CN114970016B - Pi-shaped support inclined strut displacement calculation method, pi-shaped support design method and support method - Google Patents
Pi-shaped support inclined strut displacement calculation method, pi-shaped support design method and support method Download PDFInfo
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- G06F30/17—Mechanical parametric or variational design
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D17/00—Excavations; Bordering of excavations; Making embankments
- E02D17/02—Foundation pits
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- E—FIXED CONSTRUCTIONS
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- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D5/00—Bulkheads, piles, or other structural elements specially adapted to foundation engineering
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Abstract
The invention provides a method for calculating the displacement of an n-shaped support diagonal brace, a method for designing the n-shaped support and a supporting method. Meanwhile, design parameters of the n-shaped support and the angle theta of the inclined strut can be optimized by combining the horizontal displacement and the vertical displacement, and risk avoidance is achieved.
Description
Technical Field
The invention relates to the field of geotechnical engineering, in particular to a method for calculating the diagonal bracing displacement of an n-shaped support, a method for designing the n-shaped support and a supporting method.
Background
The foundation pit supporting inner supporting structure adopted at present is mainly horizontal support and a pit inner inclined strut, the pit inner inclined strut is mostly adopted for foundation pits with large plane size and shallow depth, steel pipes or combined section steel are mostly adopted for inclined strut materials, the support is arranged at the bottom of the foundation pit for providing reliable support counter force, and a pile foundation or a basement bottom plate utilizing middle early construction is adopted for supporting. The foundation pit earthwork of the existing inclined strut technology adopts a basin-type excavation mode, the middle earthwork is excavated firstly, the edge earthwork is excavated to the position near the bottom of the inclined strut to release a slope, and the soil body below the inclined strut is excavated after the inclined strut is applied. The prior art has the following problems:
1. the support pile foundation length of bracing is longer, causes the waste. Because the current industry standard only stipulates the length calculation formula of the elastic pile with the converted buried depth alpha h being more than or equal to 2.4 and does not have the length calculation formula aiming at the support pile with the converted buried depth alpha h being less than 2.4, only the long pile can be selected in the engineering application, and the waste of resources and cost is caused.
2. The deformation calculation of the support pile foundation of the inclined strut is inaccurate, and the risk that the support pile-shaped edge is excessively supported unstably in the construction process exists. The existing support pile foundation deformation calculation is calculated on the basis of supposing that the rigidity of a pedestal is infinite, and larger errors often exist, so that the engineering risk is increased.
Disclosure of Invention
In order to overcome the defect that the deformation calculation of the support pile foundation of the inclined strut is inaccurate in the prior art, the invention provides a method for calculating the displacement of the n-shaped support inclined strut, which can accurately calculate the transverse displacement and the longitudinal displacement of the inclined strut.
In the method for calculating the inclined strut displacement of the n-shaped support, the n-shaped support comprises a strip-shaped pedestal and two support piles for supporting the pedestal; the n-shaped support is used for supporting an inclined stay bar, and the horizontal displacement delta x and the vertical displacement delta y of the n-shaped support are calculated according to the following formulas in a supporting state;
wherein, F θ Axial support force provided for the diagonal brace; theta is an inclined strut angle, namely an included angle between the inclined strut and the horizontal direction; l is x Indicating the height of the support pile, B indicating the platformThe length of the seat;
k 1 、k 2 、z 0 and δ is a calculation coefficient, and:
k 1 ＝6E s L x D；
k 2 ＝4E s Bb；
d represents the equivalent diameter of the support pile; e s The expression soil body compression modulus is obtained through in-situ test; b represents a pedestal width, and d represents a pedestal height.
In order to overcome the defects that the length of a support pile foundation of the inclined strut is long and materials are wasted in the prior art, the invention further provides a design method of the n-shaped support, the size of the n-shaped support can be set according to the surrounding environment of a foundation pit and the nature of a soil layer, and materials are saved.
