A conversion method of various dynamic penetration test indexes considering multiple collisions

Abstract

The application discloses a conversion method among various dynamic penetration test indexes considering multiple collisions in the field of geotechnical engineering in-situ test, which firstly calculates the initial value of the acceleration of the soil to the probe rod, then calculates the falling hammer speed, the probe rod speed and the probe rod kinetic energy increment after the i-th collision, until the speed of the falling hammer is equal to the speed of the probe rod or the speed of the falling hammer is equal to 0, and the calculation is stopped; the sum of the probe rod kinetic energy increment after each collision and the sum of the kinetic energy at the final time of the falling hammer are used as the dynamic penetration effective hammering energy, the acceleration of the soil to the probe rod is corrected by using the dynamic penetration effective hammering energy, and the dynamic penetration effective hammering energy is corrected by using the iterative method; the dynamic penetration test effective hammering energy before conversion is calculated, and the dynamic penetration hammering number after conversion is calculated by using the iterative method. The application can provide a guidance for the mutual conversion among different kinds of dynamic penetration test indexes.

Description

Technical Field

[0001] This invention relates to the field of in-situ testing in geotechnical engineering, and in particular to a method for converting various dynamic penetration test indices that take into account multiple collisions. Background Technology

[0002] The cone penetration test is an in-situ geotechnical engineering test that uses a certain hammer impact energy to drive a cone probe of a certain specification into the soil. The changes in soil layers are judged based on the magnitude of the impedance during penetration, the soil layers are divided into layers, the physical and mechanical properties of the soil layers are estimated, and the density of the soil is identified. It is simple and easy to perform and is widely used in the field of in-situ investigation and testing of geotechnical engineering.

[0003] Various types of dynamic penetration testing equipment are currently used in geotechnical engineering investigation and testing fields both domestically and internationally. Different types of dynamic penetration testing equipment have their own evaluation indicators. Therefore, the test results of different types of dynamic penetration testing equipment cannot be directly compared and analyzed, which brings many inconveniences to engineering investigation, testing, design, and construction. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for converting various dynamic penetration test indicators that take into account multiple collisions, so as to overcome the shortcomings of the prior art.

[0005] To achieve the above objectives, the embodiments of the present invention adopt the following technical solutions:

[0006] This invention provides a method for converting various dynamic penetration test parameters considering multiple collisions, comprising the following steps:

[0007] Step S1, calculate the initial value of the soil acceleration 'a' on the probe using the following formula:

[0008]

[0009] m = lm' + m"

[0010] Where M is the mass of the falling hammer; h is the falling distance of the falling hammer; m is the mass of the probe rod; N is the number of hammer blows in the dynamic penetration test; l is the length of the probe rod; m' is the weight of the probe rod per meter; and m” is the total mass of the guide rod, hammer pad, and probe.

[0011] Step S2, calculate the ratio k of the gravitational acceleration g to the acceleration a of the soil on the probe:

[0012] Step S3: Use the following formulas to calculate the hammer velocity V1 and probe velocity v1 after the first collision, and the probe kinetic energy increment ΔE1 after the first collision.

[0013]

[0014]

[0015]

[0016] Where e is the collision recovery coefficient of the steel used in the dynamic penetration test;

[0017] Step S4, calculate the falling hammer velocity V before the second collision. 2,0 probe speed v 2,0 :

[0018]

[0019]

[0020] Where, Δv n-1 =V n-1 -v n-1 If n = 2, then Δv1 = V1 - v1;

[0021] Step S5, use the following formula to calculate the hammer velocity V2 and probe velocity v2 after the second collision, and the probe kinetic energy increment ΔE2 during the second collision: where n=3,

[0022]

[0023]

[0024]

[0025] Step S6: Update the value of n sequentially, and repeat steps S4 and S5 above to obtain the falling hammer velocity V after the i-th collision. i and probe speed v i And the increase in probe kinetic energy ΔE during the i-th collision. i until V i =v i or V i =0, which is recorded as the j-th collision, and the calculation ends;

