Method for determining soil pressure of ultrahigh box type counterfort retaining wall under dynamic compaction vibration

Abstract

The invention belongs to the technical field of civil engineering, and relates to a method for determining the soil pressure of an ultrahigh box type counterfort retaining wall under dynamic compaction vibration. According to the method, aiming at the problem of soil pressure calculation deviation caused by the dynamic coupling effect of dynamic compaction vibration and a soil retaining structure in a high fill project, a retaining wall is divided into an upper layer, a middle layer and a lower layer along the height, and a vibration effect and unloading benefit coupling mechanism is considered respectively; vibration angle rotation is introduced to represent the retaining wall torsion effect caused by dynamic compaction vibration, and vibration wave time-history characteristics are simulated through a pulse function; vibration attenuation parameters are fitted based on a dimension consistency principle, and soil pressure distribution of each layer is accurately calculated by combining a layered soil pressure integral formula. The method overcomes the defect that the traditional static theory cannot reflect the nonlinear distribution of the soil pressure under the dynamic load, remarkably improves the calculation precision and the engineering safety, and is suitable for the design of the retaining wall under high fill conditions such as soft soil foundations.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of civil engineering, and particularly relates to a method for determining the earth pressure of an over-high box-type counterfort retaining wall under dynamic compaction vibration. BACKGROUND

[0002] In current engineering construction, with the continuous increase of the height of filling (commonly more than 15 meters, and even reaching dozens of meters), the traditional retaining structure system gradually exposes obvious deficiencies in bearing capacity, foundation adaptability, and construction safety, etc. Under this background, the over-high box-type counterfort retaining wall is gradually applied in high filling engineering due to its composite structural advantages of "reducing the self-weight of the box structure + enhancing the overall stiffness of the counterfort". However, such a retaining wall usually needs to bear high additional stress formed by large-scale filling behind the wall, and its stress environment is more complex especially under the condition of soft soil foundation. In order to improve the bearing performance and stability of the high filling foundation, the dynamic compaction method is often used for foundation reinforcement treatment in engineering practice, which has the advantages of high construction efficiency and good economy. However, under the driving factors of construction period pressure, etc., the construction of the main structure of the retaining wall and the dynamic compaction operation often exist in time and space, forming a dynamic interactive construction organization mode. Although this construction method helps to shorten the overall construction period, it will also cause complex dynamic coupling effects, which pose a potential threat to the dynamic response and stability of the retaining wall structure.

[0003] At present, the experience formula is generally used to control the influence of dynamic compaction vibration in engineering, and the retaining wall is designed based on the classical Coulomb-Rankine earth pressure theory. However, this theoretical system is established on the basis of linear assumption, and it is difficult to accurately reflect the spatial nonlinear distribution characteristics of the earth pressure behind the over-high box-type counterfort retaining wall under high filling conditions, and it is also difficult to reasonably represent the soil-structure interaction mechanism under the action of dynamic ramming load, resulting in that the safety factor value in the design lacks scientific basis, and the calculation result deviates greatly from the actual stress state. In addition, the method of using earth pressure cells for measurement can only obtain data of discrete points, and cannot comprehensively reflect the stress distribution of the entire over-high retaining wall, and the overall layout cost is high and difficult to implement, which is difficult to be widely used in engineering. The existing static or quasi-static earth pressure theory (such as Rankine and Coulomb theory) cannot accurately describe and capture the severe and transient dynamic coupling interaction of soil and retaining wall caused by the huge impact energy of dynamic compaction, resulting in that the calculation result is seriously inconsistent with the actual situation.

[0004] Because the dynamic soil pressure cannot be accurately calculated, the designer tends to adopt a conservative scheme, resulting in oversized structure of the retaining wall, waste of materials, and rising cost; meanwhile, there is a risk of structural instability and damage of the retaining wall due to underestimation of the peak value of the dynamic soil pressure caused by dynamic compaction. Therefore, it is urgent to build a theoretical analysis model and calculation method more in line with the distribution law of the soil pressure of the super-high box-type counterfort retaining wall under the action of dynamic compaction load, and to deeply reveal the evolution mechanism of the soil pressure in the complex construction environment, so as to provide solid theoretical support and technical guidance for the design optimization, construction control and safety protection of the structure. SUMMARY

[0005] The purpose of the embodiment of the present application is to provide a method for determining the soil pressure of a super-high box-type counterfort retaining wall under dynamic compaction vibration, which solves the problem of difficulty in accurately calculating the soil pressure of the super-high box-type counterfort retaining wall under the action of dynamic compaction load, and lays a foundation for selecting a dynamic compaction scheme with the smallest impact on the safety of the retaining wall, the lowest cost and the shortest construction period.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is a method for determining the soil pressure of a super-high box-type counterfort retaining wall under dynamic compaction vibration, comprising the following steps:

[0007] S1, dividing the super-high box-type counterfort retaining wall into three layers of upper, middle and lower structures; for the upper retaining wall, introducing the vibration angle rotation effect, combining with the dynamic compaction vibration wave acceleration pulse function, and calculating the upper soil pressure;

[0008] S2, for the middle retaining wall, simultaneously considering the vibration angle rotation effect, the unloading benefit generated by the unloading plate and the action of dynamic compaction vibration wave, and determining the soil pressure of the middle retaining wall through coupling mechanism;

[0009] S3, for the lower retaining wall, using the effective value of the vibration angle rotation conversion key parameter, combining the unloading benefit and vibration effect coupling to calculate the lower soil pressure.

[0010] Further, the layer structure division in S1 meets:

[0011] The upper layer height is 1 / 4 to 1 / 3 of the total height of the retaining wall;

[0012] The middle layer height is 1 / 4 to 1 / 2 of the total height of the retaining wall;

[0013] The lower layer height is 1 / 5 to 1 / 3 of the total height of the retaining wall.

[0014] Further, the vibration angle rotation effect is represented by the vibration angle η:

[0015]

[0016] Wherein, k h and kv Horizontal and vertical vibration acceleration coefficients respectively:

[0017]

[0018] Wherein, R h is the horizontal distance from the ramming point; R v is the vertical distance from the ramming point; W is the dynamic compaction energy; E s is the compression modulus; f is the vibration frequency; k is the equivalent coefficient; ξ is the attenuation index, and g is the gravity acceleration.

[0019] Further, the determination method of the equivalent coefficient k and the attenuation index ξ is as follows:

[0020] First, the relationship between the vibration acceleration a, the dynamic compaction energy W, the compression modulus E s , the distance R from the ramming point to the measuring point, and the vibration frequency f is determined:

[0021]

[0022] Taking the logarithm of both sides, we have:

[0023]

[0024] Through the vibration acceleration a, the dynamic compaction energy W, the compression modulus E s , the distance R from the ramming point to the measuring point, and the vibration frequency f measured and recorded on site; the intermediate variables x and y are calculated:

[0025]

[0026] The (x, y) data of multiple measuring points are plotted on a scatter plot; linear regression is performed using the least squares method, and a straight line y = ξx + b is fitted, the slope of the straight line is the attenuation index ξ, and the intercept b is used to determine the equivalent coefficient k: k = e b , e is the base of natural logarithm.

[0027] Further, the specific process of calculating the upper soil pressure in combination with the dynamic compaction vibration wave acceleration pulse function in S1 is as follows:

[0028] The pulse function is used to represent the dynamic compaction vibration wave acceleration:

[0029]

[0030] Wherein, a h (z, t) and a v (z, t) are the horizontal and vertical accelerations of the dynamic compaction vibration wave respectively; k h and k vrespectively, are the horizontal and vertical vibration wave acceleration coefficients; g is the gravity acceleration; e is the base of natural logarithm; β is the attenuation coefficient; t represents the time of vibration wave propagation; z represents the distance of any soil strip in the soil body from the top of the wall; ω is the angular acceleration of vibration, ω = 2π / T, T represents the period of vibration; V s and V p respectively, are the propagation velocities of the transverse and longitudinal vibration waves in the fill; h 1s represents the effective value of the wall height of the upper retaining wall after rotation by the vibration angle;

[0031] The mass m1(z) of any soil strip in the upper soil body is:

[0032]

[0033] wherein ε represents the wall back inclination angle; γ s represents the effective value of the soil bulk density; and α is the angle between the rupture surface and the horizontal direction;

[0034] Based on the horizontal and vertical accelerations a h (z, t) and a v (z, t) of the ramming vibration wave, and the mass m1(z) of any soil strip in the upper soil body, the horizontal vibration force F 1h is obtained:

[0035]

[0036] wherein γ s represents the effective value of the soil bulk density, and α is the angle between the rupture surface and the horizontal direction; and ε represents the wall back inclination angle;

[0037] The vertical vibration force F 1v of the upper retaining wall is:

[0038]

[0039] The vibration earth pressure P1 of the upper retaining wall is

[0040]

[0041] wherein δ is the friction angle between the wall back and the fill; represents the internal friction angle; ε represents the wall back inclination angle; and E represents the traditional earth pressure not considering the vibration earth pressure:

[0042]

[0043] K a is the active earth pressure coefficient.

[0044] Further, the effective value h 1sand the effective value of soil weight γ s The specific determination method is as follows:

[0045]

[0046] Where h1 represents the height of the upper retaining wall; ε represents the wall back inclination angle; γ represents the soil weight; and η represents the vibration angle.

[0047] Furthermore, the process for determining the unloading benefit is as follows:

[0048] The middle and lower retaining walls are divided into three sections: lower, middle, and upper, and the parameters of the unloading plate's effective range are determined:

[0049]

[0050]

[0051] Among them, h BFs h represents the effective value of the back height of the intermediate retaining wall. FLs h represents the effective value of the back height of the lower retaining wall. BF Indicates the height of the middle retaining wall; h FL Indicates the height of the lower retaining wall; h 2s h is the effective range of the unloading plate of the upper middle retaining wall; 3s h is the effective range of the unloading plate of the middle section retaining wall; 4s h is the effective range of the unloading plate of the upper section of the lower retaining wall; 5s The effective range of the unloading plate of the lower retaining wall in the middle section; Indicates the angle of internal friction; h AF Indicates the total height of the upper retaining wall plus the middle retaining wall; γ s η represents the effective value of soil weight; η represents the vibration angle; θ represents the angle of the fracture surface.

[0052] Among them, the earth pressure E in the fully unloaded section of the middle retaining wall a13 for:

[0053]

[0054] Earth pressure E in the unloading section of the middle retaining wall a34 for:

[0055]

[0056] Earth pressure E in the unloaded section of the intermediate retaining wall a45 for:

[0057]

[0058] Among them, the earth pressure E in the fully unloaded section of the lower retaining walla67 is:

[0059]

[0060] E is the earth pressure of the lower retaining wall section under unloading a78 is:

[0061]

[0062] E is the earth pressure of the lower retaining wall section under unloading a89 is:

[0063]

[0064] wherein, α is the attenuation index; h 1s represents the effective value of the upper retaining wall height after rotation by the vibration angle; ε represents the wall back inclination angle; ΔE a中 is the earth pressure of the middle retaining wall under unloading; ΔE a下 is the earth pressure of the lower retaining wall under unloading; K a is the active earth pressure coefficient; h B is the distance from the middle retaining wall top point to the position of the sought earth pressure; h F is the distance from the lower retaining wall top point to the position of the sought earth pressure; γ s represents the effective value of the soil bulk density.

[0065] Further, the earth pressure of the middle retaining wall is specifically:

[0066]

[0067] The earth pressure of the lower retaining wall is specifically:

[0068]

[0069] wherein, δ is the friction angle between the wall back and the fill; represents the internal friction angle; ε represents the wall back inclination angle; E represents the traditional earth pressure without considering the vibration earth pressure; F 3v represents the vertical vibration force of the lower retaining wall; F 3h represents the horizontal vibration inertial force of the lower retaining wall; F 2v represents the vertical vibration force of the middle retaining wall; F 2h represents the horizontal vibration inertial force of the middle retaining wall; α is the angle between the fracture surface and the horizontal direction.

[0070] Further, the vertical vibration force F 2v is:

[0071]

[0072] The horizontal vibration inertia force F of the middle retaining wall 2h is:

[0073]

[0074] The vertical vibration force F of the lower retaining wall 3v is:

[0075]

[0076] The vertical vibration force F of the lower retaining wall 3h is:

[0077]

[0078] wherein h BFs represents the effective value of the height of the back of the middle retaining wall; h FLs represents the effective value of the height of the back of the lower retaining wall; γ s represents the effective value of the specific gravity of the soil; ε represents the inclination angle of the back of the wall; k h and k v are the horizontal and vertical vibration wave acceleration coefficients respectively; g is the acceleration of gravity; e is the base of the natural logarithm; α is the included angle between the fracture surface and the horizontal direction; β is the attenuation coefficient; t represents the time of vibration wave propagation in the dynamic compaction; z represents the distance of any soil strip in the soil from the top of the wall; ω is the angular acceleration of vibration, ω = 2π / T, T represents the period of vibration; V s and V p are the propagation speeds of the transverse and longitudinal vibration waves in the fill respectively.

[0079] Further, the middle and lower retaining walls are unloaded by the soil pressure ΔE a中 and ΔE a下 has the determination method:

[0080]

[0081] h AFs represents the effective value of the height of the upper wall plus the middle retaining wall.

[0082] Compared with the prior art, the beneficial effects of the present application are: the limitations of the traditional static or quasi-static theory in describing the insufficient interaction mechanism of soil-structure under dynamic load are broken through. The method innovatively considers the redistribution effect of the stress field of the soil by the upper and lower unloading plates in the box-type structure of such retaining wall and the unloading mechanism, simultaneously introduces the propagation law, attenuation characteristics and time-frequency dynamic response characteristics of the impact-type vibration wave in the heterogeneous soil in the dynamic compaction construction process, and realizes the fine simulation of the coupling process of the soil-structure under dynamic load.

[0083] By fusing the field measured data, including the vibration acceleration time history under different ramming energy levels, the physical and mechanical parameters of the foundation soil (such as density, elastic modulus, Poisson's ratio, internal friction angle, and cohesive force), and the wave propagation related dynamic parameters (such as wave speed and damping ratio), a soil pressure analysis model based on the dynamic response mechanism is constructed. The model can more realistically reflect the spatial distribution pattern and time evolution law of the soil pressure under the action of the strong ramming vibration load, and significantly improves the accuracy and reliability of the stress analysis of the retaining structure under dynamic load conditions.

[0084] The present application provides a theoretical basis and calculation tool for revealing the dynamic response mechanism between the dynamic load caused by the strong ramming operation and the super-high box-type counterfort retaining wall, effectively solving the distortion problem of the calculation results caused by ignoring the dynamic coupling effect in the traditional design method: on the one hand, avoiding the over-conservative structure design, material waste and rising engineering cost caused by overestimating the soil pressure; on the other hand, preventing the safety hazards caused by underestimating the dynamic soil pressure, such as insufficient stability of the structure against overturning and sliding.

[0085] Based on the method of the present application, the arrangement position and extension length of the unloading plate can be reasonably optimized in the engineering design stage, effectively relieving the concentrated distribution of the soil pressure behind the wall, and realizing the collaborative optimization of the structural safety and economy. At the same time, the method can provide stability evaluation basis for the complex working conditions of the strong ramming ground treatment and the alternating construction of the retaining wall structure, support the selection of the optimal strong ramming process parameters (such as ramming energy, ramming point arrangement, and ramming number), and on the premise of ensuring the ground reinforcement effect and the safety of the retaining wall structure, maximize the reduction of the adverse effects of construction on the existing structure, and realize the optimization of mechanical configuration, construction period and comprehensive cost, which has important engineering application value and popularization significance. BRIEF DESCRIPTION OF DRAWINGS

[0086] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, a brief introduction will be given below to the drawings needed to be used in the embodiments or prior art description, and obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0087] Figure 1 is the structure and calculation diagram of the super-high box-type counterfort retaining wall of the present embodiment;

[0088] Figure 2 is a diagram for considering the torsional effect of the retaining wall by rotating the vibration angle;

[0089] Figure 3 is a diagram of fitting data of the determination results and the field data of the present embodiment; wherein (a) is the upper retaining wall; (b) is the middle retaining wall; and (c) is the lower retaining wall. DETAILED DESCRIPTION

[0090] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0091] The retaining wall not only bears static load (such as the self-weight of the filled soil and external load), but also is affected by dynamic load (such as vibration and dynamic compaction vibration). The dynamic compaction vibration can cause soil compression, shear and dynamic response, and affect the stability and safety of the retaining wall. The vibration produces additional dynamic soil pressure through inertial effect, and the amplitude is positively correlated with acceleration and frequency; at the same time, the impact and periodicity of the dynamic load can cause cumulative displacement of the retaining wall-soil system, reduce the shear strength of the soil, and even induce sand liquefaction. The present embodiment provides a method for determining the earth pressure of an ultrahigh box-type counterfort retaining wall under dynamic compaction vibration; the main steps are as follows:

[0092] Step S1, the ultrahigh box-type counterfort retaining wall is divided into three layers to calculate the earth pressure, the uppermost layer is the counterfort retaining wall, the vibration angle rotation is introduced to consider the torsion effect of the retaining wall to make the earth pressure, and the upper layer retaining wall earth pressure is calculated in combination with the vibration effect.

[0093] In some specific embodiments, the present embodiment divides the ultrahigh box-type counterfort retaining wall into three layers, such as Figure 1 , the first layer is above the unloading plate (i.e. the BG section in Figure 1 ), generally from the top to 1 / 4-1 / 3 of the retaining wall, the second layer is between the unloading plate (i.e. the BG section in Figure 1 ) and the second layer unloading plate (i.e. the FK section in Figure 1 ), generally from below the first layer, accounting for 1 / 4-1 / 2 of the retaining wall, and the third layer is between the second layer unloading plate (i.e. the FK section in Figure 1 ) and the bottom plate (i.e. the FL section in Figure 1 ), generally from below the second layer, accounting for 1 / 5-1 / 3 of the retaining wall.

[0094] Step S2, the middle layer retaining wall is a box-type structure, the vibration angle rotation and the vibration earth pressure are considered, and the unloading benefit generated by the unloading plate of the box-type structure is coupled and calculated;

[0095] Step S3, the lower layer retaining wall is a box-type structure, the vibration angle rotation is also used to convert the key parameters into effective values under the vibration, and then the vibration effect and the unloading benefit are coupled and calculated to obtain the final earth pressure calculation formula.

[0096] Specifically, the method of the embodiment is performed according to the following steps:

[0097] S1, the super-high box-type counterfort retaining wall is divided into three layers of structures, and firstly, the earth pressure of the upper layer of the retaining wall is analyzed. When analyzing the earth pressure of the upper layer of the retaining wall alone, the influence factors of the lower two layers of the retaining wall are ignored, and only the upper layer of the retaining wall is analyzed. Since the upper layer is not affected by the unloading plate, the vibration effect is mainly considered in determining the earth pressure of the upper layer. At this time, the structure of the upper layer of the retaining wall is a counterfort retaining wall, and the distance between an arbitrary soil strip and the top is z, and 0≤z≤h1. Since the dynamic compaction vibration may cause the torsional response of the retaining wall structure, in order to more accurately reflect the actual stress state, the vibration angle rotation parameter is introduced in the calculation of the earth pressure in the embodiment, so as to consider the influence of the torsional effect on the earth pressure distribution, thereby improving the accuracy and engineering applicability of the calculation results.

[0098] wherein the vibration angle η (such as Figure 2 , specifically the vibration angle of the retaining wall around the vertical line along the dynamic compaction vibration method) is specifically:

[0099]

[0100] wherein, k h and k v are the horizontal and vertical vibration acceleration coefficients respectively:

[0101]

[0102] wherein, R h is the horizontal distance from the ramming point; R v is the vertical distance from the ramming point; W is the dynamic compaction ramming energy; E s is the compression modulus; R is the distance from the ramming center to the measuring point; f is the vibration main frequency; the equivalent coefficient k and the attenuation index ξ can be calculated by the dimensionless method:

[0103] For the equivalent coefficient k and the attenuation index ξ, the function relationship between a (vibration acceleration), W (dynamic compaction ramming energy), E s (compression modulus), R (distance from the ramming point to the measuring point), and f (vibration frequency) can be obtained by using the principle of dimensional consistency:

[0104]

[0105] Taking the logarithm of both sides, we have:

[0106]

[0107] In the formula, k is the equivalent coefficient, and ξ is the attenuation index. The k and ξ are fitted by using the measured data on site.

[0108] For example, the fitting process of k and ξ is as follows: first, the acceleration sensor is arranged at multiple measuring points (at least 3 measuring points at different distances R to ensure data redundancy) in the backfill area of the retaining wall. Each measuring point records a set of data: a (vibration acceleration), W (compaction energy), E s (compressive modulus), R (distance between compaction point and measuring point), f (vibration frequency). For each measuring point data, the intermediate variable The (x, y) data of multiple measuring points are plotted on a scatter plot; linear regression is performed using the least squares method to fit a straight line y = ξx + b, the slope ξ is the attenuation index, and the intercept b is used to determine the equivalent coefficient k: k = e b , e is the base of natural logarithm.

[0109] Based on the ratio of vibration acceleration a to gravitational acceleration, k is determined by formula (2) (3) h and k v :

[0110]

[0111] After introducing the vibration angle rotation, the bulk density of the soil becomes the effective bulk density, and the three-layer retaining wall height of the super-high box-type retaining wall also becomes the corresponding effective value:

[0112]

[0113] h1 represents the wall height of the upper layer; h 1s represents the effective value of the wall height of the upper layer after vibration angle rotation; represents the internal friction angle; ε represents the wall back inclination angle; h AF represents the total height of the upper wall plus the middle layer retaining wall; γ s represents the effective value of the soil bulk density (effective bulk density);

[0114] The mass of any soil strip in the upper layer of soil is obtained as

[0115]

[0116] z represents the distance of any soil strip in the soil from the wall top; γ s represents the effective value of the soil bulk density.

[0117] In some specific embodiments, a pulse function is used to represent the input of the compaction vibration wave acceleration, which can well simulate the intense vibration occurring in a short time, making the result more truly reflect the actual situation. The acceleration expressions of the compaction vibration wave in the horizontal and vertical directions are as follows:

[0118]

[0119] where, a h(z, t) and a v (z, t) are horizontal and vertical vibration wave acceleration respectively; k h and k v are horizontal and vertical vibration wave acceleration coefficients respectively; g is the gravity acceleration, taking 9.8 N / kg; β is the attenuation coefficient, used to control the rapid dissipation characteristics of dynamic compaction, usually taking 0.1-0.3; ω is the vibration angular acceleration, ω = 2π / T; V s and V p are the propagation speeds of transverse and longitudinal vibration waves in the fill respectively; T represents the period of vibration; e is the base of natural logarithm.

[0120] Based on the horizontal and vertical accelerations of the vibration wave and the mass of any soil strip in the upper soil body, the horizontal vibration force F 1h The calculation formula is:

[0121]

[0122] Wherein, t represents the time of propagation of the dynamic compaction vibration wave;

[0123] The vertical vibration force F 1v The calculation formula is

[0124]

[0125] Finally, the upper wall vibration soil pressure P1 is

[0126]

[0127] E represents the traditional soil pressure not considering the vibration soil pressure:

[0128]

[0129] Wherein, K a is the active soil pressure coefficient.

[0130] S2, determination of the soil pressure of the middle retaining wall: the middle retaining wall is provided with an unloading plate structure on the upper part, and the soil pressure distribution of the middle retaining wall is jointly affected by the unloading effect and the vibration effect. The embodiment comprehensively considers the coupling effect of the two, establishes an unloading-vibration synergistic mechanism, so as to more accurately determine the soil pressure of the middle retaining wall of the middle retaining wall under the action of the dynamic compaction load.

[0131] As Figure 1, DF segment is the middle retaining wall in the middle retaining wall, which is not affected by the unloading section, that is, the lower section of the middle retaining wall, CD segment is the middle retaining wall partially unloading section, that is, the middle section of the middle retaining wall, due to the isolation of the unloading plate from the soil pressure above the unloading plate, the unloading benefit range of the unloading plate is divided into two stages, B point is the top point of the middle retaining wall, A point is the top point of the upper wall, C point is the critical point of the complete unloading of the middle retaining wall, D point is the unloading critical point of the middle retaining wall, F point is the top point of the lower wall, I point is the critical point of the complete unloading of the lower wall, J point is the critical point of the unloading plate of the lower wall, L point is the bottom plate point of the wall, DF segment retaining wall is not affected by the unloading plate, so its soil pressure distribution rule is consistent with the conventional unloading plate retaining wall, while the CD segment retaining wall in the middle is under the influence of the unloading benefit decay area of the unloading plate, gradually affected by the soil pressure and soil overload of the upper wall. The calculation formula of the unloading plate action range (the unloading plate action range of the upper section of the middle retaining wall h 2s , the unloading plate action range of the middle section of the middle retaining wall h 3s ) is as follows:

[0132]

[0133] h BFs represents the effective value of the height of the back of the middle retaining wall; h BF represents the height of the back of the middle retaining wall; h 2s represents the height of the back of the middle retaining wall;

[0134] As Figure 1 , the calculation process of the soil pressure unloading benefit of the back of the middle retaining wall is as follows:

[0135] The complete unloading section of the middle retaining wall, that is, Figure 1 Middle 1-3 section:

[0136]

[0137] The partially unloading section of the middle retaining wall, that is, Figure 1 Middle 3-4 section:

[0138]

[0139] The unloading section of the middle retaining wall, that is, Figure 1 Middle 4-5 section:

[0140]

[0141] In the formula, h B is the distance from the top point B of the middle retaining wall to the position of the soil pressure to be calculated; wherein, S Δ1342 is the unloading soil pressure of the middle retaining wall, E a45 is the unloading soil pressure of the middle retaining wall, ΔE a中 is the unloading soil pressure of the middle retaining wall, Ea34 E is the earth pressure of the middle retaining wall section unloading stage a13 E is the earth pressure of the middle retaining wall completely unloading stage

[0142] Further, the vibration angle is:

[0143]

[0144] In the formula, k h and k v are the horizontal and vertical vibration acceleration coefficients respectively.

[0145] Similarly, the input of the dynamic compaction vibration wave acceleration is expressed by the impulse function, which can well simulate the strong vibration occurring in a short time, so that the result can more truly reflect the actual situation. The expressions of the horizontal and vertical vibration wave accelerations are:

[0146]

[0147] In the formula, a h (z,t) and a v (z,t) are the horizontal and vertical vibration wave accelerations respectively; k h and k v are the horizontal and vertical vibration wave acceleration coefficients respectively; g is the gravity acceleration, which is taken as 9.8 N / kg; β is the attenuation coefficient, which is used to control the rapid dissipation characteristics of the dynamic compaction, and is usually taken as 0.1-0.3; ω is the angular acceleration, ω=2π / T; V s and V p are the transverse and longitudinal vibration wave propagation speeds in the filling respectively; z represents the distance of any soil strip in the soil body from the wall top.

[0148] In the above example of the active earth pressure of the wall back, taking any soil strip in the soil wedge ABG, the distance from the filling top is z, and 0≤z≤h1, the mass of the soil strip is:

[0149]

[0150] The horizontal vibration inertial force is the product of the mass of the soil strip and the horizontal vibration acceleration m1(z)a h (z,t), and the horizontal vibration inertial force F 2h of the middle retaining wall is obtained by integrating:

[0151]

[0152] The vertical vibration force F 2v of the middle retaining wall is calculated by the formula:

[0153]

[0154] Further, the soil pressure calculation formula of the middle retaining wall considering the unloading benefit and vibration effect is:

[0155]

[0156] wherein δ is the internal friction angle between the wall back and the soil body; is the internal friction angle of the soil body.

[0157] S3, soil pressure analysis of lower retaining wall: the lower retaining wall has unloading plate structure on the upper part, and the analysis of its soil pressure needs to consider the coupling analysis of unloading benefit and vibration benefit. First, determine the unloading plate action range:

[0158]

[0159]

[0160] The soil pressure calculation formula of the lower wall unloading is: FLs h 4s is the effective value of the height of the lower retaining wall back; h 5s is the unloading plate action range of the upper section of the lower retaining wall; h FL h

[0161] The lower wall completely unloading section, that is, Figure 1 Middle 6-7 section:

[0162]

[0163] The lower wall partially unloading section, that is, Figure 1 Middle 7-8 section:

[0164]

[0165] The lower wall section not affected by unloading, that is, Figure 1 Middle 8-9 section:

[0166]

[0167] wherein h F is the distance from the top point F of the lower retaining wall to the position of the soil pressure to be calculated; ΔE a下 is the unloading soil pressure of the lower retaining wall; h AF h AFs represents the total height of the upper wall plus the middle retaining wall; h

[0168] Horizontal vibration inertia force F 3h :

[0169]

[0170] Vertical vibration force F 3v The calculation formula is

[0171]

[0172] Further, the soil pressure calculation formula considering the unloading benefit and vibration effect is:

[0173]

[0174] In this embodiment, the strong ramming test site in Longgang District, Shenzhen is taken as an example. The soil quality of the test site is clayey sand, and the shear strength characteristics are cohesive force 20.47 kPa and friction angle 27.7°. The vibration soil pressure test data of a group of retaining walls with strong ramming energy level of 3000 KN·m are used for solving and description, and other related calculation parameters are shown in Table 1.

[0175] Table 1 Calculation parameter table

[0176]

[0177] As Figure 3 (a)-(c), the calculation results of the present embodiment are basically consistent with the measured data in the overall trend, and the fitting degree is high. The present application accurately reflects the real stress state of the super-high box type retaining wall, and especially overcomes the defects that the existing theory cannot reasonably consider the stress redistribution effect of the double unloading plate and the soil-structure dynamic coupling effect caused by the strong ramming dynamic load, resulting in distorted design results, conservative structure or safety hazards. The present application realizes the rapid and accurate acquisition of the full-section soil pressure distribution of the retaining wall without a large amount of field soil pressure monitoring, and significantly improves the accuracy of the structure stress analysis under dynamic load. The core advantages are: on the one hand, the unloading plate design can be optimized to relieve stress concentration and achieve the coordinated balance of safety and economy; on the other hand, it provides a stability evaluation method for the alternating construction of strong ramming and retaining wall, supports the selection of the optimal strong ramming scheme with small impact on the structure, good foundation treatment effect and low comprehensive cost, effectively avoids material waste and safety hazards, shortens the construction period, and has important engineering application value and popularization significance.

[0178] Each embodiment in the specification is described in a related manner, and the same and similar parts between each embodiment can be referred to each other. Each embodiment mainly explains the difference from other embodiments. Especially, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the related parts can be referred to the part of the method embodiment.

[0179] The above merely provides the preferred embodiments of the application, and not intended to limit the protection scope of the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the application shall fall within the protection scope of the application.

Claims

1. A method for determining the earth pressure of an ultra-high box-type counterfort retaining wall under dynamic compaction vibration, characterized in that, The method comprises the following steps: S1, dividing the super-high box retaining wall into three layers of upper layer, middle layer and lower layer; introducing the vibration angle rotation effect for the upper layer retaining wall, and combining the strong compaction vibration wave acceleration pulse function to calculate the upper layer soil pressure; S2, for the middle layer retaining wall, the vibration angle rotation effect, the unloading benefit generated by the unloading plate and the strong compaction vibration wave are considered synchronously, and the middle layer retaining wall soil pressure is determined through the coupling mechanism; S3, for the lower layer retaining wall, the effective value of the vibration angle rotation conversion key parameter is used, and the unloading benefit and the vibration effect are coupled to calculate the lower layer soil pressure.

2. The method according to claim 1, wherein the method is characterized by, The layer structure division in S1 meets: The upper layer height is 1 / 4-1 / 3 of the total height of the retaining wall; The middle layer height is 1 / 4-1 / 2 of the total height of the retaining wall; The lower layer height is 1 / 5-1 / 3 of the total height of the retaining wall.

3. The method according to claim 1, wherein the method is characterized by, The vibration angle rotation effect is represented by the vibration angle η: where k h and k v are horizontal and vertical vibration acceleration coefficients, respectively: where R h is the horizontal distance from the ramming point; R v is the vertical distance from the ramming point; W is the ramming energy; E s is the compression modulus; f is the main frequency of vibration; k is the equivalent coefficient; ξ is the attenuation index, and g is the acceleration of gravity.

4. The method according to claim 3, wherein, The determination method of the equivalent coefficient k and the attenuation index ξ is as follows: First, the relationship between the vibration acceleration a, the compaction energy W, the compression modulus E s , the distance R between the compaction point and the measuring point, and the vibration frequency f is determined. Taking logarithm on both sides, we get: Through the field measurement and record of vibration acceleration a, dynamic compaction ramming energy W, compression modulus E s , ramming point distance from measuring point distance R, vibration frequency f; Calculate intermediate variables x and y: (x, y) data of multiple measurement points are plotted on a scatter plot; linear regression is performed using the least squares method, and a straight line y = ξx + b is fitted, the slope of the straight line is the decay index ξ, and the intercept b is used to determine the equivalent coefficient k: k = e b , e is the base of natural logarithm.

5. The method according to claim 3, wherein, The specific process of calculating the upper layer soil pressure in S1 by combining the strong compaction vibration wave acceleration pulse function is as follows: The pulse function is used to represent the strong compaction vibration wave acceleration: wherein a h (z, t) and a v (z, t) are the horizontal and vertical accelerations of the dynamic compaction vibration wave, respectively; k h and k v are the horizontal and vertical vibration wave acceleration coefficients, respectively; g is the acceleration of gravity; e is the base of the natural logarithm; β is the attenuation coefficient; t represents the time of propagation of the dynamic compaction vibration wave; z represents the distance of any soil strip in the soil body from the top of the wall; ω is the angular acceleration of vibration, ω = 2π / T, T representing the period of vibration; V s and V p are the transverse and longitudinal propagation velocities of the vibration wave in the fill; h 1s represents the effective value of the wall height of the upper retaining wall after angular rotation. Subsequently, the mass m1(z) of any soil strip in the upper layer soil body is determined as: wherein ε represents the wall back inclination; γ s denotes the effective value of soil bulk density; and α is the angle between the fracture surface and the horizontal direction. Based on the horizontal and vertical direction acceleration a h (z,t) and a v (z,t); and any soil strip mass m1(z) in the upper soil body to obtain the horizontal vibration force F 1h : where γ s represents the effective value of soil bulk density, and α is the angle between the fracture surface and the horizontal direction; ε represents the wall back inclination angle; The vertical vibration force F of the upper retaining wall 1v is: The upper layer retaining wall vibration soil pressure P1 is where δ is the friction angle between the wall back and the fill; where φ is the internal friction angle; ε is the wall back inclination angle; E is the conventional earth pressure that does not take into account the vibrating earth pressure; K a Active earth pressure coefficient.

6. The method according to claim 5, wherein, The effective value h of the upper retaining wall height after the vibration angular rotation 1s The effective value γ of the soil body specific weight s The specific determination method is: Wherein, h1 represents the wall height of the upper layer retaining wall; ε represents the wall back inclination angle; γ represents the soil body specific weight; η represents the vibration angle.

7. The method according to claim 1, wherein, The unloading benefit determination process is as follows: The middle layer and the lower layer retaining wall are divided into three sections of lower section, middle section and upper section, and the unloading plate action range parameters are determined: wherein h BFs represents the effective value of the height of the back of the middle layer retaining wall; h FLs represents the effective value of the height of the back of the lower layer retaining wall; h BF represents the height of the back of the middle layer retaining wall; h FL represents the height of the back of the lower layer retaining wall; h 2s represents the range of action of the unloading plate of the upper segment of the middle layer retaining wall; h 3s represents the range of action of the unloading plate of the middle segment of the middle layer retaining wall; h 4s represents the range of action of the unloading plate of the upper segment of the lower layer retaining wall; h 5s represents the range of action of the unloading plate of the middle segment of the lower layer retaining wall; represents the internal friction angle; h AF represents the total height of the upper layer retaining wall plus the middle layer retaining wall; η represents the vibration angle; θ represents the angle of the fracture surface; ε represents the angle of the back of the wall; Wherein, the middle layer retaining wall completely unloading section soil pressure E a13 Is: Earth pressure E in the partially unloading section of the middle retaining wall a34 is: Earth pressure E of middle retaining wall section not subjected to unloading a45 Is: Wherein, the soil pressure E of the completely unloading section of the lower retaining wall a67 is: Lower retaining wall portion unloading section earth pressure E a78 Is: The earth pressure E of the lower retaining wall section not subjected to unloading is: a89 is: wherein h 1s represents the effective value of the upper retaining wall height after angular vibration rotation; ΔE a中 is the unloading soil pressure of the middle retaining wall; ΔE a下 is the unloading soil pressure of the lower retaining wall; K a is the active earth pressure coefficient; h B is the distance from the vertex of the middle retaining wall to the position of the sought soil pressure; h F is the distance from the vertex of the lower retaining wall to the position of the sought soil pressure; γ s represents the effective value of the soil bulk density.

8. The method according to claim 1, wherein the method is characterized by, The middle layer retaining wall soil pressure is specifically: The lower layer retaining wall soil pressure is specifically: wherein δ is the friction angle between the wall back and the fill; denotes the internal friction angle; ε denotes the wall back inclination; E denotes the traditional earth pressure not considering the vibrating earth pressure; F 3v denotes the vertical vibrating force of the lower retaining wall; F 3h denotes the horizontal vibrating inertial force of the lower retaining wall; F 2v denotes the vertical vibrating force of the middle retaining wall; F 2h denotes the horizontal vibrating inertial force of the middle retaining wall; α is the angle between the rupture surface and the horizontal direction.

9. The method according to claim 8, wherein the method is characterized in that, The middle layer retaining wall vertical vibration force F 2v Is: The middle layer retaining wall horizontal vibration inertia force F 2h Is: The lower retaining wall vertical vibration force F 3v is: The vertical vibration force F of the lower retaining wall 3h is: where h BFs represents the effective value of the height of the middle retaining wall back; h FLs represents the effective value of the height of the lower retaining wall back; γ s represents the effective value of the specific weight of the soil; ε represents the wall back inclination angle; k h and k v are the horizontal and vertical vibration wave acceleration coefficients, respectively; g is the gravity acceleration; e is the base of the natural logarithm; α is the angle between the fracture surface and the horizontal direction; β is the attenuation coefficient; t represents the time of the dynamic compaction vibration wave propagation; z represents the distance of any soil strip in the soil from the wall top; ω is the vibration angular acceleration, ω = 2π / T, T represents the vibration period; V s and V p are the transverse and longitudinal vibration wave propagation speeds in the fill, respectively.

10. The method according to claim 7, wherein the method is characterized by, The middle and lower retaining walls are unloaded by the earth pressure ΔE a中 and ΔE a下 The determination method is that: h AFs The height of the effective value of the wall plus the middle layer retaining wall.

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