CN111827268B - Long and short pile composite foundation design method and device - Google Patents
Long and short pile composite foundation design method and device Download PDFInfo
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- CN111827268B CN111827268B CN202010542238.2A CN202010542238A CN111827268B CN 111827268 B CN111827268 B CN 111827268B CN 202010542238 A CN202010542238 A CN 202010542238A CN 111827268 B CN111827268 B CN 111827268B
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- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
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Abstract
The invention discloses a method and a device for designing a long and short pile composite foundation, wherein the method comprises the following steps: preliminary selection of long and short pile lengthl 1、l 2And total replacement rate of long and short pile areasmThe value range of (a); according to the initial selection result, the long pile length corresponding to the minimum target function is obtained according to the design of uniformly distributing long and short piles, the bearing capacity is used as a limiting condition, the engineering cost is used as a target functionl 1Length of short pilel 2And total replacement rate of long and short pile areasm(ii) a According to the length of the long pilel 1Length of short pilel 2And long and short pile area replacement ratemCalculating the preliminary calculated value of long and short pile composite foundation settlement under the uniform pile arrangement types'(ii) a Calculating the preliminary calculated value of sedimentations'And a sedimentation tolerance value [ 2 ]s]And selecting a corresponding parameter modification scheme according to the deviation value until the final settlement checking calculation is passed. The method is simple, has clear design mechanism, and can fully mobilize and exert the respective bearing capacity and the sedimentation control capacity of the long and short piles, thereby enabling the design of the composite foundation to be more reasonable.
Description
Technical Field
The invention relates to a method and a device for designing a long and short pile composite foundation, and belongs to the technical field of geotechnical engineering composite foundations.
Background
After decades of development, the use of the composite foundation technology is more and more common, and the types of the composite foundation are more and more, and the multi-pile type composite foundation is a new technology developed from a single-pile type composite foundation technology. The multi-pile composite foundation is a composite foundation formed by reinforcing bodies made of two or more different materials or reinforcing bodies made of the same material and different lengths. When the settlement requirements of different areas of the structure in the field are inconsistent, piles with larger rigidity or length can be adopted in the areas with strict settlement requirements, and piles with smaller rigidity or length are adopted in the areas with smaller settlement requirements, and the variable rigidity leveling design is a type of the multi-pile type composite foundation. If the foundation soil has larger collapsibility, the foundation soil is usually compacted by first inserting one pile, and then the bearing capacity is improved and the settlement is reduced by inserting another pile, which is another common type of multi-pile type composite foundation. The use types of the two multi-pile type composite foundations are still in the category of a single-pile type composite foundation, and the variable-rigidity leveling design is that the whole area adopts two pile types, but the whole area belongs to the single-pile type composite foundation; the compaction pile is constructed firstly and then, the stressed pile is constructed, the compaction pile mainly plays a role in eliminating the collapsible property and can be regarded as the soil among the piles of the stressed pile, so the compaction pile also belongs to the category of single pile type composite foundations essentially.
The foundation soil has two better bearing layers, the two bearing layers can be used by the long and short pile composite foundation respectively, or the long and short pile composite foundation can be designed when the single pile type composite foundation has more surplus in settlement. The upper part of the composite foundation adopts the combined action of long piles and short piles to improve the bearing capacity, and the lower part of the composite foundation adopts the long piles to reduce the settlement. For the multi-pile type composite foundation, namely a long-short pile composite foundation, the design thinking way is more reasonable than that of a single-pile type composite foundation, and the pile bodies with different pile lengths and types are arranged to reinforce different depth positions of foundation soil and reasonably control the bearing capacity and settlement of the composite foundation. However, the problems caused by the method are that the design parameters are too much, the calculation parameters are reasonably selected, and the like, and the design difficulty is higher than that of a single pile type composite foundation.
The long and short pile composite foundation design usually assumes the basic information of pile length, pile diameter and the like, then carries out settlement and bearing capacity checking calculation, and finishes the design by passing and does not pass, and repeatedly adjusts parameters for redesigning. It can be seen that the method has the advantages of large blindness and weak pertinence, and cannot give full play to the capabilities of bearing and controlling settlement of the composite foundation.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, provides a long and short pile composite foundation design method and a long and short pile composite foundation design device, and solves the problems that the existing long and short pile composite foundation design method is large in blindness and weak in pertinence, and cannot give full play to the bearing and settlement control capabilities of a composite foundation.
