Dynamic compaction equivalent static pressure model test device and calculation method thereof

Abstract

The invention discloses a dynamic compaction equivalent static pressure model test device and a calculation method. The device comprises a model system, a loading system and an acquisition system, wherein the model system comprises a support, a base, a model box, an adjustable hanging bracket, an underlying soil layer and a treatment soil layer; the loading system is divided into a dynamic compaction hammering subsystem and an electro-hydraulic servo quasi-static subsystem, an impact load is simulated through free falling of a rammer, and a static load is applied by an electro-hydraulic servo actuator; the acquisition system integrates a displacement meter, a pore pressure meter and a force sensor and monitors settlement, pore water pressure and load data in real time. According to the calculation method, the equivalent static pressure and the soil deformation modulus are iteratively calculated based on the compaction settlement sequence and the static pressure curve, and the dynamic compaction design parameter standardization problem is solved. The device is simple in structure, high in automation degree and scientific and visual in method, and provides reliable theoretical support for engineering.

Description

Technical Field

[0001] The present invention relates to the technical field of geotechnical engineering tests, and more particularly to a dynamic compaction equivalent static pressure model test device and a calculation method thereof. Background Art

[0002] Dynamic compaction is a highly effective foundation treatment technology that compacts soil through the impact energy generated by the free fall of a heavy hammer. It is widely used to reinforce fill, sand, and soft soil foundations. The core of its design lies in determining the equivalent static pressure, that is, the equivalent conversion relationship between the effects of dynamic impact loads and static loads on the soil. However, in actual engineering, soil has significant heterogeneity (such as differences in soil layer composition, diverse soil types, and changes in moisture content), resulting in complex and variable soil responses under dynamic compaction. The theoretical derivation and experimental verification of the equivalent static pressure have the following difficulties:

[0003] 1) Unclear dynamic-static load conversion mechanism: Traditional methods estimate equivalent static pressure based on empirical formulas or simplified assumptions (e.g., homogeneous elastic body model). These methods cannot accurately reflect the nonlinear deformation, pore water pressure dissipation, and recompression characteristics of actual soils, resulting in design parameters deviating from actual working conditions.

[0004] 2) Limitations of the test methods: Existing model test devices mostly focus on a single load mode (pure dynamic impact or static loading) and lack the ability to simulate the equivalent effects of dynamic and static loads. In addition, the data acquisition system has a low level of integration and cannot synchronously obtain the real-time dynamic changes of the tamping amount, pore water pressure, and load.

[0005] 3) Insufficient standardization of the evaluation system: In the current specifications, the evaluation of dynamic compaction effects mainly relies on on-site testing (such as dynamic probing and load testing). However, the testing cycle is long and the cost is high. In addition, it is impossible to directly correlate the quantitative relationship between the impact energy and the equivalent static pressure, which restricts design optimization and construction quality control.

[0006] These issues have led to a long-term reliance on empirical parameters in dynamic compaction engineering design, resulting in significant uncertainty in the prediction of reinforcement effects and a tendency to waste resources due to insufficient foundation treatment or excessive compaction. Therefore, developing a test device that can accurately simulate the equivalent effects of dynamic and static loads, monitor multi-parameter responses in real time, and establish scientific calculation methods is an urgent need to improve the standardization and reliability of dynamic compaction technology. Summary of the Invention

[0007] The purpose of the present invention is to provide a dynamic compaction equivalent static pressure model test device and its calculation method to solve the problem of dynamic compaction design parameter standardization. The device has a simple structure, a high degree of automation, and a scientific and intuitive method, providing reliable theoretical support for engineering.

