Method for controlling loess dam settlement and settlement amount calculation method

Abstract

The application discloses a method for controlling loess dam subsidence, comprising: determining a first area in a loess dam body where the compressive stress is greater than a preset threshold; removing loess in the first area; filling gravel in the first area after the loess is removed, and the first area after the gravel is filled is referred to as a gravel-mixed area; and the loess dam containing the gravel-mixed area is referred to as a soil-rock composite body. The method discards the traditional method which only relies on increasing the compaction degree, adopts the core concept of equal-volume replacement, directly replaces part of the compressible loess volume by rigid gravel particles, physically reduces the total amount of soil bodies which can be compressed and deformed in the loess dam body, and effectively bears and transmits the overlying load by using the stable framework formed by the gravel, the method essentially improves the soil structure, and thus the subsidence is inhibited from the root.

Description

Technical Field

[0001] This application relates to methods for controlling the settlement of loess dams and methods for calculating settlement, which belong to the field of homogeneous dam stability control. Background Technology

[0002] Loess dams are widely used in water conservancy and transportation projects in areas where loess is widely distributed due to their availability of local materials and low cost. However, loess itself is characterized by its loose structure and well-developed pores, making it prone to significant and continuous compressive settlement under the self-weight of the dam. This settlement caused by the self-weight of the loess dam can lead to loss of dam crest elevation, changes in cross-sectional shape, and may cause safety hazards such as cracking of the anti-seepage body and delamination of the dam abutment contact zone. Therefore, loess dam self-weight settlement is one of the core issues affecting the long-term safe and stable operation of loess dams.

[0003] Currently, the main approaches to addressing the self-weight settlement problem of loess dams are to increase compaction effort (such as increasing the number of compaction passes and using heavy compaction equipment) or optimize filling techniques (such as strictly controlling the moisture content of the fill and spreading it in thin layers). While these methods have some effect, they also have limitations: on the one hand, excessive compaction may damage the natural cementation structure of loess, which in some cases may reduce the strength of the loess; on the other hand, their settlement control effect is limited, and for high dams or projects with strict settlement requirements, it is often difficult to meet the control targets on its own. Summary of the Invention

[0004] To address the problem of self-weight settlement of loess dams, a method for controlling loess dam settlement is proposed, including:

[0005] Identify the first region in the loess dam body where the compressive stress exceeds a preset threshold.

[0006] Remove the loess from the first area;

[0007] Gravel is filled into the first area after the loess is removed. The first area after the gravel is filled is called the gravel-mixed area; the loess dam containing the gravel-mixed area is called a soil-stone composite.

[0008] The first region is located below the middle of the loess dam body.

[0009] This invention also discloses a method for calculating the settlement of loess dams, including:

[0010] The soil-rock composite is divided into a loess zone and a gravel-mixed zone; both the loess zone and the gravel-mixed zone are divided into multiple layers.

[0011] Calculate the settlement of the loess region;

[0012] The gravel stress in each layer of the gravel-mixed zone is determined based on the equivalent unit weight of the gravel-mixed zone and the unit weight of the loess.

[0013] The settlement of each layer in the gravel-mixed zone is calculated based on the gravel stress and the thickness of the corresponding layer, and the sum of the settlement of each layer in the gravel-mixed zone is taken as the settlement of the gravel-mixed zone.

[0014] The settlement of the soil-rock composite is calculated based on the settlement of the loess area and the settlement of the gravel-mixed area.

[0015] The calculation of the settlement in the loess region includes:

[0016] Calculate the loess stress in each layer of the loess region;

[0017] The settlement amount of each layer is determined based on the loess stress and the corresponding layer thickness, and the sum of the settlement amounts of each layer in the loess region is taken as the settlement amount of the loess region.

[0018] The determination of gravel-soil stress in each layer of the gravel-mixed zone based on the equivalent unit weight of the gravel-mixed zone and the unit weight of loess includes:

[0019] Determine the equivalent density of the gravel-doped region;

[0020] The stress of gravel soil in each layer of the gravel-mixed zone is determined based on the equivalent unit weight of the gravel-mixed zone and the unit weight of loess.