In order to achieve the purpose, the invention is realized by adopting the following technical scheme:
in a first aspect, the invention provides a long and short pile composite foundation design method, which comprises the following steps:
preliminarily selecting the value ranges of the length of the long pile and the short pile and the total replacement rate m of the area of the long pile and the short pile;
according to the initial selection result, the design of evenly arranging long piles and short piles, the bearing capacity as the limiting condition and the engineering cost as the objective function are adopted to obtain the corresponding target function when the objective function is minimumLength of long pile1Length of short pile2And the total replacement rate m of the long pile area and the short pile area;
according to the length l of the long pile1Length of short pile2Calculating a preliminary settlement calculation value s' of the long and short pile composite foundation under the uniform pile arrangement type according to the long and short pile area replacement rate m;
and calculating the deviation between the preliminary sedimentation calculation value s' and the sedimentation allowable value [ s ], and selecting a corresponding parameter modification scheme according to the deviation value until the final sedimentation checking is passed.
With reference to the first aspect, further, the value range of the total replacement rate m of the area of the long pile and the short pile is 2.2% to 8.7%.
With reference to the first aspect, further, the method for determining the pile length of the long and short piles includes:
preliminarily selecting two soil layers as supporting layers of the long pile and the short pile according to a geological survey report;
selecting the distances from the upper top surface and the lower top surface of the long pile holding layer to the pile top of the long pile as the upper and lower value limits of the length of the long pile;
and selecting the distances from the upper top surface and the lower top surface of the short pile holding layer to the short pile top as the upper and lower value limits of the short pile length.
With reference to the first aspect, further, the calculation formula of the preliminary settlement calculation value s' of the long and short pile composite foundation is as follows:
s′＝γ1s1+γ2s2
in the formula: s1For the settlement of a single-pile type composite foundation when the replacement area is entirely long piles, s2For settlement of single-pile type composite foundations when the replacement area is entirely short piles, gamma1The ratio of the replacement area of the long pile to the total replacement area is adopted; gamma ray2The ratio of the replacement area of the stub to the total replacement area is disclosed.
In combination with the first aspect, further, s1And s2The calculation of (2) is solved according to the existing technical specification of building foundation treatment;
with reference to the first aspect, further, the method for selecting the corresponding parameter modification scheme according to the deviation value includes the following steps:
(a) if s' < [ s ]]And the deviation of the two is larger than the preset difference value, the proportion gamma of the replacement area of the long pile to the total replacement area is reduced1 Hold 11、l2Calculating the new total replacement rate m of the long pile and the short pile area by taking the bearing capacity as a limiting condition without changingnewAnd is based on mnewCalculating final calculated value s of sedimentation: if s < [ s ]]If so, ending the design; otherwise, the proportion gamma of the replacement area of the long pile to the total replacement area is increased1Until the requirements are met;
(b) if s' < [ s ]]And the deviation between the two is not more than the preset difference value, and s is less than s]If so, ending the design; if s is not less than s]Increasing the pile length l of the long pile1Or increasing the length l of the short pile2Until the requirements are met;
(c) if s' ≧ s ], either of two modifications are employed:
the modification scheme I is as follows: proportion gamma of replacement area to total replacement area by adopting long piles1Protocol > 0.5, calculate Settlement allowance [ s ]]Corresponding gamma1If s < [ s ]]If so, ending the design; otherwise, increasing the proportion gamma of the replacement area of the long pile to the total replacement area1Or increasing the length l of long pile1Until the requirements are met;
the second modification scheme is that the proportion gamma of the replacement area of the long piles to the total replacement area is adopted1The scheme of 0.5 is that the length of the short pile is kept unchanged, and the length of the long pile is increased until s is less than s]。
With reference to the first aspect, further, in the second modification scheme, if the length of the long pile reaches the upper limit value and does not meet the requirement of the final settlement checking calculation, the length of the short pile is increased until the final settlement checking calculation meets the requirement.
With reference to the first aspect, further, the ratio γ of the long pile replacement area to the total replacement area1The upper and lower limits of (1) are 0.25 and 0.75, respectively, if gamma is1And if the calculated value exceeds the limit value, taking the corresponding limit value.