The invention provides a design method of an n-shaped support, wherein the n-shaped support comprises a strip-shaped pedestal and two support piles for supporting the pedestal; the design method comprises the following steps:
s1, setting a diagonal bracing inclination angle theta and a bracing force target value F, and defining a design parameter set { L x D, B, B, D, L }, wherein L x The height of the support pile is shown, and D represents the equivalent diameter of the support pile; b represents the length of the pedestal, B represents the pedestal width, and d represents the pedestal height; the two support piles are arranged along the length direction of the pedestal, and l represents the clear distance between the axes of the two support piles;
a is the horizontal cross-sectional area of the support pile, and pi is the circumferential rate;
s2, selecting different values according to parameters in the design parameter set, and constructing a plurality of design parameter sets serving as sample sets, wherein at least one parameter in any two sample sets is different;
s3, calculating a predicted supporting force value F corresponding to each sample set according to the following formula (1) θ Arranging the predicted values of the supporting force larger than F in the order from small to large to form a supporting force candidate queue;
wherein: alpha is the angular correlation coefficient and alpha is the angular correlation coefficient,
ζ is a coefficient of area correlation,
S u the shear strength of the soil body without drainage is obtained through an in-situ test;
A f is the effective projection area of the n-shaped support in the horizontal direction, A f ＝η 1 L x D+η 2 bd； (4)
η 1 Is a size correlation coefficient, η 1 ＝0.28(l/D) 0.45 ； (5)
η 2 The coefficient related to the loose degree of the soil body behind the pedestal is taken as the value in the interval of 0 to 1, eta 2 Is an empirical value;
s4, enabling a first predicted value F in the supporting force candidate queue θ As design value of holding force F u ；
S5, binding F u The corresponding sample set calculates the value range of theta according to the following formulas (6) and (7);
v represents the required horizontal force at the fulcrum, and is a design value; the supporting point is the intersection of the diagonal brace and the enclosure structure;
s6, selecting a selected median value from the theta value range according to a set angle screening rule, and combining F u Traversing each selected median value in the theta value range by the corresponding sample set and the pi-shaped support inclined strut displacement calculation method to calculate the corresponding horizontal displacement delta x and vertical displacement delta y;
s7, defining parameter screening conditions, namely delta x is less than or equal to a preset transverse deviation threshold value x 0 Δ y is less than or equal to a preset vertical offset threshold y 0 (ii) a Judging whether the { delta x, delta y } in the S6 meets the parameter screening condition or not;
if yes, selecting a group from { delta x, delta y } meeting parameter screening conditions as optimal displacement, and acquiring theta corresponding to the optimal displacement as a target value theta of the angle of the inclined strut 0 Will F u Corresponding sample set as target parameter set { L x ', D', B ', B', D ', L' }, wherein L x 'denotes the stand-off pile height, D' denotes the equivalent diameter of the stand-off pile; b ' represents the length of the pedestal, B ' represents the pedestal width, and d ' represents the pedestal height; the two support piles are arranged along the length direction of the pedestal, and l' represents the clear distance between the axes of the two support piles;
if not, the next predicted value F in the supporting force candidate queue is used θ As design value of holding force F u And returns to step S5.
Preferably, the angle screening rule in S6 is: acquiring all integer values in a value range of theta as a selected value;
or selecting a selected median value from the theta value range according to the set interval value;
or, the number of selected median values is set according to the span of the theta value range, and then the selected median values are equidistantly selected from the theta value range according to the number of the selected median values.
Preferably, in S7, the threshold value x is laterally shifted 0 Equal to 3 per mill of support pile length and vertical deviation threshold y 0 Equal to 1 thousandth of the pile length of the support pile.
Preferably, in S7, a group of displacements is selected from { Δ x, Δ y } meeting the parameter screening condition according to a preset displacement selection rule as an optimal displacement; the displacement selection rule is as follows: acquiring { delta x, delta y } of the corresponding evaluation value, which is minimum, as the optimal displacement; the evaluation value is the sum of Δ x and Δ y.
Preferably, η in S5 above 2 Value of and eta in S3 2 The values of (A) are consistent.
The invention further provides a supporting method applying the n-shaped support, the inclined strut angle can be optimized, and a more stable and reliable supporting structure is realized.
A supporting method applying a n-shaped support is characterized in that a target parameter set { L } is obtained according to the design method of the n-shaped support x ', D', B ', B', D ', l' } and a target value of the diagonal tilt angle θ 0 According to the target parameter set { L x ', D', B ', B', D ', l' } designing and manufacturing a n-shaped support; according to the target value theta of the inclined strut angle 0 And installing the diagonal brace.
