first embodiment of the present invention;

[0103] Figure 6a This is a front view of a sheet pile connection assembly in the roadbed widening method provided in the first embodiment of the present invention;

[0104] Figure 6b A side view of a sheet pile connection assembly in the roadbed widening method provided in Example 1 of the present invention;

[0105] Figure 6c A top view of a sheet pile connection assembly in the roadbed widening method provided in Example 1 of the present invention;

[0106] Figure 7a This is a force analysis diagram of the first layer anchoring stage in the roadbed widening method provided in Example 1 of the present invention;

[0107] Figure 7b This is a force analysis diagram of the second layer anchoring stage in the roadbed widening method provided in Example 1 of the present invention;

[0108] Figure 7c This is a force analysis diagram of the kth layer anchoring stage in the roadbed widening method provided in Example 1 of the present invention.

[0109] Reference numerals:

[0110] 1-Original roadbed; 2-Sheet pile; 3-Reinforced anchor rod; 31-Reinforced rod body; 32-Casing; 33-Nut; 34-Tray; 4-Waterproof membrane; 5-Prestressed anchor rod; 6-L-type panel; 7-One-way drain pipe; 8-Internal geocell; 9-Panel connection assembly; 91-Transverse rib; 92-Vertical rib; 93-Sleeve; 94-Panel threaded rod; 95-Bolt; 96-Geocell clamp; 10-Casting body; 11-Sheet pile connection assembly; 111-Connecting column; 112-Sheet pile threaded rod; 113-Horizontal connecting plate; 114-Vertical connecting plate; 115-First oblique connecting plate; 116-Second oblique connecting plate; 12-Triangular baffle; 13-Surface geocell. DETAILED DESCRIPTION

[0111] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, wherein the accompanying drawings constitute a part of the present invention and are used to explain the principles of the present invention together with the embodiments of the present invention.

[0112] Example 1

[0113] This embodiment provides a method for widening a roadbed, comprising the following steps:

[0114] The roadbed construction and widening method include the following steps:

[0115] Step 1: Use a pile driver to drive sheet piles into the ground at the shoulder of the original roadbed to the embedding depth, excavate the original roadbed, and when the excavation reaches the designed position of the reinforcement anchor rod, drive the reinforcement anchor rod as required, and pour anchor mortar around the reinforcement anchor rod to form an anchor mortar layer. Excavate to the base of the original roadbed;

[0116] Step 2: Lay a waterproof membrane on the original roadbed base after excavation and fix the waterproof membrane;

[0117] Step 3: Place the L-shaped panels according to the designed position, lay the bottom layer of internal geocells, and fix the internal geocells to the L-shaped panels and sheet piles respectively. Construct a cast body (for example, self-compacting lightweight concrete) on the internal geocells to obtain an internal cast body layer. The casting thickness of the cast body is flush with the top surface of the L-shaped panel, and the upper surface of the formed cast body layer is roughened.

[0118] Step 4: Repeat step 3 until the topmost internal cast unit layer is cast.

[0119] Step 5: Place the top L-shaped panel according to the designed position, drill holes at the designed positions of the prestressed anchor rods with a diameter of 80mm to 110mm and a distance of 40cm to 50cm between the center of the hole and the inner side of the vertical panel. Insert the prestressed anchor rods with the axis of the prestressed anchor rods aligned with the axis of the hole. Then, use a pressure pump to inject cement slurry into the hole. During the grouting process, it is advisable to use the widening method of grouting while pulling out the pipe until the hole is full to obtain the grouting layer.

[0120] Step 6: When the cement slurry strength reaches more than 80% of the design strength, the prestressed anchor rods are tensioned. After the tensioning is completed, the fixed ends of the prestressed anchor rods are locked. After the prestressed tendons are tensioned, the ducts should be grouted in time, no later than 72 hours after tensioning.

[0121] Step 7: Lay the surface geocell 13 and fix the surface geocell 13 to the L-shaped panel and sheet piles respectively, and construct a cast body (for example, self-compacting lightweight concrete) on the surface geocell 13 to obtain a surface cast body layer, thereby completing the construction of the widened roadbed.

[0122] Compared with the prior art, the roadbed widening method provided in this embodiment can, on the one hand, widen the roadbed under conditions of limited land occupation, reduce the land use area and damage to the surrounding environment, reduce project costs, and shorten the construction period; on the other hand, sheet piles 2 and reinforced anchor rods 3 are set in the original roadbed 1, and the two form a tension anchor support system, forming a whole with the original roadbed that is jointly subjected to force, which can maximize the self-strength of the original roadbed and improve the overall bending stiffness; on the other hand, surface geocells, internal geocells 8, prestressed anchor rods 5, vertical panels and transverse panels are set in the cast body 10, and the vertical panels and transverse panels together constitute the retaining panels of the cast body 10, which have strong anti-overturning ability, high overall stiffness, high stability, strong durability and bending and shear resistance, can form a whole with the original roadbed, effectively solve problems such as uneven settlement between the new and old roadbeds, and extend its service life.

