CN-114943107-B - Bag type recoverable pull-press composite anchor rod and bearing capacity calculation method thereof

CN114943107BCN 114943107 BCN114943107 BCN 114943107BCN-114943107-B

Abstract

The invention discloses a bag-type recoverable pressure type anchor rod, which comprises an anchor head anchor device, a rod body, a supporting body and an anchor body, wherein the rod body comprises a steel strand and a protective sleeve, the protective sleeve is sleeved on the periphery of the steel strand, the supporting body is positioned at the tail end of the rod body of the anchor rod and is connected with the steel strand, the anchor body comprises a cement-soil anchor body and a cement slurry anchor body, the cement-soil anchor body is formed by cement slurry and surrounding soil through a high-pressure rotary spraying process, and the cement slurry anchor body is formed by injecting cement slurry into a bag wrapped around the rod body through a reserved grouting pipe. The anchor rod enables the shear stress distribution of the interface between the anchor body and the soil body to be more uniform, effectively prevents the cement-soil anchor body from being damaged by compression, and fully exerts the bearing performance of the anchor body. The invention also provides a bearing capacity calculation method of the bag-type recoverable pressure type anchor rod, and the method can obtain ultimate bearing capacity data of the anchor rod simply, efficiently and accurately.

Inventors

YUAN JING
YE ZHENGMING
HE YANCHENG
HU MINYUN
TONG LEI
YAO HONGBO

Assignees

浙江省建筑设计研究院
浙江工业大学

Dates

Publication Date: 20260505
Application Date: 20220330

Claims (1)