Preferably, firstly, the non-drainage shear strength S of the soil body at the n-shaped support construction position is obtained through an in-situ test u Then, a target parameter set { L } is obtained according to the design method of the n-shaped support x ', D', B ', B', D ', l' } and a target value of the strut angle theta 0 (ii) a The soil body at the construction position of the n-shaped support is an original soil body or an improved soil body.
The invention has the advantages that:
(1) The method for calculating the displacement of the inclined strut of the n-shaped support can accurately calculate the transverse displacement and the longitudinal displacement of the inclined strut, so that risk prediction and management and control are carried out on a supporting structure, and the safety of structure construction is improved. Meanwhile, design parameters of the n-shaped support and the angle theta of the inclined strut can be optimized by combining the horizontal displacement and the vertical displacement, and risk avoidance is achieved.
(2) The design method of the n-shaped support provided by the invention realizes the targeted design of the n-shaped support according to the surrounding environment and soil layer properties of the foundation pit so as to save materials. Meanwhile, risk control of design parameters of the n-shaped support according to the horizontal displacement delta x and the vertical displacement delta y is realized, and a finally obtained target parameter set { L }is ensured x ', D', B ', B', D ', l' } is designed to obtainThe n-shaped support has higher stability and reliability, ensures the safety of engineering construction and effectively improves the construction efficiency.
(3) The angle screening rule is given, the point value test of the theta value range is realized, the optimization of the angle of the inclined strut is conveniently and rapidly realized, and the calculated amount is reduced. The invention provides a displacement selection rule for selecting the optimal displacement so as to quickly determine the target value theta of the angle of the inclined strut 0 And the convergence speed of the algorithm is improved.
(4) Eta in S5 of the invention 2 Value of and eta in S3 2 The values of the inclined strut are consistent, errors caused by inconsistent parameters are avoided, and the reliability of the angle optimization of the inclined strut is ensured.
(5) The invention provides a supporting method applying an n-shaped support, which is based on a target value theta of an angle of an inclined strut 0 The inclined strut angle of the inclined strut is arranged, and the most stable supporting structure is realized under the condition that the size of the n-shaped support is fixed.
(6) According to the invention, prestress is applied to the diagonal brace through the prestress applying device, the prestress value is 60% -75% of the axial force design value of the diagonal brace, the prestress loss in locking is fully considered, and a more reliable prestress setting mode is adopted.
(7) The invention is beneficial to further optimizing the size design of the n-shaped support by improving the foundation soil and simultaneously is beneficial to reducing the construction difficulty.
Drawings
FIG. 1 is a schematic size diagram of a Pi-shaped support;
FIG. 2 is a flow chart of a design method of an n-shaped support;
fig. 3 is a schematic view of a design scheme of a foundation pit supporting structure applying an n-shaped support;
FIG. 4 is a schematic diagram of construction conditions in the embodiment of the present invention;
FIG. 5 is a schematic view of an embodiment of the invention illustrating the installation of a diagonal brace;
FIG. 6 is a schematic view of the basement construction according to the embodiment of the invention;
1. an enclosure structure; 2. an n-shaped support; 3. a crown beam; 4. a support pile; 5. a pedestal; 6. enclosing purlins; 7. a diagonal brace; 8. a prestress applying device; 9. a water stop ring; 10. an underground structural floor; 11. a plain concrete force transfer belt; 12. underground structural frame columns; 13. an underground structural exterior wall; 14. an intermediate layer beam slab of the underground structure; 15. a transfer beam plate; 16. a subsurface structure roof; 17. a natural ground; 18. undisturbed soil at the bottom of the foundation pit; 19. a peripheral soil bench; 20. backfilling the fertilizer groove; 21. improving the foundation soil.
Detailed Description
II-shaped support
As shown in fig. 1, the pi-shaped support in this embodiment includes an elongated pedestal 5 and two support piles 4 for supporting the pedestal, where the pedestal 5 is a flat plate structure and has a length, a width and a height of B, b and d, respectively; the height and equivalent diameter of the standoff piles 4 are denoted Lx and D, respectively. Two support piles are arranged along the length direction of the pedestal, and l represents the axle center clear distance of the two support piles.
