CN114718105B - Pile foundation layout method and verification method for existing pile foundation condition - Google Patents
Pile foundation layout method and verification method for existing pile foundation condition Download PDFInfo
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Abstract
The invention provides a pile foundation layout method and a verification method thereof under the existing pile foundation condition. The pile foundation layout method is characterized in that four new piles B are laid around an unavailable existing pile foundation A at each L-shaped corner part at the outer side of a building in a quadrilateral manner, and the intersection points of two diagonal lines of the quadrilateral pass through the pile foundation A; three new piles B are arranged around the unavailable existing pile foundation C at each T-shaped intersection part of the shear wall of the building in a triangular shape, and the pile center of the pile foundation C is positioned in the triangular shape; two new piles B are symmetrically arranged on two sides of an unavailable existing pile foundation D at a line-shaped wall part of a shear wall of a building; the invention effectively avoids construction at the existing pile foundation position, ensures engineering quality, is particularly suitable for reinforcing the original pile foundation when the constructed pile foundation has defects, and judges whether pile distribution is reasonable or not by calculating whether the geometric centroid of the outer contour of the upper structure is coincident with the counterforce center of the pile group (including the original old pile with bearing capacity).
Description
Technical Field
The invention relates to the field of new geotechnical engineering, in particular to a pile foundation layout method and a verification method thereof applied to the condition that existing pile foundations exist in pile foundations.
Background
The pile foundation has the advantages of good integrity, high bearing capacity, small settlement, flexible structural arrangement and the like, and is widely used in structural design. Along with the improvement of the national foundation level, the urban planning is reasonably adjusted, a plurality of buildings are newly built on site after being dismantled, the original buildings are mostly used as pile foundations, the pile foundations are deeply buried in foundation soil, and if pile foundations are adopted in the newly built buildings, two problems are brought if the existence of the original pile foundations is ignored in foundation design, and the new buildings are treated according to general foundation soil: firstly, the construction difficulty is high, if a newly laid pile coincides with an original pile foundation, the pile digging process is actually a process of breaking reinforced concrete, and the quality of pile foundation pore-forming is difficult to ensure; and secondly, larger eccentric bending moment can be generated, even if the newly laid pile foundation is not overlapped with the original pile, the original pile foundation counter force still exists objectively, so that larger eccentric bending moment can be generated, larger settlement is generated on one side of the building with larger stress, and even the whole inclination of the building is caused.
In addition, due to the reasons of design, construction and the like, after the construction of part of pile foundations in a building is finished, the requirement cannot be met through detection, the bearing capacity required by an upper structure cannot be provided, the pile foundations can only be removed, but the original pile foundations are generally deep and exceed the elevation of the bottom of a foundation pit of a newly built building, foundation soil is disturbed by the removal, the stress of the newly laid pile foundations is changed, and the removal is difficult and high in cost, so that the removal is not feasible; if pile foundations are additionally arranged, the problem is that the most favorable position for arranging the pile foundations is occupied by the existing pile foundations, the pile foundations which are subjected to post-repair driving can only be arranged at the reserved positions of the original pile foundations, and if the pile foundations which are arranged at the original pile positions are all concrete pile foundations, pile driving can not be carried out on concrete, so that the problems of difficult construction and difficulty in guaranteeing the pile quality can be caused. Based on the reasons, how to lay the pile foundation under the condition that the existing pile foundation exists and how to evaluate whether the pile foundation is laid reasonably are problems to be solved.
Disclosure of Invention
The invention aims to provide a pile foundation layout method and a verification method thereof under the existing pile foundation condition, and the pile foundation layout method can effectively solve the problem that the favorable position is occupied by the existing pile foundation, avoid construction at the existing pile foundation position and ensure the engineering quality; the checking method can check whether the layout of the pile foundation is reasonable or not, and if not, the position of the pile foundation can be adjusted in time so as to avoid the problem that a large eccentric bending moment is generated in a building.
