Reservoir bank water level variation area bridge pile foundation bearing characteristic test method

Abstract

The invention relates to the technical field of bridge construction, in particular to a method for testing the bearing characteristic of a bridge pile foundation in a reservoir bank water level variation area. According to the method for testing the bearing characteristics of the bridge pile foundation in the reservoir bank water level variation area, an indoor model is established according to the similar principle, and the landform characteristics and geological conditions of the area to be constructed are accurately simulated; by simulating the water storage and precipitation process in the whole process and synchronously monitoring key parameters such as a foundation infiltration line, pile-soil system displacement, pile body axial force and turning friction resistance, systematic research on the pile foundation bearing characteristic under the water level change is achieved. Through a similar model and multi-parameter monitoring, it is ensured that a test result can reflect the interaction rule of the pile foundation and the foundation in actual engineering, and a reliable test basis is provided for bridge pile foundation design and safety evaluation of areas to be constructed and other similar landform areas.

Description

Technical Field

[0001] This invention relates to the field of bridge construction technology, and in particular to a test method for the bearing capacity characteristics of bridge pile foundations in reservoir bank water level fluctuation zones. Background Technology

[0002] Reservoir banks refer to the land along the edges of water bodies such as reservoirs, lakes, and rivers. In cross-river bridge projects, bridge foundations often face unique challenges posed by the reservoir bank environment. Due to the long-term scouring action of rivers, reservoir bank topography is often steep, requiring bridge foundations to penetrate deep overburden layers, necessitating direct construction of pile foundations on the water-facing slope. Simultaneously, the periodic rise and fall of reservoir water levels continuously impact the soil and rock mass of the water-bearing foundation, causing a series of complex physical, chemical, and mechanical changes. These changes directly lead to significant alterations in the water content, internal structure, and mechanical properties of the soil and rock, resulting in phenomena such as foundation settlement or expansion. These changes in foundation properties have a significant adverse impact on the bearing capacity of reservoir bank pile foundations, becoming one of the key factors affecting the structural safety and stability of cross-river bridges. Summary of the Invention

[0003] The main objective of this invention is to provide a test method for the bearing capacity characteristics of bridge pile foundations in reservoir bank water level fluctuation zones, so as to study the impact of water level changes on the bearing capacity characteristics of bridge pile foundations in reservoir areas and improve the safety of bridges spanning water areas.

[0004] To achieve the above objectives, the present invention provides a test method for the bearing capacity characteristics of bridge pile foundations in reservoir bank water level fluctuation zones, comprising the following steps: S1, Based on the geomorphological features and geological conditions of the area to be constructed, an indoor model is established in the test tank using the principle of similarity; S2, Arrange model piles and monitoring equipment in the indoor model, where the model piles correspond to the bridge pile foundation parameters in the area to be constructed, and are established through the principle of similarity; S3 simulates the water level change process in an indoor model, which includes the water storage stage and the precipitation stage. S4. During the two water level changes in step S3, monitor the foundation saturation line, pile-soil system displacement, pile axial force, pile side friction, pile end pressure, and the load sharing ratio between the pile end and pile side. S5. Based on the monitoring data from step S4, analyze the variation law of pile foundation bearing characteristics during different water level changes.

[0005] Furthermore, in step S1, the geometric similarity ratio of the indoor model is 1:33.

[0006] Furthermore, the geomorphological features and geological conditions of the area to be constructed include: the slope of the reservoir bank, the thickness of the overburden layer, the distribution of soil and rock masses, and the morphology of the water-facing slope.

[0007] Furthermore, in step S2, the model pile uses grade II steel bars as the main reinforcement, and the diameter of the main reinforcement is 4mm; pile core specimens are reserved simultaneously when the model pile is made, and the pile core specimens are subjected to uniaxial compressive strength test after natural curing.

[0008] Furthermore, in step S1, the foundation material of the indoor model is a mixture of sand and mudstone with a ratio of 8:2; the foundation is constructed by layered backfilling and compaction.

[0009] Furthermore, step S3 includes: A vertical dead load of 0.2 kN is applied to the top of the model pile; Simulated water storage phase: Water is injected into the test tank, and the water level rises from 0cm to 60cm over a period of 600 minutes. Simulated precipitation phase: The water level in the test tank dropped from 100cm to 0cm over a period of 100 minutes.