The calculation formula of the equivalent diameter D is as follows:
wherein A is the horizontal cross-sectional area of the support pile, and pi is the circumferential rate.
Method for calculating displacement of inclined strut of n-shaped support
In the embodiment, the horizontal displacement Δ x and the vertical displacement Δ y of the n-shaped support 2 in the supporting state are calculated according to the following formulas; the supporting state is the state that the n-shaped support 2 supports the inclined support rod 7.
Wherein, F θ The axial supporting force provided for the diagonal strut 7; theta is an inclined strut angle, namely an included angle between the inclined strut 7 and the horizontal direction; l is x The height of the support pile is shown, and B is the length of the pedestal;
k 1 、k 2 、z 0 and δ is a calculation coefficient, and:
k 1 ＝6E s L x D；
k 2 ＝4E s Bb；
d represents the equivalent diameter of the support pile; e s The expression soil body compression modulus is obtained through in-situ test; b represents the pedestal width and d represents the pedestal height.
According to the formula, the horizontal displacement delta x and the vertical displacement delta y of the n-shaped support 2 can be predicted under the condition that the design parameters and the inclined strut angle theta of the n-shaped support 2 are known, so that risk prediction and management and control are carried out on the supporting structure, and the safety of structure construction is improved. Meanwhile, design parameters of the n-shaped support 2 and the angle theta of the inclined strut can be optimized by combining the horizontal displacement delta x and the vertical displacement delta y, and risk avoidance is achieved.
Design method of n-shaped support
In this embodiment, the supporting force F provided by the inclined strut 7 using the pi-shaped support 2 is calculated according to the following formula (1) θ ：
Wherein: alpha is a coefficient of angular dependence of the angle,
ζ is a coefficient of area correlation,
S u the shear strength of the soil body without drainage is obtained through an in-situ test;
A f effective projection area of n-shaped support in horizontal direction，A f ＝η 1 L x D+η 2 bd； (4)
η 1 Is a size correlation coefficient, η 1 ＝0.28(l/D) 0.45 ； (5)
η 2 The coefficient related to the loose degree of the soil body behind the pedestal is taken as the value in the interval of 0 to 1, eta 2 Are empirical values.
It can be seen that, according to the above equations (1) - (5), the parameters { L } can be designed at known angles θ and pi-shaped support 2 x Directly calculating the supporting force F on the basis of D, B, B, D, l θ 。
The design method of the n-shaped support provided by the embodiment comprises the following steps:
s1, setting a diagonal bracing angle theta and a supporting force target value F, and defining a design parameter set { L } x D, B, B, D, L }, wherein L x The height of the support pile is shown, and D represents the equivalent diameter of the support pile; b represents the length of the pedestal, B represents the pedestal width, and d represents the pedestal height; two support piles are arranged along the length direction of the pedestal, and l represents the axle center clear distance of the two support piles.
S2, different values are selected according to parameters in the design parameter set, a plurality of design parameter sets serving as sample sets are constructed, and at least one parameter in any two sample sets is different, so that repeated sample sets and redundant work are avoided.
S3, calculating a supporting force predicted value F corresponding to each sample set according to formulas (1) - (5) θ Arranging the predicted values of the supporting force larger than F in the order from small to large to form a supporting force candidate queue;
s4, enabling a first predicted value F in the supporting force candidate queue θ As design value F of supporting force u ；
S5, binding F u The corresponding sample set calculates the value range of theta according to the following formulas (6) and (7);
wherein alpha is an angle correlation coefficient, zeta is an area correlation coefficient, S u The shear strength of the soil body without drainage is obtained through an in-situ test; v represents the required horizontal force at the fulcrum, and is a design value; the supporting point is the intersection of the diagonal brace 7 and the enclosure structure 1; a. The f Effective projected area, eta, of n-shaped support in horizontal direction 1 Is a size correlation coefficient, η 2 The coefficient is related to the loose degree of the soil body behind the pedestal; α, ζ, A f And η 1 The sample sets { Lx, D, B, B, D, l } are respectively substituted into the above formulas (2) - (5).
S6, selecting a selected median value from the theta value range according to a set angle screening rule, and combining F u And traversing each selected median value in the theta value range by the corresponding sample set and the method for calculating the inclined strut displacement of the pi-shaped support to calculate the corresponding horizontal displacement delta x and vertical displacement delta y.
