Method for accurately calculating the depth of placement of an engineering pile

Abstract

The present application relates to geotechnical engineering technical field, especially to a kind of method for accurately calculating the depth required to be arranged of engineering pile, comprising the following steps: S1, obtaining the parameters of each soil layer of test pile position and actual engineering pile position required to be arranged;S2, test each layer of soil provided by test pile position side resistance f i (i=1,2,3…); S3, the side resistance coefficient a of each layer of soil of test pile position is calculated i ;S4, the side resistance coefficient a of actual engineering pile position required to be arranged is calculated i 、 ;S5, the distribution thickness of each soil layer where the pile body of engineering pile is h i (i=1,2,3…), the ultimate bearing capacity of engineering pile is engineering requirement engineering pile bearing capacity F A , the minimum depth value required to be arranged of engineering pile is calculated by Qua≥F A， . The present application can accurately calculate the depth required to be arranged of engineering pile, improve the accuracy of engineering pile arrangement depth acquisition, improve engineering safety, save engineering cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geotechnical engineering, and in particular to a method for accurately calculating the required arrangement depth of an engineering pile. BACKGROUND

[0002] At present, the detection purposes of the static load compression test of a single pile are: 1. determining the vertical compression ultimate bearing capacity of the single pile; 2. determining whether the vertical compression bearing capacity meets the design requirements; and 3. determining the pile side resistance and pile end resistance through the pile body strain and displacement test, and verifying the single pile vertical compression bearing capacity detection result of the high strain method. The important principle is to detect whether the sinking or rising of the pile meets the detection specification requirements by increasing the vertical pressure or uplift force of the single pile.

[0003] The bearing capacity of a bored pile is obtained by the side resistance of the soil layer around the pile wall and the end resistance provided by the pile end, wherein the side resistance is mainly friction, which is related to the contact area, friction coefficient and pressure stress, that is, f = s x N x tan μ, in the formula: s is the contact area of the pile wall and the soil layer, N is the lateral pressure provided by the surrounding soil layer; μ is the internal friction angle of the soil layer; tan μ is the friction coefficient between the soil layer and the pile wall, the side resistance coefficient a of the soil layer = N x tan μ, and at present, through in-situ test and soil test, the estimated value of the side resistance coefficient of the soil layer and the safe value of the end resistance can be obtained, and the arrangement depth of the engineering pile is designed based on the same.

[0004] At present, when the arrangement depth of the bored pile is designed and calculated, the side resistance coefficients of each soil layer estimated according to the engineering experience and the survey data are not accurate, and the influence of the self-weight stress of the soil is ignored at the same time. Therefore, the arrangement depth of the pile cannot be accurately estimated, and under the premise of safety, the arrangement depth of the pile can only be increased, which greatly increases the engineering cost. SUMMARY

[0005] The present application aims to solve one of the above technical problems.

[0006] To solve one of the above technical problems, the present application provides a method for accurately calculating the required arrangement depth of an engineering pile, comprising the following steps:

[0007] S1, obtaining the distribution characteristics of each soil layer, the water level line, the natural unit weight, the buoyant unit weight and the end resistance safety value P of the test pile position and the actual required arrangement engineering pile position through geotechnical engineering investigation i ;

[0008] S2, determining the test pile position, performing the single pile static load compression test of the test pile, and testing the side resistance f provided by each layer of soil of the test pile position i (i = 1, 2, 3…);

[0009] S3, determining the side resistance f provided by each layer of soil of the test pile position according to the obtained side resistance fi , the side resistance coefficient a of each layer of soil at the test pile position is calculated i ;

[0010] S4, the side resistance coefficient a of the actual engineering pile position to be arranged is set i ` the distribution thickness of each soil layer is h i (i=1, 2, 3…), according to the distribution thickness of each soil layer at the position of the engineering pile, the side resistance coefficient a of the actual engineering pile position to be arranged is calculated through self-weight correction i `;

[0011] S5, when the engineering pile is at a depth of H, the distribution thickness of each soil layer where the pile body is located is h i (i=1, 2, 3…), the arrangement depth H of the engineering pile is h1+h2+h3+h4+…, and the ultimate bearing capacity of the engineering pile at this depth is P x the end resistance safety value of each soil layer, the bearing capacity required by the engineering pile is F A , the minimum depth value required by the engineering pile to be arranged is calculated through Qua≥F A .