[0021] Determining the equivalent density of the gravel-doped region includes:

[0022] Loess is determined based on the gravel content and loess unit weight.

[0023] The gravel weight is determined based on the gravel inclusion rate and gravel unit weight.

[0024] The sum of the equivalent weight of the loess and the equivalent weight of the gravel is taken as the equivalent density of the gravel-mixed area.

[0025] The determination of the gravel-soil stress in each layer of the gravel-mixed zone based on the equivalent unit weight of the gravel-mixed zone and the unit weight of loess includes:

[0026] The integral kernel of loess mass from the top of the loess dam to the corresponding depth is calculated based on the width of the dam body at each depth of the loess dam.

[0027] The gravel weight integral kernel of each layer from the top of the loess dam to the gravel-mixed zone is calculated based on the width of the dam body at each depth of the loess dam and the loess mass integral kernel.

[0028] The gravel stress in each layer of the gravel-mixed zone is determined based on the width of the dam body at each depth, the loess mass integral kernel, and the gravel weight integral kernel.

[0029] Furthermore, before removing the loess, the process also includes:

[0030] The loess dam is divided into multiple layers;

[0031] Calculate the self-weight stress of loess in each layer;

[0032] The settlement of the loess dam is calculated based on the self-weight stress of each layer of loess, and the total settlement of the loess dam is calculated based on the settlement of each layer.

[0033] Furthermore, the calculation method also includes: calculating the settlement reduction based on the total settlement of the loess dam and the settlement of the gravel-mixed area, or calculating the settlement reduction rate based on the total settlement of the loess dam and the settlement of the gravel-mixed area.

[0034] The beneficial effects that this application can produce include:

[0035] This invention abandons the traditional method of relying solely on increasing compaction, and instead adopts the core concept of equal-volume replacement. By directly replacing a portion of the compressible loess volume with rigid gravel particles, it physically reduces the total amount of compressible soil within the loess dam, and utilizes the stable framework formed by the gravel to effectively bear and transfer the overlying load. This method fundamentally improves the soil structure, thereby suppressing settlement at its source. Furthermore, since the bottom of the loess dam bears the greatest self-weight stress and is the main area of ​​settlement, this invention sets the first area at the bottom of the loess dam. This not only achieves the most significant settlement control effect with the least amount of replacement, but also reduces the amount of gravel used and the project cost. Moreover, the replacement construction is compatible with conventional filling techniques, requires no complex equipment or special processes, and is easy to implement and promote in various loess dam projects, possessing good engineering applicability.

[0036] Furthermore, in calculating settlement, the layered calculation proposed in this embodiment of the invention is based on classical soil mechanics theory. The settlement before and after gravel addition and the reduction effect can be quickly calculated through conventional survey and geotechnical test parameters, avoiding the barrier of using complex numerical simulation software. This allows engineering technicians to conduct analysis efficiently in the design stage and improve the scientific nature of the project. At the same time, the gravel addition area, thickness and gravel addition rate can be flexibly adjusted according to the specific conditions of the project. It can be applied to the design of new dams as well as the settlement treatment and reinforcement of existing dams, with wide applicability and strong universality. Attached Figure Description

[0037] Figure 1 This is a schematic flowchart of a method for controlling the subsidence of loess dams provided in an embodiment of the present invention;

[0038] Figure 2 A schematic diagram of a loess dam with gravel inclusion provided in an embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram of a method for calculating the settlement of a loess dam, provided as an embodiment of the present invention. Detailed Implementation

[0040] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments. Figure 1 As shown, this embodiment of the invention provides a method for controlling the settlement of loess dams, including:

[0041] S11. Determine the first region in the loess dam body where the compressive stress is greater than a preset threshold.