[0123] In addition, in the above-mentioned widening method, the paving work of the internal cast body layer is completed first, then the construction of the prestressed anchor rods is carried out, and finally the paving work of the surface cast body layer is completed. This can effectively ensure the construction quality of the prestressed anchor rods and better play the anchoring role. The addition of prestressed anchor rods can improve the overall anti-overturning ability and bending and shearing ability of the new roadbed, thereby extending the service life of the new roadbed; the part within the overlapping range of the original roadbed and the new roadbed (usually the slope and / or shoulder) is excavated, and the excavated soil can be backfilled for the construction of the new roadbed, which is conducive to rapid construction and reducing project costs.

[0124] The above step 1 includes the following steps:

[0125] Calculate the embedded depth of the sheet piles in stages, based on the sequence of excavation and anchor placement. At each stage, treat the sheet pile structure between the anchor point on the excavation surface and the imaginary support point below the excavation surface as a simply supported beam. The calculated support reaction force is then held constant and used as an external force to calculate the support point of the next beam section, with only the horizontal force component considered at the anchor point.

[0126] For example, the following method is used to calculate the embedding depth of the sheet pile:

[0127] Step a: First layer anchoring stage. Theoretically, the first layer anchoring must ensure the stability of the original roadbed before the second layer anchoring. That is, the total depth of the excavation depth h1 required for setting the first layer anchoring and the excavation depth h2 required for setting the second layer anchoring is taken to calculate the anchor force required to strengthen the anchor rods in the first layer anchoring, such as Figure 7a shown.

[0128] Specifically, based on the principle that the active earth pressure and passive earth pressure are equal, the vertical distance between the point where the active earth pressure and passive earth pressure are equal in the first layer of anchors and the excavation bottom surface is calculated:

[0129]

[0130] Where: y1 - the vertical distance between the point where the active earth pressure and the passive earth pressure in the first layer of anchor are equal and the bottom surface of the excavation, m;

[0131] e a1 - Active earth pressure strength at the excavation surface in the first layer of anchors, kN / m 2 ;

[0132] K a - active earth pressure coefficient;

[0133] K p - passive earth pressure coefficient;

[0134] γ-average density of original roadbed filler, kN / m 3 ;

[0135] q - ground load, kPa.

[0136] The sheet pile AB1 of unit width between the point where the active earth pressure and the passive earth pressure are equal in the first layer of anchor and the design position of the reinforcement anchor is regarded as a simply supported beam. The moment of the point B1 where the active earth pressure and the passive earth pressure are equal in the first layer of anchor is taken, and ∑M B1 =0, calculate the anchor force required to strengthen the anchor in the first layer of anchor:

[0137]

[0138] Where: T1-anchor force required to strengthen the anchor in the first layer of anchor, kN;

[0139] z a1 -The height between the active earth pressure action point in the first layer of anchor and the original roadbed surface, m;

[0140] E a1 - The active earth pressure above point B1 of the original roadbed base corresponding to the first layer of anchors, kN / m;

[0141] h1-the excavation depth required for the first layer of anchoring, m;

[0142] h2-the excavation depth required for the second layer of anchoring, m.

[0143] Step b: In the second anchoring stage, the total depth of the excavation depth h1 required for the first anchoring layer, the excavation depth h2 required for the second anchoring layer, and the excavation depth h3 required for the third anchoring layer is used to calculate the anchor force required to strengthen the anchor rods in the second anchoring layer, such as Figure 7b shown.

[0144] Specifically, based on the principle that the active earth pressure and passive earth pressure are equal, the vertical distance between the point where the active earth pressure and passive earth pressure in the second layer of anchor are equal and the excavation bottom surface is calculated:

[0145]

[0146] Where: y2 - the vertical distance between the point where the active earth pressure and the passive earth pressure in the second layer of anchor are equal and the bottom surface of the excavation, m;

[0147] e a2 - Active earth pressure strength at the excavation surface in the second layer of anchors, kN / m 2 ;

[0148] K a - active earth pressure coefficient;

[0149] K p - passive earth pressure coefficient;

[0150] γ-average density of original roadbed filler, kN / m 3 ;

[0151] q - ground load, kPa.

[0152] The sheet pile AB2 of unit width between the point where the active earth pressure and the passive earth pressure are equal in the second layer of anchor and the design position of the reinforcement anchor is regarded as a simply supported beam. The moment of the point B2 where the active earth pressure and the passive earth pressure are equal in the second layer of anchor is taken, and ∑M B2 =0, at this time, T1 is used as a known point force to calculate the anchor force required to strengthen the anchor in the second layer of anchoring:

[0153]

[0154] Where: T2-anchor force required to strengthen the anchor in the second layer of anchor, kN;

[0155] z a2 -The height between the active earth pressure action point in the second layer of anchor and the original roadbed surface, m;

[0156] E a2 - The active earth pressure above point B2 on the original roadbed base corresponding to the second layer of anchors, kN / m;

[0157] h1-the excavation depth required for the first layer of anchoring, m;

[0158] h2-the excavation depth required for the second layer of anchoring, m;

[0159] h3 - Excavation depth required for the third layer of anchoring, m.

[0160] Step c: According to the method of step b, calculate to the k-1th layer anchoring stage and obtain T1, T2, ..., T k-1 .

