CN116204966A - Design method of sand pile composite foundation for open caisson construction - Google Patents
Design method of sand pile composite foundation for open caisson construction Download PDFInfo
- Publication number
- CN116204966A CN116204966A CN202310278358.XA CN202310278358A CN116204966A CN 116204966 A CN116204966 A CN 116204966A CN 202310278358 A CN202310278358 A CN 202310278358A CN 116204966 A CN116204966 A CN 116204966A
- Authority
- CN
- China
- Prior art keywords
- bearing capacity
- pile
- foundation
- open caisson
- sand
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
Images
Classifications
-
- G—PHYSICS
- G06—COMPUTING; CALCULATING OR COUNTING
- G06F—ELECTRIC DIGITAL DATA PROCESSING
- G06F30/00—Computer-aided design [CAD]
- G06F30/10—Geometric CAD
- G06F30/13—Architectural design, e.g. computer-aided architectural design [CAAD] related to design of buildings, bridges, landscapes, production plants or roads
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D15/00—Handling building or like materials for hydraulic engineering or foundations
- E02D15/02—Handling of bulk concrete specially for foundation or hydraulic engineering purposes
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D23/00—Caissons; Construction or placing of caissons
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D27/00—Foundations as substructures
- E02D27/10—Deep foundations
- E02D27/12—Pile foundations
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D33/00—Testing foundations or foundation structures
-
- E—FIXED CONSTRUCTIONS
- E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
- E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
- E02D37/00—Repair of damaged foundations or foundation structures
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A10/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE at coastal zones; at river basins
- Y02A10/11—Hard structures, e.g. dams, dykes or breakwaters
Landscapes
- Engineering & Computer Science (AREA)
- General Engineering & Computer Science (AREA)
- Structural Engineering (AREA)
- Civil Engineering (AREA)
- Paleontology (AREA)
- Mining & Mineral Resources (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Physics & Mathematics (AREA)
- Geometry (AREA)
- Theoretical Computer Science (AREA)
- General Physics & Mathematics (AREA)
- Computer Hardware Design (AREA)
- Mathematical Optimization (AREA)
- Pure & Applied Mathematics (AREA)
- Evolutionary Computation (AREA)
- Mathematical Analysis (AREA)
- Computational Mathematics (AREA)
- Architecture (AREA)
- Investigation Of Foundation Soil And Reinforcement Of Foundation Soil By Compacting Or Drainage (AREA)
Abstract
The invention relates to a design method of a sand pile composite foundation for open caisson construction. The method comprises the following steps: (a) dividing the high-rise construction stage of the open caisson into: the steel shell mounting and steel shell concrete pouring stage, the first time of heightening, the second time of heightening and the third time of heightening; (b) Respectively calculating the weight and the construction load of the open caisson corresponding to each high-rise connecting stage; calculating the stressed area of the foundation at the bottom surface of the open caisson; determining design parameters of the sand pile and the design parameters of the cushion layer; respectively calculating the consolidation degree of the foundation soil corresponding to each high-connection stage; (c) According to the parameters obtained in the step (b), respectively calculating pile top bearing capacity, cushion layer top bearing capacity and settlement corresponding to each high-stage; (d) And carrying out a site load test, wherein the difference value between the actual measurement value and the theoretical value of the pile top bearing capacity is less than or equal to 10%, and confirming that the pile top bearing capacity is qualified. The method saves the foundation reinforcement cost; the verification result is accurate, and the staged bearing capacity value and sedimentation quantity value can be conveniently used for guiding construction.
Description
Technical Field
The invention relates to the field of open caisson construction, in particular to a design method of a sand pile composite foundation for open caisson construction.
Background
The large land sinking well has a very wide application range, and the construction method comprises the steps of firstly manufacturing the sinking well on the ground, then sinking to a preset position, and generally dividing into 3 times of height connection and 3 times of sinking, wherein each time of height connection is divided into 2-4 times, each time of construction is about 30 days, and the total time of first time of height connection is 60-120 days. Because the open caisson is heavy, after the open caisson which is connected to high for the first time is manufactured, if the foundation is soft and cannot meet the requirement of the open caisson on the bearing capacity, the foundation is required to be reinforced. At present, the sand pile composite foundation reinforcement of open caisson engineering is designed by referring to the foundation reinforcement method of permanent engineering, and foundation soil consolidation reinforcement effect in the process of open caisson sectional elevation is not considered, so that the replacement rate of the sand piles is higher.
