Residual soil slope collapse calculation method based on fracture hydrostatic pressure

Abstract

The invention discloses a residual soil slope collapse calculation method based on fracture hydrostatic pressure, and relates to the field of geotechnical engineering. The method specifically comprises the following steps: acquiring residual soil slope collapse and damage related parameters; selecting fracture depth according to actual working conditions; performing mechanical equilibrium analysis according to the specific form of the collapse failure surface within the height, and calculating the weight of the collapse body according to different forms; and calculating the safety coefficient considering the influence of the hydrostatic pressure of the slope fracture. The method can objectively reflect the influence of the non-uniformity and anisotropy of the residual soil on the slope stability.

Description

Technical Field

[0001] The invention belongs to the field of geotechnical engineering, and in particular relates to a residual soil slope collapse calculation method based on fissure hydrostatic pressure. Background Art

[0002] Collapse is the main failure form of slopes with high liquid limit soil, red clay, granite residual soil, etc. The collapse failure surface is straight and smooth, like a knife cut, nearly vertical and without sliding marks, mainly from the top of the slope, that is, the upper failure surface is nearly upright, and the lower failure surface is nearly a gentle straight line, which obviously does not conform to the arc sliding surface of the simplified Bishop method. At the same time, after the residual soil slope is excavated and exposed, and undergoes repeated dry-wet cycles, it is easy to develop slope cracks of varying degrees. The existence of cracks provides an infiltration channel for slope rainfall, which increases the bulk density of the soil, reduces the strength, and reduces the anti-sliding force on the sliding surface. In addition, the water column in the vertical cracks will generate hydrostatic pressure, which will produce horizontal thrust on the collapsed body. Obviously, if the collapse calculation does not take the above influences into account, the calculated safety factor will be dangerous. A large number of engineering practices also show that the stability of many residual soil slopes in the design phase is not a problem, but a large number of slope collapses still occur in actual projects, indicating that the conventional collapse calculation method is unreasonable for residual soil slopes. Therefore, the collapse calculation of residual soil slopes must take into account the influence of cracks. It is an urgent problem for technicians in this field to propose a collapse calculation method for residual soil slopes based on the hydrostatic pressure of cracks to objectively reflect the influence of residual soil heterogeneity and anisotropy. Summary of the invention

[0003] The invention proposes a residual soil slope collapse calculation method based on fissure hydrostatic pressure to solve the problems existing in the prior art.

[0004] The calculation method of residual soil slope collapse based on fissure hydrostatic pressure includes the following steps:

[0005] S1. Obtaining parameters related to residual soil slope collapse and failure;

[0006] S2. Select the crack depth h according to the actual working conditions;

[0007] S3. Perform mechanical equilibrium analysis based on the specific morphology of the collapse failure surface within the height h, and calculate the weight G of the collapsed body according to different morphologies;

[0008] S4. The calculation formula of stability safety factor considering the influence of hydrostatic pressure in vertical cracks is:

[0009]

[0010] Among them, G is the weight of the collapsed body, F wis the hydrostatic pressure in the vertical cracks of the disturbed soil area, α is the angle between the sliding direction and the horizontal direction; L is the length of the sliding surface; T is the tangential component on the sliding surface; c h is the cohesion of soil after the dry-wet cycle. It is the internal friction angle of soil after the dry-wet cycle.

[0011] The soil dry-wet cycle should be carried out in accordance with the provisions of the "Highway Geotechnical Test Code" (JTG 3430), and the number of dry-wet cycles is 5 times.

[0012] Residual soil slopes include high liquid limit soil and red clay, granite residual soil, expansive soil and other highly plastic clay slopes that are prone to water loss and cracking.

[0013] In the above method, optionally, the relevant parameters in S1 include: soil bulk density, shear strength and fracture hydrostatic pressure.

[0014] In the above method, optionally, the soil bulk density may be expressed as saturated density.

[0015] In the above method, optionally, the specific form of the collapse failure surface within the height h in S3 includes:

[0016] The upper failure surface is simplified as a vertical sliding surface, and the lower failure surface is simplified as a straight sliding surface.

[0017] In the above method, optionally, when the vertical crack is located at the top of the slope, the weight G of the collapsed body is calculated as follows:

[0018]

[0019] Among them, γ sat is the saturated bulk density of the collapse body; z is the length from the top of the slope to the bottom of the vertical crack; h is the length of the vertical crack. When the vertical crack is located at the top of the slope, h=z; H is the length from the top of the slope to the shear outlet of the sliding surface; β is the angle between the slope and the horizontal direction.