[0161] Step d: Dig to the original roadbed excavation design depth, such as Figure 7c As shown in the figure, according to the principle that the active earth pressure intensity and the passive earth pressure intensity are equal, the vertical distance between the point where the active earth pressure and the passive earth pressure are equal in the k-th layer anchor and the excavation bottom surface is calculated:

[0162]

[0163] Where: y k -The vertical distance between the point where the active earth pressure and the passive earth pressure in the k-th anchor layer are equal and the bottom surface of the excavation, m;

[0164] e ak - Active earth pressure strength at the excavation surface in the kth layer of anchor, kN / m 2 ;

[0165] K a - active earth pressure coefficient;

[0166] K p - passive earth pressure coefficient;

[0167] γ-average density of original roadbed filler, kN / m 3 ;

[0168] q - ground load, kPa.

[0169] The sheet pile AB of unit width between the point where the active earth pressure and the passive earth pressure are equal in the kth layer anchor and the design position of the reinforcement anchor is k As a simply supported beam, the point B corresponding to the equal active earth pressure and passive earth pressure in the k-th anchor layer is k Take the moment and let ∑M Bk =0, at this time, T1, T2, T3, ..., T k-1 The anchor force and B required to strengthen the anchor in the kth layer are calculated by taking the known point force into account. k The support reaction force of the point:

[0170]

[0171] P Bk =E ak -∑T k

[0172] Where: T k - Anchor force required to strengthen the anchor in the kth layer of anchor, kN;

[0173] P Bk-Support reaction force at the point where the active earth pressure is equal to the passive earth pressure in the k-th anchor layer, kN;

[0174] z ak -The height between the active earth pressure action point in the second layer of anchor and the original roadbed surface, m;

[0175] H-total excavation depth, m;

[0176] E ak - The original roadbed base B corresponding to the kth layer of anchor k Resultant active earth pressure above the point, kN / m.

[0177] Step e: Calculate the point B corresponding to the equalization of active earth pressure and passive earth pressure in the kth layer anchor k Height to bottom of sheet pile:

[0178]

[0179] Where: x is the point B where the active earth pressure is equal to the passive earth pressure in the k-th anchor layer k Height to the bottom of the sheet pile, m;

[0180] P Bk -Support reaction force at the point where the active earth pressure is equal to the passive earth pressure in the k-th anchor layer, kN;

[0181] K a - active earth pressure coefficient;

[0182] K p - passive earth pressure coefficient;

[0183] γ-average density of original roadbed filler, kN / m 3 .

[0184] Step f: Calculate the embedment depth of the sheet pile;

[0185] t0=x+y k

[0186] Where: t0 - embedment depth of sheet pile, if the soil quality is poor, it needs to be multiplied by 1.1-1.2, that is: h d =(1.1~1.2)t0.

[0187] In order to determine whether the sheet pile embedding depth obtained by the above calculation method is reasonable, the following steps are also included after the above step f: the sheet pile strength is calculated using the maximum bending moment kernel, and the sheet pile AB per unit width between the point where the active earth pressure and the passive earth pressure are equal in the kth layer anchor and the design position of the reinforcement anchor is examined. k For simply supported beams, perform stress analysis based on the stress conditions of the sheet piles and calculate the maximum bending moment the sheet piles can withstand, which should be at the point where the shear force is zero:

[0188]

[0189] Where: σ-stress of the sheet pile when it is subjected to the maximum bending moment, MPa,

[0190] M-maximum bending moment supported by the sheet pile, kN·m;

[0191] W x -Sectional modulus of sheet pile, cm 3 ;

[0192] [σ] - Strength of sheet pile, MPa.

[0193] Accordingly, the above step 1 also includes the following steps:

[0194] Calculate the length of the reinforcing anchor and the effective length of the prestressed anchor.

[0195] Exemplarily, calculating the length of the reinforcement anchor includes the following steps:

[0196] Step a': Based on the design safety factor, determine the design value of the axial tension of the reinforced anchor rod according to the anchor rod force required for the reinforced anchor rod. t ,Pa;

[0197] Step b': Determine the cross-sectional area A of the reinforced anchor rod according to the axial tension design value of the reinforced anchor rod, m 2 :

[0198]

[0199] Where: N t -Design value of axial tension of reinforcing anchor, Pa;

[0200] K-design safety factor of the reinforced anchor;

[0201] f ptk -Standard value of tensile strength of the anchor body, kPa.

[0202] Step c': Calculate the anchoring length of the anchor body (including the anchor body and the anchoring mortar layer on the outer wall of the anchor body) and the original roadbed filling material:

[0203]

[0204] Where: l a - Anchorage length between anchor body and original roadbed filling material, m;

[0205] N t -Design value of axial tension of reinforcing anchor, Pa;

[0206] K-design safety factor of the reinforced anchor;

[0207] D-diameter of anchor body, m;

[0208] q s - Bond strength between the anchor body and the surrounding original roadbed filler, kPa;

[0209] Calculate the anchoring length between the anchor rod and the anchoring mortar layer:

[0210]

[0211] Where: l b - Anchorage length between the anchor rod and the anchoring mortar layer, m;

[0212] N t -Design value of axial tension of reinforcing anchor, Pa;

[0213] K-design safety factor of the reinforced anchor;

[0214] d-diameter of the anchor body, m;

[0215] τ s -Bond strength between the anchor body and the anchor mortar layer, kPa.