The existing design method of the sand pile composite foundation bearing capacity of the open caisson engineering is to calculate the bearing capacity of the foundation required by construction according to the total weight of the open caisson after the open caisson is connected with high, and calculate and draw parameters such as the diameter, the interval, the replacement rate, the thickness of a pile top filling layer and the like of the sand pile, and then measure the foundation bearing capacity according to the test method recommended in the building foundation treatment technical Specification. If the measured bearing capacity of the foundation is larger than the compressive stress required to be born by the foundation, judging that the construction requirement is met; if not, the design parameters of the composite foundation are modified to be tested again until the requirements are met.
The foundation bearing capacity determining method recommended by the building foundation treatment technical specification at present adopts bearing capacity and sedimentation double control, and generally has stricter deformation control requirements, so that the corresponding sedimentation value of the measured foundation ultimate bearing capacity is far less than the sedimentation control value of open caisson engineering construction. According to the standard test requirements, when the sedimentation value reaches 6% of the length of the edge of the load plate, the loading is stopped, and the soil body is considered to be damaged. If the test load plate size is 0.84m by 0.84m, the amount of settlement allowed by the load test is 54mm. However, the sand pile composite foundation of the open caisson engineering is usually a temporary engineering, and only the high stability of the open caisson is required to be met. In the process of connecting the height, the open caisson is allowed to sink greatly, and the key to be controlled is uneven sedimentation, so that the inclination of the open caisson structure or the exceeding of structural stress is avoided. The actual sand pile load test also shows that the foundation has great bearing potential after the deformation exceeds the settlement allowed by the specification.
Engineering practice shows that the open caisson has long construction period, usually 1 section is required to be connected up to 1 month, and 3 sections are required to be connected up to more than 3 months in duration. In the process of connecting the open caisson to the high, the dead weight load is gradually applied to the foundation, and the open caisson load is larger, and the foundation is obviously consolidated due to the fact that the sand piles have the drainage channel function, so that the bearing capacity of the foundation is higher than a design value without considering the consolidation effect. The consolidation effect has a non-negligible effect on the bearing capacity of the sand pile composite foundation.
The existing sand pile composite foundation bearing capacity design theory is that foundation bearing capacity is measured according to total weight calculation foundation compressive stress after the open caisson is connected with high, and then according to a recommended test method of building foundation treatment technical Specification, when the measured foundation bearing capacity is larger than the calculated foundation compressive stress, the foundation bearing capacity is judged to meet the requirement. On one hand, as the test method of building foundation treatment technical Specification has stricter condition of termination loading and lower test result, the foundation bearing capacity required by open caisson construction cannot be truly reflected; on the other hand, the consolidation effect of foundation soil during the high construction period of the open caisson is not considered, so that the foundation is reinforced more strongly.
In view of this, the present invention has been made.
Disclosure of Invention
The invention relates to a design method of a sand pile composite foundation for open caisson construction, which comprises the following steps:
(a) Dividing the high-connection construction stage of the open caisson into: the steel shell mounting and steel shell concrete pouring stage, the first time of heightening, the second time of heightening and the third time of heightening;
(b) Respectively calculating the weight and the construction load of the open caisson corresponding to the steel shell installation stage, the first height connection stage, the second height connection stage and the third height connection stage; calculating the stressed area of the foundation at the bottom surface of the open caisson; determining design parameters of the sand pile and the design parameters of the cushion layer; respectively calculating the consolidation degree of foundation soil corresponding to the steel shell installation stage, the first height connection stage, the second height connection stage and the third height connection stage;
(c) According to the parameters obtained in the step (b), respectively calculating pile top bearing capacity, bedding top bearing capacity and settlement corresponding to the steel shell installation and steel shell concrete pouring stage, the first height connection, the second height connection and the third height connection;
(d) And carrying out a site load test, wherein the difference value between the actual measurement value and the theoretical value of the pile top bearing capacity is less than or equal to 10%, and confirming that the pile top bearing capacity is qualified.
The design method of the sand pile composite foundation for open caisson construction saves the foundation reinforcement cost; the verification result is accurate, and the staged bearing capacity value and sedimentation quantity value can be conveniently used for guiding construction.
The invention also relates to a construction method of the open caisson, which comprises the design method of the sand pile composite foundation for open caisson construction.
Compared with the prior art, the invention has the beneficial effects that:
(1) The method for analyzing and determining the bearing capacity is calculated according to the steps of sectional construction, respectively judged according to the bearing capacity requirement of the foundation constructed in each step, and the settlement is given according to the construction stage; taking the foundation consolidation effect of the construction period of each stage into consideration; the ultimate bearing capacity is adopted instead of the allowable bearing capacity; the upper and lower limit allowable deviation ranges for the test verification are given.