[0008] The technical solution adopted by the present invention to solve this technical problem is: a dynamic compaction equivalent static pressure model test device, including: a model system, a loading system and a collection system;

[0009] The model system includes a support, a base, a model box, columns, assembled beams, an underlying soil layer and a treated soil layer, wherein the columns and the assembled beams constitute a hanger system;

[0010] The loading system includes a dynamic compaction subsystem and a pseudo-static subsystem:

[0011] The dynamic compaction subsystem includes a steel wire rope and a rammer, one end of the steel wire rope is connected to the assembled crossbeam, and the other end is hung with the rammer;

[0012] The pseudo-static subsystem includes a load plate, a rigid plate, and an electro-hydraulic servo pseudo-static actuator. One end of the electro-hydraulic servo pseudo-static actuator is connected to the assembled crossbeam, and the other end is connected to the rigid plate. The load plate is located directly below the rigid plate and the center is aligned.

[0013] The acquisition system includes a displacement meter, a piezometer, a force sensor, a jack and an acquisition and processing system; the piezometer is buried at different depths in the treated soil layer, the force sensor is fixed to the surface of the rammer, the jack is connected to the electro-hydraulic servo pseudo-static actuator and the rigid plate, the displacement meter is fixed to the rigid plate, the piezometer, displacement meter and force sensor are connected to the acquisition and processing system to transmit the acquired data, and the acquisition and processing system has the function of data acquisition and processing.

[0014] As a further solution of the present invention, the model box is located above the base and below the assembled crossbeam, with three sides made of steel plates and one side made of transparent tempered glass for observing soil settlement; the support is equipped with a braking mechanism to support dynamic adjustment of the position of the model box.

[0015] As a further solution of the present invention, the assembled crossbeam is adjustable in vertical height along the column; the rammer is a cylinder with air holes, and the weight of the rammer is determined by using a similarity ratio according to the actual engineering situation before the test; the model of the electro-hydraulic servo pseudo-static actuator matches the impact energy level of the ramming subsystem.

[0016] As a further solution of the present invention, the load plate is a smooth steel plate, circular or square in shape, and has an area equal to or close to the projected area of the rigid plate.

[0017] As a further solution of the present invention, the force sensor has a measuring range of 0 to 50 tons, the displacement meter has a measuring range of 0 to 100 mm, and the piezometer is used to monitor excess pore water pressure to evaluate the soil reinforcement effect.

[0018] As a further solution of the present invention, the acquisition system also includes an operating table, and the acquisition and processing system is placed on the operating table.

[0019] As a further solution of the present invention, an automatic uncoupling mechanism is arranged between the steel wire rope and the suspended rammer of the dynamic tamping subsystem to achieve the free fall of the rammer.

[0020] The present invention also provides a method for calculating the equivalent static pressure of dynamic compaction based on the device, comprising the following steps:

[0021] 1) Carry out the tamping test through the dynamic tamping subsystem and record the tamping sinking amount of each blow at a certain energy level (S1, S2, S3...S n ) until the hammer is closed;

[0022] 2) Adjust the position of the rigid plate so that it is in close contact with the load plate, and apply load to the treated soil layer at a certain speed until the vertical displacement is equal to S1. Draw the S1~P curve. The pressure at this time is the pseudo-static pressure P1 corresponding to the first impact. Repeat the operation to generate S2~P2, S3~P3, ...S n ~P n curve;

[0023] 3) According to the S-P curve (pseudo-static curve), calculate the deformation modulus E0 and recompression modulus E of the soil after each impact r ;

[0024] 4) Calculate the equivalent static pressure increment Δp based on the iterative formula i :

[0025] Δp i =E0·ΔS i / [(1-μ 2 )·ω b ]

[0026] Where, ΔS i =S i+1 -S (i+1)·R , S (i+1)·R =[(1-μ 2 )·ω b ·p i ] / E r Where, ω b is the settlement coefficient of the rigid foundation, which is 0.79 for a circle and 0.88 for a square; μ is the Poisson's ratio of the soil.

[0027] As a further solution of the present invention, in step 3), the deformation modulus E0 and the recompression modulus E r , determined by the slope of the pseudo-static curve and the unloading rebound section data.

[0028] As a further solution of the present invention, in step (4), the final value of the equivalent static pressure is calculated by adding increments one by one:

[0029] p (i+1) =p i +Δp i , where i = 1, 2, ..., n-1.