In order to achieve the technical purpose, the invention provides a pile foundation layout method used under the existing pile foundation condition, which is characterized in that: the layout method comprises the following steps:
(1) Core pulling detection is carried out on existing pile foundations in a building construction area, and all existing pile foundations with complete core samples in the existing pile foundations are determined to be available pile foundations, and existing pile foundations with incomplete core samples are determined to be unavailable pile foundations;
(2) And arranging new piles around the unavailable pile foundation in the following manner:
a. Four new piles B are arranged around the unavailable existing pile foundation A at each L-shaped corner part at the outer side of the building, pile center connecting lines of the four new piles B are quadrangles with mutually perpendicular diagonal lines, and intersection points of two diagonal lines of the quadrangles pass through the existing pile foundation A at the part;
b. Three new piles B are arranged around the unavailable existing pile foundation C at each T-shaped intersection part of the shear wall of the building, pile centers of the three new piles B are connected to form a triangle, and the pile centers of the existing pile foundation C are positioned in the triangle formed by the pile center connection of the three new piles B;
c. Two new piles B are symmetrically arranged on two sides of an existing pile foundation D which is unavailable at a straight wall part of the building shear wall, the two new piles B are symmetrically distributed below the shear wall by taking the existing pile foundation D as a center, or pile center connecting lines of the two new piles B pass through pile centers of the existing pile foundation D and are perpendicular to the shear wall.
The invention has the preferable technical scheme that: after the new pile is laid, finely adjusting the position of the newly laid pile foundation according to the condition of the adjacent pile foundations; and drawing a new and old pile foundation mixed layout chart in an AutoCAD software according to the actual size of a building by taking a millimeter as a unit.
The invention has the preferable technical scheme that: in the step a of the step (2), pile center connecting lines of four new piles B which are arranged around the unavailable existing pile foundation A at the L-shaped corner part are square.
The invention has the preferable technical scheme that: in the step (2), pile centers of three new piles B which are arranged around the unavailable existing pile foundation C at the T-shaped crossing part are connected to form an equilateral or isosceles triangle; the three new piles B are all positioned at the shear wall of the building, and the pile center of the existing pile foundation C is positioned at the midpoint of the bottom edge of an equilateral or isosceles triangle formed by connecting the pile centers of the three new piles B; or the new pile B with the vertex of the equilateral or isosceles triangle is positioned at the shear wall of the building, and the pile center of the existing pile foundation C is positioned at the geometric centroid of the equilateral or isosceles triangle formed by connecting the pile centers of the three new piles B.
The invention also provides a checking method for pile foundation layout under the existing pile foundation condition, which is characterized by checking the pile foundation layout method under the existing pile foundation condition, and comprises the following specific steps:
(1) Calculating geometric centroid coordinates (x 0,y0) of the newly built building; drawing an outer contour line of a new building according to the size of a new pile foundation mixed layout, taking an intersection point of extension lines of two outer lines which are mutually perpendicular in the new building as a coordinate origin O, dividing a closed range formed by the outer contour of the building into n rectangles, wherein the centroid of each rectangle is an intersection point of diagonal lines of the rectangle, the centroid coordinate of the ith rectangle is (x i,yi), the area of the ith rectangle is A i, multiplying the centroid abscissa x i of the ith rectangle with the area A i of the ith rectangle to obtain the area moment of the area of the ith rectangle to the coordinate longitudinal axis, accumulating the area moment of the n rectangles to the coordinate longitudinal axis to obtain the area moment of the area A of the outer contour of the whole new building to the coordinate longitudinal axis, and obtaining a formula ①:
Similarly, multiplying the centroid ordinate y i of the ith rectangle by the area A i of the centroid ordinate y i of the ith rectangle to obtain the area moment of the area of the ith rectangle to the coordinate transverse axis, and then accumulating the area moment of the n rectangles to the coordinate transverse axis to obtain the area moment of the area A of the outer contour of the whole new building to the coordinate transverse axis, and obtaining a formula ②:
X 0,y0 in the above formulas ① and ② are respectively the geometric centroid coordinates of the new building, and the geometric centroid coordinates (x 0,y0) of the new building are calculated by the area moment calculation formulas ① and ②, and the calculation formulas are as follows:
Wherein: (x i,yi) is the coordinates of each rectangular centroid of the segment relative to the origin of coordinates O;
a i is the area of the ith rectangle;
A is the sum of all subarea areas, namely the area of the outer contour of the whole newly-built building;