[0010] Furthermore, in step S4, the pile-soil system displacement includes pile top settlement and pile surrounding soil settlement; the pile side friction includes positive and negative friction at different pile depths; and the load sharing ratio is the load sharing ratio between pile end pressure and pile side friction.

[0011] Furthermore, in step S2, the monitoring equipment includes: a dial gauge for measuring the displacement of the pile top and the surrounding soil, a vibrating wire pressure gauge for measuring the pile end pressure, a water level observation tube for determining the phreatic line of the foundation, and a resistance strain gauge and strain tester for collecting the stress and strain of the pile body.

[0012] Furthermore, strain gauges are symmetrically arranged at different depth positions on both sides of the model pile.

[0013] Furthermore, in step S5, the variation law of bearing characteristics at different water level stages includes: the cumulative increase law of negative skin friction on the pile side during the water storage stage, the change law of pile end pressure and soil pressure first decreasing and then increasing; the transformation law of negative skin friction on the upper part of the pile body to positive skin friction during the dewatering stage, the gradual increase of pile end resistance, and the trend of the vertical load sharing ratio of the pile foundation first increasing and then decreasing.

[0014] The beneficial effects of this invention are: This invention provides a test method for the bearing capacity characteristics of bridge pile foundations in reservoir bank water level fluctuation zones, comprising the following steps: S1, Based on the geomorphological features and geological conditions of the area to be constructed, an indoor model is established in the test tank using the principle of similarity; S2, Arrange model piles and monitoring equipment in the indoor model, where the model piles correspond to the bridge pile foundation parameters in the area to be constructed, and are established through the principle of similarity; S3 simulates the water level change process in an indoor model, which includes the water storage stage and the precipitation stage. S4. During the two water level changes in step S3, monitor the foundation saturation line, pile-soil system displacement, pile axial force, pile side friction, pile end pressure, and the load sharing ratio between the pile end and pile side. S5. Based on the monitoring data from step S4, analyze the variation law of pile foundation bearing characteristics during different water level changes.

[0015] An indoor model was established using the principle of similarity to accurately simulate the geomorphological features and geological conditions of the area to be constructed. By simulating the entire process of water storage and precipitation, key parameters such as the foundation saturation line, pile-soil system displacement, pile axial force, and rotational skin friction were monitored simultaneously, enabling a systematic study of the bearing characteristics of pile foundations under fluctuating water levels. Through the similarity model and multi-parameter monitoring, the experimental results ensure that they reflect the interaction between pile foundations and the ground in actual engineering projects, providing reliable experimental basis for bridge pile foundation design and safety assessment in similar geomorphological areas, including the area to be constructed. Attached Figure Description

[0016] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 A flowchart of a test method for the bearing capacity characteristics of bridge pile foundations in reservoir bank water level fluctuation zones, provided as an embodiment of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0019] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0020] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0021] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. In addition, the terms "first," "second," "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0022] Furthermore, terms such as "horizontal," "vertical," and "sag" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal relative to "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0023] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0024] The following detailed description of some embodiments of the present invention is provided in conjunction with the accompanying drawings. Unless otherwise specified, the following embodiments and features can be combined with each other.

[0025] like Figure 1 As shown, this embodiment of the invention provides a test method for the bearing capacity characteristics of bridge pile foundations in reservoir bank water level fluctuation zones. The test method for the bearing capacity characteristics of bridge pile foundations in reservoir bank water level fluctuation zones includes the following steps: S1, Based on the geomorphological features and geological conditions of the area to be constructed, an indoor model is established in the test tank using the principle of similarity; S2, Arrange model piles and monitoring equipment in the indoor model, where the model piles correspond to the bridge pile foundation parameters in the area to be constructed, and are established through the principle of similarity; S3 simulates the water level change process in an indoor model, which includes the water storage stage and the precipitation stage. S4. During the two water level changes in step S3, monitor the foundation saturation line, pile-soil system displacement, pile axial force, pile side friction, pile end pressure, and the load sharing ratio between the pile end and pile side. S5. Based on the monitoring data from step S4, analyze the variation law of pile foundation bearing characteristics during different water level changes.