[0030] The present invention has at least the following beneficial effects:

[0031] 1) Accurate equivalent conversion of dynamic and static loads: By integrating dynamic compaction impact and electro-hydraulic servo static loading systems, scientific equivalent simulation of dynamic impact and static loads is achieved, restoring the actual stress state of the foundation and solving the problem of unclear dynamic-static conversion mechanism in traditional methods.

[0032] 2) Real-time synchronous monitoring of multiple parameters: Displacement meters, piezometers, and force sensors work together to collect real-time data on tamping volume, pore water pressure, and load, significantly improving test accuracy and efficiency and reducing human error.

[0033] 3) Modular and flexible adaptable design: Adjustable hangers, assembled beams, and actuators of various specifications support flexible adjustment of height and tamping energy level to adapt to different soil layers and engineering requirements, shortening the test preparation cycle.

[0034] 4) Scientific quantitative calculation method: Iterative calculation of equivalent static pressure and soil modulus (deformation modulus E0, recompression modulus E0) based on the tamping amount sequence and static pressure curve r ), breaking through the reliance on empirical parameters and providing a reliable quantitative basis for design.

[0035] 5) Functional details optimize practicality: The rammer's air vents eliminate the air cushion effect, the wire rope automatically unhooks to ensure the accuracy of free fall, and the tempered glass observation window intuitively displays the soil response, enhancing test operability and the credibility of the results.

[0036] This device and method fill the gap in the standardized evaluation technology of equivalent static pressure of dynamic compaction, and have the advantages of high precision, high automation and low cost, providing an integrated solution for the design optimization, construction quality control and effect evaluation of foundation treatment projects.

[0037] Other advantages, objectives and features of the present invention will be reflected in part through the following description, and in part will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 This is a layout diagram of the dynamic compaction model test device described in the present invention.

[0039] Figure 2 This is a layout diagram of the dynamic compaction pseudo-static model test device of the present invention;

[0040] Figure 3This is a curve showing the relationship between the amount of compaction per blow and the load at a certain compaction energy level described in the present invention.

[0041] Among them, 1-floor, 2-support, 3-base, 4-column, 5-assembled beam, 6-model box, 7-operating table, 8-underlying soil layer, 9-treated soil layer, 10-wire rope, 11-force sensor, 12-rammer, 13-hole pressure gauge, 14-acquisition and processing system, 15-load plate, 16-rigid plate, 17-electro-hydraulic servo pseudo-static actuator, 18-jack, 19-displacement meter. DETAILED DESCRIPTION

[0042] The present invention is described in detail and completely below with reference to the accompanying drawings. Those skilled in the art will be able to implement the present invention based on this description. Before describing the present invention with reference to the accompanying drawings, it should be noted that the technical solutions and technical features provided in various parts of the present invention, including those described below, may be combined with each other unless they conflict.

[0043] In addition, the embodiments of the present invention described below are generally only part of the embodiments of the present invention, rather than all of the embodiments. Therefore, based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without making any creative efforts should fall within the scope of protection of the present invention.

[0044] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The specific implementation process is as follows:

[0045] like Figure 1-3 As shown, a preferred embodiment of the present invention provides a dynamic compaction equivalent static pressure model test device, characterized in that it includes a model system, a loading system, and a collection system; wherein,

[0046] The model system includes a support 2, a base 3, a model box 6, a column 4, an assembled beam 5, an underlying soil layer 8 and a treated soil layer 9, and the column 4 and the assembled beam 5 constitute a hanger system;

[0047] The loading system is divided into a dynamic compaction system and a pseudo-static system. The dynamic compaction system includes a steel wire rope 10 and a rammer 12. One end of the steel wire rope 10 is connected to the assembled crossbeam 5, and the other end is suspended from the rammer 12. The pseudo-static system includes a load plate 15, a rigid plate 16, and an electro-hydraulic servo pseudo-static actuator 17. One end of the electro-hydraulic servo pseudo-static actuator 17 is connected to the assembled crossbeam 5, and the other end is connected to the rigid plate 16.