[0012] The method for accurately calculating the arrangement depth of the engineering pile can calculate the accurate value of the side resistance coefficient of the actual engineering pile position through the side resistance coefficient a of each layer of soil at the test pile position i , and then calculate the depth required by the engineering pile to be arranged, thereby improving the accuracy of the engineering pile arrangement depth, and further improving the engineering safety, and improving the accuracy of the engineering cost and budget, and saving the engineering cost.

[0013] Further, step S2 comprises:

[0014] S21, installing a steel reinforcement meter at the bottom of each soil layer, and installing multiple steel reinforcement meters in each layer;

[0015] S22, performing a single pile static load compression test on the test pile position, measuring the ultimate bearing capacity F0 of the pile, and measuring the internal force F1, F2…F of the pile at the bottom of each soil layer through the steel reinforcement meter i ;

[0016] S23, the side resistance provided by each soil layer is f1, f2…f i , according to f i =F i-1 -F i (i=1, 2, 3…) to calculate the side resistance f i provided by each soil layer.

[0017] Further, step S3 comprises:

[0018] S31, through geotechnical engineering investigation, the natural density and buoyant density parameters of each soil layer are measured;

[0019] S32, according to the formula f = s x N x tan μ, the side resistance coefficient a of the soil layer = N x tan μ, then f i = a i x s i , s i = u x h i , so a i = f i / (u x h i ), wherein u is the pouring circumference of the engineering pile, h i is the thickness of each layer of soil.

[0020] Further, step S4 comprises:

[0021] S41, according to the a i value calculated, the test pile position corresponding to the side resistance coefficient a i value is determined, and the self-weight stress t i at the midpoint of each layer of soil is calculated, according to a = N x tan μ, N = T x K0, T is the self-weight stress of the soil, K0 is the static side pressure coefficient of the soil, which is related to the properties of the soil, K0 of the same layer of soil is consistent, and K0 can be measured through geotechnical exploration, therefore, t i = a i / (K0 x tan μ), μ is the internal friction angle of the soil layer, and the internal friction angle μ of the same layer of soil is constant, and μ can be measured through geotechnical exploration;

[0022] S42, the actual position of the engineering pile is determined, the self-weight stress T of each layer of soil is corrected according to the distribution thickness h i (i = 1, 2, 3...) of each layer of soil, the self-weight stress T of each layer of soil at the midpoint of the actual position of the engineering pile is calculated, then the side resistance coefficient a i ` of each layer of soil at the actual position of the engineering pile is calculated according to a i ` = T i / t i x a i .

[0023] Further, in step S21, the number of reinforcement meters installed at the bottom of each layer of soil is greater than or equal to 6, when reading the reinforcement meter data of each layer of soil, unreasonable data is removed, and then the data of other reinforcement meters in the same layer of soil is averaged, so that the error is reduced, and the data used for calculation is relatively more accurate.

[0024] Further, the test pile is formed by drilling and pouring, and the reinforcement meter is arranged on the reinforcement cage inside the drilling and pouring pile.

[0025] Further, when installing the steel meter, the original steel bars in the steel cage at the installation position of the steel meter need to be cut off, and then the steel meter is connected to the cut-off steel bar gap, and the two ends of the steel meter are respectively welded to the steel bars at both ends of the gap.

[0026] Further, when welding the two ends of the steel meter to the steel bars at both ends of the gap, the steel bar welding method is adopted to ensure that the steel meter and the original steel bar stress direction are in a straight line, and the steel meter needs to be protected during welding to avoid damage to the steel meter due to heat.