[0020] In the above method, optionally, when the vertical crack is located on the slope, the weight G of the collapsed body is calculated as follows:

[0021]

[0022] Alternatively, the hydrostatic thrust of the water column in the slope crack on the collapsed body can be calculated according to the hydrostatic pressure F w Size, that is:

[0023]

[0024] It can be seen from the above technical solutions that, compared with the prior art, the present invention provides a residual soil slope collapse calculation method based on fissure hydrostatic pressure, which has the following beneficial effects:

[0025] The physical and mechanical parameters applicable to the calculation of residual soil slope collapse were proposed, the failure forms of residual soil slope collapse were proposed, a simplified mechanical model for the calculation of residual soil slope collapse was constructed, and a calculation method for residual soil slope collapse considering the static water pressure of fissures was proposed, which effectively improved the accuracy of residual soil slope collapse calculation and ensured the stability and safety of residual soil slopes. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0027] Figure 1 It is a flow chart of the residual soil slope collapse calculation method based on fissure hydrostatic pressure disclosed in the present invention;

[0028] Figure 2 A diagram of the collapse and destruction scene of the residual soil slope disclosed in the present invention;

[0029] Figure 3 To simplify the Bishop method numerical simulation structure statistics diagram;

[0030] Figure 4 To improve and simplify the Bishop method numerical simulation structure statistics diagram. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] In this application, relational terms such as first and second, etc. are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. The terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of more restrictions, the elements defined by the sentence "comprise one..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0033] Reference Figure 1 As shown in FIG. 1 , the residual soil slope collapse calculation method based on fissure hydrostatic pressure includes the following steps:

[0034] S1. Obtaining parameters related to residual soil slope collapse and failure;

[0035] S2. Select the crack depth h according to the actual working conditions;

[0036] S3. Perform mechanical equilibrium analysis based on the specific morphology of the collapse failure surface within the height h, and calculate the weight G of the collapsed body according to different morphologies;

[0037] S4. The calculation formula of the stability safety factor considering the influence of hydrostatic pressure in the vertical cracks of the slope is:

[0038]

[0039] Among them, G is the weight of the collapsed body, F w is the hydrostatic pressure in the vertical cracks of the disturbed soil area, α is the angle between the sliding direction and the horizontal direction; L is the length of the sliding surface; T is the tangential component on the sliding surface; c h is the cohesion of soil after the dry-wet cycle. It is the internal friction angle of soil after the dry-wet cycle.

[0040] The soil dry-wet cycle should be carried out in accordance with the provisions of the "Highway Geotechnical Test Code" (JTG 3430), and the number of dry-wet cycles is 5 times.

[0041] Residual soil slopes include high liquid limit soil and red clay, granite residual soil, expansive soil and other highly plastic clay slopes that are prone to water loss and cracking.

[0042] Furthermore, the relevant parameters in S1 include: soil bulk density, shear strength and fracture hydrostatic pressure.

[0043] Furthermore, the soil bulk density adopts the saturated density.

[0044] Furthermore, the specific form of the collapse failure surface within the height h in S3 includes:

[0045] The upper failure surface is simplified as a vertical sliding surface, and the lower failure surface is simplified as a straight sliding surface.

[0046] Furthermore, when the vertical crack is located at the top of the slope, the weight G of the collapsed body is calculated as follows:

[0047]

[0048] Among them, γ sat is the saturated bulk density of the collapse body; z is the length from the top of the slope to the bottom of the vertical crack; h is the length of the vertical crack. When the vertical crack is located at the top of the slope, h=z; H is the length from the top of the slope to the shear outlet of the sliding surface; β is the angle between the slope and the horizontal direction.

[0049] Furthermore, when the vertical crack is located on the slope, the weight G of the collapsed body is calculated as follows:

[0050]

[0051] Furthermore, the hydrostatic thrust of the water column in the slope crack on the collapsed body can be calculated according to the hydrostatic pressure F w Size, that is:

[0052]

[0053] In a specific embodiment of the present invention, referring to Figure 2 As shown in Figure 1, a residual soil slope is 6m high, a first-level slope, and a slope ratio of 1:1. The soil parameters are shown in Table 1, where the cohesion stability value c under dry-wet cycles is h Take 50% of the cohesion c under the natural moisture content state, and the stable value of the friction angle under the action of dry-wet cycle φ h Take 50% of the internal friction angle φ under the natural water content state. The shear strength parameter value is basically consistent with the stable value under the saturated state.