In a second aspect, the invention provides a long and short pile composite foundation design device, which comprises a processor and a storage medium;
the storage medium is used for storing instructions;
the processor is configured to operate in accordance with the instructions to perform the steps of the method of any of the first aspects.
In a third aspect, the invention provides a computer-readable storage medium having stored thereon a computer program which, when executed by a processor, performs the steps of the method of any one of the first aspect.
Compared with the prior art, the invention can at least achieve the following beneficial effects:
the invention provides a long and short pile composite foundation design method and a device, the method is designed according to a mode of uniformly distributing piles, the bearing capacity is taken as a limiting condition, the engineering cost is taken as a target function, the corresponding total replacement rate and the long and short pile length when the target function takes the minimum value are obtained, the long and short pile composite foundation settlement is calculated, and a corresponding parameter modification scheme is selected by comparing the relationship between a preliminary settlement calculation value and a settlement allowable value until the final settlement check calculation is passed; the calculation method is simple, the design is extremely clear, and the calculation amount can be reduced; the method and the device can overcome the defects of large blindness and weak pertinence of the existing long and short pile composite foundation design method, and can fully exert the bearing and settlement control capabilities of the composite foundation.
Drawings
Fig. 1 is a flow chart of a long and short pile composite foundation design method provided by the invention;
fig. 2 is a relationship between the bearing capacity of the long-short pile composite foundation and the combination coefficient of the long pile in the long-short pile composite foundation design method provided by the invention;
FIG. 3 is a composite foundation adjustment scheme provided in case (a) of an embodiment of the present invention;
FIG. 4 is a non-uniform piling adjustment scheme provided in a first modification of (c) the first embodiment of the present invention;
fig. 5 is a uniform pile arrangement adjustment scheme for adjusting only the pile length of long piles according to the first modification (c) of the first embodiment of the present invention;
fig. 6 is a uniform pile arrangement adjustment scheme for simultaneously adjusting the lengths of long piles and short piles according to the first modification scheme (c) of the first embodiment of the present invention.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
The first embodiment is as follows:
as shown in fig. 1, the invention provides a long and short pile composite foundation design method, which comprises the following steps:
preliminarily selecting the value ranges of the length of the long pile and the short pile and the total replacement rate m of the area of the long pile and the short pile;
according to the initial selection result, the long pile length l corresponding to the minimum target function is obtained according to the design of uniformly distributing long piles and short piles, the bearing capacity is used as a limiting condition, the engineering cost is used as a target function1Length of short pile2And the total replacement rate m of the long pile area and the short pile area;
according to the length l of the long pile1Length of short pile2Calculating a preliminary settlement calculation value s' of the long and short pile composite foundation under the uniform pile arrangement type according to the total replacement rate m of the long and short pile areas;
and calculating the deviation between the preliminary sedimentation calculation value s' and the sedimentation allowable value [ s ], and selecting a corresponding parameter modification scheme according to the deviation value until the final sedimentation checking is passed.
As shown in fig. 2, the relationship between the long pile and short pile composite foundation bearing capacity and the long pile combination coefficient is obtained by the following calculation:
for the composite foundation with the total replacement rate of the area of the long pile and the short pile being m, when the long pile or the short pile is completely replaced, the bearing capacity is respectively shown in formulas (1) and (2):
in the formula: f. ofskp1The bearing capacity of the long pile composite foundation,fskp2The bearing capacity of the short pile composite foundation is provided; m is the total replacement rate of the long pile area and the short pile area; a. thep1The cross-sectional area of the pile body of the long pile, Ap2The cross section area of the pile body of the short pile is shown; ra1Characteristic value of bearing capacity of single pile, R, for long pilea2The characteristic value of the bearing capacity of the single short pile is obtained; lambda [ alpha ]1The bearing capacity of the long pile exerts coefficient, lambda2The bearing capacity of the short pile is given play to the coefficient; beta is the bearing capacity exertion coefficient of the soil between the piles; f. ofskThe characteristic value of the bearing capacity of the soil between the piles of the composite foundation after treatment.