[0216] Step d': Take l a With l b The larger value between the two is used as the length of the reinforcing anchor.

[0217] Calculating the effective length of a prestressed anchor includes the following steps:

[0218] Step a”: Determine the self-weight of the new roadbed surface layer and calculate the effective prestressing force of a single prestressed anchor rod:

[0219] N g =N z -N s

[0220] Where: N g -Effective prestressing force of a single prestressed anchor, kN;

[0221] N z -Control tension of prestressed anchor, kN;

[0222] N s - Various values ​​of loss of prestress in prestressed anchor rods, kN.

[0223] Step b”: Find a new roadbed that satisfies both the anti-sliding stability and the anti-overturning stability requirements, so that the anti-sliding stability coefficient K c ≥1.3, anti-overturning stability coefficient K s≥1.5, then according to the specification (Highway Roadbed Design Specification JTG D30-2015), the required number of prestressed anchor rods can be calculated: c ≥1.3, determine n1, by K s ≥1.5, determine n2, according to the design requirements, take n=max{n1,n2};

[0224] Step c”: Calculate the effective pretension of a single anchor rod and lay a row of anchor rods along the road at the new roadbed. The number of anchor rods is n. Then, under the action of the horizontal thrust E, the friction force (kN) of the new roadbed base is:

[0225] F=(G+nN g )f

[0226] Where: G-self-weight of new roadbed surface layer, kN;

[0227] N g -Effective prestressing force of a single prestressed anchor, kN;

[0228] n-number of prestressed anchor rods;

[0229] f-friction coefficient;

[0230] Step d": Determine the effective length of the prestressed anchor rod:

[0231] L e ≥KP / πDτ

[0232] Where: L e -Effective length of prestressed anchor, m;

[0233] K - safety factor considering roadbed conditions and working conditions;

[0234] P-the maximum pull-out force allowed for the anchor, kN;

[0235] D-diameter of the prestressed anchor body (including the prestressed anchor rod and the grouting layer on the outer wall of the prestressed anchor rod), m;

[0236] τ - average shear strength between grouting layer and borehole wall, kPa.

[0237] By designing the values ​​based on the above calculation results, the new roadbed can simultaneously meet the requirements of anti-slip and anti-overturning stability, and then anchor rods, drainage holes and prefabricated L-shaped panels can be laid.

[0238] For example, the widened roadbed structure obtained by the above roadbed widening method is shown in FIG. Figure 1, including reinforcing the original roadbed and a new roadbed connected to the original roadbed, wherein the reinforced original roadbed includes the original roadbed 1 and a pile-anchor support assembly, the pile-anchor support assembly includes sheet piles 2 (for example, steel sheet piles) and reinforcing anchor rods 3, the sheet piles 2 are arranged on the side of the original roadbed 1 along the vertical direction of the road, the reinforcing anchor rods 3 are arranged in the original roadbed 1, and one end of the reinforcing anchor rods 3 is fixedly connected to the sheet piles 2, the new roadbed includes a cast body 10, prestressed anchor rods 5, surface geocells 13, and multiple layers of internal geocells 8 and multiple layers of L-shaped panels 6 arranged vertically along the road, the vertical panels of the L-shaped panels 6 are arranged vertically along the road, and the horizontal panels of the L-shaped panels 6 are arranged horizontally along the road, see Figures 4a to 4c The surface geocell 13 is provided on the upper surface of the cast body 10, the internal geocell 8, the prestressed anchor rod 5 and the transverse panel are provided in the cast body 10, one end of the surface geocell 13 is fixedly connected to the vertical panel, the other end of the surface geocell 13 is fixedly connected to the sheet pile 2, one end of the internal geocell 8 is fixedly connected to the sheet pile 2, the other end of the internal geocell 8 is fixedly connected to one end of the transverse panel, and the prestressed anchor rod 5 passes through the transverse panel along the vertical direction of the road.

[0239] In order to promote the realization of the "dual carbon" goal, the material of the above-mentioned cast body 10 is self-compacting lightweight concrete. The raw materials of the self-compacting lightweight concrete include processed industrial waste slag and / or construction waste, so that industrial waste slag or construction waste can be reduced and recycled, thereby reducing project costs.

[0240] Specifically, the maximum particle size of industrial waste and / or construction waste is ≤20mm, and the mud content is

[0241] ≤1.0wt.%, mud block content ≤0.5wt.%, needle-like particle content ≤8wt.%, void ratio ≤40%. The self-compacting lightweight concrete using this formula has good fluidity and homogeneity under the action of its own gravity, can achieve self-compacting, and does not require vibration.

[0242] Likewise, the raw materials of the L-shaped panel 6 include processed industrial waste residues and / or construction waste, which reduces the amount of industrial waste residues or construction waste and makes them available as resources, thereby lowering the project cost.