(2) According to the sand pile composite foundation design method for open caisson construction, disclosed by the invention, the foundation bearing capacity is calculated in stages according to the construction stage by considering the consolidation effect, the accuracy is higher, the problem that building foundation treatment technical specifications are not applicable is corrected, and the foundation reinforcement cost can be saved; the invention has accurate verification result, and the staged bearing capacity value and sedimentation quantity value can be conveniently used for guiding construction.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is a plot of the load and settlement PS for scheme 2 provided by an embodiment of the present invention;
fig. 2 is a plot of loading and sedimentation PS for scheme 3 provided by an embodiment of the present invention.
Detailed Description
The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and detailed description, but it will be understood by those skilled in the art that the examples described below are some, but not all, examples of the present invention, and are intended to be illustrative of the present invention only and should not be construed as limiting the scope of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
The invention relates to a design method of a sand pile composite foundation for open caisson construction, which comprises the following steps:
(a) Dividing the high-connection construction stage of the open caisson into: the steel shell mounting and steel shell concrete pouring stage, the first time of heightening, the second time of heightening and the third time of heightening;
(b) Respectively calculating the weight and the construction load of the open caisson corresponding to the steel shell installation stage, the first height connection stage, the second height connection stage and the third height connection stage; calculating the stressed area of the foundation at the bottom surface of the open caisson; determining design parameters of the sand pile and the design parameters of the cushion layer; respectively calculating the consolidation degree of foundation soil corresponding to the steel shell installation stage, the first height connection stage, the second height connection stage and the third height connection stage;
(c) According to the parameters obtained in the step (b), respectively calculating pile top bearing capacity, bedding top bearing capacity and settlement corresponding to the steel shell installation and steel shell concrete pouring stage, the first height connection, the second height connection and the third height connection;
(d) And carrying out a site load test, wherein the difference value between the actual measurement value and the theoretical value of the pile top bearing capacity is less than or equal to 10%, and confirming that the pile top bearing capacity is qualified.
The design method of the sand pile composite foundation for open caisson construction saves the foundation reinforcement cost; the verification result is accurate, and the staged bearing capacity value and sedimentation quantity value can be conveniently used for guiding construction.
Preferably, the design parameters of the sand pile include: the characteristic value of the bearing capacity of a single pile of the sand pile, the distance between the sand piles and the treatment depth of the sand piles.
Preferably, the calculation formula of the single pile bearing capacity characteristic value of the sand pile is as follows:
wherein R is a The vertical bearing capacity characteristic value of the single pile is measured in kPa; u (u) p The circumference of the pile is m; q si The unit kPa is the side resistance characteristic value of the soil of the layer around the pile; l (L) pi The unit is m for the thickness of the ith layer of soil in the pile length range; alpha p Exerting a coefficient for pile end resistance; q p Is the characteristic value of pile end resistance; ap is the cross-sectional area of the pile in m 2 ；
Preferably, the calculation formula of the sand pile treatment depth is as follows:
wherein l pi The unit is m for the thickness of the ith layer of soil in the pile length range.
Preferably, the sand pile spacing is 0.9-1.4 m (e.g., 0.9m, 1.0m, 1.1m, 1.2m, 1.3m, or 1.4 m).
Preferably, the diameter of the sand pile is 0.6-0.8 m (e.g. 0.6m, 0.7m or 0.8 m).
Preferably, the sand pile has a length of 10 to 20m (e.g., 10m, 12m, 14m, 16m, 18m or 20 m).
Preferably, the replacement rate of the sand pile is 0.166-0.403 (e.g., 0.166, 0.18, 0.20, 0.24, 0.28, 0.32, 0.36, 0.40, or 0.403).
Preferably, the design parameters of the cushion layer include: the bottom surface of the cushion layer is compounded with the ultimate bearing capacity of the foundation and the replacement depth of the cushion layer.
Preferably, the calculation formula of the bearing capacity characteristic value of the composite foundation at the bottom surface of the cushion layer is as follows:
f skp =[1+m(n-1)]f sk ；
wherein f spk The unit is kPa for the characteristic value of the bearing capacity of the composite foundation on the bottom surface of the cushion layer; f (f) sk The unit is kPa for the characteristic value of the bearing capacity of the soil between the piles after treatment; n is the stress ratio of the composite foundation soil and is related to factors such as bearing capacity of single piles, bearing capacity of soil among piles and the like; m is the area substitution rate.