[0054] Table 1 Values ​​of soil parameters of residual soil

[0055]

[0056] The vertical crack of the residual soil slope is located at the upper part of the slope, the vertical crack depth h = z = 2.0m, the length from the top of the slope to the shear outlet of the sliding surface H = 4.0m, the angle between the slope and the horizontal direction is 45°, the angle between the failure surface and the horizontal direction is about 30°, and the length of the lower sliding surface is about 1.3m. The weight of the collapsed body G:

[0057]

[0058] Vertical fracture water pressure thrust F w

[0059]

[0060] Stability factor F of the collapsed body s :

[0061]

[0062] If the influence of fissure water pressure thrust is not considered, the stability factor F s :

[0063]

[0064] The hydrostatic pressure in the slope fissures has a significant impact on the collapse of residual soil slopes. When the hydrostatic pressure in the slope fissures is not considered, it does not conform to the actual collapse of residual soil slopes.

[0065] In order to compare and analyze the collapse calculation method considering the hydrostatic pressure of the fissure, combined with the engineering example and soil parameters, as shown in Table 2, the simplified Bishop method of Geo-studio numerical software was used to calculate the stability coefficient of the slope. The numerical simulation diagram is shown in Figures 3 and 4. Figure 4 .

[0066] Table 2 Minimum slope stability coefficient values ​​calculated by different methods

[0067]

[0068]

[0069] As shown in Table 2, the maximum safety factor calculated by the simplified Bishop method is 2.252, the maximum safety factor calculated by the improved simplified Bishop method is 1.124, the stability factor of the unbalanced thrust method considering the fissure water pressure thrust is 0.842, and the stability factor of the unbalanced thrust method not considering the fissure hydrostatic pressure is 2.196. It can be seen that for the fissure disturbance of residual soil slopes, fissure water filling and water seepage softening are the main factors controlling the stability of the slope. If the influence of soil deterioration and fissure hydrostatic pressure cannot be considered in the stability analysis, the calculation result of the stability safety factor will be dangerous. The unbalanced thrust balance method considering the fissure hydrostatic pressure can better reflect the actual stability of the slope. This method is suitable for the collapse calculation of residual soil slopes.

[0070] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the system or system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0071] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A residual soil slope collapse calculation method based on fissure hydrostatic pressure, characterized in that: The following steps are involved: S1. Obtaining parameters related to residual soil slope collapse and failure; S2. Select the crack depth h according to the actual working conditions; S3. Perform mechanical equilibrium analysis based on the specific morphology of the collapse failure surface within the height h, and calculate the weight G of the collapsed body according to different morphologies; S4. The safety factor calculation formula considering the influence of vertical fracture hydrostatic pressure is: Among them, G is the weight of the collapsed body, F w is the hydrostatic pressure in the vertical cracks of the disturbed soil area, α is the angle between the sliding direction and the horizontal direction; L is the length of the sliding surface; T is the tangential component on the sliding surface; c h is the cohesion of soil after the dry-wet cycle. It is the internal friction angle of soil after the dry-wet cycle.

2. The residual soil slope collapse calculation method based on fissure hydrostatic pressure according to claim 1 is characterized in that: The relevant parameters in S1 include soil bulk density, shear strength and fracture hydrostatic pressure.

3. The residual soil slope collapse calculation method based on fissure hydrostatic pressure according to claim 2 is characterized in that: The soil bulk density adopts saturated density.

4. The residual soil slope collapse calculation method based on fissure hydrostatic pressure according to claim 1 is characterized in that: The specific forms of the collapse failure surface within the h height in S3 include: The upper failure surface is simplified as a vertical sliding surface, and the lower failure surface is simplified as a straight sliding surface.

5. The residual soil slope collapse calculation method based on fissure hydrostatic pressure according to claim 4 is characterized in that: When the vertical crack is located at the top of the slope, the weight G of the collapsed body is calculated as follows: Among them, γ sat is the saturated bulk density of the collapse body; z is the length from the top of the slope to the bottom of the vertical crack; h is the length of the vertical crack. When the vertical crack is located at the top of the slope, h=z; H is the length from the top of the slope to the shear outlet of the sliding surface; β is the angle between the slope and the horizontal direction.

6. The residual soil slope collapse calculation method based on fissure hydrostatic pressure according to claim 4 is characterized in that: When the vertical crack is located on the slope, the weight G of the collapsed body is calculated as follows:

7. The method for calculating residual soil slope collapse based on fissure hydrostatic pressure according to claim 1 is characterized in that: The hydrostatic thrust of the water column in the slope crack on the collapsed body can be calculated according to the hydrostatic pressure F w Size, that is:

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