(2) Calculating the counter-force center coordinates (x 1,y1) of all piles after pile re-distribution; firstly, marking the geometric centroid coordinates (x 0,y0) of the new building calculated in the step (1) in an outline drawing of the new building, marking the geometric centroid coordinates as a point E, and carrying out the following calculation by taking the position of the point E as a coordinate origin; then overlapping the outer contour map of the new building with the mixed layout map of the new pile foundation to obtain the mixed layout map of the new pile foundation by taking the geometric centroid E of the new building as the origin of coordinates; according to the moment balance principle, the reaction force N i of the ith pile is multiplied by the pile center abscissa x i to obtain the moment of the reaction force N i of the ith pile on the coordinate longitudinal axis, then the moment of the reaction force of N piles on the coordinate longitudinal axis is accumulated to obtain the moment of the reaction force sum N of all piles on the coordinate longitudinal axis, and the formula ③ is obtained:
similarly, the reaction force N i of the ith pile is multiplied by the pile center ordinate y i to obtain the moment of the reaction force N i of the ith pile on the coordinate transverse axis, then the moment of the reaction force of N piles on the coordinate transverse axis is added, the value is equal to the moment of the sum of the reaction forces N of all piles on the coordinate transverse axis, and the formula ④ is obtained:
The reaction force centers (x 1,y1) of all piles after pile re-arrangement are calculated by the formulas ③ and ④, wherein the calculation formula is as follows:
Wherein: (x i,yi) is the coordinates of the core of the ith pile relative to the origin of coordinates E;
N i is the counter force of the ith pile, and the value of the counter force is equal to the standard value of the vertical bearing capacity of the single pile of the ith pile;
N is the counter force of all piles, and the value of the counter force is equal to the sum of the standard values of the vertical bearing capacity of the single piles of all piles;
(3) Marking the counter force center coordinates (x 1,y1) of all piles after pile re-distribution, which are obtained in the step (2), in a new and old pile mixing layout; when the counter-force centers (x 1,y1) of all piles are coincident or basically coincident with the geometric centroid coordinates E of the newly built building, namely |x 1 | < 500mm and |y 1 | < 500mm, the fact that the geometric center of the upper structure and the counter-force centers of all piles have no larger eccentricity and no larger eccentric bending moment occurs is indicated, and the new piles are reasonably distributed; when the I x 1 I is more than or equal to 500mm or the I y 1 I is more than or equal to 500mm, the geometric center of the upper structure and the counter-force center of all piles are indicated to have larger eccentric bending moment, and the position of a new pile is required to be adjusted.
The invention has the preferable technical scheme that: when the counter force center coordinates (x 1,y1) of all piles after pile re-arrangement are calculated in the step (2), all piles comprise available existing piles and newly arranged piles, when the ith pile is the available existing pile, the counter force N i is the vertical limit bearing capacity of the available existing pile, and the standard value of the vertical limit bearing capacity of the single pile provided in the original design drawing is directly taken or is determined through a field pile foundation bearing capacity test; when the ith pile is a newly arranged pile, the counterforce N i is the vertical ultimate bearing capacity of the newly arranged pile, and the vertical ultimate bearing capacity is calculated according to the following formula:
Quk＝uΣqsikli+qpkAp
q uk -vertical ultimate bearing capacity of single pile;
u- -pile body perimeter;
q sik -standard value of limiting side friction resistance of the ith layer of soil at the pile side;
l i -length of pile body in the ith layer of soil;
q pk - -the standard value of the limiting resistance;
A p - -pile end area.
The invention has the preferable technical scheme that: in the step (1), drawing an outer contour line of a newly built building in an AutoCAD software according to an actual size by taking millimeter as a unit, and moving a coordinate origin of AutoCAD to a coordinate origin O; the centroid of each rectangle is the intersection of its diagonals, and the coordinates (x i,yi) of the centroid are determined by AutoCAD software capture.
The invention has the preferable technical scheme that: the overlapping process of the outer contour map of the new building and the mixed layout map of the new pile foundation in the step (2) is to select three reference points in AutoCAD software so as to overlap the outer contour map of the new building and the mixed layout map of the new pile foundation and the old pile foundation; the coordinates (x i,yi) of the pile core of the ith pile relative to the coordinate origin E are obtained by moving the coordinate origin of AutoCAD to the point E and then capturing the pile core by utilizing AutoCAD software.
Judging whether the existing pile foundation can be utilized according to core pulling, wherein the judging process is to judge the integrity of a core sample through core pulling, judging whether a significant fracture exists in the extracted core sample or not, judging whether a cavity exists in the geological condition of the bottom of the pile foundation through core pulling, and judging that the cavity exists below the bottom of the pile foundation if the core sample cannot be extracted, wherein the existing pile foundation at the positions is an unavailable pile foundation; if the loose core is complete, the pile foundation is available, and the pile foundation is not needed to be newly added at the position when the pile is distributed; in the verification stage, the pile group reaction force centers are calculated by taking the reaction forces of the piles into account.