1. The bag-type recoverable pull-press composite anchor rod comprises an anchor head anchor, a rod body, a supporting body and an anchor body, wherein the anchor body comprises a cement-soil anchor body and a cement slurry anchor body, the cement slurry anchor body is positioned in the cement-soil anchor body and positioned at the rear side part, the cement slurry anchor body is formed by pouring cement slurry into a bag, the supporting body is radially arranged in the cement slurry anchor body in the bag, a plurality of high-strength fiber ribs are transversely distributed in the bag and fixedly connected with the supporting body, the rod body comprises steel strands and a sleeve, the sleeve is sleeved on the steel strands, the steel strands are positioned at the front side of the supporting body and are connected with the supporting body, an unlocking anchor and an unlocking anchor protective sleeve are arranged at the rear end of the rod body, the cement-soil anchor body and surrounding soil body are formed through a high-pressure rotary spraying process, and the cement slurry anchor body is formed by filling cement slurry into the bag which is wrapped around the rod body through a reserved grouting pipe; The bearing capacity calculating method is characterized by comprising the following steps of: step 1, determining critical anchoring length of cement paste anchoring body in bearing area The expression is as follows: (20) wherein: the critical anchoring length of the cement slurry anchoring body in the bearing area; is the diameter of the cement slurry anchor; the comprehensive elastic modulus of the cement slurry anchoring body in the bearing area; Shear modulus for a cement-soil anchor; determining the critical anchoring length of the cement slurry anchoring body in the bearing area according to the expression; step 2, determining the bearing capacity of the cement slurry anchoring body in the bearing area The cement slurry anchoring body in the bearing area is in a normal working state and is not damaged by compression and simultaneously cannot slip with surrounding structural bodies; the bearing capacity of the cement slurry anchor body in the bearing area is smaller value in bearing capacity of the cement slurry anchor body at the front end of the bearing body and interfacial friction between the cement slurry anchor body in the bearing area and surrounding cement-soil anchor bodies; the bearing capacity of the cement paste anchor body at the front end of the bearing body under pressure is calculated as follows: (21) wherein: is the ultimate compressive stress bearable by cement slurry anchors, The diameter of the cement slurry anchoring body is; the interfacial friction force of the cement slurry anchoring body in the bearing area and the surrounding structural body is as follows: (22) wherein: shear strength is the interface between the cement slurry anchoring body and the surrounding structural body; The length of the cement slurry anchoring body in the bearing area; the critical anchoring length of the cement slurry anchoring body in the bearing area; according to formulas (21) and (22), the bearing capacity of the cement slurry anchoring body in the bearing area is as follows: (23) step 3, determining critical anchoring length of cement paste anchoring body in tension zone The expression is as follows: (24) wherein: Critical anchoring length of cement slurry anchoring body in tension zone; is the diameter of the cement slurry anchor; the comprehensive elastic modulus of the cement slurry anchoring body in the tension zone; Shear modulus for a cement-soil anchor; determining the critical anchoring length of the cement slurry anchoring body in the tension zone according to the expression; Step 4, determining the bearing capacity of the cement slurry anchoring body in the tension zone The high-strength fiber ribs positioned in the range of the cement slurry anchoring body are not required to slip off the cement slurry anchoring body in the tension area under the normal working state of the cement slurry anchoring body in the tension area, and the cement slurry anchoring body in the tension area is not required to slip off the surrounding cement soil anchoring body; The bearing capacity of the cement slurry anchoring body in the tension area is smaller value in the bond strength between the high-strength fiber ribs and the reinforced soil body in the cement slurry anchoring body range and the interfacial friction resistance between the cement slurry anchoring body in the tension area and the surrounding cement soil anchoring body; bond strength between high-strength fiber ribs and reinforced soil body in the range of cement slurry anchoring body: (25) wherein: the interfacial shear strength of the high-strength fiber reinforced plastic and the cement slurry anchoring body is achieved; Taking the smaller value of the length of the high-strength fiber ribs in the cement slurry anchoring body in the bearing area and the cement slurry anchoring body in the tension area; the diameter of the fiber ribs with high strength; Interfacial friction of the cement slurry anchor in the tension zone with the surrounding cement-soil anchors: (26) wherein: The length of the cement slurry anchoring body in the tension zone; Critical length of cement slurry anchor for tension zone; According to formulas (25), (26), the bearing capacity of the cement slurry anchor in the tension zone is: (27) step 5, determining the integral bearing capacity of the cement slurry anchoring body According to (23) and (27), the overall bearing capacity of the cement slurry anchoring body is (28) Step 6, determining the critical anchoring length of the cement-soil anchoring body in the area I The expression is as follows: (29) wherein: the critical anchoring length of the cement-soil anchoring body in the area I; is the diameter of the cement-soil anchoring body; the comprehensive elastic modulus of the cement-soil anchoring body in the area I; Shear modulus for the surrounding soil mass; determining the critical anchoring length of the cement-soil anchoring body in the area I according to the expression; Step 7, determining the bearing capacity of the cement-soil anchoring body in the area I The bearing capacity of the cement-soil anchoring body in the area I is a smaller value in the compression bearing capacity of the cement-soil anchoring body in the area I at the front end of the cement-slurry anchoring body and the interfacial friction resistance between the cement-soil anchoring body in the area I and surrounding rock-soil bodies; the compression bearing capacity of the cement-soil anchor body in the area I at the front end of the cement slurry anchor body is as follows: (30) wherein: is the extreme compressive stress bearable by the cement-soil anchoring body, Is the diameter of the cement-soil anchoring body; the interfacial friction between the cement-soil anchoring body in the area I and surrounding rock-soil mass is as follows: (31) wherein: The shear strength of the interface between the cement-soil anchoring body and the surrounding rock-soil body is achieved; the length of the cement-soil anchoring body in the area I; The critical length of the cement-soil anchoring body in the area I; According to formulas (30) and (31), the bearing capacity of the cement-soil anchoring body in the area I is as follows: (32) Step 8, determining the critical anchoring length of the cement-soil anchoring body in the zone II The expression is as follows: (33) wherein: critical anchoring length of the cement-soil anchoring body in the II area; is the diameter of the cement-soil anchoring body; the comprehensive elastic modulus of the cement-soil anchoring body in the II area; Shear modulus for the surrounding soil mass; determining the critical anchoring length of the cement-soil anchoring body in the zone II according to the expression; step 9, determining the bearing capacity of the cement-soil anchoring body in the zone II The cement-soil anchoring body in the II area is in a normal working state, the cement-soil anchoring body in the II area and surrounding rock-soil body cannot slip, and meanwhile, the cement slurry anchoring body in the cement-soil anchoring body in the II area is also in a normal working state; The bearing capacity of the cement-soil anchoring body in the area II is smaller than the interfacial friction between the cement-soil anchoring body in the area II and surrounding rock-soil body and the bearing capacity of the cement slurry anchoring body in the cement-soil anchoring body in the area II; In practical engineering application, the anchoring length of the cement slurry anchoring body is far smaller than the critical anchoring length of the cement slurry anchoring body, so that the interfacial shear stress distribution of the cement slurry anchoring body and the cement soil anchoring body tends to be average, the anchoring length of the cement soil anchoring body in the II area is also far smaller than the critical anchoring length of the cement soil anchoring body in the II area, the interfacial shear stress distribution of the cement soil anchoring body in the II area and surrounding rock soil bodies is simplified to be average, and the interfacial limit shear stress is multiplied by the corresponding reduction coefficient for the sake of safety ; The interfacial friction between the cement-soil anchoring body in the zone II and the surrounding rock-soil body is as follows: (34) wherein: The length of the cement-soil anchoring body in the zone II; according to formulas (28), (34), the bearing capacity of the cement-soil anchoring body in the zone II is: (35) Step 10, determining the bearing capacity of the whole anchoring body According to formulas (32), (35), the overall anchor load capacity is: (36) Step 11, determining the bearing capacity of the bag-type recoverable tension-compression composite anchor rod The integral bearing capacity of the bag-type recoverable pull-press composite anchor rod is smaller values among the integral bearing capacity of the anchor body, the bearing capacity of the steel strand and the normal working limit bearing capacity of the unlocking anchor; The bearing capacity of the steel strand is as follows: (37) wherein: taking 0.80-0.95 for the strength reduction coefficient of the steel strand; designing a value for the tensile strength of the steel strand; is the effective sectional area of the steel strand; the integral bearing capacity of the bag-type recoverable pull-press composite anchor rod is as follows: (38) wherein: The normal working limit bearing capacity of the unlocking anchor is provided by a manufacturer test report.