[0243] As for the material of the surface geocell 13 and the internal geocell 8, illustratively, the raw material includes polyethylene (PE), that is, the surface geocell 13 and the internal geocell 8 include a plurality of PE strips arranged horizontally and vertically in an alternating manner, and the yield tensile strength per unit width of the PE strip is ≥260N / cm, the yield elongation is ≤15%, and the longitudinal and transverse right-angle tearing strength is ≥200N. The height of the cell strips of the surface geocell 13 and the internal geocell 8 is 5cm to 15cm, and the cell side length is 15cm to 50cm.

[0244] In order to facilitate drainage inside the new roadbed, drainage holes are opened on the surface geocell 13 and the internal geocell 8, and the diameter of the drainage holes is 0.15 cm to 0.3 cm.

[0245] In order to ensure the structural strength of the L-shaped panel 6, for example, the width a of the vertical panel is 20cm~30cm, the total width b of the L-shaped panel 6 is 80cm~120cm, the height c of the vertical panel exceeding the upper surface of the horizontal panel is 40cm~60cm, and the length d of the L-shaped panel 6 is 1m~1.5m.

[0246] Exemplarily, there are multiple groups of pile-anchor support assemblies, which are arranged continuously along the longitudinal direction of the road. In each group of pile-anchor support assemblies, there is one sheet pile 2 and multiple reinforcing anchor rods 3, which are arranged vertically along the longitudinal direction of the road.

[0247] In order to avoid the occurrence of a group anchor effect and reduce the anchoring force, for example, the distance between two adjacent reinforcing anchor rods 3 is 1.5m to 4m, and the length of the anchoring section of the reinforcing anchor rod 3 is 3m to 10m.

[0248] In order to facilitate grouting construction, the reinforcing anchor rods 3 are arranged to be tilted downward in a direction gradually away from the sheet piles 2 .

[0249] In order to ensure the quality of grouting, improve the rationality of force and support effect, and ensure economy, for example, the inclination angle of the reinforcing anchor rod 3 is 15° to 30°.

[0250] In order to achieve a stable inclined connection between the sheet pile 2 and the reinforcing anchor rod 3, the widened roadbed structure further includes a triangular baffle 12, a through hole is provided on the sheet pile 2, and the structure of the reinforcing anchor rod 3 specifically includes a reinforcing rod body 31, a sleeve 32, a nut 33 and a tray 34. The side of the triangular baffle 12 away from the sheet pile 2 is an inclined surface that gradually slopes downward away from the sheet pile 2. A through hole is provided on the triangular baffle 12, and the sleeve 32 is sleeved on the outer wall of the end of the reinforcing rod body 31. The end of the sleeve 32 passes through the sheet pile 2, the triangular baffle 12, the tray 34 and the nut 33 in sequence and is fixedly connected to the sheet pile 2, the triangular baffle 12, the tray 34 and the nut 33 respectively. Figures 2 to 3 .

[0251] Exemplarily, the reinforcing rod 31 is a steel strand, the sleeve 32 is a metal seamless steel pipe, and the outer wall of the sleeve 32 is processed with threads that match the nut 33, that is, the sleeve 32 and the nut 33 are threadedly connected.

[0252] Specifically, the structure of the prestressed anchor rod 5 uses threaded steel bars, including a prestressed rod body, a nut, and a pad. One end of the prestressed anchor rod 5 is defined as the embedded end, and the other end is defined as the fixed end. The nut and pad are set at the fixed end of the prestressed anchor rod 5. The embedded end of the prestressed anchor rod 5 passes through multiple layers of transverse panels in sequence and is inserted into the foundation. The fixed end of the prestressed anchor rod 5 is fixedly connected to the top transverse panel through the nut and pad. In this way, the provision of the pad can better achieve force transmission and improve the anchoring effect. However, it is worth noting that the number of pads should not be excessive to avoid increasing the loss of prestress.

[0253] Regarding the determination of the structural parameters of the prestressed anchor rod 5, specifically, its diameter is determined by the specific design tension, the spacing between two adjacent prestressed anchor rods 5 is 2m to 3m, and the anchoring depth of the prestressed anchor rod 5 is determined by calculation based on actual conditions.

[0254] In order to achieve a stable connection between the L-shaped panel 6 and the surface geocell 13 and the internal geocell 8, the widened roadbed structure further includes a panel connection assembly 9. Figure 5a to Figure 5b The horizontal panels are connected to the internal geocell 8 through the panel connection assembly 9, and the vertical panels are connected to the surface geocell 13 through the panel connection assembly 9.

[0255] Regarding the structure of the panel connection assembly 9, specifically, it includes transverse ribs 91, vertical ribs 92, bolts 95 and geocell clamps 96. The number of transverse ribs 91 and vertical ribs 92 is two, and the transverse ribs 91 and vertical ribs 92 form a well shape. One end of the surface geocell 13 and the internal geocell 8 is clamped between the geocell clamp 96 and the vertical ribs 92. One end of the geocell clamp 96 is fixedly connected to one of the transverse ribs 91 by a bolt 95, and the other end of the geocell clamp 96 is fixedly connected to the other transverse rib 91 by a bolt 95.