Preferably, the area substitution rate is calculated by the following formula:
m＝d 2 /d e 2 ；
wherein d is the average diameter of the pile body, and the unit is m; d, d e The equivalent circle diameter of the treatment foundation area shared by one pile is expressed as m.
Preferably, the composite foundation bearing capacity limit value is 2 times of the composite foundation bearing capacity characteristic value.
Preferably, the calculation formula of the cushion layer replacement depth is as follows:
wherein p is z The unit is kPa for the compressive stress value at the bottom surface of the cushion layer, namely the limit value of the bearing capacity of the composite foundation; b is the width of the bottom surface of the open caisson blade foot, and the unit is m; p is p k When the standard combination is corresponding to the action, the average compressive stress value of the bottom surface of the open caisson blade foot is expressed as kPa; z is the cushion layer filling depth, and the unit is m;
is the stress diffusion angle of the cushion layer.
Preferably, the pile top bearing capacity is 2 times of the characteristic value of the single pile bearing capacity of the sand pile.
Preferably, the calculation formula of the bearing capacity of the pad layer top is as follows:
wherein p is k The unit is kPa for the bearing capacity of the top of the cushion layer; p is p z The unit is kPa for the compressive stress value at the bottom surface of the cushion layer, namely the limit value of the bearing capacity of the composite foundation; b is the width of the bottom surface of the open caisson blade foot, and the unit is m; z is the cushion layer filling depth, and the unit is m;
is the stress diffusion angle of the cushion layer.
Preferably, the calculation formula of the sedimentation amount is:
wherein s is the settlement amount, and the unit is mm; s' is the foundation settlement calculated according to the layering sum method, and the unit is mm;
calculating an empirical coefficient for sedimentation; n is the number of soil layers divided in the foundation deformation calculation depth range; p is p 0 For additional pressure at the base surface corresponding to the quasi-permanent combination of actions in kPa; e (E) si The compression modulus of the ith layer of soil below the foundation bottom surface is expressed in MPa; z i 、z i-1 The unit of the distance from the bottom surface of the foundation to the bottom surface of the first layer soil and the i-1 layer soil is m; />
And calculating the average additional stress coefficient from the point to the ith layer of soil and the ith-1 layer of soil bottom surface for the foundation bottom surface.
Preferably, the stress area of the foundation of the bottom surface of the open caisson is calculated according to the stress diffusion angle, the thickness of the cushion layer and the width of the bottom of the open caisson.
Preferably, the degree of consolidation of the foundation soil is calculated using a modified sand-based method or a modified Gao Mujun medium method.
The formula for calculating the consolidation degree by adopting the modified Gao Mujun medium method is as follows:
wherein qi is the i-th and load average loading speed (kPa/d); alpha, beta can be taken as the value according to the table 1;
TABLE 1
In Table 1, C v Is vertical consolidation coefficient (m 2 /s)；
C r For radial consolidation coefficient (m 2 /s)；
n is the well diameter ratio, i.e. the effective drainage diameter d of the sand well e Diameter d of sand well w Ratio of;
d e is the effective drainage diameter (m) of the sand well, d when the sand well is square arranged on a plane e =1.128 d; when arranged in an equilateral triangle, d e ＝1.05d；
d is the interval (m) of sand wells;
H 1 、H 2 the depth of the sand well and the thickness (m) of the compressed soil layer below the sand well.
With the increase of the consolidation degree, the strength increase of the soil mass between the sand piles is calculated according to the following formula:
wherein Ut is the consolidation degree of a given point at a given time, and the average consolidation degree of a soil layer can be taken;
phi' is the effective internal friction angle of the soil;
Δσ is the normal compressive stress delta caused by a given out-of-point load.
The ratio of the strength increase value of the soil body between piles to the strength of the soil body between piles without considering the consolidation degree is the strength increase ratio alpha of the soil body between piles, thus the' f skp ＝[1+m(n-1)]f sk "middle f sk By f sk (1+α) instead. Namely, when the bearing capacity of the sand pile composite foundation is calculated, the bearing capacity of soil among piles is increased along with the increase of consolidation degree.
The invention also relates to a construction method of the open caisson, which comprises the design method of the sand pile composite foundation for open caisson construction.
Embodiments of the present invention will be described in detail below with reference to examples.