[0027] Further, the steel cage stirrup is installed at the top of the engineering pile to strengthen the strength of the engineering pile, and a steel pipe protective sleeve is arranged outside the lead wire of the steel meter, which protects the lead wire of the steel meter, and the steel pipe extends from the side of the engineering pile to the ground surface.

[0028] Further, when measuring the pile internal force by the steel meter, the engineering pile internal force is calculated according to the following formula:

[0029] Where Nc is the support internal force, that is, the pile internal force F i , σ s is the steel stress, is the steel meter monitoring average stress, k j is the jth steel meter calibration coefficient, f ji is the jth steel meter monitoring frequency, f j0 is the initial frequency after the jth steel meter is installed, A js is the cross-sectional area of the jth steel meter, E c is the elastic modulus of concrete, s is the steel elastic modulus, A c is the cross-sectional area of the concrete pile, A s is the total cross-sectional area of the steel.

[0030] The beneficial effects of the present application are that the method for accurately calculating the required arrangement depth of the engineering pile can calculate the accurate value of the side resistance coefficient at the actual arrangement position of the engineering pile through the side resistance coefficient a i of each layer of soil at the experimental pile position, and then calculate the required arrangement depth of the engineering pile, thereby improving the accuracy of obtaining the arrangement depth of the engineering pile, and further improving the engineering safety, also improving the accuracy of the engineering cost and budget, and saving the engineering cost. BRIEF DESCRIPTION OF DRAWINGS

[0031] The present application will be further described below in conjunction with the drawings and examples.

[0032] Fig. 1is a flowchart of the method for accurately calculating the required arrangement depth of an engineering pile according to the present application.

[0033] Fig. 2 is a schematic diagram of the installation position of a reinforcement meter in an embodiment of the present application.

[0034] Fig. 3 is a schematic diagram of the connection of a reinforcement meter and reinforcement on a cast-in-place pile in an embodiment of the present application.

[0035] In the figure: 1, cast-in-place pile; 2, reinforcement meter; 3, reinforcement cage; 4, steel bar; 5, steel pipe protective sleeve. DETAILED DESCRIPTION

[0036] Embodiments of the present application are described in detail below with reference to the accompanying drawings, in which the same or similar numerals or characters represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application and cannot be understood as a limitation of the present application.

[0037] In the description of the present application, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application. In addition, the features defined as "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise specified, the meaning of "a plurality of" is two or more. In the description of the present application, it should be noted that, unless otherwise specified and limited, the terms "mounting", "connecting", "connecting" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be connected inside two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0038] As Figs. 1 to 3 shown, it is the most preferred embodiment of the present application, a method for accurately calculating the required arrangement depth of an engineering pile, comprising the following steps:

[0039] S1, through geotechnical engineering investigation, obtain the test pile position and the distribution characteristics of each soil layer of the actual engineering pile position to be arranged, water level line, natural unit weight, buoyant unit weight and end resistance safety value P i ;

[0040] S2, determine the test pile position, carry out single pile static load compression test of the test pile, and test the side resistance f provided by each layer of soil at the test pile position i (i=1, 2, 3…);

[0041] S3, according to the side resistance f provided by each layer of soil at the test pile position i , calculate the side resistance coefficient a of each layer of soil at the test pile position i ;

[0042] S4, set the side resistance coefficient of the actual engineering pile position to be arranged as a i ` and the distribution thickness of each soil layer as h i (i=1, 2, 3…), according to the distribution thickness of each soil layer at the position of the engineering pile, the side resistance coefficient a of the actual engineering pile position to be arranged is calculated through self-weight correction i `;

[0043] S5, when the engineering pile is at a depth of H, the distribution thickness of each soil layer where the pile body is located is h i (i=1, 2, 3…), the arrangement depth H of the engineering pile is h1+h2+h3+h4+…, then the ultimate bearing capacity of the engineering pile at this depth is P x The end resistance safety value of each soil layer, the bearing capacity required by the engineering pile is F A , the minimum depth value required by the engineering pile to be arranged is calculated through Qua≥F A .