[0256] In order to connect multiple panel connection components 9 into a whole, improve the overall stability of the new roadbed, and facilitate the construction of the entire new roadbed, the above-mentioned panel connection component 9 also includes a sleeve 93 and a panel threaded rod 94. The sleeve 93 is arranged at one end of the vertical rib 92, and the panel threaded rod 94 is arranged at the other end of the vertical rib 92. The panel threaded rod 94 and the vertical rib 92 are integrally formed. Between two vertically adjacent vertical ribs 92, the sleeve 93 of one vertical rib 92 is threadedly connected to the panel threaded rod 94 on the other vertical rib 92, so that multiple panel connection components 9 can be connected into a whole, thereby improving the overall stability of the new roadbed and facilitating the construction of the entire new roadbed.

[0257] During implementation, first, one end of the surface geocell 13 and the internal geocell 8 is extended between the geocell clamp 96 and the vertical rib 92, and the bolt 95 is inserted. Then, the bolt 95 is further inserted into the vertical panel or the horizontal panel of the L-shaped panel 6 and tightened to complete the connection between the L-shaped panel 6 and the surface geocell 13 or the internal geocell 8 of the same layer, preventing the L-shaped panel 6 from separating from the surface geocell 13 or the internal geocell 8 and reducing the risk of uneven settlement; then, the vertical rib 92 of the upper layer is connected to the vertical rib 92 of the next layer through the sleeve 93 and the panel threaded rod 94 that are threaded together to complete the assembly of the two adjacent layers of panel connection components 9, and the above steps are repeated to finally form a continuous whole, which is conducive to improving the overall stability of the new roadbed.

[0258] It can be understood that a connection hole is provided at one end of the transverse panel of the L-shaped panel 6 facing the panel connection assembly 9 , and the bolt 95 is inserted into the connection hole.

[0259] Exemplarily, the number of connection holes is 4, arranged in a 2×2 pattern, the distance e between the center of the connection hole and the surface of the horizontal panel is 2cm to 10cm, the distance f between two adjacent connection holes is 5cm to 15cm, the diameter of the connection hole is 1cm to 2cm, and the depth of the connection hole is 5cm to 10cm.

[0260] It should be noted that the specific size of the panel connection assembly 9 is determined by the size of the connection holes of the surface geocell 13 , the internal geocell 8 , and the L-shaped panel 6 .

[0261] In order to achieve a stable connection between the sheet piles 2 and the surface geocell 13 and the internal geocell 8, the widened roadbed structure further includes a sheet pile connection assembly 11, through which the sheet piles 2 are fixedly connected to the surface geocell 13 and the internal geocell 8 respectively.

[0262] For the structure of the sheet pile connection assembly 11, specifically, see Figures 6a to 6c The structure includes a connecting post 111, a sheet pile threaded rod 112, and a connecting plate. One end of the sheet pile threaded rod 112 is fixedly connected to the sheet pile 2, and the other end is suspended in the air. The connecting plate is sleeved on the outside of the sheet pile threaded rod 112 and threadedly connected to the sheet pile threaded rod 112. The connecting post 111 is fixed to the connecting plate, and the other ends of the surface geocell 13 and the internal geocell 8 are sleeved on the connecting post 111. In this way, by twisting the connecting plate, it can move along the axial direction of the sheet pile threaded rod 112 through the threaded structure, thereby achieving tensioning of the surface geocell 13 and the internal geocell 8.

[0263] In order to better cooperate with the surface geocell 13 and the internal geocell 8, for example, the above-mentioned connecting plate includes a horizontal connecting plate 113, a vertical connecting plate 114, a first oblique connecting plate 115 and a second oblique connecting plate 116. A threaded hole is opened on the horizontal connecting plate 113, and the threaded hole is threadedly connected to the sheet pile threaded rod 112. The horizontal connecting plate 113 is vertically arranged to the sheet pile threaded rod 112. One end of the first oblique connecting plate 115 is connected to the horizontal connecting plate 113, and one end of the second oblique connecting plate 116 is connected to the horizontal connecting plate 113. The other end of the first oblique connecting plate 115 and the other end of the second oblique connecting plate 116 are fixedly connected to the threaded connecting rod. The first oblique connecting plate 115, the second oblique connecting plate 116 and the horizontal connecting plate 113 form a triangle. The connecting column 111 is arranged at the corner of the triangle and is perpendicular to the plane in which the triangle is located.

[0264] It should be noted that the specific size of the sheet pile connection assembly 11 is determined by the sizes of the surface geocell 13 , the internal geocell 8 and the sheet pile 2 .

[0265] To improve the waterproofing of the new roadbed, the widened roadbed structure also includes a waterproof membrane 4 (e.g., an impermeable composite geomembrane) located at the bottom of the cast structure 10. This waterproof membrane 4 forms an anti-seepage system that prevents moisture from penetrating into the existing roadbed or foundation during construction of the cast structure 10, minimizing any impact on the stability of the existing roadbed and foundation.

[0266] As for the structure of the waterproof membrane 4, specifically, it includes multiple layers of geotextiles stacked in sequence and a plastic film arranged between two adjacent layers of geotextiles, wherein the geotextile is a filament non-woven fabric, and the plastic film is a high-density polyethylene film or a polyvinyl chloride film, and the thickness of the plastic film is 0.3mm to 2.0mm.