When part of the foundation is replaced by long piles or short piles, the composite foundation is a long-short pile composite foundation, and the ratio of the replacement area of the long piles to the total replacement area is gamma1The ratio of the replacement area of the stub to the total replacement area is gamma2Then γ1+γ 21. At the same time, the area replacement rate m of the long pile can be obtained1＝mγ1Replacement rate m of area of stub1＝mγ2。
Defining the proportion of the replacement area as a combination coefficient, namely the combination coefficient of the long pile is gamma1The combination coefficient of the stub is gamma2。
Formula (1) multiplied by gamma1Plus equation (2) multiplied by gamma2Obtaining:
namely:
the formula (4) is a calculation formula of the bearing capacity of the long and short pile composite foundation. From the formula, it can be known that: the bearing capacity of the long-short pile composite foundation is obtained by linearly superposing the long-short pile composite foundation and the short-short pile composite foundation according to the proportion of the replacement area.
Specifically, in the most common long-short pile composite foundation, the replacement areas of the long pile and the short pile are equal, that is, the combination of the long-pile composite foundation and the short-pile composite foundationThe coefficients are all 0.5, i.e. gamma1＝γ2＝0.5。
Further, the design parameters of the long and short pile composite foundation are as follows: pile diameter d of long pile1Pile diameter d of short pile2(ii) a Pile spacing D1、D2(ii) a Length of long pile1Length of short pile2(ii) a Long pile area replacement rate m1Short pile area replacement rate m2. The replacement rate is calculated by the pile diameter and the pile spacing, so the design parameter can only take the replacement rate m of the long pile area1Short pile area replacement rate m2Length of long pile1And length of short pile2。
Considering that the long-pile and short-pile composite foundation is formed by overlapping the long-pile composite foundation and the short-pile composite foundation according to the combination coefficient, the design parameter can also be the combination coefficient gamma of the long pile1Total replacement rate of long and short pile area m and long pile length l1And length of short pile2。
Specifically, the composite foundation is usually constructed by arranging piles in a triangular or square shape, the distance between the piles is 3 d-6 d, d is the diameter of the pile, and the total replacement rate m of the long pile area and the short pile area ranges from 2.2% to 8.7% when the square pile arrangement is assumed.
When the square pile arrangement is assumed, the method for determining the pile length of the long pile and the short pile comprises the following steps:
preliminarily selecting two soil layers as supporting layers of the long pile and the short pile according to a geological survey report;
selecting the distances from the upper top surface and the lower top surface of the long pile holding layer to the pile top of the long pile as the upper and lower value limits of the length of the long pile;
and selecting the distances from the upper top surface and the lower top surface of the short pile holding layer to the short pile top as the upper and lower value limits of the short pile length.
The long and short pile composite foundation is divided into long and short piles with same replacement rate (gamma)10.5) and non-uniform pile distribution with different long and short pile replacement rates. When gamma is1When the number of the long piles is more than 0.5, the long piles are unevenly distributed, and when the number of the long piles is more than that of the short piles, the number of the short piles is gamma1When the number of the long piles is less than 0.5, the long piles are unevenly distributed, and the number of the long piles is less than that of the short piles.
Because the long-short pile composite foundation needs to meet the bearing capacity and settlement conditions, the settlement calculation is relatively complex, and the calculation expression is changed along with the change of the pile length and the replacement rate, the method of firstly designing according to the bearing capacity conditions and then checking the settlement conditions is adopted.
Specifically, the design is firstly carried out according to a uniformly distributed pile type, namely gamma1＝γ2When the area replacement rate is 0.5, only 3 variables of the area replacement rate m and the long pile length l exist1And length of short pile2And (4) carrying the formula (3) to obtain a bearing capacity expression. The required solution area replacement rate m and the length l of the long pile1And length of short pile2Specific values, to which an objective function is to be added, and engineering costs are selected as the objective function, i.e.
A＝m[k1γ1l1+k2γ2l2] (5)
In the formula: k is a radical of1Cost k for unit length of long pile2The construction cost of the unit length of the short pile is low. The computer program is programmed to solve the total replacement rate m of long and short pile areas and the length l of long pile when the construction cost is lowest1And length of short pile2The specific value.
The checking calculation of the settlement is divided into two steps, wherein the first step is preliminary checking calculation of the settlement. The settlement initial calculation value adopts the mode of superposition of long pile composite foundation settlement and short pile composite foundation settlement, namely
s′＝γ1s1+γ2s2 (6)
In the formula: s1For the settlement of a single-pile type composite foundation when the replacement area is entirely long piles, s2For the settlement of composite foundations of single pile type with the replacement area being entirely short piles, s1And s2The calculation of (2) is solved according to the existing technical specification of building foundation treatment.