[0044] Step S2 includes:

[0045] S21, install a steel reinforcement meter at the bottom of each soil layer, and install multiple steel reinforcement meters in each layer;

[0046] S22, carry out single pile static load compression test on the test pile position, measure the ultimate bearing capacity F0 of the pile, and measure the internal force F1, F2…F of the pile at the bottom of each soil layer through the steel reinforcement meter i ;

[0047] S23, the side resistance provided by each soil layer is f1, f2…f i , according to f i =F i-1 -F i (i=1, 2, 3…) to calculate the side resistance f provided by each soil layer i .

[0048] In step S21, the number of installed rebar meters 2 at the bottom of each soil layer is greater than or equal to 6, and when reading the data of the rebar meters 2 of each soil layer, unreasonable data is removed, and then the data of other rebar meters 2 in the same soil layer is averaged, which can reduce errors and make the data used for calculation more accurate. The test pile is formed by cast-in-place drilling, and the rebar meter 2 is arranged on the reinforcement cage 3 inside the cast-in-place drilling pile 1.

[0049] When installing the rebar meter 2, the original steel in the reinforcement cage 3 at the installation position of the rebar meter 2 needs to be cut off, and then the rebar meter 2 is connected to the cut-off steel gap, and the two ends of the rebar meter 2 are welded to the steel at both ends of the gap. When welding the two ends of the rebar meter 2 to the steel at both ends of the gap, a steel bar 4 is used for welding to ensure that the rebar meter 2 and the original steel are in the same straight line, and the rebar meter 2 needs to be protected when welding to avoid damage caused by heat.

[0050] A reinforcement cage 3 hoop is installed at the top of the engineering pile to strengthen the strength of the engineering pile, and a steel pipe protective sleeve 5 is arranged outside the lead wire of the rebar meter 2, which protects the lead wire of the rebar meter 2, and the steel pipe extends from the side of the engineering pile to the ground surface.

[0051] When measuring the internal force of the pile by the rebar meter, the internal force of the engineering pile is calculated according to the following formula:

[0052] where N c is the support internal force, i.e. the internal force F j of the pile, σ s is the steel stress, is the average stress monitored by the rebar meter, k j is the calibration coefficient of the jth rebar meter, f ji is the monitoring frequency of the jth rebar meter, f j0 is the initial frequency after installation of the jth rebar meter, A js is the cross-sectional area of the jth rebar meter, E c is the elastic modulus of concrete, E s is the elastic modulus of steel, A c is the cross-sectional area of the concrete pile, and A s is the total cross-sectional area of the steel.

[0053] Step S3 includes:

[0054] S31, by geotechnical engineering investigation, the natural specific gravity and floating specific gravity parameters of each soil layer are measured;

[0055] S32, according to the formula f = s x N x tan μ, the side resistance coefficient a of the soil layer is N x tan μ, then f i=a i ×s i s i =u×h i Therefore, a i =f i / (u×h i ), where u is the grouting perimeter of the engineering pile, h i The thickness of each soil layer.

[0056] According to a = N × tanμ, the internal friction angle μ of the same soil layer is constant. According to N = G × K0, G is the soil self-weight stress, G = γ × h, γ is the natural unit weight or buoyant unit weight of the soil layer covering each soil layer. The γ is different for different pile locations in the same soil layer, h is the depth of the soil layer, and K0 is the static lateral pressure coefficient of the soil, which is related to the properties of the soil. K0 is consistent for the same soil layer and can be obtained through geotechnical exploration. Therefore, the lateral pressure N of the soil at different pile locations is actually different.

[0057] Step S4 includes:

[0058] S41, based on the already calculated a i Determine the side drag coefficient a i The corresponding test pile location was used to calculate the self-weight stress t at the midpoint of each soil layer. i According to a = N × tanμ, N = T × K0, where T is the soil's self-weight stress and K0 is the soil's static lateral pressure coefficient, which is related to the soil's properties. K0 is consistent across the same soil layer and can be obtained through geotechnical investigation. Therefore, t i =a i / (K0×tanμ), μ is the internal friction angle of the soil layer. For the same soil layer, the internal friction angle μ is constant and can be obtained through geotechnical exploration.