[0026] Step S7, calculate the kinetic energy of the falling hammer in the final state using the following formula:

[0027]

[0028] Among them, V 终止 Calculate the velocity of the falling hammer at the end of the collision cycle;

[0029] Step S8, calculate the effective hammer energy of the dynamic penetration test using the following formula:

[0030]

[0031] Step S9: Calculate the acceleration a according to the following formula, and calculate the effective hammering energy E by iterative method;

[0032]

[0033] Step S10: Using steps S1 to S9, calculate the hammer impact energy E(M1,m1',m1”,l1,N1) before conversion and the hammer impact energy E(M2,m2',m2”,l2,N2) after conversion. When calculating the hammer impact energy E(M2,m2',m2”,l2,N2) after conversion for the first time, let N2 = N1, and calculate the number of hammer impacts N2 obtained from the first iteration according to the following formula.

[0034]

[0035] Where A1 is the cross-sectional area of ​​the dynamic cone penetration test probe before conversion, A2 is the cross-sectional area of ​​the dynamic cone penetration test probe after conversion, M1 is the weight of the falling hammer in the dynamic cone penetration test before conversion, m1' is the mass of the probe rod per meter before conversion, m1” is the total mass of the guide rod, hammer pad, and probe before conversion, l1 is the length of the probe rod before conversion, and N1 is the number of hammer blows measured before conversion; M2 is the weight of the falling hammer after conversion, m2' is the mass of the probe rod per meter after conversion, m2” is the total mass of the guide rod, hammer pad, and probe after conversion, l2 is the length of the probe rod after conversion, and N2 is the number of hammer blows after conversion.

[0036] Step S11: Substitute the converted hammer blow number N2 obtained from the first iteration into steps S1 to S9 to calculate the converted hammer blow energy E(M2,m2',m2”,l2,N2), and calculate the converted hammer blow number N2 obtained from the second iteration according to the formula in step S10.

[0037] Step S12: Substitute the converted hammer number N2 obtained from the i-th iteration into steps S1 to S9 to calculate the converted hammer energy E(M2,m2',m2”,l2,N2), and calculate the converted hammer number N2 obtained from the (i+1)-th iteration according to the formula in step S10.

[0038] Step S13: If the number of hammer blows calculated in the i-th iteration is equal to the number of hammer blows calculated in the (i+1)-th iteration, then the loop iteration calculation ends, and the number of hammer blows calculated in the last iteration is used as the final number of hammer blows obtained.

[0039] In step S1, N is the number of hammer blows when the penetration is 10cm.

[0040] The step S3 is preceded by:

[0041] Obtain the collision recovery coefficient e of the steel used in the dynamic penetration test, which was determined through field testing.

[0042] The method for calculating the effective hammering energy through iteration in step S9 includes:

[0043] Substitute the acceleration 'a' calculated in step S9 into step S2, and continue the calculation until step S9 is reached to calculate a new acceleration 'a'. Then, substitute the new acceleration 'a' into step S2, and continue the calculation until step S9 is reached to calculate an updated acceleration 'a'. Repeat this process until the difference between the accelerations 'a' calculated in two consecutive steps is less than a preset difference. Finally, use the effective hammer energy obtained from the last calculation as the final effective hammer energy calculation result.

[0044] The preset difference value is 0.001 m / s. 2 .