The second step is the final checking calculation of sedimentation. And calculating the final calculated value s of the long and short pile composite foundation settlement according to the existing technical specification of building foundation treatment.
Specifically, the method for selecting the corresponding parameter modification scheme according to the deviation value comprises the following steps:
(a) if s' < [ s ]]And a deviation of bothIf the difference value is larger than the preset difference value, the proportion gamma of the replacement area of the long pile to the total replacement area is reduced1 Hold 11、l2Calculating the new total replacement rate m of the long pile and the short pile area by taking the bearing capacity as a limiting condition without changingnewAnd is based on mnewCalculating final calculated value s of sedimentation: if s < [ s ]]If so, ending the design; otherwise, the proportion gamma of the replacement area of the long pile to the total replacement area is increased1Until the requirements are met
(b) If s' < [ s ]]And the deviation between the two is not more than the preset difference value, and s is less than s]If so, ending the design; if s is not less than s]Increasing the pile length l of the long pile1Or increasing the length l of the short pile2Until the requirements are met;
(c) if s' ≧ s ], either of two modifications are employed:
the modification scheme I is as follows: proportion gamma of replacement area to total replacement area by adopting long piles1Protocol > 0.5, as shown in FIG. 4, calculate Settlement allowance s]Corresponding gamma1Maintaining the length of long pile1Length of short pile2Changing partial short piles into long piles with the total replacement rate m of the areas of the long piles and the short piles unchanged, if s is less than s]If so, ending the design; otherwise, increasing the proportion gamma of the replacement area of the long pile to the total replacement area1Or increasing the length l of long pile1Until the requirements are met;
the second modification scheme is that the proportion gamma of the replacement area of the long piles to the total replacement area is adopted1Scheme 0.5, as shown in fig. 5, s- γ1For decreasing function, if the settlement checking calculation is needed, the settlement s of the long pile composite foundation is decreased1The most obvious effect is that the pile length of the short pile is maintained unchanged, and the pile length of the long pile is increased until s is less than s]。
It should be noted that, step (a) belongs to the situation that settlement is relatively easy to satisfy, and can be designed into a non-uniform pile arrangement type with a long pile replacement rate smaller than a short pile replacement rate, that is, a gamma-ray pile arrangement type, based on the design concept of a long-short pile composite foundation1Scheme < 0.5. Other conditions are not changed, and only the proportion gamma of the replacement area of the long pile to the total replacement area is reduced1Although the settlement is reasonably designed, the bearing capacity does not meet the requirement, so the replacement area of the long pile is reducedRatio of total displacement area gamma1Meanwhile, the length l of the long pile should be adjusted1Length of short pile2And the total replacement rate m of the long pile area and the short pile area and the like to meet the bearing capacity condition.
Specifically, for design convenience, the proportion γ of the long pile replacement area to the total replacement area1The value of (a) can be statically selected according to the figure 3, and the long pile length l is kept1And length of short pile2Recalculating total replacement rate m of long and short piles according to bearing capacity conditions without changenew. Calculating the design parameter gamma1，mnew，l1，l2Performing final settlement checking calculation, and if the final settlement calculation value s is less than s]If yes, the calculation is finished; if not, increasing the proportion gamma of the replacement area of the long pile to the total replacement area1Until the requirements are met.
And in the second modification scheme, if the length of the long pile reaches the upper limit value and does not meet the requirement of the final settlement checking calculation, the length of the short pile is increased as shown in fig. 6 until the final settlement checking calculation meets the requirement.
Thirdly, when square pile arrangement is adopted, in order to prevent too few or too many long piles, the square unit formed by limiting 4 piles has at least 1 long pile or at most 3 long piles, namely the proportion gamma of the replacement area of the long piles to the total replacement area1The upper and lower limits of (a) are 0.25 and 0.75, respectively. If gamma is1And if the calculated value exceeds the limit value, taking the corresponding limit value.
Example two:
the present embodiment is based on a specific application scenario of the long and short pile composite foundation design method provided in the first embodiment, and the following embodiments are only used to more clearly illustrate the technical solution of the present invention, and the protection scope of the present invention is not limited thereby.
In a 16-storey high-rise house, 3 underground stories are built, the foundation is buried by 11.9m, the foundation is in the form of a raft, the length of the raft is 65m, and the width of the raft is 17.7 m; the underground water is 6.6m below the natural ground, the field stratum mainly comprises artificial filling soil, silty clay, clay silty soil, silty sand and fine medium sand of a fourth system flood-flushing accumulation cause, the bearing capacity characteristic value of the composite foundation after foundation treatment is not less than 310kPa, settlement is not more than 60mm, and the design is carried out by adopting a long-short pile composite foundation scheme.
The method comprises the following specific steps:
step 1:
the lower limit of the total replacement rate m of the area of the primarily selected composite foundation long and short piles is 0.022, and the upper limit is 0.087.
Selecting powdery clay as long pile supporting layer, and using top surface and bottom surface of powdery clay as upper and lower limits of long pile length, so that upper and lower limits of main pile length are respectively 10.5m and 17 m.
Selecting silty clay (r) as a bearing layer of the short pile, wherein the upper limit and the lower limit of the length of the short pile are respectively 8m and 10.5 m.
According to gamma1＝γ2The design is carried out under the condition of 0.5, the bearing capacity exertion coefficients of the long pile, the short pile and the soil among the piles are respectively 1.0, 0.8 and 1.0, and the bearing capacity obtained by the formula (3) is
Therefore the bearing capacity condition is
175ml1+140ml2+158m+160≥310
Assuming that the long and short piles are of one pile type, the construction cost per unit length is the same, the construction cost per unit length is 1, the minimum value of the construction cost A can be solved by programming to be 0.4427, and the corresponding m is 0.038, l1＝15.1，l2＝8.2。
Step 2:
according to the existing technical specification for building foundation treatment, for a single pile type composite foundation with a replacement rate of 0.038 and a pile length of 15.1m, within the calculated depth, the modulus equivalent value is 23.1MPa, the settlement coefficient is 0.24, and the final settlement is 24 mm.
Similarly, for a single pile type composite foundation with a replacement rate of 0.038 and a pile length of 8.2m, the modulus equivalent value within the calculated depth is 14.9MPa, the settlement coefficient is 0.4, and the final settlement is 62 mm.
The preliminary calculated value of the long and short pile composite foundation settlement can be calculated to be 43mm according to the formula (6).
This is the case for step (a) in one of the parameter modifications described in the examples, since the sedimentation is allowed to be 60 mm. According to the figure 3, the long pile combination coefficient gamma is obtained by calculation1Is 0.053 and is less than the combination coefficient gamma of the long pile1The lower limit value of (2) is actually 0.25, namely every 4 piles are long piles.
Keeping the length of the long pile and the short pile unchanged, taking the replacement rate of the short pile to be 3 times of that of the long pile, and calculating to obtain m according to the bearing capacity condition1＝0.011，m2＝0.033。
To m1＝0.011，m2＝0.033，l1＝15.1，l2And (3) performing final settlement calculation on the long and short pile composite foundation of 8.2, wherein the calculated modulus equivalent value is 18.3MPa, the settlement coefficient is 0.3, and the final calculated value of settlement is 38mm, so that the settlement requirement is met.
When the pile diameter is 500mm, the total replacement rate m is 0.044, when square pile arrangement is adopted, the pile spacing is calculated to be 2.1m, every four piles form a square unit, 3 short piles and 1 long pile are arranged, and the long pile and the short pile can adopt CFG piles.
Example three:
the embodiment of the invention provides a long and short pile composite foundation design device, which comprises a processor and a storage medium, wherein the processor is used for processing long piles and short piles;
the storage medium is used for storing instructions;
the processor is configured to operate in accordance with the instructions to perform the steps of the method of embodiment one.
Embodiments of the present invention also provide a computer-readable storage medium, on which a computer program is stored, where the computer program, when executed by a processor, implements the steps of the method according to one embodiment.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (8)
1. A long and short pile composite foundation design method is characterized by comprising the following steps:
preliminarily selecting the value ranges of the length of the long pile and the short pile and the total replacement rate m of the area of the long pile and the short pile;
according to the initial selection result, according to the design of uniformly distributing long and short piles, taking the bearing capacity of the long and short pile composite foundation as a limiting condition and the engineering cost as a target function, the corresponding long pile length l when the target function is minimum is obtained1Length of short pile2And the total replacement rate m of the long pile area and the short pile area;
according to the length l of the long pile1Length of short pile2Calculating a preliminary settlement calculation value s' of the long and short pile composite foundation under the uniform pile arrangement type according to the total replacement rate m of the long and short pile areas; the calculation formula of the preliminary settlement calculation value s' of the long and short pile composite foundation is as follows:
s′＝γ1s1+γ2s2
in the formula: s1For the settlement of a single-pile type composite foundation when the replacement area is entirely long piles, s2For settlement of single-pile type composite foundations when the replacement area is entirely short piles, gamma1The ratio of the replacement area of the long pile to the total replacement area is adopted; gamma ray2The proportion of the short pile replacement area to the total replacement area is adopted;
calculating the deviation between the preliminary sedimentation calculation value s' and the sedimentation allowable value [ s ], and selecting a corresponding parameter modification scheme according to the deviation value until the final sedimentation checking calculation is passed; the method for selecting the corresponding parameter modification scheme according to the deviation value comprises the following steps:
(a) if s' < [ s ]]And the deviation of the two is larger than the preset difference value, the proportion gamma of the replacement area of the long pile to the total replacement area is reduced1Keeping the length of the long pile1Length of short pile2Calculating the new total replacement rate m of the long pile and the short pile area by taking the bearing capacity of the long pile and the short pile composite foundation as a limiting condition without changingnewAnd is based on mnewCalculating final calculated value s of sedimentation: if s < [ s ]]If so, ending the design; otherwise, the proportion gamma of the replacement area of the long pile to the total replacement area is increased1Until the requirements are met;
(b) if s' < [ s ]]And the deviation between the two is not more than the preset difference value, and s is less than s]If so, ending the design; if s is not less than s]Increasing the pile length l of the long pile1Or increasing the length l of the short pile2Until the requirements are met;
(c) if s' ≧ s ], either of two modifications are employed:
the modification scheme I is as follows: proportion gamma of replacement area to total replacement area by adopting long piles1Protocol > 0.5, calculate Settlement allowance [ s ]]Corresponding gamma1If s < [ s ]]If so, ending the design; otherwise, increasing the proportion gamma of the replacement area of the long pile to the total replacement area1Or increasing the length l of long pile1Until the requirements are met;
the second modification scheme is that the proportion gamma of the replacement area of the long piles to the total replacement area is adopted1The scheme of 0.5 is that the length of the short pile is kept unchanged, and the length of the long pile is increased until s is less than s]。
2. The long and short pile composite foundation design method according to claim 1, wherein the value range of the total replacement rate m of the long and short pile area is 2.2% -8.7%.
3. The long and short pile composite foundation design method according to claim 1, wherein the method for determining the pile length of the long and short piles comprises:
preliminarily selecting two soil layers as supporting layers of the long pile and the short pile according to a geological survey report;
selecting the distances from the upper top surface and the lower top surface of the long pile holding layer to the pile top of the long pile as the upper and lower value limits of the length of the long pile;
and selecting the distances from the upper top surface and the lower top surface of the short pile holding layer to the short pile top as the upper and lower value limits of the short pile length.
4. A long and short pile composite foundation design method according to claim 1, wherein s is1And s2The calculation of (2) is solved according to the existing technical specification of building foundation treatment.
5. The long and short pile composite foundation design method according to claim 1, wherein in the second modification, if the length of the long pile reaches the upper limit value and does not meet the final settlement checking requirement, the length of the short pile is increased until the final settlement checking requirement is met.
6. A long and short pile composite foundation design method according to claim 1, wherein the ratio γ of the long pile replacement area to the total replacement area1The upper and lower limits of (1) are 0.25 and 0.75, respectively, if gamma is1And if the calculated value exceeds the limit value, taking the corresponding limit value.
7. A long and short pile composite foundation design device is characterized by comprising a processor and a storage medium;
the storage medium is used for storing instructions;
the processor is configured to operate in accordance with the instructions to perform the steps of the method according to any one of claims 1 to 6.
8. Computer-readable storage medium, on which a computer program is stored which, when being executed by a processor, carries out the steps of the method according to any one of claims 1 to 6.
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