The beneficial effects of the invention are as follows:
(1) On the premise of meeting the bearing capacity requirement of the upper structure, different pile distribution forms are adopted at different positions, the pile is prevented from being overlapped with the original pile foundation at the positions, the pile foundations newly added at the periphery of the pile foundation bear the stress of the original pile together, and the problem of pile foundation distribution when the position of the favorable pile distribution is occupied is solved;
(2) By the pile distribution method, construction at the existing pile foundation position is effectively avoided, engineering quality is guaranteed, and the pile distribution method is particularly suitable for reinforcing the original pile foundation when the constructed pile foundation has defects.
(3) The invention judges whether pile distribution is reasonable by calculating whether the geometric centroid of the outline of the upper structure is coincident with the counterforce center of the pile group (including the original old pile with bearing capacity). If the pile is overlapped or basically overlapped, the pile distribution is reasonable; if the distance difference is large, pile distribution is unreasonable; the checking method can judge whether the layout of the pile foundation is reasonable or not, fully considers and utilizes the bearing capacity of the existing pile foundation, and avoids resource waste; the problem that the building generates larger eccentric bending moment due to the fact that the bearing capacity of the existing pile foundation is not considered is avoided, so that engineering accidents are caused.
Drawings
FIG. 1 is a schematic view of the novel pile layout at the L-shaped corner of the outside of a building according to the present invention;
FIG. 2 is a schematic view of a new pile layout at the T-shaped intersection of a shear wall of a building in accordance with the present invention;
FIG. 3 is a schematic diagram showing the layout of new piles symmetrically distributed below a shear wall in a straight wall part of the shear wall of a building;
FIG. 4 is a schematic view of the layout of new piles perpendicular to the shear wall at the in-line wall portion of the shear wall of the building according to the present invention;
FIG. 5 is a diagram of the location of the pile foundation in the embodiment;
FIG. 6 is a diagram of a hybrid arrangement of new and old pile foundations according to an embodiment;
FIG. 7 is a schematic view of rectangular segmentation of the outline of a building in an embodiment;
FIG. 8 is an exterior building outline labeled with geometric centers in an embodiment;
FIG. 9 is a schematic diagram of the coordinates established by taking the geometric centroid of the outline map of the building as the origin in the embodiment;
Fig. 10 is a schematic view of the outer contour of a building marked with pile group reaction centers in an embodiment;
FIG. 11 is a schematic diagram showing the overlapping of the new and old pile foundation mixing layout and the new building outline.
In the figure: e-geometric centroid of building outer contour, F-counter force center of pile group, G-building outer contour line.
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION
The invention is further illustrated below with reference to examples. The following technical solutions presented in the drawings are specific to embodiments of the present invention and are not intended to limit the scope of the claimed 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 invention provides a pile foundation layout method for the existing condition of pile foundation, which is characterized in that: the layout method comprises the following steps:
(1) Core pulling detection is carried out on existing pile foundations in a building construction area, and all existing pile foundations with complete core samples in the existing pile foundations are determined to be available pile foundations, and existing pile foundations with incomplete core samples are determined to be unavailable pile foundations;
(2) And arranging new piles around the unavailable pile foundation in the following manner:
a. Four new piles B are arranged around the unavailable existing pile foundation A at each L-shaped corner part on the outer side of the building, as shown in figure 1, pile center connecting lines of the four new piles B are quadrangles with mutually perpendicular diagonal lines, the optimal state is square, and two diagonal line intersecting points of the quadrangles pass through the existing pile foundation A at the part; called as a four sheep square bottle;
b. Three new piles B are arranged around the unavailable existing pile foundation C at each T-shaped intersection part of the shear wall of the building, as shown in figure 2, pile centers of the three new piles B are connected to form a triangle, and the pile centers of the existing pile foundation C are positioned in the triangle formed by the pile centers of the three new piles B, which is called as 'tripod standing'. The best state is that pile centers of three new piles B are connected to form an equilateral or isosceles triangle; there are two cases: one is that three new piles B are all positioned at the shear wall of the building, and the pile center of the existing pile foundation C is positioned at the midpoint of the bottom edge of an equilateral or isosceles triangle formed by connecting the pile centers of the three new piles B; the other condition is that a new pile B with the vertex of an equilateral or isosceles triangle is positioned at the shear wall of the building, and the pile center of the existing pile foundation C is positioned at the geometric centroid of the equilateral or isosceles triangle formed by connecting the pile centers of the three new piles B.
