A method for determining the minimum setback distance of buildings located on the top of stable rock slopes

Abstract

The present invention discloses a method for determining the minimum setback distance of a building located on the top of a stable rock slope, which belongs to the technical field of foundation bearing capacity analysis and includes the following steps: S1. determining the basic parameters required for calculating the minimum setback distance of a building located on the top of a stable rock slope; S2. analyzing the force of the building foundation; S3. establishing a rock mechanics equilibrium relationship model equation; S4. solving the mechanics equilibrium relationship model equation to obtain the minimum setback distance L of the building located on the top of a stable rock slope. This method fills the gap in the requirements of the current relevant design specifications for the minimum setback distance of a building located on a stable rock slope, and the analysis method is rigorous in theory, the solution calculation process is simple, and the result is accurate.

Description

Technical Field

[0001] The invention belongs to the technical field of foundation bearing capacity analysis, and in particular relates to a method for determining a minimum setback distance of a building located at the top of a stable rock slope. Background Art

[0002] With the continuous development of my country's construction industry, building on the top of stable rock slopes has become a common architectural form. How to consider the minimum setback distance between the building and the edge of the slope has always been a difficult problem in the engineering community. Too little setback will affect the stability of the slope and the stability of the building foundation, while too much setback will affect the site, building layout, and site utilization.

[0003] At present, my country's building foundation design specifications have empirical minimum setback distance regulations for buildings located on the top of a stable soil slope, based on the calculation of foundation stability using the circular sliding surface method. However, due to the large differences in the geotechnical properties of rock and soil, this calculation model is not applicable to the setback distance of buildings located on the top of a stable rock slope. The relevant design specifications lack a method to determine the minimum setback distance of buildings located on the top of a stable rock slope. Summary of the invention

[0004] The purpose of the present invention is to provide a method for determining the minimum setback distance of a building located on the top of a stable rock slope, so as to solve the technical problem that there is no method for determining the minimum setback distance of a building on the top of a rock slope in the existing design specifications.

[0005] The present invention discloses a method for determining a minimum setback distance of a building located at the top of a stable rock slope, comprising the following steps:

[0006] S1. Determine the basic parameters required for calculating the minimum setback distance of buildings located on the top of stable rock slopes;

[0007] S2. Analyze the stress on the building foundation;

[0008] S3. Establish the rock mass mechanical equilibrium relationship model equation;

[0009] S4. Solve the mechanical equilibrium relationship model equation and obtain the minimum retreat distance L of the building located on the top of the stable rock slope.

[0010] Furthermore, the basic parameters for calculating the minimum setback distance include:

[0011] Determine the basic parameters of the rock slope foundation soil layer;

[0012] Determine the basic parameters of concrete foundation and concrete frame short columns;

[0013] Determine the basic parameters of foundation pit backfill soil.

[0014] Furthermore, the basic parameters for determining the rock slope foundation soil layer include: rock failure body rupture angle θ, rock slope angle β, rock internal friction angle Rock cohesion c r , rock tensile strength σ T , rock bulk density γ1.

[0015] Furthermore, the basic parameters for determining the concrete foundation and the concrete frame short column include: the width of the concrete foundation B, the height of the concrete strip foundation H2, the length and width of the concrete frame short column D, the height of the concrete frame short column below the ground H3, the height of the concrete frame short column above the ground H4, the equivalent load N transmitted to the top of the short column by the building superstructure k , the bulk density of reinforced concrete is γ2.

[0016] Furthermore, the basic parameters for determining the foundation pit backfill soil include: the bulk density γ3 of the foundation pit backfill soil.

[0017] Furthermore, the building foundation stress analysis in step S2 is specifically as follows:

[0018] The foundation of the building located on the top of the stable rock slope consists of three parts: reinforced concrete short columns and foundation, foundation trench backfill soil, and rock foundation under the foundation;

[0019] Perform foundation stress analysis, the equivalent load N acting on the top of the short column k , the normal foundation reaction force N acting at the junction of the foundation bottom and the rock foundation p , self-weight of foundation G1, self-weight of short column G2, self-weight of foundation pit backfill soil G3.

[0020] Force analysis of rock slope failure body, the interface between rock failure body and foundation has normal force N' p , the rock failure body has a tangential stress τ acting on its failure surface, a normal stress σ acting on its failure surface, and a deadweight G4 acting at the centroid of the rock failure body.

[0021] Furthermore, the rock failure body has its own weight G4=[(2L+tanβ / (H1+H2+H3))(H1+H2+H3) / 2+BH1-H1(L+B+tanβ / (H1+H2+H3)) / 2]γ1, where L is the minimum setback distance of the building on the top of the stable rock slope, β is the angle of the rock slope, B is the width of the concrete foundation, H1 is the thickness of the rock failure body under the base, H2 is the height of the concrete strip foundation, H3 is the height of the top of the foundation from the ground, and γ1 is the rock density.

[0022] Furthermore, in step S3, a rock mass mechanical equilibrium model needs to be established to perform a rock foundation stress analysis. The normal foundation reaction force N acting at the junction of the foundation bottom and the rock foundation p On the contrary, there is a reverse normal force N' at the interface between the rock failure body and the foundation p , N p =N' p =N K +G1+G2+G3;

[0023] Where: N p is the normal foundation reaction force acting at the junction of the foundation bottom and the rock foundation; N k is the equivalent load acting on the top of the short column; G1 is the deadweight of the foundation; G2 is the deadweight of the short column; G3 is the deadweight of the backfill soil in the foundation pit.

[0024] Furthermore, the self-weight at the centroid of the foundation short column G1=BH2γ2, where γ2 is the bulk density of reinforced concrete.

[0025] Furthermore, the deadweight G2 at the centroid of the short column is D 2 (H3+H4)γ2, γ2 is the bulk density of reinforced concrete.

[0026] Furthermore, the self-weight of the backfill soil in the foundation pit G3 = [B(H2+H3)-BH2-D 2 H3]γ3, γ3 is the bulk density of the foundation pit backfill soil.

[0027] Furthermore, in step S3, it is necessary to establish a mechanical equilibrium equation of the rock mass failure surface, specifically:

[0028] τ-(N' p +G4)sin 2 θ / H1=0;

[0029] Where: τ is the tangential stress acting on the failure surface of the rock failure body, N' p is the normal force acting at the interface between the rock failure body and the foundation, θ is the rupture angle of the rock failure body, H1 is the thickness of the rock failure body under the base, and G4 is the deadweight acting at the centroid of the rock failure body.

[0030] Furthermore, in step S3, the shear failure constraint condition of the rock failure surface needs to be established, specifically:

[0031]

[0032] σ≤-σ T

[0033] Where, τ is the tangential stress acting on the failure surface of the rock failure body, σ is the normal stress acting on the failure surface of the rock failure body, and σ T is the tensile strength of rock, is the internal friction angle of rock, c r For rock cohesion.

[0034] The beneficial effects of the present invention are:

[0035] 1. It is proposed that the stable rock slope will fail along the fracture angle under the action of additional building and foundation loads, and a mechanical equation is established based on the mechanical equilibrium relationship and the stress equilibrium relationship of the failure surface, so that engineers can more accurately calculate the minimum safe distance from the foundation to the slope edge based on the geotechnical mechanics parameters and building load parameters;

[0036] 2. This method fills the gap in the current relevant design specifications for the minimum setback distance requirements for buildings located on stable rock slopes. The analysis method is rigorous in theory, the solution and calculation process is simple, and the results are accurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 It is a flow chart of the method for determining the minimum setback distance of the building on the top of the stable rock slope in the present invention;

[0039] Figure 2 A schematic diagram of a calculation model for the minimum setback distance of buildings on the top of a stable rock slope according to the present invention;

[0040] Figure 3 It is a schematic diagram of the stress state of the rock destruction body under the foundation in the present invention. DETAILED DESCRIPTION

[0041] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features of the embodiments may be combined with each other.

[0042] Example 1

[0043] A method for determining a minimum setback distance of a building located on a top of a stable rock slope, step 1, determining basic parameters required for calculating a minimum setback distance of a building located on a top of a stable rock slope, the basic parameters for calculating the minimum setback distance that can be set include:

[0044] (1) Determine the basic parameters of the rock slope foundation soil layer. The basic parameters of the rock slope foundation soil layer determined from the project's geological survey report include: the rock failure body rupture angle θ is 65°, the rock slope angle β is 80°, and the rock internal friction angle is 45°, the rock cohesion cr is 900 kPa, and the rock tensile strength σ T is 750kPa, and the rock bulk density γ1 is 24kN / m3;

[0045] (2) Determine the basic parameters of the concrete foundation and the concrete frame short columns. The basic parameters of the concrete foundation and the concrete frame short columns include: the width B of the concrete foundation is 3.0 m, the height H2 of the concrete strip foundation is 1.2 m, the length (width) D(D) of the concrete frame short columns are both 0.5 m, the height H3 of the concrete frame short columns is 2.0 m (below the ground) and H4 is 1.0 m (above the ground), and the equivalent load N transmitted to the top of the short column by the building superstructure is k is 1200kN, and the concrete density γ2 is 26kN / m3

[0046] (3) Determine the basic parameters of the foundation pit backfill soil, the basic parameters of the foundation pit backfill soil include: the bulk density γ3 of the foundation pit backfill soil is 18kN / m 3 .

[0047] Step 2, analyzing the force on the building foundation, can set the force analysis of the building foundation, specifically:

[0048] (1) Foundation force analysis calculation model Figure 2 As shown in the figure, the foundation of the building on the rock slope consists of three parts: reinforced concrete frame short column HJKM and foundation ABGF, foundation trench backfill soil, and rock foundation rock. The length and width of the reinforced concrete frame short column are both D, the height is H3+H4, and the top of the short column has an equivalent load N k ; The width of the concrete foundation is B, and the height of the foundation is H2; Under the limit state, there is a rock failure body ABCDE under the foundation, the height of the rock fault failure body is H1, and BC is the failure surface where the foundation becomes unstable. The self-weight of the foundation, G1 = BH2γ2 = 3.0 × 1.2 × 26 = 93.6 kN, the self-weight of the reinforced concrete frame short column, G2 = D 2 (H3+H4)γ2=0.5 2 ×(2.0+1.0)×26=19.5kN, self-weight of foundation pit backfill soil G3=[B(H2+H3)-BH2-D 2 H3]γ3=[3.0×(1.2+2.0)-3.0×1.2-0.5 2 ×2.0]×18=99kN

[0049] Step 3: Establish the rock mass mechanical equilibrium relationship model equation to analyze the rock foundation stress. The foundation stress state is as follows: Figure 3 As shown, the normal foundation reaction force N acts at the junction of the foundation bottom and the rock foundation pOn the contrary, there is a reverse normal force N' at the interface between the rock failure body and the foundation p , N p =N' p =N K +G1+G2+G3=1200+93.6+19.5+99=1412.1kN; the tangential stress τ and normal stress σ act on the failure surface, and the gravity G4 acts at the centroid of the rock failure body.

[0050] Figure 2 There are the following geometric relationships: (1) tanβ = (H1 + H2 + H3) / m; (2) tanθ = H1 / (m + B + L)

[0051] Substitute the following parameters: (1) tan80° = (H1 + 1.2 + 2.0) / m; (2) tan65° = H1 / (m + 3.0 + L)

[0052] Thus, the algebraic relationship between H1 and L is obtained: H1=12.3+3.45L, and this formula is substituted into G4.

[0053] G4=[(2L+tanβ / (H1+H2+H3))(H1+H2+H3) / 2+BH1-H1(L+B+tanβ / (H1+H2+H3)) / 2]γ1=[(2L+tan8 0° / (H1+1.2+2.0))×(H1+1.2+2.0) / 2+3.0×H1-H1×(L+3.0+tan80° / (H1+1.2+2.0)) / 2]×24=40L 2 +371L+548.

[0054] The tangential stress on the failure surface is equal to the sum of the tangential stress of the rock failure body's deadweight along the failure surface at the centroid and the tangential stress of the reverse normal force at the interface between the rock failure body and the foundation along the failure surface. The mechanical equilibrium equation of the rock failure surface is established, τ-(N' p +G4)sin 2 θ / H1=0, establish the shear failure constraint condition of rock failure surface, σ≤-σ T .

[0055] Step 4, solving the mechanical equilibrium relationship model equation, can solve the minimum setback distance L of the building located on the top of the stable rock slope.

[0056]

[0057] τ=(N' p +G4)sin 2 θ / H1=(1412.1+G4)sin265° / H1=(40L2 +371L+548+1412.1)×0.82 / (12.3+3.45L);

[0058] The formula can be simplified to 40L 2 -260L-291=0

[0059] It can be solved that L=7.5m.

[0060] Table 1 Statistical table of calculation results of the embodiment

[0061]

Claims

1. A method for determining the minimum setback distance of a building located at the top of a stable rock slope, characterized in that: The following steps are involved: S1. Determine the basic parameters required for calculating the minimum setback distance of buildings located on the top of stable rock slopes; S2. Analyze the stress on the building foundation; S3. Establish the rock mass mechanical equilibrium relationship model equation; S4. Solve the mechanical equilibrium relationship model equation to obtain the minimum setback distance L of the building located on the top of the stable rock slope; The building foundation stress analysis in step S2 is specifically as follows: The foundation of the building located on the top of the stable rock slope consists of three parts: reinforced concrete short columns and foundation, foundation trench backfill soil, and rock foundation under the foundation; Perform foundation stress analysis, the equivalent load N acting on the top of the short column k , the normal foundation reaction force N acting at the junction of the foundation bottom and the rock foundation p , self-weight of foundation G1, self-weight of short column G2, self-weight of foundation trench backfill soil G3; Force analysis of rock slope failure body, the interface between rock failure body and foundation has normal force N' p The rock failure body has a tangential stress τ acting on the failure surface, a normal stress σ acting on the failure surface, and a deadweight G4 acting at the centroid of the rock failure body. The rock failure body has a deadweight G4=[(2L+tanβ / (H1+H2+H3))(H1+H2+H3) / 2+BH1-H1(L+B+tanβ / (H1+H2+H3)) / 2]γ1, where L is the minimum distance of the building setback on the top of the stable rock slope, β is the rock slope angle, B is the width of the concrete foundation, H1 is the thickness of the rock failure body under the base, H2 is the height of the concrete strip foundation, H3 is the height of the top of the foundation from the ground, and γ1 is the rock density; In step S3, a rock mass mechanical equilibrium model needs to be established to perform rock foundation stress analysis. The normal foundation reaction force N acting at the junction of the foundation bottom and the rock foundation is p On the contrary, there is a reverse normal force N' at the interface between the rock failure body and the foundation p , N p =N' p =N K +G1+G2+G3; Where: N p is the normal foundation reaction force acting at the junction of the foundation bottom and the rock foundation; N k is the equivalent load acting on the top of the short column; G1 is the deadweight of the foundation; G2 is the deadweight of the short column; G3 is the deadweight of the backfill soil in the foundation pit; In step S3, the mechanical equilibrium equation of the rock mass failure surface needs to be established, specifically: τ-(N' p +G4)sin 2 θ / H1=0; Where: τ is the tangential stress acting on the failure surface of the rock failure body, N' p is the normal force acting at the junction of the top of the rock failure body and the foundation, θ is the rupture angle of the rock failure body, H1 is the thickness of the rock failure body under the base, and G4 is the deadweight acting at the centroid of the rock failure body; In step S3, the shear failure constraint conditions of the rock mass failure surface need to be established, specifically: t-stanφ-c r ≤0; σ≤-σ T Where, τ is the tangential stress acting on the failure surface of the rock failure body, σ is the normal stress acting on the failure surface of the rock failure body, and σ T is the tensile strength of rock, φ is the internal friction angle of rock, c r For rock cohesion.

2. A method for determining the minimum setback distance of a building located at the top of a stable rock slope according to claim 1, characterized in that: The basic parameters for calculating the minimum retreat distance include: Determine the basic parameters of the rock slope foundation soil layer; Determine the basic parameters of concrete foundation and concrete frame short columns; Determine the basic parameters of foundation pit backfill soil.

3. The method for determining the minimum setback distance of a building located at the top of a stable rock slope according to claim 2, characterized in that: The basic parameters for determining the rock slope foundation soil layer include: rock failure body rupture angle θ, rock slope angle β, rock internal friction angle φ, rock cohesion c r , rock tensile strength σ T , rock bulk density γ1.

4. The method for determining the minimum setback distance of a building located at the top of a stable rock slope according to claim 2, characterized in that: The basic parameters for determining the concrete foundation and the concrete frame short column include: the width of the concrete foundation B, the height of the concrete strip foundation H2, the length and width of the concrete frame short column D, the height of the concrete frame short column below the ground H3, the height of the concrete frame short column above the ground H4, the equivalent load N transmitted to the top of the short column by the building superstructure k , the bulk density of reinforced concrete is γ2.

5. The method for determining the minimum setback distance of a building located at the top of a stable rock slope according to claim 2, characterized in that: The basic parameters for determining the foundation pit backfill soil include: the bulk density γ3 of the foundation pit backfill soil.

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