[0026] In this embodiment, firstly, the geomorphological features and geological conditions of the area to be constructed need to be obtained to facilitate the subsequent establishment of an indoor model and simulation experiments. These geomorphological features and geological conditions include: reservoir bank slope, overburden thickness, soil and rock distribution, and water-side slope morphology. Then, based on these features and conditions, an indoor model of the area is established within a test trench using the principle of similarity. Specifically, the model is created by scaling the model proportionally. Preferably, the geometric similarity ratio of the indoor model is 1:33. The test trench includes a bottom plate and water-retaining plates around the bottom plate. One side of the water-retaining plate facing away from the inside of the test trench can be used to install a water tank to facilitate subsequent simulation of water level changes. After the indoor model is established, model piles and matching monitoring equipment are placed within it. The model piles correspond to the design parameters of the bridge pile foundations in the area to be constructed, and are also established using the principle of similarity, with the geometric similarity ratio being the same as that of the indoor model. Once the model piles are established, the water level change process can be simulated in the indoor model. This process includes two parts: the water storage stage and the dewatering stage. During the simulation, the ground saturation line, pile-soil system displacement, pile axial force, pile side friction, pile end pressure, and the load sharing ratio between the pile end and pile side are monitored at different water level changes to analyze the variation patterns of the pile foundation bearing characteristics under different water level conditions.

[0027] The test method for the bearing capacity of bridge pile foundations in reservoir bank water level fluctuation zones provided in this embodiment establishes an indoor model based on the principle of similarity, accurately simulating the geomorphological features and geological conditions of the area to be constructed. By simulating the entire process of water storage and precipitation, key parameters such as the soil saturation line, pile-soil system displacement, pile axial force, and rotational skin friction are monitored simultaneously, enabling a systematic study of the bearing capacity of pile foundations under water level fluctuations. Through the similarity model and multi-parameter monitoring, the test results ensure that they reflect the interaction between the pile foundation and the soil in actual engineering, providing a reliable test basis for the design and safety assessment of bridge pile foundations in similar geomorphological areas, including the area to be constructed.

[0028] Optionally, in this embodiment, in step S2, the model pile uses grade II steel bars as the main reinforcement, and the diameter of the main reinforcement is 4mm; when making the model pile, the pile core specimen is reserved simultaneously, and the pile core specimen is subjected to uniaxial compressive strength test after natural curing.

[0029] In this embodiment, by reserving pile core specimens, the mechanical properties of the model pile are ensured to be consistent with the material properties of the actual pile foundation, thus avoiding test errors caused by material differences.

[0030] Optionally, in this embodiment, in step S1, the foundation material of the indoor model is a sand-mudstone mixture with a ratio of 8:2; the foundation is constructed by layered backfilling and compaction, so that the soil and rock type and structural form of the model foundation are consistent with the actual project, ensuring the authenticity of the foundation response under water level changes.

[0031] Optionally, in this embodiment, step S3 includes: A vertical dead load of 0.2 kN is applied to the top of the model pile; Simulated water storage phase: Water is injected into the test tank, and the water level rises from 0cm to 60cm over a period of 600 minutes. Simulated precipitation phase: The water level in the test tank dropped from 100cm to 0cm over a period of 100 minutes.

[0032] In this embodiment, a vertical constant load of 0.2 kN is applied to the top of the model pile using a hydraulic jack.

[0033] In this embodiment, the actual reservoir water storage and flood discharge process is reproduced by accurately simulating the water level rise and fall rate and load conditions, ensuring the similarity between the test scenario and the actual engineering.

[0034] Optionally, in this embodiment, in step S4, the pile-soil system displacement includes pile top settlement and pile surrounding soil settlement; the pile side friction includes positive and negative skin friction at different pile depths; and the load sharing ratio is the load sharing ratio between pile end pressure and pile side friction.

[0035] Optionally, in this embodiment, in step S2, the monitoring equipment includes: a dial gauge for measuring the displacement of the pile top and the soil around the pile, a vibrating wire pressure gauge for measuring the pile end pressure, a water level observation tube for determining the phreatic line of the foundation, and a resistance strain gauge and strain tester for collecting the stress and strain of the pile body.

[0036] In this embodiment, dial gauges for measuring the displacement of the pile top and the surrounding soil are arranged at the upper end and edge of the test trench. When arranging the vibrating wire pressure gauge, the axis of the vibrating wire pressure gauge must be aligned with the axis of the test pile and placed at the bottom of the pile. Strain gauges are symmetrically arranged at different depth positions on both sides of the model pile.