[0059] S42, Determine the actual location of the engineering piles based on the distribution thickness h of each soil layer. i (i = 1, 2, 3...), correct the self-weight stress T of each soil layer, and calculate the self-weight stress T at the midpoint of each soil layer at the actual location of the engineering pile. i Then, the side resistance coefficient 'a' of each soil layer at the actual location of the engineering pile is... i `=T i / t i ×a i .

[0060] The beneficial effect of this invention is that the method for accurately calculating the required depth of engineering piles can be achieved by using the side resistance coefficient α of each soil layer at the test pile location. iThe side resistance coefficient of the actual pile arrangement position is calculated, and then the required arrangement depth of the engineering pile is calculated, so as to improve the accuracy of the engineering pile arrangement depth, improve the engineering safety, improve the accuracy of the engineering cost and budget, save the engineering cost, and improve the engineering safety.

[0061] The above is based on the ideal embodiment of the application, and the above description can be varied and modified without deviating from the technical idea of the application. The technical scope of the application is not limited to the content of the specification, and must be determined by the scope of the claims.

Claims

1. A method for accurately calculating the required installation depth of an engineering pile, characterized in that: The method comprises the following steps: S1, through geotechnical engineering investigation, obtaining the test pile position and the distribution characteristics of each soil layer of the actual engineering pile position to be arranged, water level line, natural gravity, buoyant gravity and end resistance safety value P i ; S2, determine the test pile position, carry out the single pile static load resistance test of the test pile, and test the side resistance f provided by each layer of soil at the test pile position i , i = 1, 2, 3, … S3, provide the side resistance f of each layer of soil according to the obtained test pile position i ; calculate the side resistance coefficient a of each layer of soil of the test pile position i ; S4, the lateral resistance coefficient of the actual position of the engineering pile to be arranged is a i 、 The distribution thickness of each soil layer is h i i=1, 2, 3…, according to the distribution thickness of each soil layer at the position of the engineering pile, the lateral resistance coefficient a of the actual position of the engineering pile to be arranged is calculated through self-weight correction i 、 The method comprises the steps of: The distribution thickness of each soil layer is hi, i=1, 2, 3…, the self-weight stress ti at the midpoint of each layer of soil is calculated according to the determined test pile position corresponding to the side resistance coefficient ai value, the actual position of the engineering pile is determined, the self-weight stress T of each layer of soil is corrected according to the distribution thickness hi of each layer of soil, i=1, 2, 3…, the self-weight stress Ti at the midpoint of each layer of soil at the actual position of the engineering pile is calculated, and the side resistance coefficient a of the actual arranged engineering pile position is calculated based on the self-weight stress ti at the midpoint of each layer of soil, the self-weight stress Ti at the midpoint of each layer of soil at the actual position of the engineering pile, and the side resistance coefficient ai of each layer of soil at the test pile position i 、 ; S5, the distribution thickness of each soil layer where the pile body is located is h when the depth of the engineering pile is H i , i = 1, 2, 3…, the arrangement depth H of the engineering pile is h1+h2+h3+h4+…, and the ultimate bearing capacity of the engineering pile at the depth is ;P x The end resistance safety value of each soil layer, the bearing capacity of the engineering pile is required to be F A , and the minimum depth value required for the arrangement of the engineering pile is calculated by Qua≥F A， .

2. The method for accurately calculating the depth of placement required for an engineering pile according to claim 1, characterized by: Step S2 comprises: S21, install a steel meter at the bottom of each soil layer, and install multiple steel meters in each layer; S22, single pile static load resistance test is carried out on the test pile position, limit bearing capacity F0 of the pile is measured, and the pile internal force F1, F2…F of the bottom of each soil layer is measured through the reinforcement meter i ; S23, each soil layer provides a lateral resistance respectively f1, f2…f i , according to f i =F i-1 -F i , i=1, 2, 3…, each soil layer provides a lateral resistance f i .