Description

Bag type recoverable pull-press composite anchor rod and bearing capacity calculation method thereof Technical Field The invention relates to a bag-type recoverable pull-press composite anchor rod and a bearing capacity calculation method thereof, which are mainly applied to foundation pit engineering, side slope engineering, tunnel engineering and the like. Background Along with the development of engineering construction and the development and utilization of underground space in China, the number and scale of foundation pit engineering are continuously enlarged. The anchor-pulling type enclosure structure provides a fulcrum for the soil retaining structure through the prestress anchor rods, and compared with the support forms of row piles, support and the like in foundation pit support, the anchor-pulling type enclosure structure can actively strengthen a rock-soil body, provides more allowance space for subsequent foundation pit excavation and basement construction, saves support construction and demolition time, can improve construction speed and construction efficiency, has better economical efficiency, and is widely applied to foundation pit support engineering at present. Conventional prestressed anchors are classified into tension type anchors and compression type anchors. The tensile anchor rod transmits the received external load to the rock-soil body through the bonding action between the rib body and the anchoring body. The tensile anchor rod is easy to surpass the ground red line in the use process, the rib body of the tensile anchor rod can become an obstacle for the subsequent development of underground space, and the tensile anchor rod is greatly limited in practical application, so that the compressive anchor rod is developed. The pressure type anchor rod directly transmits load to the bearing body consisting of the bearing piece, the unlocking anchor and the peripheral protective sleeve of the bottom end (the end far away from the free section) of the anchor rod through the steel stranded wire with the sleeve or the unbonded prestressed steel stranded wire. The pressure type anchor rod can realize the recovery of the reinforcement through the reinforcement tail end unlocking device, and the anchor rod is recovered after the use function is finished, so that the problem that the anchor rod exceeds a red line is solved, the anchor rod is prevented from becoming an underground barrier for subsequent engineering construction, the sustainable development and the double-carbon target requirements are met, and the resource is saved and the environment is friendly. However, the pressure type anchor rod can generate stress concentration at the position of the bearing body, so that the anchor body at the front end of the bearing body is easily damaged by compression, and the bearing performance of the anchor body cannot be fully exerted. In order to overcome the application defects of the tension type and pressure type anchor rods, the invention develops a bag type recoverable tension-compression composite type prestressed anchor rod (hereinafter referred to as a bag type recoverable tension-compression composite type anchor rod), but at home and abroad, no calculation theory of the bag type recoverable tension-compression composite type anchor rod exists, the novel anchor rod is used as a novel anchor rod, the calculation formula of the anchor rod bearing capacity in the prior national standard is inapplicable, and the bearing capacity of each load transmission interface cannot be calculated by the prior theory. Disclosure of Invention The invention aims to solve the technical problem of providing a bag-type recoverable pulling-pressing composite anchor rod, which ensures that the shear stress distribution of an anchor body and a soil body interface is more uniform, and the compression area of a cement-soil anchor body at the front end of the anchor body can be increased, and the stress level of the cement-soil anchor body can be reduced, so that the cement-soil anchor body is effectively prevented from being damaged by compression, and the bearing performance of the anchor body is fully exerted. The invention also provides a bearing capacity calculation method of the bag-type recoverable tension-compression composite anchor rod, and the method can simply, efficiently and accurately acquire the ultimate bearing capacity data of the anchor rod. The bag-type recoverable pulling-pressing composite anchor rod comprises an anchor head anchor device, a rod body, a supporting body and an anchor body, wherein the anchor body comprises a cement soil anchor body and a cement slurry anchor body, the cement slurry anchor body is positioned in the cement soil anchor body and positioned at the rear side part, the cement slurry anchor body is formed by pouring cement slurry into a bag, the supporting body is radially arranged in the cement slurry anchor body in the bag, a plurality of high-strength fiber ribs ar