Example 1
The design method of the sand pile composite foundation for open caisson construction provided by the invention can be carried out according to the following steps:
the first step: calculating the weight of the open caisson which is connected with the high part at each time according to the concrete pouring construction stage, and adding the actual construction load;
and a second step of: calculating the stressed area of the foundation at the bottom surface of the open caisson, and calculating the foundation compressive stress of each time of high connection as the required foundation bearing capacity according to the stressed area;
and a third step of: determining design parameters of sand piles and cushion layers, and calculating bearing capacity and settlement of a foundation step by step, wherein the method mainly comprises the following steps:
1) The characteristic value of the single pile bearing capacity of the sand pile is calculated by adopting a passive soil pressure method, and the characteristic value is specifically as follows:
calculating the single pile bearing capacity of the sand pile, taking the diameter of the sand pile, the internal friction angle of the sand pile and the replacement rate of the sand pile, and calculating the expansion influence depth z of the sand pile; taking the consolidation non-drainage shear strength and the surface load of the soil between piles according to the geological survey parameters, and finally calculating to obtain the characteristic value of the single pile bearing capacity of the sand pile;
2) Calculating the ultimate bearing capacity of the composite foundation on the bottom surface of the gravel cushion layer, specifically:
the calculation formula of the bearing capacity characteristic value of the sand pile composite foundation comprises the following steps: [ f spk ]＝m[f pk ]+(1-m)[f sk ]Calculating to obtain a corresponding ultimate bearing capacity value;
3) Calculating the replacement depth of the gravel cushion, specifically:
calculating the limit value of the bearing capacity of the foundation at the edge tread of each stage and the limit bearing capacity of the top surface of the sand pile composite foundation according to the depth from the edge tread to the top surface of the composite foundation and the stress diffusion angle of the cushion material;
calculating according to the width of the well wall, the height of the cutting edge and the diffusion angle and the stress diffusion formula to obtain the gravel filling depth;
4) The sand pile spacing and the sand pile treatment depth are calculated, and the sand pile spacing and the sand pile treatment depth are specifically as follows:
calculating pile distance according to the diameter, arrangement form and replacement rate of the sand piles; the sand pile spacing under various pile diameters can be calculated for further selection and comparison;
the treatment depth of the sand pile is not only considered from the aspect of bearing capacity, but also the influence of the treatment range of the sand pile and the abrupt change of stratum settlement between lower silt layers on open caisson construction is considered, and the sand pile is required to penetrate through a silt clay layer generally;
5) Calculating the consolidation degree by adopting a modified sand-based method or a modified Gao Mujun medium method;
6) Summarizing the design value of pile top bearing capacity, the design value of cushion layer top bearing capacity and the sedimentation value of each stage, and respectively judging whether the design value of pile top composite bearing capacity and cushion layer top bearing capacity of each stage meets the bearing capacity value required by construction;
fourth step: according to the test method of building foundation treatment technical Specification, carrying out field load test, and confirming qualification when the actual measurement value and the theoretical value of pile top bearing capacity differ by not more than 10%; and when the parameters are exceeded, the parameters are adjusted to carry out the test again.
Experimental example
1. Engineering overview
The length and width of the foundation of the north anchorage open caisson are 75m and 70m respectively, the elevation of the top surface of the foundation is +3.50m, the elevation of the bottom surface of the foundation is-53.50 m, and the height of the open caisson is 57m, which is divided into 11 sections. Section 1 is a steel shell concrete structure, and the height is 8m; the sections 2 to 11 are reinforced concrete structures, wherein the height of the section 2 is 6m, the heights of the sections 3 and 4 are 4m, the heights of the sections 5, 6, 9 and 10 are 4.5m, the heights of the sections 7 and 8 are 5m, and the heights of the section 11 are 7m. The well cover of the open caisson is 7m thick, and the concrete of the back cover is 11m thick.
The well wall thickness of the open caisson standard section (section 3 to section 10) is 2.2m, the partition wall thickness is 1.5m, 36 rectangular well bores are arranged in the middle, the standard size of the well bores is 10.5mx9.7m, wherein 6 well bores at the rear end are filled with C20 plain concrete, and 30 well bores at the front end are filled with clear water. The height of the edge foot of the open caisson is 2.2m, the tread width of the edge foot is 0.2m, the elevation of the bottom of the partition wall is the same as that of the edge foot, the chamfer height of the bottom of the partition wall is 2.2m, the top width is 1.3m, and the bottom width is 0.5m.