[0045] The embodiments of the present invention have the following beneficial effects:

[0046] This invention provides a method for converting various dynamic penetration test indices considering multiple collisions. First, the initial acceleration of the soil on the probe is calculated. Then, the drop hammer velocity, probe velocity, and probe kinetic energy increment after the i-th collision are calculated until the drop hammer velocity equals the probe velocity or the drop hammer velocity equals 0, at which point the calculation stops. The sum of the probe kinetic energy increments after each collision and the final kinetic energy of the drop hammer are taken as the effective impact energy of the dynamic penetration test. The effective impact energy is used to correct the soil acceleration on the probe, and an iterative method is used to correct the effective impact energy. The effective impact energy of the dynamic penetration test before conversion is calculated, and the number of dynamic penetration blows after conversion is calculated using an iterative method. This invention proposes a method for converting various dynamic penetration test indices, which considers the non-perfectly elastic collision between the drop hammer and the probe, multiple collisions between the drop hammer and the probe, and the resistance of the soil on the probe, and can provide guidance for the mutual conversion between different types of dynamic penetration test indices.

[0047] Of course, implementing any product or method of the present invention does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1 This is a flowchart illustrating a method for converting various dynamic penetration test parameters considering multiple collisions, as described in an embodiment of the present invention. Detailed Implementation

[0050] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. 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. It should be noted that, without conflict, the embodiments and features in the embodiments of the present invention can also be combined with each other.

[0051] It should be noted that similar reference numerals 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. In the description of the invention, the terms "first," "second," "third," "fourth," etc., are used only to distinguish descriptions and should not be construed as merely or implying relative importance.

[0052] This invention provides a method for converting various dynamic penetration test parameters considering multiple collisions. The method first calculates the initial acceleration of the soil on the probe, then calculates the hammer velocity, probe velocity, and probe kinetic energy increment after the first collision; calculates the hammer velocity and probe velocity before the second collision; calculates the hammer velocity, probe velocity, and probe kinetic energy increment after the second collision; and so on, calculating the hammer velocity, probe velocity, and probe kinetic energy increment after the third, fourth, fifth, ... collisions until the hammer velocity equals the probe velocity or the hammer velocity equals 0, at which point the calculation stops. The sum of the probe kinetic energy increments after each collision and the final kinetic energy of the hammer are taken as the effective hammer impact energy of the dynamic penetration test. The effective hammer impact energy is used to correct the soil acceleration on the probe, and an iterative method is used to correct the effective hammer impact energy. The effective hammer impact energy of the dynamic penetration test before conversion is calculated, and the number of hammer blows after conversion is calculated using an iterative method. This invention takes into account the characteristics of non-perfectly elastic collision between the drop hammer and the probe rod, multiple collisions between the drop hammer and the probe rod, and the resistance of the soil to the probe rod, and can provide guidance for the mutual conversion between different types of dynamic penetration test indicators.

[0053] like Figure 1 The diagram shown is a flowchart of a method for converting various dynamic penetration test indices considering multiple collisions, provided by an embodiment of the present invention. The method includes the following steps:

[0054] Step S1: Calculate the initial value of the acceleration 'a' of the soil on the probe.

[0055]

[0056] m=lm'+m” (2)

[0057] Where M is the mass of the falling hammer; h is the falling distance of the falling hammer; m is the mass of the probe rod (including the guide rod, hammer pad, and probe); N is the number of hammer blows in the dynamic penetration test, which is taken here as the number of blows when the penetration is 10cm; l is the length of the probe rod; m' is the weight of the probe rod per meter; and m” is the total mass of the guide rod, hammer pad, and probe.

[0058] Step S2, calculate the ratio k of the gravitational acceleration g to the acceleration a of the soil on the probe:

[0059] k = g / a (3)

[0060] Step S3: Calculate the hammer velocity V1 and probe velocity v1 after the first collision, and the probe kinetic energy increment ΔE1 after the first collision.

[0061]

[0062]

[0063]

[0064] Where e is the collision recovery coefficient of the steel used in the dynamic penetration test, which can be determined by field test before step S3.

[0065] Step S4, calculate the falling hammer velocity V before the second collision. 2,0 probe speed v 2,0 :

[0066]

[0067]

[0068] Where, Δv n-1 =V n-1 -v n-1 Here, we take n = 2, then Δv1 = V1 - v1.

