Method for evaluating reinforcement effect of gravel pile composite foundation based on dynamic sounding

Abstract

The invention discloses a gravel pile composite foundation reinforcement effect evaluation method based on dynamic sounding. The method comprises the steps that a target area is selected; the dynamic penetration hammering number N, the dynamic penetration resistance F and the composite foundation bearing capacity data are obtained; the unconfined compressive strength Cu of soil between piles and the friction angle delta p in the piles are obtained; on the basis of the unconfined compressive strength Cu of the soil between the piles and the friction angle delta p in the pile body, the theoretical ultimate bearing capacity fef of the gravel pile is obtained; and based on the ultimate bearing capacity fef of the gravel pile theory, the bearing capacity fsp, d of the composite foundation is obtained. The method can establish an empirical relationship between the dynamic penetration hammering number or the dynamic penetration resistance and the bearing capacity of the composite foundation on a semi-infinite foundation, is used for evaluating the bearing capacity of the composite foundation, solves the problem of insufficient number of existing load plate tests, can be used for reinforcing effect evaluation and bearing capacity estimation of the gravel pile composite foundation, and also can be used for evaluating the bearing capacity of the composite foundation. And the method can also be widely applied to reinforcing effect evaluation and bearing capacity estimation of discrete material pile composite foundations such as sand piles.

Description

Technical Field

[0001] This application belongs to the field of composite foundation reinforcement technology, specifically involving a method for evaluating the reinforcement effect of crushed stone pile composite foundation based on dynamic penetration testing. It is also applicable to the evaluation of the reinforcement effect and bearing capacity estimation of composite foundations made of loose materials such as sand piles. Background Technology

[0002] As the most important indicator of the reinforcement effect of crushed stone pile composite foundation, the bearing capacity of the composite foundation is usually verified by load plate test. However, load plate test has a long cycle and high cost, and usually only a small number of verification tests can be carried out. However, for large-area foundation reinforcement, different blocks may have different geological conditions or construction quality, which may lead to a certain degree of dispersion in the quality of crushed stone piles. Relying solely on load plate test for limited detection and verification sometimes has the problem of insufficient representativeness.

[0003] Dynamic penetration testing (DPPT), a common in-situ method for testing the strength of foundation soil, is frequently used for the reinforcement of various soil types, such as sand, gravel, and pebbles. Researchers have established empirical relationships between dynamic penetration testing and the bearing capacity of different soil types in different regions based on a large amount of statistical data. However, these relationships are all for semi-infinite foundations. In the case of gravel piles, the number of blows in dynamic penetration testing not only characterizes the density and strength of the pile material itself, but also reflects the restraining effect of the surrounding soil. In particular, for gravel piles with a specific material, particle size, and construction process, the number of blows and dynamic penetration resistance of dynamic penetration testing reflect the strength characteristics of the surrounding soil more.

[0004] Therefore, developing a method for evaluating the reinforcement effect and bearing capacity of composite foundations will compensate for the insufficient number of load plate tests. Summary of the Invention

[0005] In view of the shortcomings or deficiencies of the prior art, the technical problem to be solved by this application is a method for evaluating the reinforcement effect of crushed stone pile composite foundation based on dynamic penetration testing.

[0006] To solve the above-mentioned technical problems, this application provides the following technical solution: This application proposes a method for evaluating the reinforcement effect of crushed stone pile composite foundations based on dynamic penetration testing, including: Select the target area; Obtain data on dynamic penetration test blow count N, dynamic penetration resistance F, and composite foundation bearing capacity; Obtain the unconfined compressive strength C of the soil between piles u and the internal friction angle of the pile ; Based on the above-mentioned unconfined compressive strength C of the soil between piles u and the internal friction angle of the pile To obtain the ultimate bearing capacity of the crushed stone pile theory f ef ; Ultimate bearing capacity based on the aforementioned crushed stone pile theory f ef To obtain the bearing capacity of composite foundation f sp,d .