The foundation is reinforced by adopting a sand pile composite foundation. The open caisson is constructed for 22 meters in total before 4 sections are first sunk, the weights of 1-4 sections are 28380t, 33610t, 16930t and 16930t respectively, the construction load is 2000t, and the total weight reaches 95890t. The construction period of 1-4 sections is 21 days, 35 days, 16 days and 16 days respectively.
The stratum in the project area is relatively uniform, the surface layer 11m is about silt powdery clay, and the bearing capacity is relatively poor. The main physical and mechanical parameters of each stratum are shown in table 1.
Table 1 foundation load bearing characteristics table
3 sand pile composite foundation schemes are planned, and parameters are respectively as follows:
scheme 1 sand pile length 16m, diameter 0.6m, spacing 0.9m, replacement 0.403; scheme 2 pile length 16m, diameter 0.6m, spacing 1.2m, replacement 0.227; scheme 3 sand pile length 16m, diameter 0.6m, spacing 1.4m, replacement 0.166. The calculation results are shown in tables 2, 3 and 4.
Table 2 scheme 1 calculation of the multiple high bearing capacity of the open caisson composite foundation
Table 3 scheme 2 calculation of the multiple high bearing capacity of the open caisson composite foundation
Table 4 scheme 3 calculation of the multiple high bearing capacity of the open caisson composite foundation
Load tests, load and settlement PS graphs 1 and 2 are carried out on sand pile composite foundation reinforcement of project schemes 2 and 3 of experimental calculation examples.
The PS graph is shown by a load test: the PS load curve of the pile spacing of 1.2m is steeply reduced when 287Kpa, and the PS load curve is very high in coincidence with a calculated value 285 Kpa; the PS load curve for 1.4m pile spacing showed a steep drop at 242Kpa, with a deviation of about 10% from the calculated value of 270Kpa, which was substantially accurate.
The supporting area is the contact area of the open caisson and the foundation.
The dead weight load is the weight of the open caisson structure.
The calculated compressive stress is: (dead load + construction load)/support area.
The calculation process at consolidation is not considered: 1. and calculating the bearing capacity of the sand pile composite foundation. 2. The allowable bearing capacity at the top of the mat is calculated. 3. And calculating the compressive stress and calculating the actual bearing load of the sand pile composite foundation. 4. And calculating the settlement of the sand pile composite foundation according to the calculation result of the actual bearing load of the sand pile composite foundation.
The calculation process at consolidation is considered: 1. calculating the soil consolidation degree between piles according to the working condition of the repeated height connection; 2. and calculating the soil strength increment value between piles according to the soil consolidation degree between piles. 3. And calculating the bearing capacity of the sand pile composite foundation. 4. The allowable bearing capacity at the top of the mat is calculated. 5. And calculating the actual bearing load of the sand pile composite foundation according to the calculated compressive stress. 6. And calculating the settlement of the sand pile composite foundation according to the calculation result of the actual bearing load of the sand pile composite foundation. And the settlement amount in the layering and high-pressure connection process is calculated by considering the influence of the consolidation degree.
While the invention has been illustrated and described with reference to specific embodiments, it is to be understood that the above embodiments are merely illustrative of the technical aspects of the invention and not restrictive thereof; those of ordinary skill in the art will appreciate that: modifications may be made to the technical solutions described in the foregoing embodiments, or equivalents may be substituted for some or all of the technical features thereof, without departing from the spirit and scope of the present invention; such modifications and substitutions do not depart from the spirit of the corresponding technical solutions; it is therefore intended to cover in the appended claims all such alternatives and modifications as fall within the scope of the invention.
Claims (10)
1. The design method of the sand pile composite foundation for open caisson construction is characterized by comprising the following steps:
(a) Dividing the high-connection construction stage of the open caisson into: the steel shell mounting and steel shell concrete pouring stage, the first time of heightening, the second time of heightening and the third time of heightening;
(b) Respectively calculating the weight and the construction load of the open caisson corresponding to the steel shell installation stage, the first height connection stage, the second height connection stage and the third height connection stage; calculating the stressed area of the foundation at the bottom surface of the open caisson; determining design parameters of the sand pile and the design parameters of the cushion layer; respectively calculating the consolidation degree of foundation soil corresponding to the steel shell installation stage, the first height connection stage, the second height connection stage and the third height connection stage;
(c) According to the parameters obtained in the step (b), respectively calculating pile top bearing capacity, bedding top bearing capacity and settlement corresponding to the steel shell installation and steel shell concrete pouring stage, the first height connection, the second height connection and the third height connection;
(d) And carrying out a site load test, wherein the difference value between the actual measurement value and the theoretical value of the pile top bearing capacity is less than or equal to 10%, and confirming that the pile top bearing capacity is qualified.