[0069] Step S5: Calculate the hammer velocity V2 and probe velocity v2 after the second collision, and the probe kinetic energy increment ΔE2 during the second collision, where n = 3.

[0070]

[0071]

[0072]

[0073] Step S6: Update the value of n sequentially, and repeat steps S4 and S5 above to obtain the falling hammer velocity V after the i-th collision. i and probe speed v iAnd the increase in probe kinetic energy ΔE during the i-th collision. i until V i =v i or V i =0, end the calculation. For example, if n=3, repeat step S4; if n=4, repeat step S5 to obtain the hammer velocity V3 and probe velocity v3 after the 3rd collision, and the probe kinetic energy increment ΔE3 in the 3rd collision. Repeat steps S4 and S5 to calculate the 4th, 5th, 6th, ..., i, ... nth collisions, and use ΔE to calculate the increase in probe kinetic energy. i It means, until V i =v i or V i =0, which is recorded as the j-th collision, and the calculation ends.

[0074] Step S7, calculate the kinetic energy of the falling hammer in the final state:

[0075]

[0076] Among them, V 终止 The velocity of the falling hammer is calculated at the end of the collision cycle.

[0077] Step S8, calculate the effective hammer energy of the dynamic penetration test:

[0078]

[0079] Step S9: Calculate the acceleration a, and calculate the effective hammer energy E using an iterative method.

[0080]

[0081] Since the initial value of the soil acceleration on the probe given in step S1 is an estimated value, in order to solve it accurately, the acceleration a needs to be calculated according to the above formula (14), and then the effective hammer energy E is calculated by iterative method. The specific method is as follows: Substitute the acceleration a obtained in step 9 into step S2, and calculate sequentially to step S9 to calculate the new acceleration a. Then substitute the new acceleration a into step S2, and calculate sequentially to step S9 to calculate the updated acceleration a. Repeat this calculation until the difference between the acceleration a obtained from two adjacent calculations is less than the preset difference. The effective hammer energy obtained from the last calculation is taken as the final effective hammer energy calculation result. The preset difference is 0.001 m / s. 2 .

[0082] Step S10: Using steps S1 to S9, calculate the hammer impact energy before conversion E(M1,m1',m1”,l1,N1) and the hammer impact energy after conversion E(M2,m2',m2”,l2,N2). When calculating the hammer impact energy after conversion for the first time, let N2 = N1, and calculate the number of hammer impacts N2 obtained from the first iteration according to the following formula (15).

[0083] That is, substitute the weight of the falling hammer M1, the mass of the probe rod per meter m1', the total mass of the guide rod, hammer pad, and probe m1”, the probe rod length l1, and the measured number of hammer blows N1 from the dynamic penetration test before conversion into steps S1 to S9 to calculate the hammer energy E(M1,m1',m1”,l1,N1) when the falling hammer weight is M1, the mass of the probe rod per meter is m1', the total mass of the guide rod, hammer pad, and probe is m1”, the probe rod length is l1, and the number of hammer blows is N1.

[0084] In the converted dynamic penetration test, the weight of the falling hammer is M2, the mass per meter of probe rod is m2', the total mass of the guide rod, hammer pad, and probe is m2”, the probe length is l2, the probe cross-sectional area is A2, and the converted number of blows is N2. Here, we first take N2 = N1, and substitute it into steps S1 to S9 to calculate the hammer energy E(M2,m2',m2”,l2,N2) when the weight of the falling hammer is M2, the mass per meter of probe rod is m2', the total mass of the guide rod, hammer pad, and probe is m2”, the probe length is l2, and the number of blows is N2. Substituting into the following formula, we can obtain the converted number of blows N2 calculated in the first iteration.

[0085]

[0086] Where A1 is the cross-sectional area of ​​the dynamic penetration test probe before conversion, and A2 is the cross-sectional area of ​​the dynamic penetration test probe after conversion.

[0087] Step S11: Substitute the converted hammer number N2 obtained from the first iteration into steps S1 to S9 to calculate the hammer energy E(M2,m2',m2”,l2,N2), and calculate the converted hammer number N2 obtained from the second iteration according to the formula in step S10.

[0088] That is, by substituting the converted hammer blow count N2 obtained from the first iteration into steps S1 to S9, the hammer weight M2, the mass of each meter of probe rod m2', the total mass of the guide rod, hammer pad, and probe is m2”, the probe rod length is l2, and the hammer blow count N2 is calculated to obtain the hammer blow energy E(M2,m2',m2”,l2,N2). Substituting this into equation (15) yields the converted hammer blow count N2 obtained from the second iteration.

[0089] Step S12: Substitute the converted hammer number N2 obtained from the i-th iteration into steps S1 to S9 to calculate the hammer energy E(M2,m2',m2”,l2,N2), and calculate the converted hammer number N2 obtained from the (i+1)-th iteration according to the formula in step S10.

[0090] That is, by substituting the converted hammer blow count N obtained from the i-th iteration into steps S2 to S10, we can calculate the hammer blow count E(M2,m2',m2”,l2,N2) when the hammer weight is M2, the mass of each meter of probe rod is m2', the total mass of the guide rod, hammer pad, and probe is m2”, the probe rod length is l2, and the hammer blow count is N2. Substituting this into equation (15) yields the converted hammer blow count N2 obtained from the (i+1)-th iteration.

[0091] Step S13: If the number of hammer blows calculated in the i-th iteration is equal to the number of hammer blows calculated in the (i+1)-th iteration, then the loop iteration calculation ends, and the number of hammer blows calculated in the last iteration is used as the final number of hammer blows obtained.

[0092] That is, repeat step S12 until the number of hammer blows calculated in the i-th iteration is equal to the number of hammer blows calculated in the (i+1)-th iteration, then end the loop. The hammer blow count calculated in the last iteration is taken as the final number of hammer blows N2.

[0093] In the above calculation process, the derivation process of equations (4), (5), and (6) in step S3 is as follows:

[0094] Calculate the hammer velocity before the first impact:

[0095]

[0096] Where g is the acceleration due to gravity; h is the drop distance of the hammer.

[0097] Based on the conservation of impulse before and after the first collision, we can obtain equation (17):

[0098] MV 1,0 +mv 1,0 =MV1+mv1 (17)

[0099] Where M is the mass of the falling weight; V 1,0 V0 is the hammer velocity before the first impact; g is the acceleration due to gravity; h is the hammer drop distance; V1 is the hammer velocity after the first impact; m is the mass of the probe (including the guide rod, hammer pad, and probe); v0 1,0 v is the velocity of the probe before the first collision. 1,0 =0; v1 is the probe velocity after the first collision.

[0100] According to the definition of the collision restitution coefficient, we can obtain equation (18):

[0101]

[0102] From equations (16), (17), and (18), the velocities of the hammer and probe after the first collision can be obtained, as shown in equations (19) and (20):

[0103]

[0104]

[0105] By combining equation (21) with the kinetic energy calculation method, the kinetic energy increment ΔE1 of the probe after the first collision can be obtained.

[0106]

[0107] In step S5, the derivation process of equations (9), (10), and (11) is as follows:

[0108] As shown in equation (19), the hammer still possesses a certain amount of kinetic energy after the first collision. After the first collision, the probe's velocity decreases due to the constraint of the soil layer. Due to gravity, regardless of whether the hammer's velocity direction after the first collision is upward or downward, it will collide with the probe a second time, transferring the energy carried by the hammer back into the probe. To more accurately calculate the hammering energy transferred from the hammer to the probe, this patent considers the first collision and subsequent collisions until the hammering energy is sufficiently small to be ignored or the hammer and probe velocities remain the same and no further collisions occur.

[0109] Here we perform the collision calculation for the (n-1)th collision. It is assumed that the probe's velocity before the (n-1)th collision is v. n-1,0 The speed of the falling hammer is V n-1,0 .