[0037] Optionally, in this embodiment, in step S5, the variation law of bearing characteristics at different water level stages includes: the cumulative increase law of negative skin friction on the pile side during the water storage stage, the change law of pile end pressure and soil pressure decreasing first and then increasing; the transformation law of negative skin friction on the upper part of the pile body to positive skin friction during the dewatering stage, the gradual increase of pile end resistance, and the trend of the vertical load sharing ratio of the pile foundation increasing first and then decreasing.

[0038] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A test method for the bearing capacity characteristics of bridge pile foundations in reservoir bank water level fluctuation zones, characterized in that, Including the following steps: S1, Based on the geomorphological features and geological conditions of the area to be constructed, an indoor model is established in the test tank using the principle of similarity; S2, Arrange model piles and monitoring equipment in the indoor model, where the model piles correspond to the bridge pile foundation parameters in the area to be constructed, and are established through the principle of similarity; S3 simulates the water level change process in an indoor model, which includes the water storage stage and the precipitation stage. S4. During the two water level changes in step S3, monitor the foundation saturation line, pile-soil system displacement, pile axial force, pile side friction, pile end pressure, and the load sharing ratio between the pile end and pile side. S5. Based on the monitoring data from step S4, analyze the variation law of pile foundation bearing characteristics during different water level changes.

2. The test method for the bearing capacity characteristics of bridge pile foundations in reservoir bank water level fluctuation zones according to claim 1, characterized in that, In step S1, the geometric similarity ratio of the indoor model is 1:

33.

3. A test method for the bearing capacity characteristics of bridge pile foundations in reservoir bank water level fluctuation zones according to claim 1 or 2, characterized in that, The geomorphological features and geological conditions of the area to be constructed include: the slope of the reservoir bank, the thickness of the overburden layer, the distribution of soil and rock masses, and the shape of the water-facing slope.

4. The test method for the bearing capacity characteristics of bridge pile foundations in reservoir bank water level fluctuation zones according to claim 1, characterized in that, In step S2, the model pile uses grade II steel bars as the main reinforcement, and the diameter of the main reinforcement is 4mm. When making the model pile, the pile core specimen is reserved at the same time, and the pile core specimen is subjected to uniaxial compressive strength test after natural curing.

5. The test method for the bearing capacity characteristics of bridge pile foundations in reservoir bank water level fluctuation zones according to claim 1, characterized in that, In step S1, the foundation material of the indoor model is a mixture of sand and mudstone with a ratio of 8:2; the foundation is constructed by backfilling in layers and compacting each layer.

6. The test method for bearing capacity characteristics of bridge pile foundations in reservoir bank water level fluctuation zones according to claim 1, characterized in that, Step S3 includes: A vertical dead load of 0.2 kN is applied to the top of the model pile; Simulated water storage phase: Water is injected into the test tank, and the water level rises from 0cm to 60cm over a period of 600 minutes. Simulated precipitation phase: The water level in the test tank dropped from 100cm to 0cm over a period of 100 minutes.

7. The test method for the bearing capacity characteristics of bridge pile foundations in reservoir bank water level fluctuation zones according to claim 1, characterized in that, In step S4, the pile-soil system displacement includes pile top settlement and pile surrounding soil settlement; the pile side friction includes positive and negative friction at different pile depths; the load sharing ratio is the load sharing ratio of pile end pressure and pile side friction.

8. The test method for bearing capacity characteristics of bridge pile foundations in reservoir bank water level fluctuation zones according to claim 1, characterized in that, In step S2, the monitoring equipment includes: a dial gauge for measuring the displacement of the pile top and the surrounding soil, a vibrating wire pressure gauge for measuring the pile end pressure, a water level observation tube for determining the phreatic line of the foundation, and a resistance strain gauge and strain tester for collecting the stress and strain of the pile body.

9. The test method for the bearing capacity characteristics of bridge pile foundations in reservoir bank water level fluctuation zones according to claim 8, characterized in that, Strain gauges are symmetrically arranged at different depths on both sides of the model pile.

10. The test method for the bearing capacity characteristics of bridge pile foundations in reservoir bank water level fluctuation zones according to claim 1, characterized in that, In step S5, the variation law of bearing characteristics at different water level stages includes: the cumulative increase of negative skin friction on the pile side during the water storage stage, and the change law of pile end pressure and soil pressure first decreasing and then increasing; the transformation law of negative skin friction on the upper part of the pile body to positive skin friction during the dewatering stage, the gradual increase of pile end resistance, and the trend of the vertical load sharing ratio of the pile foundation first increasing and then decreasing.

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