CN112883506B - Simple measuring and calculating method for prestress loss of anchor cable on slope creep body - Google Patents
Simple measuring and calculating method for prestress loss of anchor cable on slope creep body Download PDFInfo
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Abstract
A simple measuring and calculating method for prestress loss of a prestressed anchor cable in a slope creep body is used for reasonably measuring and calculating the prestress loss of the prestressed anchor cable in a rock-soil body and providing a design basis for the design and calculation of the prestress anchor cable supertension value in the slope creep body. The method comprises the following steps: firstly, acquiring parameters of rock and soil bodies of each layer of the slope creep body and indexes of a prestressed anchor cable through preliminary design data; selecting a region with a larger free section length of the anchor cable as a key region, and establishing a simplified model to calculate the deformation of the slope creep body along the anchor cable direction; thirdly, selecting a post-construction deformation proportional coefficient eta of the rock-soil body under the action of the prestressed anchor cable according to the type of the rock-soil body; fourthly, calculating the prestress T of the loss of the anchor cable according to the following formula:
s r in the formula S (1-. eta.), S r And the value is the post-construction deformation value of the rock-soil body, and S is the total deformation of the slope creep body under the action of the anchor cable.
Description
Technical Field
The invention belongs to the technical field of geotechnical engineering, and relates to a simple measuring and calculating method for prestress loss of a prestressed anchor cable in a slope creep body.
Background
The prestressed anchor cable is used as a common anti-sliding structure and is widely applied to reinforcement engineering of various slope creep bodies. Generally speaking, one end of an anchor cable is fixed on a slope surface through a frame beam and other structures, the other end of the anchor cable is anchored in a stable rock-soil body below a sliding surface, and the rock-soil body of the slope creep body is in a compressed state by applying prestress so as to enhance the integrity of the slope creep body and improve the mechanical property of the rock-soil body, thereby improving the stability of the slope creep body and controlling the deformation of the rock-soil body. Under the action of the pressure of the anchor cable, the slope creep body rock-soil body can generate deformation along the direction of the anchor cable. During the construction period of the prestressed anchor cable structure, the deformation can be completed in a certain proportion; after the construction period, the anchored rock-soil body is still continuously developed under the action of pressure and then consolidation creep deformation, so that the loss of the prestress of the anchor cable is caused, and the reinforcing effect of the prestressed anchor cable structure is finally influenced.
A recommended over-tension value is given by partial industry specifications considering the prestress loss of the anchor cable (such as design specifications of railway subgrade retaining structures (TB 10025-. The invention patent specification of the publication number CN104196024A discloses a prestress loss calculation method based on the coupling of anchor cable prestress loss and rock-soil body creep, the solving process of the method is complicated, a series of parameters such as instantaneous elastic modulus, hysteresis elastic modulus, viscosity coefficient and the like are difficult to obtain, and inconvenience is brought to the practical application of the method.
Therefore, the prediction of the prestress loss of the prestressed anchor cable structure in most slope creep body reinforcement projects still stays at the level of experience and visual perception judgment, and a set of simple, reliable and strong-operability prestress loss measuring and calculating method does not exist, so that the design theory of the prestressed anchor cable structure is severely restricted.
Disclosure of Invention
The invention aims to solve the technical problem of providing a simple measuring and calculating method for prestress loss of a prestress anchor cable in a slope creep body, so as to reasonably measure and calculate the prestress loss of the prestress anchor cable in a rock-soil body and provide a design basis for the design and calculation of the prestress anchor cable supertension value in the slope creep body.
The technical scheme adopted by the invention for solving the technical problems is as follows:
the invention discloses a simple measuring and calculating method for prestress loss of a prestressed anchor cable in a slope creep body, which comprises the following steps of:
firstly, obtaining parameters of each layer of rock and soil mass of the slope creep body and indexes of the prestressed anchor cable through preliminary design data, wherein the parameters of each layer of rock and soil mass comprise severe gamma, cohesive force c and internal friction angle
An elastic modulus E; each index of the prestressed anchor cable comprises an anchor cable elastic modulus E 0 Nominal area A of single-bundle anchor cable, number n of anchor cable bundles, length L of anchor cable, design tension F of anchor cable and transverse distance d of anchor cable 1 And the longitudinal spacing d of the anchor cable 2 ；
Selecting a region with a larger free section length of the anchor cable as a key region, and establishing a simplified model to calculate the deformation of the slope creep body along the anchor cable direction;
thirdly, selecting a post-construction deformation proportional coefficient eta of the rock-soil body under the action of the prestressed anchor cable according to the type of the rock-soil body;
fourthly, calculating the prestress T of the loss of the anchor cable according to the following formula:
s r ＝S(1-η)
in the formula, s r For the value of the after-construction deformation of the rock-soil mass, S is the slope creep body in the anchor cableTotal deformation with.