3. The method for accurately calculating the depth of placement required for an engineering pile according to claim 2, wherein: Step S3 comprises: S31, measure the natural specific gravity and floating specific gravity parameters of each soil layer through geotechnical engineering investigation; S32, according to the formula f = s x N x tan µ, the side resistance coefficient a of the soil layer = N x tan µ, then f i = a i x s i , s i = u x h i , so a i = f i / (u x h i ), wherein u is the pouring perimeter of the engineering pile, h i is the thickness of each layer of soil, and µ is the internal friction angle of the soil layer.

4. The method for accurately calculating the depth of placement required for an engineering pile according to claim 3, characterized in that: Step S4 comprises: S41, the thickness of each soil layer is h. i i = 1, 2, 3..., based on the already calculated a i Determine the side drag coefficient a i The corresponding test pile location was used to calculate the self-weight stress t at the midpoint of each soil layer. i According to a = N × tanµ, N = T × K0, where T is the soil's self-weight stress and K0 is the soil's static lateral pressure coefficient, which is related to the soil's properties. K0 is consistent across the same soil layer and is obtained through geotechnical investigation. Therefore, t i =a i / (K0×tanµ),µ is the internal friction angle of the soil layer. For the same soil layer, the internal friction angleµ is constant.µ is obtained through geotechnical exploration. S42, Determine the actual location of the engineering piles based on the distribution thickness h of each soil layer. i For i=1, 2, 3…, the self-weight stress T of each soil layer is corrected, and the self-weight stress T at the midpoint of each soil layer at the actual location of the engineering pile is calculated. i Then, the side resistance coefficient 'a' of each soil layer at the actual location of the engineering pile is... i 、 =T i / t i ×a i .

5. The method for accurately calculating the depth of placement required for an engineering pile according to claim 2, wherein: In step S21, the number of steel meters (2) installed at the bottom of each soil layer is greater than or equal to 6, and when reading the data of the steel meters (2) in each soil layer, unreasonable data is removed, and then the data of other steel meters (2) in the same soil layer is averaged.

6. The method for accurately calculating the depth of placement required for an engineering pile according to claim 2, wherein: The test pile is formed by bored pile, and the steel meter (2) is arranged on the reinforcement cage (3) inside the bored pile (1).

7. The method for accurately calculating the depth of placement required for an engineering pile according to claim 6, wherein: When installing the steel meter (2), the original steel in the reinforcement cage (3) at the installation position of the steel meter (2) needs to be cut off, and then the steel meter (2) is connected to the cut-off steel gap, and the two ends of the steel meter (2) are respectively welded to the steel at both ends of the gap.

8. The method for accurately calculating the depth of placement required for an engineering pile according to claim 7, wherein: When welding the two ends of the steel meter (2) to the steel at both ends of the gap, a steel bar (4) is used for welding to ensure that the steel meter (2) and the original steel are in the same straight line, and the steel meter (2) needs to be protected when welding the steel meter (2) to avoid damage to the steel meter (2) due to heat.

9. The method for accurately calculating the depth of placement required for an engineering pile according to claim 2, wherein: A reinforcement cage (3) hoop is installed at the top of the engineering pile to strengthen the strength of the engineering pile, and a steel pipe protective sleeve (5) is arranged outside the lead wire of the steel meter (2), which protects the lead wire of the steel meter (2), and the steel pipe extends from the side of the engineering pile to the ground surface.

10. The method for accurately calculating the depth of placement required for an engineering pile according to claim 2, wherein: When measuring the internal force of the pile by the steel meter, the internal force of the engineering pile is calculated according to the following formula: , wherein is the support internal force, i.e. the pile internal force F i , is the steel stress, is the average stress monitored by the rebar meter, is the jth rebar meter calibration coefficient, is the jth rebar meter monitoring frequency, is the initial frequency of the jth rebar meter after installation, is the jth rebar meter cross-sectional area, and is the concrete elastic modulus, is the steel elastic modulus, is the cross-sectional area of the concrete pile, is the total cross-sectional area of the steel.

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