S7, defining parameter screening conditions, namely delta x is less than or equal to a preset transverse deviation threshold value x 0 Δ y is less than or equal to a preset vertical offset threshold y 0 (ii) a Judging whether the { delta x, delta y } in the S6 meets the parameter screening condition or not; lateral shift threshold x 0 Equal to 3 per mill of support pile length and vertical deviation threshold y 0 Equal to 1 thousandth of the pile length of the support pile;
if yes, selecting a group from { delta x, delta y } meeting parameter screening conditions as optimal displacement, and acquiring theta corresponding to the optimal displacement as a target value theta of the angle of the inclined strut 0 Will F u Corresponding sample set as target parameter set { L x ',D',B',b',d',l'}；
If not, the next predicted value F in the supporting force candidate queue is used θ As design value of holding force F u And returns to step S5.
The steps S6 and S7 are combined to realize risk control of the design parameter of the Π -shaped support 2 according to the horizontal displacement Δ x and the vertical displacement Δ y, and ensure stability and reliability of the Π -shaped support 2 designed and obtained according to the finally obtained target parameter set { Lx ', D ', B ', D ', l ' }.
And S7, optimizing the angle of the inclined strut further according to the optimal displacement, so that a target value theta of the angle of the inclined strut is provided for the construction of subsequent support 0 Advantageously according to the target value theta of the angle of the diagonal brace 0 The optimal axial supporting force of the inclined strut is achieved, and the reliability of the supporting structure is further improved.
Eta in S5 2 Value of and eta in S3 2 The values of the inclined strut angle are consistent, so that the reliability of the inclined strut angle optimization is ensured. In the step S6, the point value test of the theta value range is realized by setting the selected median, so that the optimization of the angle of the inclined strut is conveniently and rapidly realized, and the calculation amount is reduced. Specifically, the angle filtering rule may be set as: and acquiring all integer values in the value range of theta as selected values, namely, only calculating the horizontal displacement delta x and the vertical displacement delta y corresponding to each integer value. The selection of the integer value realizes the uniform value taking in the value taking range of theta and effectively controls the calculation times.
In specific implementation, if the value range of θ is too large, a selected median may be selected from the value range of θ according to a set interval value, for example, the minimum end value in the value range of θ is used as the first selected median, and then one selected median is selected every 3 ° intervals.
Or, the number of selected median values is set according to the span of the theta value range, and then the selected median values are equidistantly selected from the theta value range according to the number of the selected median values. For example, the value range of theta is more than or equal to 35 degrees and less than or equal to 64.3 degrees, the selected value is respectively as follows by setting the selected value number to 10: 35 °, 38.26 °, 41.25 °, 44.78 °, 48.04 °, 51.3 °, 54.56 °, 57.82 °, 61.08 °, 64.3 °.
S6, selecting a group of optimal displacements from the { delta x, delta y } meeting the parameter screening conditions according to a preset displacement selection rule; the displacement selection rule is as follows: acquiring { delta x, delta y } of the corresponding evaluation value, which is minimum, as the optimal displacement; the evaluation value is the sum of Δ x and Δ y.
Example 1
Referring to fig. 3 to 6, in this embodiment, in combination with a real case, axial supporting force, horizontal displacement, and vertical displacement of the sprag under different sprag angles are compared for an n-shaped support with a fixed size.
Table 1: data statistics of example 1
The design parameters of the support in the upper table are original design parameters, and more accurate axial supporting force F of the diagonal brace can be obtained through angle optimization θ Horizontal displacement Δ x and vertical displacement Δ y.
As can be seen from the above table, in the present embodiment, by optimizing the angle of the inclined strut, the axial supporting force of the inclined strut 7 can be significantly increased and the maximum displacement in a single direction can be reduced after the design parameters of the n-shaped support 2 are fixed.
Moreover, as can be seen from table 1 above, in this embodiment, under the condition that the size of the pi-shaped support 2 is fixed, the axial supporting force of the diagonal brace is greatly improved for all the optimized 3 kinds of diagonal brace angles, and according to the demonstration of this embodiment, the design size of the pi-shaped support 2 can be further optimized by using the method in the specific construction process, so as to achieve the purposes of saving materials, reducing the height of the pi-shaped support 2, and reducing the construction difficulty.