The beneficial effects of the invention are mainly embodied in the following aspects:
aiming at different rock-soil body types of the slope creep body, the corresponding slope creep body deformation completion proportion in the prestressed anchor cable construction period is provided, and the engineering practice is better met;
secondly, a simple calculation method for the prestress loss of the anchor cable in the slope creep body is provided, and the design and calculation theory of the prestress anchor cable is perfected;
and thirdly, the method is simple to operate, the parameters are easy to obtain, and the method has strong practicability.
Drawings
The specification includes the following five figures:
FIG. 1 is a schematic illustration of a cable frame beam reinforced ramp creep body;
fig. 2 is a plan view of the anchor cable frame beam;
FIG. 3 is a cross-sectional view of an anchor cable frame beam;
fig. 4 is a simplified diagram of a numerical simulation of the anchor cable frame beam area;
Fig. 5 is a cloud picture of vertical deformation of rock-soil mass under equivalent load.
The labels and corresponding meanings in the figures are as follows: the method comprises the following steps of A, B, C, D, rock stratum 4, frame beams 5, anchor cables 6, a key analysis area 7, anchor cable free sections 8 and anchor cable anchoring sections 9.
Detailed Description
The invention will be further explained with reference to the drawings and examples.
Referring to fig. 1 to 3, the invention provides a simple method for measuring and calculating prestress loss of a prestressed anchor cable in a slope creep body, comprising the following steps:
firstly, obtaining parameters of each layer of rock and soil mass of the slope creep body and indexes of the prestressed anchor cable through preliminary design data, wherein the parameters of each layer of rock and soil mass comprise severe gamma, cohesive force c and internal friction angle
An elastic modulus E; each index of the prestressed anchor cable comprises the elasticity of the anchor cableModulus E 0 Nominal area A of single-bundle anchor cable, number n of anchor cable bundles, length L of anchor cable, design tension F of anchor cable and transverse distance d of anchor cable 1 And the longitudinal spacing d of the anchor cable 2 ；
Selecting a region with a larger free section length of the anchor cable as a key region, and establishing a simplified model to calculate the deformation of the slope creep body along the anchor cable direction;
thirdly, selecting a post-construction deformation proportional coefficient eta of the rock-soil body under the action of the prestressed anchor cable according to the type of the rock-soil body;
Fourthly, calculating the prestress T of the loss of the anchor cable according to the following formula:
s r ＝S(1-η)
in the formula, s r And the value is the post-construction deformation value of the rock-soil body, and S is the total deformation of the slope creep body under the action of the anchor cable.
In the step II, the deformation of the slope creep body along the anchor cable direction can be calculated through the following two methods.
The method comprises the following steps:
s201, establishing a model of a horizontal soil layer according to a stratum penetrated by an anchor hole, determining a foundation layering delta h, and calculating a self-weight stress p 1i And vertical additional stress p generated by prestressed anchor cable 2i ；
S202, taking the sum of the average value of the self-weight stress and the average value of the additional stress of each layer as the total stress p after the layers are pressed 3i ；
S203, determining the depth z of a compression layer, and calculating the compression quantity delta s of each layer i ；
S204, calculating the total deformation S according to the following formula:
the second method comprises the following steps:
s201, establishing a cuboid numerical model of a horizontal soil layer according to a stratum penetrated by an anchor hole;
s202, simulating the pressure of the anchor cable on the rock-soil body by applying vertical uniform distribution force sigma to the upper surface of the cuboid numerical model, wherein the vertical uniform distribution force sigma is calculated according to the following formula:
and S203, directly outputting the total deformation S through modeling calculation.
In the third step, the suggested value of the deformation completion proportionality coefficient eta in the construction period is comprehensively determined by combining the foundation condition, the foundation treatment measure, the placement time for finishing the roadbed filling and the regional experience, and the values are obtained according to the following table when no experience exists:
Compression factor a of low-low compressibility soil in table v0.1-0.2 Under 0.1-0.3 MPa -1 Compression coefficient a of soil with low compressibility v0.1-0.2 Less than 0.1MPa -1 。
Example (b):
referring to fig. 1 to 3, a certain slope creep body is composed of a soil layer A1, a soil layer B2, a soil layer C3 and a rock layer D4, and in order to control deformation of a rock-soil body of the slope creep body, the middle part of the slope is reinforced by adopting an anchor cable and frame beam structure. The simple measuring and calculating method provided by the invention is selected to estimate the prestress loss of the anchor cable in the later construction period. The design tension F is 1200kN, 8 bundles of steel strands are adopted to form the cable, and the nominal area of a single anchor cable bundle is 139mm 2 The elastic modulus of the steel strand is 195GPa, the length L of the anchor cable is 54m, and the distance between the anchor cables is 4m multiplied by 4 m.