[0007] Further, optionally, the ultimate bearing capacity of the crushed stone pile theory f ef The formula for calculating is:

[0008] in, , The internal friction angle of the crushed stone pile material is generally taken as 38 degrees. 64 degrees is acceptable; according to It can be obtained It is 61 degrees.

[0009] Further optionally, the bearing capacity of the composite foundation f sp,d The calculation formula is: ; in, m Area replacement rate When equilateral triangles d e =1.05s, square time d e =1.13s.

[0010] Further, optionally, the strength of the soil between piles is determined based on the bearing capacity obtained from the load plate test. C u Inversion and correction are performed to obtain the equivalent soil strength between piles. C u’ .

[0011] Optionally, based on the number of dynamic penetration tests N, a correlation between the number of dynamic penetration tests N and the equivalent inter-pile soil strength is established through data fitting. C u’ Empirical relation N- C u’ .

[0012] Alternatively, based on the dynamic penetration resistance F, a relationship between the dynamic penetration resistance F and the equivalent inter-pile soil strength can be established through data fitting. C u’ Empirical relation F- C u’ .

[0013] Alternatively, a load plate test may be performed on the target area.

[0014] Alternatively, for other target areas where load plate testing has not been conducted, the number of dynamic penetration tests N is obtained through dynamic penetration testing, and the empirical formula N- is used to determine the number of impact blows. C u’ Obtain equivalent soil strength between piles C u’ .

[0015] Alternatively, for other target areas where load plate tests have not been conducted, the dynamic penetration resistance F is obtained through dynamic penetration testing, and the empirical relationship F- is used. C u’ Obtain equivalent soil strength between piles C u’ .

[0016] Further, alternatively, based on the equivalent soil strength between piles C u’ Internal friction angle of the pile To obtain the ultimate bearing capacity of the crushed stone pile theory f ef Based on the ultimate bearing capacity of the crushed stone pile theory, f ef To obtain the bearing capacity of composite foundation f sp,d .

[0017] Compared with the prior art, this application has the following technical effects: This application can establish an empirical relationship between the number of dynamic penetration tests or dynamic penetration resistance and the bearing capacity of composite foundations, similar to that on semi-infinite solid foundations, to evaluate the bearing capacity of composite foundations. This makes up for the problem of insufficient number of existing load plate tests. It can be used not only for evaluating the reinforcement effect and estimating the bearing capacity of crushed stone pile composite foundations, but also for evaluating the reinforcement effect and estimating the bearing capacity of sand pile and other granular material pile composite foundations. Detailed Implementation

[0018] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0019] In one embodiment of this application, a method for evaluating the reinforcement effect of a composite foundation with crushed stone piles based on dynamic penetration testing includes: Select the target area; Obtain data on dynamic penetration test blow count N, dynamic penetration resistance F, and composite foundation bearing capacity; Obtain the unconfined compressive strength C of the soil between piles u and the internal friction angle of the pile ; Based on the above-mentioned unconfined compressive strength C of the soil between piles u and the internal friction angle of the pile To obtain the ultimate bearing capacity of the crushed stone pile theory f ef ; Ultimate bearing capacity based on the aforementioned crushed stone pile theory f ef To obtain the bearing capacity of composite foundation f sp,d .

[0020] In the above-mentioned target area, for a site with a large area of ​​crushed stone pile composite foundation construction, select an area where load plate test and dynamic penetration test were carried out at the same time, and obtain the dynamic penetration hammer blow count N, dynamic penetration resistance F (obtained by electrical measurement method), and composite foundation bearing capacity data.

[0021] In this embodiment, the ultimate bearing capacity of the crushed stone pile is preferably calculated using the Brauns granular pile ultimate bearing capacity calculation theory. The ultimate bearing capacity of the crushed stone pile theory is... f ef The formula for calculating is:

[0022] in, , The internal friction angle of the crushed stone pile material is generally taken as 38 degrees. 64 degrees can be chosen; according to It can be obtained It is 61 degrees.