It can be seen that, when embodiment 1 is implemented, better dimension parameters and inclined strut angle θ of the pi-shaped support 2 can be obtained according to the design method of the pi-shaped support 0 Then the n-shaped support 2 is produced and installed according to the size parameters of the n-shaped support 2, and then the existing foundation pit supporting construction method can be carried out according to the inclined strut angle theta 0 And (5) constructing the diagonal brace 7 to maximize the axial supporting force of the diagonal brace.
In specific implementation, the parameter design of the n-shaped support is related to soil parameters, so that soil improvement can be performed at the construction position of the n-shaped support 2 during actual construction aiming at soil with poor foundation, and the n-shaped support 2 is designed and constructed aiming at the improved soil 21, so that the optimization control of the size parameters of the n-shaped support is further realized.
The design parameters of the support in table 1 above are the design parameters selected according to the existing specifications, and the superiority of the method for optimizing the angle of the inclined strut in the invention is embodied by combining the data in table 1. To further prove the superiority of the pi-shaped support design method of the present invention, a new set of design parameters is provided by using the pi-shaped support design method of the present invention according to the application scenario of the embodiment described in table 1, as shown in table 2 below.
Table 2: data statistics of the n-shaped support design method provided by the invention aiming at the scene in embodiment 1
As can be seen from the above table 1 and the above table 2, in this embodiment, two groups of pi-shaped support design parameter sets are respectively tested, where D =5m x =0.9m; d =4m,l in the set of design parameters shown in table 2 x =0.8m. As can be seen from the above tables 1 and 2, when the angle of the diagonal brace is 0, the design parameter set shown in table 2 adopts a smaller size to realize a larger axial supporting force and a smaller horizontal displacement of the diagonal brace relative to the design parameter set shown in table 1; at θ =64.3 °, the design parameter set shown in table 2 still satisfies the design target value of the axial force supporting force of the sprag, and the maximum displacement value is reduced from 17.33mm to 16.94mm with respect to the design parameter set shown in table 1. Therefore, by combining the design method of the n-shaped support, the pile height of the support can be effectively reduced on the premise that the axial supporting force of the inclined strut meets the design target.
The invention is not to be considered as limited to the specific embodiments shown and described, but is to be understood to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.
Claims (8)
1. A method for calculating the diagonal bracing displacement of an n-shaped support is characterized in that the n-shaped support (2) comprises a strip-shaped pedestal (5) and two support piles (4) for supporting the pedestal; the n-shaped support (2) is used for supporting an inclined stay bar (7), and the horizontal displacement delta x and the vertical displacement delta y of the n-shaped support (2) are calculated according to the following formulas in a supporting state;
wherein, F θ Axial support force provided for the diagonal strut (7); theta is an inclined strut angle, namely an included angle between the inclined strut (7) and the horizontal direction; l is a radical of an alcohol x The height of the support pile is shown, and B is the length of the pedestal;
k 1 、k 2 、z 0 and δ is a calculation coefficient, and:
k 1 ＝6E s L x D；
k 2 ＝4E s Bb；
d represents the equivalent diameter of the support pile; e s The expression soil body compression modulus is obtained through in-situ test; b represents the pedestal width and d represents the pedestal height.
2. A design method of a pi-shaped support is characterized in that the pi-shaped support comprises a strip-shaped pedestal (5) and two support piles (4) for supporting the pedestal; the design method comprises the following steps:
s1, setting a diagonal bracing angle theta and a supporting force target value F, and defining a design parameter set { L } x D, B, B, D, L }, wherein L x The height of the support pile is shown, and D represents the equivalent diameter of the support pile; b represents the length of the pedestal, B represents the pedestal width, and d represents the pedestal height; two support piles are arranged along the length direction of the pedestal, wherein l represents twoClear distance of the axle center of the support pile;
a is the horizontal cross-sectional area of the support pile, and pi is the circumferential rate;
s2, selecting different values according to parameters in the design parameter set, and constructing a plurality of design parameter sets serving as sample sets, wherein at least one parameter in any two sample sets is different;
s3, calculating a predicted supporting force value F corresponding to each sample set according to the following formula (1) θ Arranging the predicted values of the supporting force larger than F in the order from small to large to form a supporting force candidate queue;
wherein: alpha is the angular correlation coefficient and alpha is the angular correlation coefficient,
ζ is a coefficient of area correlation,
S u the shear strength of the soil body without drainage is obtained through an in-situ test;
A f is the effective projection area of the n-shaped support in the horizontal direction, A f ＝η 1 L x D+η 2 bd； (4)
η 1 Is a size correlation coefficient, η 1 ＝0.28(l/D) 0.45 ； (5)
η 2 The coefficient related to the loose degree of the soil body behind the pedestal is taken as the value in the interval of 0 to 1, eta 2 Is an empirical value;
s4, enabling a first predicted value F in the supporting force candidate queue θ As design value F of supporting force u ；
S5, binding F u Corresponding sampleCalculating the value range of theta according to the following formulas (6) and (7);
v represents the required horizontal force at the fulcrum, and is a design value; the supporting point is the intersection of the diagonal brace and the enclosure structure;
s6, selecting a selected median value from the theta value range according to a set angle screening rule, and combining F u The corresponding sample set and the method for calculating the inclined strut displacement of the pi-shaped support according to claim 1 traverse each selected value in the theta value range to calculate the corresponding horizontal displacement amount Δ x and vertical displacement amount Δ y;
s7, defining parameter screening conditions, namely delta x is less than or equal to a preset transverse deviation threshold value x 0 Δ y is less than or equal to a preset vertical offset threshold y 0 (ii) a Judging whether the { delta x, delta y } in the S6 meets the parameter screening condition or not;
if not, the next predicted value F in the supporting force candidate queue is used θ As design value of holding force F u And returning to the step S5;
if yes, selecting a group from { delta x, delta y } meeting parameter screening conditions as optimal displacement, and acquiring theta corresponding to the optimal displacement as a target value theta of the angle of the inclined strut 0 Will F u Corresponding sample set as target parameter set { L x ', D', B ', B', D ', L' }, wherein L x 'denotes the stand-off pile height, D' denotes the equivalent diameter of the stand-off pile; b ' represents the length of the pedestal, B ' represents the pedestal width, and d ' represents the pedestal height; two support piles are arranged along the length direction of the pedestal, and l' represents the axle center clear distance of the two support piles.
3. The method of designing a Π -shaped support of claim 2, wherein the angular screening rules in S6 are: acquiring all integer values in a value range of theta as a selected value;
or selecting a selected median value from the theta value range according to the set interval value;
or, the number of selected median values is set according to the span of the theta value range, and then the selected median values are equidistantly selected from the theta value range according to the number of the selected median values.
4. The method of designing a Π -shaped holder of claim 2 wherein, in S7, the threshold x is laterally offset 0 Equal to 3 per mill of support pile length and vertical deviation threshold y 0 Equal to 1 per thousand of the pile length of the support pile.
5. The method according to claim 2, wherein in S7, a group of { Δ x, Δ y } satisfying the parameter selection condition is selected as an optimal displacement according to a preset displacement selection rule; the displacement selection rule is as follows: acquiring { delta x, delta y } of the corresponding evaluation value, which is minimum, as the optimal displacement; the evaluation value is the sum of Δ x and Δ y.
6. The method of designing a Π -shaped support of claim 2 wherein η in S5 is 2 Value of and eta in S3 2 The values of (A) are consistent.
7. Support method using a n-type support, characterized in that a set of target parameters { L } is obtained according to the design method of a n-type support according to any one of claims 2 to 6 x ', D', B ', B', D ', l' } and a target value of the strut angle theta 0 According to the target parameter set { L x ', D', B ', B', D ', l' } designing and manufacturing a n-shaped support (2); according to the target value theta of the inclined strut angle 0 And installing a diagonal brace (7).
8. A support method using a n-shaped support according to claim 7, wherein the non-drainage shear strength S of the soil body at the construction position of the n-shaped support is obtained through an in-situ test u Then, a set of target parameters { L } is obtained according to the method of designing a Π -type support according to any one of claims 2 to 6 x ', D', B ', B', D ', l' } and a target value of the strut angle theta 0 (ii) a The soil body at the construction position of the n-shaped support is an original soil body or an improved soil body.
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