2. The method for designing a sand pile composite foundation for open caisson construction according to claim 1, wherein the design parameters of the sand pile include: the characteristic value of the bearing capacity of a single pile of the sand pile, the spacing between the sand piles and the treatment depth of the sand piles;
preferably, the calculation formula of the single pile bearing capacity characteristic value of the sand pile is as follows:
wherein R is a The vertical bearing capacity characteristic value of the single pile is measured in kPa; u (u) p The circumference of the pile is m; q si The unit kPa is the side resistance characteristic value of the soil of the layer around the pile; l (L) pi The unit is m for the thickness of the ith layer of soil in the pile length range; alpha p Exerting a coefficient for pile end resistance; q p Is the characteristic value of pile end resistance; ap is the cross-sectional area of the pile in m 2 ；
Preferably, the calculation formula of the sand pile treatment depth is as follows:
wherein l pi The unit is m for the thickness of the ith layer of soil in the pile length range.
3. The method for designing a sand pile composite foundation for open caisson construction according to claim 2, wherein the sand pile spacing is 0.9-1.4 m;
preferably, the diameter of the sand pile is 0.6-0.8 m;
preferably, the length of the sand pile is 10-20 m;
preferably, the replacement rate of the sand pile is 0.166-0.403.
4. The method for designing a sand pile composite foundation for open caisson construction according to claim 1, wherein the design parameters of the cushion layer include: the bottom surface of the cushion layer is compounded with the ultimate bearing capacity of the foundation and the replacement depth of the cushion layer;
preferably, the calculation formula of the bearing capacity characteristic value of the composite foundation at the bottom surface of the cushion layer is as follows:
f skp ＝[1+m(n-1)]f sk ；
wherein f spk The unit is kPa for the characteristic value of the bearing capacity of the composite foundation on the bottom surface of the cushion layer; f (f) sk The unit is kPa for the characteristic value of the bearing capacity of the soil between the piles after treatment; n is the stress ratio of the composite foundation soil and is related to the bearing capacity of single piles and the bearing capacity of soil among piles; m is the area replacement rate;
preferably, the area substitution rate is calculated by the following formula:
m＝d 2 /d e 2 ；
wherein d is the average diameter of the pile body, and the unit is m; d, d e The equivalent circle diameter of the foundation area to be processed is shared by one pile, and the unit is m;
preferably, the limit value of the bearing capacity of the composite foundation is 2 times of the characteristic value of the bearing capacity of the composite foundation;
preferably, the calculation formula of the cushion layer replacement depth is as follows:
wherein p is z The unit is kPa for the compressive stress value at the bottom surface of the cushion layer, namely the limit value of the bearing capacity of the composite foundation; b is the width of the bottom surface of the open caisson blade foot, and the unit is m; p is p k To correspond to doingWhen the standard combination is used, the average compressive stress value of the bottom surface of the open caisson blade foot is measured in kPa; z is the cushion layer filling depth, and the unit is m;
is the stress diffusion angle of the cushion layer.
5. The method for designing a sand pile composite foundation for open caisson construction according to claim 1, wherein the pile top bearing capacity is 2 times of the characteristic value of the single pile bearing capacity of the sand pile.
6. The method for designing a sand pile composite foundation for open caisson construction according to claim 1, wherein the calculation formula of the bearing capacity of the cushion layer top is:
wherein p is k The unit is kPa for the bearing capacity of the top of the cushion layer; p is p z The unit is kPa for the compressive stress value at the bottom surface of the cushion layer, namely the limit value of the bearing capacity of the composite foundation; b is the width of the bottom surface of the open caisson blade foot, and the unit is m; z is the cushion layer filling depth, and the unit is m;
is the stress diffusion angle of the cushion layer.
7. The method for designing a sand pile composite foundation for open caisson construction according to claim 1, wherein the calculation formula of the settlement amount is:
wherein s is the settlement amount, and the unit is mm; s' is the foundation settlement calculated according to the layering sum method, and the unit is mm;
calculating an empirical coefficient for sedimentation; n is the number of soil layers divided in the foundation deformation calculation depth range; p is p 0 For additional pressure at the base surface corresponding to the quasi-permanent combination of actions in kPa; e (E) si The compression modulus of the ith layer of soil below the foundation bottom surface is expressed in MPa; z i 、z i-1 The unit of the distance from the bottom surface of the foundation to the bottom surface of the first layer soil and the i-1 layer soil is m; />
And calculating the average additional stress coefficient from the point to the ith layer of soil and the ith-1 layer of soil bottom surface for the foundation bottom surface.