[0023] Furthermore, in this embodiment, the bearing capacity of the composite foundation... f sp,d The calculation formula is: ; in, m Area replacement rate When an equilateral triangle is formed d e =1.05s, square time d e =1.13s.

[0024] Summarizing the above formulas, it can be seen that for a specific pile diameter and replacement ratio in a composite foundation of crushed stone piles, the bearing capacity of the composite foundation is equal to the unconfined compressive strength of the soil between the piles.C u and the internal friction angle of the pile The sensitivity analysis of the parameters of the function is as follows: Taking a foundation treated with square-arranged crushed stone piles with a pile diameter of 1m and a pile spacing of 1.95m as an example, assuming the internal friction angle of the pile material is 38 degrees, the unconfined compressive strength of the soil between the piles is... C u The relationship between the bearing capacity of the composite foundation and the bearing capacity is shown in Table 1: Table 1 Soil between piles C u Analysis of the relationship between the ultimate bearing capacity of the composite foundation (38 degrees)

[0025] If the strength of the soil between piles C u The internal friction angle of the pile material was analyzed with a pressure of 14 kPa, as shown in Table 2. Table 2. Influence of internal friction angle of pile on ultimate bearing capacity of composite foundation ( C u (14 kPa)

[0026] The above parameter sensitivity analysis shows that, for a specific construction project, the internal friction angle of the pile material exhibits relatively small variability, while the strength of the foundation soil varies considerably with depth and location. Therefore, the strength of the soil between piles is considered the primary variable. Based on the bearing capacity of the load-plate test, the soil strength between piles is inverted and corrected using the above formula to obtain the equivalent soil strength between piles. C u’ .

[0027] Furthermore, in this embodiment, based on the number of dynamic penetration tests N and the dynamic penetration resistance F, a correlation is established between the number of dynamic penetration tests N, the dynamic penetration resistance F, and the equivalent soil strength between piles through data fitting. C u’ Empirical relation N- C u’ or F- C u’ .

[0028] For other target areas where load plate tests were not conducted, the number of dynamic penetration tests N or the dynamic penetration resistance F was obtained through dynamic penetration testing, and the empirical relationship N- C u’ or F- C u’ Obtain equivalent soil strength between piles C u’ .

[0029] Furthermore, based on the above-mentioned equivalent soil strength between piles... C u’ Internal friction angle of the pile To obtain the ultimate bearing capacity of the crushed stone pile theory f ef , specifically,

[0030] in, , The internal friction angle of the crushed stone pile material is generally taken as 38 degrees. 64 degrees is acceptable; according to It can be obtained It is 61 degrees.

[0031] And based on the ultimate bearing capacity of the crushed stone pile theory f ef To obtain the bearing capacity of composite foundation f sp,d , specifically, ; in, m Area replacement rate When equilateral triangles d e =1.05s, square time d e =1.13s.

[0032] The specific experimental parameters can be found in the above content and will not be repeated here.

[0033] In practical applications, the bearing capacity of the composite foundation can be used as a basis. f sp,d And assess the effectiveness of the reinforcement in the area.

[0034] This application establishes an empirical relationship between the number of dynamic penetration tests or dynamic penetration resistance and the bearing capacity of composite foundations, similar to that on semi-infinite solid foundations. This relationship can be used to evaluate the bearing capacity of composite foundations, overcoming the problem of insufficient test quantity in existing load-plate tests. It can be used not only for evaluating the reinforcement effect and estimating the bearing capacity of gravel pile composite foundations, but also widely applied to evaluating the reinforcement effect and estimating the bearing capacity of composite foundations made of granular materials such as sand piles. In summary, this application has good market application prospects.

[0035] In the description of this application, unless otherwise expressly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0036] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0037] The above embodiments are only used to illustrate the technical solutions of this application and are not intended to limit it. The preferred embodiments have been described in detail. Those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this application without departing from the spirit and scope of the technical solutions of this application, and all such modifications and substitutions should be covered within the scope of the claims of this application.