The rock-soil body parameters of the slope creep deformation body are shown as follows:
and selecting a region with a larger length of the anchor cable free section 8 as a key analysis region 7, and establishing a simplified numerical model to estimate the deformation of the slope creep body along the anchor cable direction. And (3) establishing a cuboid numerical model of the horizontal soil layer according to the stratum penetrated by the anchor hole, as shown in figure 2. In the numerical model, the thickness of a soil layer 1A is 5m, the thickness of a soil layer 2B is 32m, the thickness of a soil layer 3C is 6m, and the thickness of a rock stratum 4D is 11 m. The dimension on the model horizontal plane is 20m × 1 m. The vertical uniform force sigma applied to the upper surface of the model is calculated according to the following formula:
The vertical deformation cloud of the numerical model is shown in fig. 3, with a maximum deformation of about 12.6 cm. As can be seen from fig. 3, the deformation of the soil body mainly occurs in the soil layer of the anchor cable free section 8, and the deformation of the anchor cable anchoring section 9 is substantially 0, so in this embodiment, the length change of the anchor cable mainly occurs in the anchor cable free section 8, that is, L is 43 m. According to the load condition and the type of the rock-soil body, the deformation proportion of the rock-soil body in the construction period under the action of the prestressed anchor cable is 90 percent, namely the value of the secondary consolidation creep is 10 percent of the total deformation. And measuring and calculating the prestress loss of the prestressed anchor cable according to the following formula.
s r ＝S(1-η)＝12.6×(1-90％)＝1.26cm
The prestress loss ratio is:
therefore, the method can reasonably measure and calculate the prestress loss of the prestressed anchor cable in the rock-soil mass, and provides a design basis for the design and calculation of the prestressed anchor cable supertension value in the slope creep body.
Claims (4)
1. A simple measuring and calculating method for prestress loss of a prestressed anchor cable in a slope creep body comprises the following steps:
firstly, obtaining parameters of each layer of rock and soil mass of the slope creep body and indexes of the prestressed anchor cable through preliminary design data, wherein the parameters of each layer of rock and soil mass comprise severe gamma, cohesive force c and internal friction angle
An elastic modulus E; each index of the prestressed anchor cable comprises an anchor cable elastic modulus E 0 Nominal area A of single-bundle anchor cable, number n of anchor cable bundles, length L of anchor cable, design tension F of anchor cable and transverse distance d of anchor cable 1 And the longitudinal distance d of the anchor cable 2 ；
Selecting a region with a larger free section length of the anchor cable as a key region, and establishing a simplified model to calculate the deformation of the slope creep body along the anchor cable direction;
thirdly, selecting a post-construction deformation proportional coefficient eta of the rock-soil body under the action of the prestressed anchor cable according to the type of the rock-soil body;
fourthly, calculating the prestress T of the loss of the anchor cable according to the following formula:
s r ＝S(1-η)
in the formula, s r And the value is the post-construction deformation value of the rock-soil body, and S is the total deformation of the slope creep body under the action of the anchor cable.
2. The simple measuring and calculating method for the prestress loss of the prestressed anchor cable in the slope creep body according to claim 1, wherein the deformation of the slope creep body along the anchor cable direction is calculated according to the following steps:
s201, establishing a model of a horizontal soil layer according to a stratum penetrated by an anchor hole, determining a foundation layering delta h, and calculating a self-weight stress p 1i And vertical additional stress p generated by prestressed anchor cable 2i ；
S202, taking the sum of the average value of the self-weight stress and the average value of the additional stress of each layer as the total stress p after the layers are pressed 3i ；
S203, determining the depth of a compression layerDegree z, calculating the compression amount deltas of each layer i ；
S204, calculating the total deformation S according to the following formula:
3. the simple measuring and calculating method for the prestress loss of the prestressed anchor cable in the slope creep body according to claim 1, wherein the deformation of the slope creep body along the anchor cable direction is calculated according to the following steps:
s201, establishing a cuboid numerical model of a horizontal soil layer according to a stratum penetrated by an anchor hole;
s202, simulating the pressure of the anchor cable on the rock-soil body by applying vertical uniform distribution force sigma to the upper surface of the cuboid numerical model, wherein the vertical uniform distribution force sigma is calculated according to the following formula:
and S203, directly outputting the total deformation S through modeling calculation.
4. The simple measuring and calculating method for the prestress loss of the prestressed anchor cable in the slope creep body according to claim 1, characterized in that the deformation completion proportionality coefficient η in the construction period is comprehensively determined by combining the values of the foundation conditions, the foundation treatment measures, the placement time for completion of roadbed filling and the regional experience, and the values are obtained according to the following table when the method is inexperienced:
compression factor a of low-low compressibility soil in table v0.1-0.2 Under 0.1-0.3 MPa -1 Compression coefficient a of soil with low compressibility v0.1-0.2 Less than 0.1MPa -1 。
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| CN114892688B (en) * | 2022-05-13 | 2023-03-21 | 中铁二院工程集团有限责任公司 | Three-dimensional design method and system for side slope anchor rod frame beam |
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