[0110] According to the conservation of impulse before and after the (n-1)th collision:

[0111] MV n-1,0 +mv n-1,0 =MV n-1 +mv n-1 (twenty two)

[0112] According to the definition of the coefficient of recovery:

[0113]

[0114] From equations (22) and (23), the falling hammer velocity and probe velocity after the (n-1)th collision can be calculated using equations (24) and (25).

[0115]

[0116]

[0117] Then, during the (n-1)th collision, the increase in the probe's kinetic energy can be calculated using equation (26):

[0118]

[0119] In step S4, the derivation process of equations (7) and (8) is as follows:

[0120] To calculate the changes in hammer velocity and probe velocity between the two collisions, the following analysis is performed:

[0121] As shown in equation (25), after the (n-1)th collision, the probe gains a large downward velocity, but this velocity will continuously decrease due to the influence of soil resistance. Here, the soil resistance on the probe is assumed to be a constant value, and the acceleration generated by the resistance is a. Then, the velocity of the probe during deceleration can be expressed by equation (27):

[0122] v = v n-1 -(ag)t (27)

[0123] As can be seen from equation (24), after the (n-1)th collision, the direction of the falling hammer's velocity may be upward, downward or 0. Here, the downward velocity is taken as positive. The velocity of the falling hammer is less than the velocity of the probe rod, but due to the influence of gravity, the velocity of the falling hammer continues to increase after the collision. Its motion process can be represented by equation (28).

[0124] V = V n-1 +gt (28)

[0125] From equations (27) and (28), the time t between the two collisions can be expressed by equation (29):

[0126]

[0127] Then the velocities of the hammer and probe before the nth collision can be expressed by equations (30) and (31), respectively:

[0128]

[0129]

[0130] To make the formula more concise, let's set it here.

[0131] k = g / a (32)

[0132] Δv n-1 =V n-1 -v n-1 (33)

[0133] Equations (30) and (31) can then be expressed as equations (34) and (35):

[0134] Vn,0 =V n-1 -2kΔv n-1 (34)

[0135] v n,0 =v n-1 +2(1-k)Δv n-1 (35)

[0136] Since the soil resistance causes the probe to decelerate continuously, once the velocity decreases to 0, the probe velocity will no longer change. Therefore, when v... n,0 When <0, take v n,0 =0, that is, when the following equation (36) holds, take v. n,0 =0.

[0137]

[0138] When equation (36) holds, the probe speed is determined by v n As the velocity decreases continuously to 0, it represents a uniform deceleration process with an acceleration of -(ag). Therefore, the distance the probe descends from the nth collision to the (n+1)th collision can be expressed by equation (37):

[0139]

[0140] According to the conservation of mechanical energy of a falling weight, equation (38) exists:

[0141]

[0142] Substituting equation (37) into equation (38), we can obtain the velocity of the falling hammer before the (n+1)th collision, which is expressed by equation (39):

[0143]

[0144] From equations (34), (35), and (39), the falling hammer velocity before the nth collision can be obtained as shown in equation (40):

[0145]

[0146] The velocity of the probe before the nth collision is shown in equation (41):

[0147]

[0148] In step S11, the derivation process of equation (15) is as follows:

[0149] When a dynamic penetration test probe penetrates into the soil, the dynamic penetration resistance R of the soil to a unit cross-sectional area of ​​the probe is related to the hammering energy as follows:

[0150]

[0151] Where E(M,m',m”,l,N) is the hammer impact energy calculated when the weight of the falling hammer is M, the mass of each meter of probe rod is m', the total mass of the guide rod, hammer pad, and probe is m”, the probe rod length is l, and the number of hammer blows is N.

[0152] In the pre-conversion dynamic penetration test, the weight of the drop hammer is M1, the mass of the probe rod per meter is m1', the total mass of the guide rod, hammer pad, and probe is m1", the probe rod length is l1, the probe cross-sectional area is A1, and the measured number of hammer blows is N1. Substituting into equation (42), we can obtain:

[0153]

[0154] The converted dynamic penetration test has a hammer weight of M2, a probe mass per meter of length of m2', a total mass of guide rod, hammer pad, and probe of m2", a probe length of l2, a probe cross-sectional area of ​​A2, and a hammer blow count of N2. Substituting into equation (42), we get:

[0155]

[0156] For the same soil, the dynamic penetration resistance per unit cross-sectional area of ​​the dynamic penetration probe is the same, i.e., R1 = R2. Combining this with equations (43) and (44), we can obtain:

[0157]

[0158] Simplifying, we get:

[0159]

[0160] As can be seen from equation (15), both sides of the equation contain the unknown N2, so it is necessary to use an iterative calculation method to solve it.

[0161] In step S9, the derivation process of equation (13) is as follows:

[0162]

[0163] Where F represents the resistance of the soil to the probe during penetration, and s represents the penetration depth per blow of the dynamic penetration test in m.

[0164] As can be seen from the above technical solutions, the embodiments of the present invention provide a method for converting various dynamic penetration test indices considering multiple collisions, belonging to the field of in-situ testing in geotechnical engineering. The method includes the following steps: calculating the initial value of the acceleration of the soil on the probe; calculating the drop hammer velocity, probe velocity, and probe kinetic energy increment after the first collision; calculating the drop hammer velocity and probe velocity before the second collision; calculating the drop hammer velocity, probe velocity, and probe kinetic energy increment after the second collision; sequentially calculating the drop hammer velocity, probe velocity, and probe kinetic energy increment after the third, fourth, fifth, ... collisions until the drop hammer velocity after the collision equals the probe velocity or the drop hammer velocity equals 0, at which point the calculation stops; taking the sum of the probe kinetic energy increment after each collision and the sum of the kinetic energy at the final drop hammer as the effective hammer impact energy of the dynamic penetration test; using the effective hammer impact energy of the dynamic penetration test to correct the acceleration of the soil on the probe; using an iterative method to correct the effective hammer impact energy of the dynamic penetration test; calculating the effective hammer impact energy of the dynamic penetration test before conversion; and using an iterative method to calculate the number of hammer impacts of the dynamic penetration test after conversion. This invention proposes a method for converting various dynamic penetration test indices, which takes into account the non-perfectly elastic collision between the drop hammer and the probe, multiple collisions between the drop hammer and the probe, and the resistance of the soil to the probe. It can provide guidance for the mutual conversion between different types of dynamic penetration test indices.

[0165] The above description is merely a preferred embodiment of the present invention and an explanation of the technical principles employed, and is not intended to limit the scope of the claimed invention, but merely to illustrate preferred embodiments of the invention. Those skilled in the art should understand that the scope of the invention is not limited to the specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for converting various dynamic penetration test parameters considering multiple collisions, characterized in that, Includes the following steps: Step S1: Calculate the acceleration of the soil on the probe using the following formula. a Initial value: , , in, M The mass of the falling hammer; h This refers to the drop distance of the hammer. m For the mass of the probe rod; N For the number of hammer blows in the power penetration test; l The length of the probe rod. m 'This refers to the weight per meter of probe rod.' m '' represents the total mass of the guide rod, hammer pad, and probe; N is the number of hammer blows when the penetration is 10cm. Step S2, calculate gravitational acceleration g The acceleration of the probe relative to the soil. a ratio k : Step S3, calculate the falling hammer velocity after the first collision using the following formula. V 1 and probe speed v 1. The increase in kinetic energy Δ of the probe during the first collision E 1; , , , in, e The collision recovery coefficient of the steel used in the dynamic penetration test; Step S4: Calculate the falling hammer velocity before the second collision. V 2,0 probe speed v 2,0 : , , Where, Δ v n-1 = V n-1 - v n-1 , n =2, then Δ v 1= V 1- v 1; Step S5, calculate the falling hammer velocity after the second collision using the following formula. V 2 and probe speed v 2. The increase in kinetic energy Δ of the probe during the second collision E 2: Among them n =3, , , , Step S6, update sequentially n Value, repeat steps S4 and S5 above to obtain the first value. i Hammer speed after the second collision V i and probe speed v i and the i The increase in kinetic energy of the probe during the secondary collision Δ E i ,until V i =v i or V i =0, denoted as the first j The calculation ends after the first collision. Step S7, calculate the kinetic energy of the falling hammer in the final state using the following formula: , in, V 终止 Calculate the velocity of the falling hammer at the end of the collision cycle; Step S8, calculate the effective hammer energy of the dynamic penetration test using the following formula: , Step S9, calculate the acceleration according to the following formula a The effective hammering energy was calculated using an iterative method. E ; , The method for calculating the effective hammering energy through iteration in step S9 includes: Substitute the acceleration a calculated in step S9 into step S2, and continue the calculation to step S9 to calculate a new acceleration a. Then, substitute the new acceleration a into step S2, and continue the calculation to step S9 to calculate an updated acceleration a. Repeat this process until the difference between the accelerations a calculated in two consecutive steps is less than a preset difference. The effective hammer energy calculated in the last step is then used as the final effective hammer energy calculation result. Step S10: Calculate the hammering energy before conversion using steps S1-S9. E ( M 1, m 1', m 1'', l 1, N 1) and the converted hammering energy E ( M 2, m 2', m 2'', l 2, N 2), where the initial calculation of the converted hammer energy E ( M 2, m 2', m 2'', l 2, N 2) When, let N 2= N 1. Calculate the number of hammer blows obtained from the first iteration according to the following formula. N 2; , in, A 1 represents the cross-sectional area of ​​the dynamic penetration test probe before conversion. A 2 represents the cross-sectional area of ​​the converted dynamic penetration test probe. M 1 represents the weight of the drop hammer in the dynamic penetration test before conversion. m 1' represents the mass of the probe per meter before conversion. m 1'' represents the total mass of the guide rod, hammer pad, and probe before conversion. l 1 represents the length of the probe before conversion. N 1 represents the actual number of hammer blows before conversion; M 2 represents the weight of the falling hammer after conversion. m 2' represents the mass of the probe per meter after conversion. m 2'' represents the total mass of the guide rod, hammer pad, and probe after conversion. l 2 represents the length of the probe after conversion. N 2 represents the number of hammer blows converted; Step S11, convert the hammer strike count obtained from the first iteration. N 2. Substitute the values ​​from steps S1 to S9 to calculate the converted hammering energy. E ( M 2, m 2', m 2'', l 2, N 2), and calculate the number of hammer blows obtained from the second iteration according to the formula in step S10. N 2; Step S12, the first i The number of hammer blows obtained from the next iteration calculation N 2. Substitute the values ​​from steps S1 to S9 to calculate the converted hammering energy. E ( M 2, m 2', m 2'', l 2, N 2), and calculate the first step according to the formula in step S10. i The number of hammer blows obtained from +1 iterations N 2; Step S13, if the first i The number of hammer blows obtained from the second iteration calculation is the same as the number of hammer blows obtained from the third iteration. i If the number of hammer blows obtained from the +1 iteration calculation is equal, the loop iteration calculation ends, and the number of hammer blows obtained from the last calculation is taken as the final number of hammer blows obtained from the transformation.

2. The method for converting various dynamic penetration test indices considering multiple collisions according to claim 1, characterized in that, Before step S3, the following is also included: Obtain the collision recovery coefficient of the steel used in the dynamic penetration test, determined through field experiments. e .

3. The method for converting various dynamic penetration test indices considering multiple collisions according to claim 1, characterized in that, The preset difference value is 0.001 m / s 2 .

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