Claims

1. A method for evaluating the reinforcement effect of crushed stone pile composite foundation based on dynamic penetration testing, characterized in that, include: Select the target area; Obtain data on dynamic penetration test blow count N, dynamic penetration resistance F, and composite foundation bearing capacity; Obtain the unconfined compressive strength C of the soil between piles u and the internal friction angle δ of the pile p ; Based on the above-mentioned unconfined compressive strength C of the soil between piles u and the internal friction angle δ of the pile p To obtain the ultimate bearing capacity f of the crushed stone pile theory ef ; Ultimate bearing capacity f based on the aforementioned crushed stone pile theory ef To obtain the bearing capacity f of the composite foundation sp,d .

2. The method for evaluating the reinforcement effect of crushed stone pile composite foundation based on dynamic penetration testing as described in claim 1, characterized in that, The ultimate bearing capacity f of the crushed stone pile theory ef The formula for calculating is: in, The internal friction angle of the crushed stone pile material is generally taken as 38 degrees, therefore δ p 64 degrees is acceptable; according to We can calculate that δ is 61 degrees.

3. The method for evaluating the reinforcement effect of crushed stone pile composite foundation based on dynamic penetration testing as described in claim 1, characterized in that, The bearing capacity f of the composite foundation sp,d The calculation formula is: favorite sp,d =mf ef +(1-m)f s,d ; Where m is the area replacement rate When d is an equilateral triangle e = 1.05s, d for square time e =1.13s.

4. The method for evaluating the reinforcement effect of crushed stone pile composite foundation based on dynamic penetration testing as described in claim 1, characterized in that, Based on the bearing capacity of the load plate test, the strength C of the soil between the piles is determined. u Inversion and correction are performed to obtain the equivalent soil strength C between piles. u '.

5. The method for evaluating the reinforcement effect of crushed stone pile composite foundation based on dynamic penetration testing according to claim 4, characterized in that, Based on the number of dynamic penetration tests (N), a correlation between the number of dynamic penetration tests (N) and the equivalent inter-pile soil strength (C) is established through data fitting. u 'Empirical Relationship NC u '.

6. The method for evaluating the reinforcement effect of crushed stone pile composite foundation based on dynamic penetration testing as described in claim 4, characterized in that, Based on the dynamic penetration resistance F, a correlation between the dynamic penetration resistance F and the equivalent inter-pile soil strength C is established through data fitting. u 'Empirical relation FC u '.

7. The method for evaluating the reinforcement effect of crushed stone pile composite foundation based on dynamic penetration testing according to any one of claims 1 to 6, characterized in that, A load plate test was conducted on the target area.

8. The method for evaluating the reinforcement effect of crushed stone pile composite foundation based on dynamic penetration testing according to claim 5, characterized in that, For other target areas where load plate testing was not conducted, the number of dynamic penetration tests (N) was obtained through dynamic penetration testing, and the empirical formula NC was used to determine the number of dynamic penetration blows. u 'Obtain the equivalent soil strength C between piles u '.

9. The method for evaluating the reinforcement effect of crushed stone pile composite foundation based on dynamic penetration testing as described in claim 6, characterized in that, For other target areas where load plate testing was not conducted, the dynamic penetration resistance F was obtained through dynamic penetration testing, and the empirical relationship FC was used. u 'Obtain the equivalent soil strength C between piles u '.

10. The method for evaluating the reinforcement effect of crushed stone pile composite foundation based on dynamic penetration testing as described in claim 8 or 9, characterized in that, Based on the equivalent soil strength C between piles u’ Internal friction angle δ of the pile p To obtain the ultimate bearing capacity f of the crushed stone pile theory ef Based on the ultimate bearing capacity f of the crushed stone pile theory ef To obtain the bearing capacity f of the composite foundation sp,d .

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