[0048] The acquisition system includes a displacement meter 19, a piezometer 13, a force sensor 11, a jack 18, an acquisition and processing system 14, and an operating table 7; during the test, the piezometer 13 is buried at different depths in the treated soil layer, the force sensor 11 is fixed on the rammer 12, the jack 18 is connected to the electro-hydraulic servo pseudo-static actuator 17 and the rigid plate 16, the displacement meter 19 is fixed on the rigid plate 16, the piezometer 13, the displacement meter 19 and the force sensor 11 are connected to the acquisition and processing system 14 to transmit the acquired data; the acquisition and processing system 14 is placed on the operating table 7.

[0049] In the above technical solution, the present invention can obtain the settlement and load conditions in real time by arranging the displacement meter 19 and the force sensor 11 (or the jack 18).

[0050] In another technical solution, the support 2 has a braking function, and the position of the model box can be adjusted according to the test needs. The support and the operating table can both be set on the floor 1.

[0051] In another technical solution, the model box 6 is located above the base 3 and below the assembled crossbeam 5, with three sides made of steel plates and one side made of tempered glass, so that the settlement of the soil layer can be clearly seen.

[0052] In another technical solution, the assembled crossbeam 5 can be freely adjusted in height vertically along the column 4 according to test requirements.

[0053] In another technical solution, the rammer 12 is a cylinder with a circular air hole in the middle. Before the test, the weight of the rammer is determined by using a similarity ratio based on the actual engineering situation.

[0054] In another technical solution, the load plate 15 is a smooth steel plate, which may be circular or square, with an area equal to or close to that of the rigid plate, and is located directly below the rigid plate, with its center coinciding with the rigid plate.

[0055] In another technical solution, the steel wire rope 10 has an automatic unhooking function during the dynamic compaction test to ensure that the rammer can achieve free fall.

[0056] In another technical solution, the electro-hydraulic servo pseudo-static actuator 17 has various specifications and models, which can be determined according to the tamping energy of the dynamic tamping system.

[0057] In another technical solution, the force sensor 11 has a measuring range of 0 to 50 t.

[0058] In another technical solution, the displacement meter 19 has a measuring range of 0 to 100 mm.

[0059] In another technical solution, the piezometer 13 is buried at different depths in the treated soil layer to measure the excess pore water pressure of the soil when subjected to external dynamic loads, so as to determine the reinforcement effect.

[0060] In another technical solution, the acquisition and processing system 14 has the functions of data acquisition and processing.

[0061] Another technical solution provides a dynamic compaction equivalent static calculation method, comprising the following steps:

[0062] (1) First, use the dynamic compaction system and record the compaction amount of each blow at a certain energy level until the hammer is stopped (N = 1, 2, 3..., nS1, S2, S3... S n );

[0063] (2) Adjust the position of the rigid plate so that it is in close contact with the load plate, and apply load to the treated soil layer at a certain speed until the vertical displacement is equal to S1. Draw the S1~P curve. The pressure at this time is the pseudo-static pressure corresponding to the first impact. Similarly, draw S2~P2, S3~P3, ... S n ~P n ;

[0064] (3) According to the pseudo-static curve, the deformation modulus (E0) and recompression modulus (E r );

[0065] (4) Pseudo-static pressure calculation

[0066] p2=p1+Δp i

[0067] Δp1=E0*Δs1 / [(1-μ 2 )*ω b ]

[0068] ΔS1=S2-S 2R

[0069] S 2R =[(1-μ 2 )*ω b ]*p1 / Er

[0070] Among them, ω b is the settlement coefficient of the rigid foundation, which is 0.79 for a circle and 0.88 for a square; μ Poisson's ratio is related to the shape of the treated soil.