8. The method for designing a sand pile composite foundation for open caisson construction according to claim 1, wherein the stress area of the open caisson bottom foundation is calculated according to the stress spread angle, the cushion layer thickness and the open caisson bottom width.
9. The method for designing a sand pile composite foundation for open caisson construction according to claim 1, wherein the consolidation degree of the foundation soil is calculated by adopting a modified sand foundation method or a modified Gao Mujun medium method.
10. A construction method of an open caisson, characterized by comprising the method for designing a sand pile composite foundation for open caisson construction according to any one of claims 1 to 9.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310278358.XA CN116204966A (en) | 2023-03-20 | 2023-03-20 | Design method of sand pile composite foundation for open caisson construction |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310278358.XA CN116204966A (en) | 2023-03-20 | 2023-03-20 | Design method of sand pile composite foundation for open caisson construction |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN116204966A true CN116204966A (en) | 2023-06-02 |
Family
ID=86517367
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202310278358.XA Pending CN116204966A (en) | 2023-03-20 | 2023-03-20 | Design method of sand pile composite foundation for open caisson construction |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN116204966A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116861531A (en) * | 2023-07-18 | 2023-10-10 | 中国电建集团华东勘测设计研究院有限公司 | CPT-based coral sand stratum pile foundation vertical limit bearing capacity calculation method |
-
2023
- 2023-03-20 CN CN202310278358.XA patent/CN116204966A/en active Pending
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116861531A (en) * | 2023-07-18 | 2023-10-10 | 中国电建集团华东勘测设计研究院有限公司 | CPT-based coral sand stratum pile foundation vertical limit bearing capacity calculation method |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Lv et al. | Field tests on bearing characteristics of X-section pile composite foundation | |
| CN116204966A (en) | Design method of sand pile composite foundation for open caisson construction | |
| Sakr et al. | Behavior of grouted single screw piles under inclined tensile loads in sand | |
| CN110761264A (en) | Secondary dynamic compaction gravel replacement and reinforcement method for coastal sludge soft soil foundation | |
| Moghadam et al. | Experimental study on the performance of plate anchor retaining walls | |
| CN111021440A (en) | CPT integrated geotechnical packaging granular pile indoor model test device and method | |
| Ng et al. | Field studies of well-instrumented barrette in Hong Kong | |
| CN112267450B (en) | Deep slab load in-situ test method for ultra-thick layer backfill soil | |
| Kim et al. | Comparison of bearing capacity characteristics of sand and gravel compaction pile treated ground | |
| Neely | Bearing capacity of expanded-base piles in sand | |
| Rao et al. | Behavior of vertical piles embedded in reinforced sand under pullout oblique loads | |
| CN101280565A (en) | Horizontal top pipe ground treatment construction method | |
| Cui | Nondestructive controllable grouting: a novel method to correct deviation of building foundation | |
| Lundskog | Large-scale testing of reinforced lightweight cellular concrete backfill for mse walls | |
| JP3678828B2 (en) | Prevention method of ground liquefaction directly under the structure | |
| Salamatpoor et al. | Mitigating the uneven settlement of nearby strip footings on loose saturated sand using concrete pedestals: A model test study | |
| Mahdi et al. | Experimental and Numerical Study on the Winged Pile-Soil Interaction under Lateral Loads | |
| Won et al. | A study of the deformation of flexible pipes buried under model reinforced sand | |
| Yoo et al. | Full-scale behavior of a surface loaded geosynthetic reinforced tiered segmental retaining wall | |
| Mansur et al. | Pile-Loading Tests, Morganza Floodway Control Structure | |
| Murao et al. | PROGRESSIVE FAILURE OF UNSATURATED FILL SLOPECAUSED BY CUMULATIVE DAMAGE UNDER SEEPAGE SURFACE | |
| Al-Neami et al. | The influence of pile groups configuration on its stability in dry sand under lateral loads | |
| CN108647424B (en) | Method for determining tensile resistance of vertical geogrid of anti-uplift composite reinforced pile | |
| CN107435345A (en) | Using the method for stress spread model prediction overlength Settlement of Pile Groups amount | |
| Strassburg | Influence of Relative Compaction on Passive Resistance of Abutments with Mechanically Stabilized Earth (MSE) Wingwalls |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |