CN113008675A - Detection method for bonding failure of undisturbed sand - Google Patents

Abstract

The invention belongs to the field of geotechnical engineering research, and particularly relates to a method for detecting undisturbed sand cementing failure, which comprises the following steps: stress ratio, body strain and axial strain are calculated through a triaxial sample of the particle aggregate, corresponding parameters are calculated, stress-strain characteristics or strength characteristics do not need to be compared with cemented undisturbed sand and cemented failed sand respectively, whether cementation fails or not is judged quickly by using only one triaxial sample, and particle cementation analysis on a microscopic view is also not needed.

Description

Detection method for bonding failure of undisturbed sand

Technical Field

The invention belongs to the field of geotechnical engineering research, and particularly relates to a method for detecting undisturbed sand cementing failure.

Background

Some undisturbed sandy soils in projects have weak cementation effects, and the cementation effects are influenced by disturbance or load. When the weakly consolidated joint fails, the stress-strain and strength characteristics of the sand change. At present, a method is lacked, namely whether cementation fails or not is judged quickly by using a sand particle aggregate sample without comparing the stress-strain characteristic or the strength characteristic with original cementation sand and cementation failed sand respectively or performing particle cementation analysis on a microscopic view.

Disclosure of Invention

The invention provides a method for detecting cementing failure of undisturbed sand, which is used for rapidly judging whether cementing fails or not by using only one sample without comparing stress-strain characteristics or strength characteristics with the cemented undisturbed sand and the cementing failure sand respectively and without performing particle cementing analysis on a microscopic view.

The invention provides a method for detecting cementing failure of undisturbed sand, which comprises the following steps:

step 1: let the vertical stress of the aggregate of sand particles be sigma₁Stress on the horizontal plane is respectively sigma₂And σ₃Where σ is₂And σ₃Is perpendicular to the direction of the particle assembly and the strain of the particle assembly is epsilon₁、ε₂And ε₃In which strain epsilon₁、ε₂And ε₃Respectively in the direction of the stress sigma₁、σ₂And σ₃The directions are the same; calculating the stress ratio R and the bulk strain ε_v：

ε_v＝ε₁+ε₂+ε₃ (2)

Step 2: let the start time recorded during loading be t₀The time recorded later is t from small to large₁,t₂,…,t_i,…,t_nWherein i is more than or equal to 1 and less than or equal to n, i is any time, and n +1 is the total recorded time;

will t be_iStress ratio R and bulk strain epsilon corresponding to time_vAnd axial strain epsilon₁Are respectively marked as RⁱAnd (ε)_v)ⁱAnd (ε)₁)ⁱ(ii) a Draw R as epsilon₁A curve of variation in which the maximum value of R is taken as R^maxTaking the stable and unchangeable value of R after the peak value is exceeded as R^criticalIf R is reduced after passing the peak value and is not changed into a stable value, taking the last recorded data point as R^critical(ii) a Calculate volume strain delta (. DELTA.. di-elect cons.)_v)ⁱAnd the shear strain increment delta (epsilon)_s)ⁱ：

(Δε_v)ⁱ＝(ε_v)ⁱ-(ε_v)^i-1 (3)

(Δε₁)ⁱ＝(ε₁)ⁱ-(ε₁)^i-1 (4)

Calculating D from the formulae (3) and (4)ⁱ：

Calculating phi from equation (5)ⁱ：

Note R^maxAnd R^criticalCorresponding times are respectively t_maxAnd t_criticalAnd t is_maxAnd t_criticalCorresponding DⁱAre respectively D^maxAnd D^critical，t_maxAnd t_criticalCorresponding phiⁱAre respectively phi^maxAnd phi^critical；

And step 3: and (5) calculating and judging whether the original-state yarn cementation is effective or ineffective based on the step 1 and the step 2.

Preferably, in step 3: calculate phi^max-φ^criticalWhen phi is^max-φ^criticalWhen the pressure is higher than 0, the original sand cementation is effective; when phi is^max-φ^criticalIf the ratio is less than 0, the undisturbed sand is in failure.

Preferably, in step 3: get A₁＝D^max，A₂＝R^max，B₁＝D^critical-D^max，B₂＝R^critical-R^maxCalculating C ═ A₁B₂-B₁A₂(ii) a When C is less than 0, the undisturbed sand is effectively cemented; and when C is more than 0, the original sand cementing is invalid.

Preferably, in step 3: computing

When in use

Then the original sand cementation is effective; when in use

In time, the undisturbed sand cement fails.

The method has the advantages that stress-strain characteristics or strength characteristics do not need to be compared with original cemented sand and cemented failed sand respectively, whether cementation fails or not is judged rapidly by using only one triaxial sample, and particle cementation analysis does not need to be conducted on a microscopic view.

Drawings

FIG. 1 is a schematic diagram of a triaxial cylindrical sample under force;

fig. 1. assembly of sand particles.

Detailed Description

In order to make the technical means, innovative features, objectives and effects of the present invention apparent, the present invention will be further described with reference to the following detailed drawings.

The invention provides a method for detecting cementing failure of undisturbed sand.

The invention relates to some abbreviations and symbols, the following are notes:

σ₁: vertical stress to which the aggregate of particles is subjected

σ₂And σ₃: horizontal stress, σ, to which the assembly of particles is subjected₂And σ₃Is directed perpendicularly to

ε₁、ε₂And ε₃: strain and respectively stress sigma₁、σ₂And σ₃Same direction

R: the ratio of the stresses to the stresses in the steel,

ε_v: bulk strain, epsilon_v＝ε₁+ε₂+ε₃

t₀,t₁,t₂,…,t_i,…,t_n: the recorded starting time in the loading process is t₀The time recorded later is t from small to large₁,t₂,…,t_i,…,t_nWhere 1. ltoreq. i.ltoreq.n, n +1 isNumber of recorded time points

Rⁱ: t th_iR corresponding to time

(ε_v)ⁱ: t th_iBody strain epsilon corresponding to time_v

(ε₁)ⁱ: t th_iBody strain epsilon corresponding to time₁

R^critical: stable value after R over peak value, or R corresponding to last recorded data point

(Δε_v)ⁱ: increase in bulk strain (Δ ε)_v)ⁱ＝(ε_v)ⁱ-(ε_v)^i-1

(Δε₁)ⁱ: increment of vertical strain (Δ ε)₁)ⁱ＝(ε₁)ⁱ-(ε₁)^i-1

Dⁱ：

φⁱ：

t_maxAnd t_critical：R^maxAnd R^criticalCorresponding times are respectively t_maxAnd t_critical

D^maxAnd D^critical：t_maxAnd t_criticalCorresponding DⁱAre respectively D^maxAnd D^critical

φ^maxAnd phi^critical：，_xt_amAnd t_criticalCorresponding phiⁱAre respectively phi^maxAnd phi^critical

The invention provides a method for detecting cementing failure of undisturbed sand, which comprises the following steps:

step 1: let the vertical stress of the aggregate of sand particles be sigma₁Stress on the horizontal plane is respectively sigma₂And σ₃Where σ is₂And σ₃Is perpendicular to the direction of the particle assembly and the strain of the particle assembly is epsilon₁、ε₂And ε₃In which strain epsilon₁、ε₂And ε₃Respectively in the direction of the stress sigma₁、σ₂And σ₃The directions are the same; calculating the stress ratio R and the bulk strain ε_v：

ε_v＝ε₁+ε₂+ε₃ (2)

Step 2: let the start time recorded during loading be t₀The time recorded later is t from small to large₁,t₂,…,t_i,…,t_nWherein i is more than or equal to 1 and less than or equal to n, i is any time, and n +1 is the total recorded time;

will t be_iStress ratio R and bulk strain epsilon corresponding to time_vAnd axial strain epsilon₁Are respectively marked as RⁱAnd (ε)_v)ⁱAnd (ε)₁)ⁱ(ii) a Draw R as epsilon₁A curve of variation in which the maximum value of R is taken as R^maxTaking the stable and unchangeable value of R after the peak value is exceeded as R^criticalIf R is reduced after passing the peak value and is not changed into a stable value, taking the last recorded data point as R^critical(ii) a Calculate volume strain delta (. DELTA.. di-elect cons.)_v)ⁱAnd the shear strain increment delta (epsilon)_s)ⁱ：

(Δε_v)ⁱ＝(ε_v)ⁱ-(ε_v)^i-1 (3)

(Δε₁)ⁱ＝(ε₁)ⁱ-(ε₁)^i-1 (4)

Calculating D from the formulae (3) and (4)ⁱ：

Calculating phi from equation (5)ⁱ：

Note R^maxAnd R^criticalCorresponding times are respectively t_maxAnd t_criticalAnd t is_maxAnd t_criticalCorresponding DⁱAre respectively D^maxAnd D^critical，t_maxAnd t_criticalCorresponding phiⁱAre respectively phi^maxAnd phi^critical；

And step 3: and (5) calculating and judging whether the original-state yarn cementation is effective or ineffective based on the step 1 and the step 2.

In the step 3: calculate phi^max-φ^criticalWhen phi is^max-φ^criticalWhen the pressure is higher than 0, the original sand cementation is effective; when phi is^max-φ^criticalIf the ratio is less than 0, the undisturbed sand is in failure.

In the step 3: get A₁＝D^max，A₂＝R^max，B₁＝D^critical-D^max，B₂＝R^critical-R^maxCalculating C ═ A₁B₂-B₁A₂(ii) a When C is less than 0, the undisturbed sand is effectively cemented; and when C is more than 0, the original sand cementing is invalid.

In the step 3: computing

When in use

Then the original sand cementation is effective; when in use

In time, the undisturbed sand cement fails.

In the present invention, the vertical direction is the axial direction, and the axial direction is the vertical direction.

Claims (4)

1. A detection method for undisturbed sand cementation failure is characterized by comprising the following steps: which comprises the following steps:

step 1: let the vertical stress of the aggregate of sand particles be sigma₁Stress on the horizontal plane is respectively sigma₂And σ₃Where σ is₂And σ₃Is perpendicular to the direction of the particle assembly and the strain of the particle assembly is epsilon₁、ε₂And ε₃In which strain epsilon₁、ε₂And ε₃Respectively in the direction of the stress sigma₁、σ₂And σ₃The directions are the same; calculating the stress ratio R and the bulk strain ε_v：

ε_v＝ε₁+ε₂+ε₃ (2)

Step 2: let the start time recorded during loading be t₀The time recorded later is t from small to large₁,t₂,…,t_i,…,t_nWherein i is more than or equal to 1 and less than or equal to n, i is any time, and n +1 is the total recorded time;

will t be_iStress ratio R and bulk strain epsilon corresponding to time_vAnd axial strain epsilon₁Are respectively marked as RⁱAnd (ε)_v)ⁱAnd (ε)₁)ⁱ(ii) a Draw R as epsilon₁A curve of variation in which the maximum value of R is taken as R^maxTaking the stable and unchangeable value of R after the peak value is exceeded as R^criticalIf R is reduced after passing the peak value and is not changed into a stable value, taking the last recorded data point as R^critical(ii) a Calculate volume strain delta (. DELTA.. di-elect cons.)_v)ⁱAnd the shear strain increment delta (epsilon)_s)ⁱ：

(Δε_v)ⁱ＝(ε_v)ⁱ-(ε_v)^i-1 (3)

(Δε₁)ⁱ＝(ε₁)ⁱ-(ε₁)^i-1 (4)

Calculating D from the formulae (3) and (4)ⁱ：

Calculating phi from equation (5)ⁱ：

Note R^maxAnd R^criticalCorresponding times are respectively t_maxAnd t_criticalAnd t is_maxAnd t_criticalCorresponding DⁱAre respectively D^maxAnd D^critical，t_maxAnd t_criticalCorresponding phiⁱAre respectively phi^maxAnd phi^critical；

And step 3: and (5) calculating and judging whether the original-state yarn cementation is effective or ineffective based on the step 1 and the step 2.

2. The method for detecting undisturbed sand consolidation failure according to claim 1, wherein the method comprises the following steps: in the step 3: calculate phi^max-φ^criticalWhen phi is^max-φ^criticalWhen the pressure is higher than 0, the original sand cementation is effective; when phi is^max-φ^criticalIf the ratio is less than 0, the undisturbed sand is in failure.

3. The method for detecting undisturbed sand consolidation failure according to claim 1, wherein the method comprises the following steps: in the step 3: get A₁＝D^max，A₂＝R^max，B₁＝D^critical-D^max，B₂＝R^critical-R^maxCalculating C ═ A₁B₂-B₁A₂(ii) a When C is less than 0, the undisturbed sand is effectively cemented; and when C is more than 0, the original sand cementing is invalid.

4. The method for detecting undisturbed sand consolidation failure according to claim 1, wherein the method comprises the following steps: in the step 3: computing

When in use

Then the original sand cementation is effective; when in use

In time, the undisturbed sand cement fails.

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