[0071] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A dynamic compaction equivalent static pressure model test device, characterized in that: include: Model system, loading system and acquisition system; The model system includes a support, a base, a model box, columns, assembled beams, an underlying soil layer and a treated soil layer, wherein the columns and the assembled beams constitute a hanger system; The loading system includes a dynamic compaction subsystem and a pseudo-static subsystem: The dynamic compaction subsystem includes a steel wire rope and a rammer, one end of the steel wire rope is connected to the assembled crossbeam, and the other end is hung with the rammer; The pseudo-static subsystem includes a load plate, a rigid plate, and an electro-hydraulic servo pseudo-static actuator. One end of the electro-hydraulic servo pseudo-static actuator is connected to the assembled crossbeam, and the other end is connected to the rigid plate. The load plate is located directly below the rigid plate and the center is aligned. The acquisition system includes a displacement meter, a piezometer, a force sensor, a jack and an acquisition and processing system; the piezometer is buried at different depths in the treated soil layer, the force sensor is fixed to the surface of the rammer, the jack is connected to the electro-hydraulic servo pseudo-static actuator and the rigid plate, the displacement meter is fixed to the rigid plate, and the piezometer, displacement meter and force sensor are connected to the acquisition and processing system to transmit the acquired data.

2. The dynamic compaction equivalent static pressure model test device according to claim 1, characterized in that: The model box is located above the base and below the assembled crossbeam. Three sides of the model box are steel plates, and one side is transparent tempered glass for observing soil settlement. The support is equipped with a braking mechanism to support dynamic adjustment of the position of the model box.

3. The dynamic compaction equivalent static pressure model test device according to claim 1, characterized in that: The vertical height of the assembled crossbeam along the column is adjustable; the rammer is a cylinder with air holes; the model of the electro-hydraulic servo pseudo-static actuator matches the ramming energy level of the dynamic ramming subsystem.

4. The dynamic compaction equivalent static pressure model test device according to claim 1, characterized in that: The load plate is a smooth steel plate with a circular or square shape and an area equal to or close to the projected area of the rigid plate.

5. The dynamic compaction equivalent static pressure model test device according to claim 1, characterized in that: The force sensor has a measuring range of 0 to 50 tons, the displacement meter has a measuring range of 0 to 100 millimeters, and the piezometer is used to monitor excess pore water pressure to evaluate the soil reinforcement effect.

6. The dynamic compaction equivalent static pressure model test device according to claim 1, characterized in that: The acquisition system also includes an operating table, and the acquisition processing system is placed on the operating table.

7. The dynamic compaction equivalent static pressure model test device according to claim 1, characterized in that: An automatic uncoupling mechanism is provided between the steel wire rope and the suspended rammer of the dynamic tamping subsystem.

8. A method for calculating the equivalent static pressure of dynamic compaction based on the device according to any one of claims 1 to 7, characterized in that: The following steps are involved: 1) Carry out the tamping test through the dynamic tamping subsystem and record the tamping sinking amount of each blow at a certain energy level (S1, S2, S3...S n ) until the hammer is closed; 2) Adjust the position of the rigid plate so that it is in close contact with the load plate, and apply load to the treated soil layer at a certain speed until the vertical displacement is equal to S1. Draw the S1~P curve. The pressure at this time is the pseudo-static pressure P1 corresponding to the first impact. Repeat the operation to generate S2~P2, S3~P3, ...S n ~P n curve; 3) According to the S-P curve, calculate the deformation modulus E0 and recompression modulus E of the soil after each impact r ; 4) Calculate the equivalent static pressure increment Δp based on the iterative formula i : Δp i =E0·ΔS i / [(1-μ 2 )·ω b ] Where, ΔS i =S i+1 -S (i+1)·R , S (i+1)·R =[(1-μ2)·ω b ·p i ] / E r Where, ω b is the settlement coefficient of the rigid foundation, which is 0.79 for a circle and 0.88 for a square; μ is the Poisson's ratio of the soil.

9. The dynamic compaction equivalent static pressure model test device according to claim 8, characterized in that: In step 3), the deformation modulus E0 and the recompression modulus E r , determined by the slope of the pseudo-static curve and the unloading rebound section data.

10. The dynamic compaction equivalent static pressure model test device according to claim 8, characterized in that: In step (4), the final value of the equivalent static pressure is calculated by adding increments one by one: p (i+1) =p i +Δp i , where i = 1, 2, ..., n-1.

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