[0042] Because the lower part of the loess dam body is prone to large compressive stress, the first region in this embodiment of the invention is defined as the lower part of the loess dam body. In practical applications, the first region is set at the bottom of the loess dam.

[0043] S12. Remove the loess in the first area;

[0044] S13. Gravel is filled into the first area after the loess is removed. The first area after the gravel is filled is called the gravel-mixed area; the loess dam containing the gravel-mixed area is called a soil-stone composite.

[0045] This invention abandons the traditional method of relying solely on increasing compaction, and instead adopts the core concept of equal volume replacement. By directly replacing a portion of the compressible loess volume with rigid gravel particles, it physically reduces the total amount of compressible soil within the loess dam. The stable framework formed by the gravel effectively bears and transfers the overlying load, thereby fundamentally suppressing loess settlement. Simultaneously, since the bottom of the loess dam bears the greatest self-weight stress and is the main area of ​​settlement, this invention sets the first area at the bottom of the loess dam. This not only achieves the most significant settlement control effect with the least amount of replacement, but also reduces the amount of gravel used and the project cost. Furthermore, the replacement construction is compatible with conventional filling techniques, requires no complex equipment or special processes, and is easy to implement and promote in various loess dam projects, demonstrating good engineering applicability.

[0046] like Figure 2 As shown, the gravel-mixed loess dam has a trapezoidal structure, with the top being the dam crest. The two sides represent the upstream dam slope corresponding to the upstream water level and the downstream dam slope corresponding to the downstream water level, respectively. The seepage line marked inside the dam body is the water surface line indicating the seepage state within the dam. The dam foundation includes a soil subgrade and a cutoff channel located inside the soil subgrade to reduce seepage. The middle section of the soil subgrade is the gravel-mixed zone. A drainage system is located at the bottom of the downstream dam slope to drain seepage water from the dam body, thereby reducing seepage pressure within the dam body.

[0047] After controlling the subsidence of the loess dam, this embodiment of the invention also provides a method for calculating the subsidence of the loess dam, through which the control effect of the loess dam subsidence can be determined.

[0048] Before calculating the settlement of loess dams, let's first introduce the relevant parameters of loess dams.

[0049] The geometric parameters of the loess dam are shown in Table 1:

[0050] Table 1 Geometric parameters of loess dams

[0051]

[0052] The material parameters of loess dams are shown in Table 2:

[0053] Table 2 Material parameters of loess dams

[0054]

[0055] like Figure 3 As shown, the method for calculating the settlement of loess dams includes the following steps:

[0056] S21. The above-mentioned soil-rock composite is divided into a loess zone and a gravel-mixed zone; both the loess zone and the gravel-mixed zone are divided into multiple layers;

[0057] As described above, gravel addition to loess dams occurs from the bottom upwards. Let the overall thickness of the loess dam be L, and the thickness of the gravel-added zone be H. Then the thickness of the loess zone is L - H. In practical applications, it can generally be divided into 10-20 layers. This division can be based on the thickness of the loess and gravel-added zones, or on their volume. For example, each layer of loess and gravel-added zone could be 0.1L or 2m. The specific thickness of each layer can be determined based on the geometric parameters of the loess dam. This embodiment of the invention does not limit the specific number of layers or the specific thickness of each layer.

[0058] S22. Calculate the settlement of the loess area;

[0059] Specifically, the loess stress in each layer of the loess region is first calculated; in this embodiment of the invention, the loess region is divided into... Layers, each layer is thick The first loess region The stress of the loess layer is ,but As shown in formula (1):

[0060] (1)

[0061] In formula (1), It is a heavily loess soil. L represents the width of the dam crest, L represents the height of the loess dam, and m represents the slope ratio. For the Loess Region Depth at the midpoint of the layer.

[0062] Then, based on the loess stress of each layer and the corresponding layer thickness, the settlement of the corresponding layer is determined, and the sum of the settlement of each layer in the loess area is taken as the settlement of the loess area.

[0063] Set the Loess Region No. The settlement of the layer is ,but As shown in formula (2):

[0064] (2)

[0065] In formula (2), The first in the Loess region Loess stress For the Loess Region Thick layers This refers to the loess compression modulus.

[0066] S23. Determine the gravel stress in each layer of the gravel-mixed zone based on the equivalent unit weight of the gravel-mixed zone and the unit weight of the loess.

[0067] In the embodiments of the present invention, the gravel-doped area is divided into Layer, gravel-mixed zone, each layer thickness .

[0068] Among them, the equivalent density of the gravel-doped region is determined. ,include:

[0069] Loess is determined based on the gravel content and loess unit weight.

[0070] As mentioned above, For gravel content, If the unit weight of loess is given, then the equivalent weight of loess is as shown in formula (3):

[0071] (3)

[0072] The gravel weight is determined based on the gravel inclusion rate and gravel unit weight.

[0073] As mentioned above, If the specific weight of the gravel is given, then the equivalent weight of the gravel is as shown in formula (4):

[0074] (4)

[0075] The sum of the equivalent weight of the loess and the equivalent weight of the gravel is taken as the equivalent unit weight of the gravel-mixed area. Equivalent density of the gravel-mixed zone As shown in formula (5):

[0076] (5)

[0077] In formula (5), It is a heavily loess soil. For gravel content, It is gravel heavy.

[0078] The stress in each layer of the gravel-mixed zone is determined based on the equivalent unit weight of the gravel-mixed zone and the unit weight of loess, specifically including:

[0079] Calculate the loess mass integral kernel from the dam crest to the corresponding depth based on the dam body width at each depth of the loess dam. ;

[0080] The integral kernel of gravel weight from the top of the loess dam to the gravel-mixed zone is calculated based on the width of the dam body at each depth and the integral kernel of loess mass. ;

[0081] The gravel stress in each layer of the gravel-mixed zone is determined based on the dam width at each depth, the loess mass integral kernel, and the gravel-mixed weight integral kernel. Stress in gravelly soil As shown in formula (6):

[0082] (6)

[0083] In formula (6), The unit weight of loess is L, and the height of the loess dam is L. For the thickness of the gravel, For the thickness of the loess region, This represents the equivalent density of the gravel-mixed zone. This is the integral kernel of loess mass from the top of the loess dam to the corresponding depth. For the gravel-mixed zone Midpoint depth of each layer This is the integral kernel for the gravel weight of each layer from the top of the earth dam to the gravel-mixed zone. For depth The width of the dam at that location.

[0084] Among them, depth dam width at the location As shown in formula (7):

[0085] (7)

[0086] In formula (7), For depth The width of the dam at that location, denoted as dam crest width, m as slope ratio, and L as loess dam height.

[0087] From the dam crest to the depth Soil weight integral kernel As shown in formula (8):

[0088] (8)

[0089] In formula (8), denoted as dam crest width, m as slope ratio, and L as loess dam height.

[0090] Gravel-mixed zone Midpoint depth of each layer As shown in formula (9):

[0091] (9)

[0092] In formula (9), The loess dam is high, For the thickness of the gravel, For the thickness of the loess region, For the number of floors, For the gravel-mixed zone Layer upon layer, thick.

[0093] S24. Calculate the settlement of each layer in the gravel-mixed zone based on the gravel-soil stress and the thickness of the corresponding layer. The first layer of the gravel-mixed zone... Settlement of the layer As shown in formula (10):

[0094] (10)

[0095] In formula (10), For the first gravel-mixed zone Stress in gravelly soil For the gravel-mixed zone Thick layers It represents the equivalent compressive modulus of the gravel-doped layer.

[0096] The settlement of each layer in the gravel-mixed zone was obtained. Then, the sum of the settlement amounts of each layer in the gravel-mixed zone is taken as the settlement amount of the gravel-mixed zone.

[0097] in, The equivalent compressive modulus of the gravel-incorporated layer after the addition of gravel. The unit is megapascal;

[0098] , The loess compression modulus, This indicates the compressibility characteristics of the soil.

[0099] S25. Calculate the settlement of the soil-stone composite based on the settlement of the loess area and the settlement of the gravel-mixed area.

[0100] Let the settlement of the loess region be The settlement of the gravel-mixed zone is Settlement of soil-rock composite As shown in formula (11);

[0101] (11)

[0102] In formula (11), This refers to the settlement in the Loess Plateau region. This represents the settlement amount in the gravel-mixed zone. The number of layers in the loess region. For the Loess Region Layer settlement The number of gravel-mixed layers. For the gravel-mixed zone Settlement of the layer.

[0103] In practical applications, the thickness and gravel mixing ratio of the gravel mixing area can be flexibly adjusted according to specific engineering conditions, such as dam height, soil properties, and material source, to obtain the corresponding settlement amount.

[0104] Furthermore, to compare the settlement of the loess dam before and after settlement control, embodiments of the present invention can also calculate the settlement of the pure loess dam before excavation of the loess. Therefore, before excavation of the loess, the following steps are also included:

[0105] The loess dam is divided into multiple layers; at this point, the loess dam is a pure loess dam.

[0106] Calculate the self-weight stress of loess in each layer of the loess dam. ;

[0107] Huangtuba No. Layer top depth As shown in formula (12):

[0108] (12)

[0109] In formula (12), For the first Layer upon layer, thick.

[0110] Huangtuba No. Layer bottom depth As shown in formula (13):

[0111] (13)

[0112] In formula (13), For the first loess dam Layer upon layer, thick.

[0113] Huangtuba No. Depth of the midpoint of the layer As shown in formula (14):

[0114] (14)

[0115] In formula (14), For the first loess dam The depth of the top of the layer, For the first loess dam The depth of the bottom layer.

[0116] Huangtuba No. Layer midpoint width As shown in formula (15):

[0117] (15)

[0118] In formula (15), The width of the dam crest. L represents the slope ratio, and L represents the height of the loess dam.

[0119] The stress of the loess soil in each layer of the loess dam is due to its own weight. As shown in formula (16):

[0120] (16)

[0121] In formula (16), It is a heavily loess soil. The width of the dam crest. L represents the slope ratio, and L represents the height of the loess dam.

[0122] The settlement of the loess dam is calculated based on the self-weight stress of each layer of loess, and the total settlement of the loess dam is calculated based on the settlement of each layer.

[0123] Set up loess dam No. The settlement of the layer is ,but As shown in formula (17):

[0124] (17)

[0125] In formula (17), For the first loess dam The self-weight stress of the loess layer For the first loess dam Thick layers This refers to the loess compression modulus.

[0126] The nonlinear correction relationship between the modulus and stress is shown in equation (18):

[0127] (18)

[0128] In formula (18), For the first loess dam Compression modulus of loess layers The loess compression modulus, The stress influence coefficient is... For the first loess dam The self-weight stress of the loess layer.

[0129] in, This is the stress influence coefficient, which is usually a negative value.

[0130] After calculating the self-weight stress of the loess in each layer of the loess dam, the settlement of the loess dam is then calculated. ,but As shown in formula (19):

[0131] (19)

[0132] In formula (19), This represents the settlement of the loess dam. For the first loess dam Layer settlement The number of floors.

[0133] After calculating the settlement amount before the loess dam settlement control, the method also includes: calculating the settlement reduction amount based on the total settlement amount of the loess dam and the settlement amount of the gravel-mixed area, or calculating the settlement reduction rate based on the total settlement amount of the loess dam and the settlement amount of the gravel-mixed area, so that the effectiveness of the loess dam settlement control method can be clearly known.

[0134] Let the absolute reduction in settlement be ,but As shown in formula (20):

[0135] (20)

[0136] In formula (20), This represents the settlement of the loess dam. This represents the settlement of the soil-rock composite.

[0137] Assume the relative reduction rate of settlement is ,but As shown in formula (21):

[0138] (twenty one)

[0139] In formula (21), This represents the absolute reduction in settlement. This represents the settlement of the loess dam.

[0140] This invention abandons the traditional method of relying solely on increasing compaction, and instead adopts the core concept of equal-volume replacement. By directly replacing a portion of the compressible loess volume with rigid gravel particles, it physically reduces the total amount of compressible soil within the loess dam, and utilizes the stable framework formed by the gravel to effectively bear and transfer overlying loads. This method actively improves the interior of the loess dam, meaning it fundamentally improves the dam structure, enhances the soil's resistance to deformation, and thus suppresses settlement. Simultaneously, since the bottom of the loess dam bears the greatest self-weight stress and is the main area of ​​settlement, this invention sets the first area at the bottom of the dam. This not only achieves the most significant settlement control effect with the least amount of replacement, but also reduces the amount of gravel used and the project cost. Moreover, the replacement construction is compatible with conventional filling techniques, requires no complex equipment or special processes, and is easy to implement and promote in various loess dam projects, possessing good engineering applicability.

[0141] Furthermore, in calculating settlement, the layered calculation proposed in this embodiment of the invention is based on classical soil mechanics theory. The settlement before and after gravel addition and the reduction effect can be quickly calculated through conventional survey and geotechnical test parameters, avoiding the barrier of using complex numerical simulation software. This allows engineering technicians to conduct analysis efficiently in the design stage and improve the scientific nature of the project. At the same time, the gravel addition area, thickness and gravel addition rate can be flexibly adjusted according to the specific conditions of the project. It can be applied to the design of new dams as well as the settlement treatment and reinforcement of existing dams, with wide applicability and strong universality.

[0142] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for calculating the settlement of a loess dam after controlling its subsidence, characterized in that: The soil-rock composite is divided into a loess zone and a gravel-mixed zone; both the loess zone and the gravel-mixed zone are further divided into multiple layers. Calculate the loess stress in each layer of the loess region; determine the settlement of the corresponding layer based on the loess stress and the corresponding layer thickness, and take the sum of the settlement of each layer of the loess region as the settlement of the loess region. The equivalent weight of loess is determined based on the gravel mixing ratio and the unit weight of loess; the equivalent weight of gravel is determined based on the gravel mixing ratio and the unit weight of gravel; the sum of the equivalent weight of loess and the equivalent weight of gravel is taken as the equivalent unit weight of the gravel mixing zone; the loess mass integral kernel from the dam crest to the corresponding depth is calculated based on the dam body width at each depth of the loess dam; the gravel weight integral kernel from the dam crest to each layer of the gravel mixing zone is calculated based on the dam body width at each depth of the loess dam and the loess mass integral kernel; the gravel stress in each layer of the gravel mixing zone is determined based on the dam body width at each depth of the loess dam body, the loess mass integral kernel, and the gravel weight integral kernel. The equivalent density of the gravel-doped zone The calculation formula is as follows: ； In the formula, It is a heavily loess soil. For gravel content, The gravel is of high density; The settlement of each layer in the gravel-mixed zone is calculated based on the gravel stress and the thickness of the corresponding layer, and the sum of the settlement of each layer in the gravel-mixed zone is taken as the settlement of the gravel-mixed zone. The settlement of the soil-rock composite is calculated based on the settlement of the loess area and the settlement of the gravel-mixed area.

2. The calculation method according to claim 1, characterized in that, Before removing the loess, the process also includes: The loess dam is divided into multiple layers; Calculate the self-weight stress of loess in each layer; The settlement of the loess dam is calculated based on the self-weight stress of each layer of loess, and the total settlement of the loess dam is calculated based on the settlement of each layer.

3. The calculation method according to claim 2, characterized in that, The calculation method further includes: calculating the settlement reduction based on the total settlement of the loess dam and the settlement of the gravel-mixed area, or calculating the settlement reduction rate based on the total settlement of the loess dam and the settlement of the gravel-mixed area.

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