[0267] In order to facilitate the drainage of water in the cast body 10, the widened roadbed structure also includes a one-way drain pipe 7. For example, the one-way drain pipe 7 is opened at the bottom end of the vertical panel and is inclined downward in a direction gradually away from the cast body 10, with an inclination angle of 3° to 5°.

[0268] In order to further improve the drainage performance of the widened roadbed structure, there are multiple one-way drainage pipes 7, which are evenly arranged along the longitudinal direction of the road. The horizontal distance between adjacent drainage pipes is 1.5m to 2.5m (for example, 2.0m), and the diameter of the one-way drainage pipe 7 is 5cm to 10cm.

[0269] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A method for widening a roadbed, characterized in that: The steps include: Step 1: Drive sheet piles into the ground at the shoulder of the original roadbed to the embedding depth, excavate the original roadbed, and when the excavation reaches the designed position of the reinforcement anchor rod, drive the reinforcement anchor rod as required, and pour anchor mortar around the reinforcement anchor rod to form an anchor mortar layer. Excavate to the base of the original roadbed; Step 2: Lay out the L-shaped panel, lay the internal geocell, and fix one end of the internal geocell to the L-shaped panel and the other end to the sheet pile. Carry out casting on the internal geocell to obtain an internal casting layer, and roughen the upper surface of the formed casting layer. Step 3: Repeat step 2 until the topmost internal cast unit layer is cast. Step 4: Place the top L-shaped panel and drill holes at the designed positions of the prestressed anchor rods. The vertical panel of the L-shaped panel is arranged along the vertical direction of the road, and the horizontal panel of the L-shaped panel is arranged along the horizontal direction of the road. The prestressed anchor rods penetrate the horizontal panel along the vertical direction of the road. The diameter of the drill hole is 80mm to 110mm, and the distance between the center of the drill hole and the inner side of the vertical panel is 40cm to 50cm. The prestressed anchor rods are lowered and cement slurry is injected into the drill hole to obtain a grouting layer. Step 5: tension the prestressed anchor rod, and after tensioning is completed, lock the fixed end of the prestressed anchor rod; Step 6: Lay the surface geocell, connect one end of the surface geocell to the L-shaped panel, and fix the other end to the sheet pile. Carry out casting on the surface geocell to obtain the surface casting layer, thus completing the construction of the widened roadbed structure. The horizontal panels are connected to the internal geocells through panel connection assemblies, and the vertical panels are connected to the surface geocells through panel connection assemblies; The panel connection assembly includes transverse ribs, vertical ribs, bolts and geocell clamps, one end of the surface geocell and the inner geocell is clamped between the geocell clamp and the vertical ribs, one end of the geocell clamp is fixedly connected to one of the transverse ribs by a bolt, and the other end of the geocell clamp is fixedly connected to the other transverse rib by a bolt; The number of the transverse ribs and the number of the vertical ribs are both two, and the transverse ribs and the vertical ribs form a well shape; The panel connection assembly further comprises a sleeve and a panel threaded rod, wherein the sleeve is arranged at one end of the vertical rib and the panel threaded rod is arranged at the other end of the vertical rib; Between two vertically adjacent vertical ribs, the sleeve of one vertical rib is threadedly connected to the panel threaded rod on the other vertical rib.

2. The roadbed widening method according to claim 1, characterized in that: The following steps are also included between step 1 and step 2: A waterproof membrane is laid on the base of the original roadbed after excavation and the waterproof membrane is fixed.

3. The roadbed widening method according to claim 1, characterized in that: In step 2, the casting thickness of the casting body is flush with the top surface of the L-shaped panel.

4. The roadbed widening method according to claim 1, characterized in that: In step 4, the axis of the prestressed anchor rod coincides with the axis of the drilling hole.

5. The roadbed widening method according to claim 1, characterized in that: In step 5, when the cement slurry strength reaches more than 80% of the design strength, the prestressed anchor rods are tensioned.

6. The roadbed widening method according to any one of claims 1 to 5, characterized in that: The step 1 also includes the following steps: Calculate the embedment depth of the sheet pile.

7. The roadbed widening method according to claim 6, characterized in that: The embedding depth of the sheet pile is calculated using the following method: Step a: Based on the principle that the active earth pressure and passive earth pressure are equal, calculate the vertical distance between the point where the active earth pressure and passive earth pressure in the first layer of reinforcement anchors are equal and the excavation bottom surface: Where: y1 - the vertical distance between the point where the active earth pressure and the passive earth pressure in the first layer of reinforcement anchor are equal and the bottom surface of the excavation, m; e a1 - Active earth pressure strength at the excavation surface in the first layer of reinforcement anchors, kN / m 2 ; K a - active earth pressure coefficient; K p - passive earth pressure coefficient; γ-average density of original roadbed filler, kN / m 3 ; q-ground load, kPa; The sheet pile AB1 of unit width between the point where the active earth pressure and the passive earth pressure are equal in the first layer of reinforcement anchor and the design position of the reinforcement anchor is regarded as a simply supported beam. The moment of the point B1 where the active earth pressure and the passive earth pressure are equal in the first layer of reinforcement anchor is taken, and the bending moment ∑M at point B1 is set to B1 =0, calculate the anchor force required for the reinforcement anchors in the first layer of reinforcement anchors: Where: T1-the anchor force required for the reinforcement anchor in the first layer, kN; z a1 -The height between the active earth pressure action point in the first layer of reinforcement anchor and the original roadbed surface, m; E a1 -The active earth pressure above point B1 of the original roadbed base corresponding to the first layer of reinforcement anchors, kN / m; h1-the required excavation depth of the first layer of reinforcement anchors, m; h2-the required excavation depth of the second layer of reinforcement anchors, m; Step b: Based on the principle that the active earth pressure and passive earth pressure are equal, calculate the vertical distance between the point where the active earth pressure and passive earth pressure in the second layer of reinforcement anchor are equal and the excavation bottom surface: Where: y2 - the vertical distance between the point where the active earth pressure and the passive earth pressure in the second layer of reinforcement anchor are equal and the excavation bottom surface, m; e a2 - Active earth pressure strength at the excavation surface in the second layer of reinforcement anchors, kN / m 2 ; K a - active earth pressure coefficient; K p - passive earth pressure coefficient; γ-average density of original roadbed filler, kN / m 3 ; q-ground load, kPa; The sheet pile AB2 of unit width between the point where the active earth pressure and the passive earth pressure are equal in the second layer of reinforcement anchor and the design position of the reinforcement anchor is regarded as a simply supported beam. The moment of the point B2 where the active earth pressure and the passive earth pressure are equal in the second layer of reinforcement anchor is taken, and the bending moment ∑M at point B2 is set to B2 =0, at this time, T1 is used as a known point force to calculate the anchor force required for the second layer of reinforcement anchors: Where: T2-anchor force required for reinforcing anchors in the second layer of reinforcing anchors, kN; T1 - Anchor force required for reinforcing anchors in the first layer of reinforcing anchors, kN; z a2 -The height between the active earth pressure action point in the second layer of reinforcement anchor and the original roadbed surface, m; E a2 - The resultant active earth pressure above point B2 on the original roadbed base corresponding to the second layer of reinforcement anchors, kN / m; h1-the required excavation depth of the first layer of reinforcement anchors, m; h2-the required excavation depth of the second layer of reinforcement anchors, m; h3-the required excavation depth of the third layer of reinforcement anchors, m; Step c: According to the method of step b, calculate to the k-1th layer reinforcement anchor stage and obtain T1, T2, ..., T k-1 ; Step d: Dig to the designed excavation depth of the original roadbed. Based on the principle that the active earth pressure and passive earth pressure are equal, calculate the vertical distance between the point where the active earth pressure and passive earth pressure in the k-th layer of reinforcement anchor are equal and the excavation bottom surface: Where: y k -The vertical distance between the point where the active earth pressure and the passive earth pressure in the k-th layer of reinforcement anchor are equal and the excavation bottom surface, m; e ak - Active earth pressure strength at the excavation surface in the kth layer reinforcement anchor, kN / m 2 ; K a - active earth pressure coefficient; K p - passive earth pressure coefficient; γ-average density of original roadbed filler, kN / m 3 ; q-ground load, kPa; The sheet pile AB of unit width between the point where the active earth pressure and the passive earth pressure are equal in the kth layer of reinforcement anchor and the design position of the reinforcement anchor is k As a simply supported beam, the point B corresponding to the equal active earth pressure and passive earth pressure in the k-th layer reinforcement anchor is k Take the moment and let B k Bending moment ∑M Bk =0, T1, T2, T3, ..., T k-1 The anchor force and B required for the k-th layer reinforcement anchor are calculated by taking the known point force into account. k The support reaction force of the point: P Bk =And ak -∑T k Where: T k - the anchor force required for the reinforcement anchor in the kth layer, kN; P Bk - Support reaction force at the point where the active earth pressure is equal to the passive earth pressure in the k-th layer reinforcement anchor, kN; z ak -The height between the active earth pressure action point in the kth layer of reinforcement anchor and the original roadbed surface, m; H-total excavation depth, m; E ak - The original roadbed base B corresponding to the kth layer of reinforcement anchor k Resultant active earth pressure above the point, kN / m; Step e: Calculate the point B where the active earth pressure is equal to the passive earth pressure in the k-th layer of reinforcement anchors k Height to bottom of sheet pile: Where: x is the point B where the active earth pressure is equal to the passive earth pressure in the k-th layer of reinforcement anchor k Height to the bottom of the sheet pile, m; P Bk - Support reaction force at the point where the active earth pressure is equal to the passive earth pressure in the k-th layer reinforcement anchor, kN; K a - active earth pressure coefficient; K p - passive earth pressure coefficient; γ-average density of original roadbed filler, kN / m 3 ; Step f: Calculate the embedment depth of the sheet pile; t0=x+y k Where: t0-embedding depth of sheet pile.

8. The roadbed widening method according to claim 7, characterized in that: After step f, the following steps are also included: performing a stress analysis based on the stress conditions of the sheet piles to calculate the maximum bending moment borne by the sheet piles: Where: σ-stress of the sheet pile when it is subjected to the maximum bending moment, MPa, M-maximum bending moment supported by the sheet pile, kN·m; W x -Sectional modulus of sheet pile, cm 3 ; [σ] - Strength of sheet pile, MPa.

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