C. Two new piles B are symmetrically arranged on two sides of an unavailable existing pile foundation D at a horizontal wall part of a building shear wall, and as shown in figure 3, the two new piles B are symmetrically distributed below the shear wall with the existing pile foundation D as a center and are called as 'two cattle lifting bars'; or as shown in fig. 4, the pile centers of two new piles B are connected through the pile center of the existing pile foundation D and are vertical to the shear wall, and the pile center is called a shoulder pole; firstly, arranging new piles under the shear wall under the general condition, and if the existing piles of the shear wall are relatively dense and the new piles cannot be arranged, arranging the new piles in the direction perpendicular to the shear wall can be considered;
(3) After the new pile is laid, finely adjusting the position of the newly laid pile foundation according to the condition of the adjacent pile foundations; and drawing a new and old pile foundation mixed layout chart in an AutoCAD software according to the actual size of a building by taking a millimeter as a unit.
Example 1: the pile foundation laying method of the present invention is further described below by using a specific embodiment, in which a certain S-type building is taken as an example, the building occupies a floor area 387m 2, the height of the building above ground is 99.90m, and the total building area 11474.88m 2. The original vertical bearing body adopts a pile foundation and shear wall structure, and the pile diameter d=1000-2000 mm, as shown in fig. 5, is 51 foundation piles in total. The pile head foundation is characterized in that a bead-shaped karst cave exists below the pile end and the rock embedding depth of the original foundation pile after investigation, the requirement of the depth of a bearing layer below the pile end required by the original design cannot be met, the original pile foundation is required to be subjected to reinforcement design in order to ensure the safety of reconstructing the upper structure, and a pile raft foundation is required to be adopted; the method comprises the following specific steps:
(1) Firstly, performing on-site investigation aiming at the project, finding that 4 out of the original 51 piles are complete rock-socketed piles (like solid marked piles in fig. 5, the numbers are 4-18-32,4-18-11,4-18-13 and 4-18-21) to obtain available existing pile foundations, wherein the single pile vertical ultimate bearing capacity of the four existing piles is required to be considered in the later calculation, and beaded karst holes exist below the pile ends of the other 47 existing foundation piles to obtain unavailable existing pile foundations, and the single pile vertical ultimate bearing capacity is not required to be considered in the later calculation;
(2) And arranging new piles around the unavailable pile foundation in the following manner:
a. Four new piles are distributed around each corner (namely L-shaped corner) on the outer side of the building, wherein the existing pile foundations are unavailable (such as the positions with the numbers of 4-18-48,4-18-51,4-18-31,4-18-39,4-18-10 and the like in figure 5), pile centers of the four piles are connected into squares, the diagonal lines of the four piles are mutually perpendicular, and the piles pass through the pile centers of the original pile foundations, namely the pile centers of the four piles are called as 'four sheep square-shaped piles', and the new piles are distributed as shown in figure 6;
b. three new piles are arranged around the unavailable existing pile foundation (such as the positions of numbers 4-18-1,4-18-33,4-18-49,4-18-50 and the like in fig. 5) at the intersection of the shear walls of the building (namely, at the T-shaped corner), the pile centers of the original pile foundations are connected into an equilateral triangle, the pile centers of the original pile foundations are positioned at the middle point of one side of the pile foundations, and the new piles are arranged as shown in fig. 6;
c. Two new piles are arranged at unavailable existing pile foundations (such as positions with the numbers of 4-18-2,4-18-15,4-18-29 and the like in fig. 5) below a single-limb shear wall (namely, below a straight-line wall), the two newly arranged pile foundations are positioned below the shear wall with the original pile foundations as centers and symmetrically distributed under the shear wall, and the new piles are arranged as shown in fig. 6;
d. two new piles are arranged at the unavailable existing pile foundations (such as the positions of numbers 4-18-4,4-18-6 and the like in fig. 5) below the single-limb shear wall (below the straight-line wall), the connecting line of the newly arranged pile cores passes through the pile cores of the original pile foundation and is vertical to the shear wall, the pile cores are called as shoulder poles, and the new piles are arranged as shown in fig. 6;
(3) The positions of newly laid pile foundations are adjusted according to the adjacent pile foundation conditions to distinguish new piles and old piles, and a new pile foundation and old pile foundation mixed layout diagram is drawn in an AutoCAD software according to the actual size of a building in millimeter units, as shown in fig. 6, broken line circles in the diagram are old piles (with the numbers of 4-18-1 to 4-18-51), black solid line unfilled circles are new piles (with the numbers of B1 to B80), and filled circles are original available piles (with the numbers of Q1, Q2, Q3 and Q4).
Example 2: after the pile foundation layout in the embodiment 1 is completed, checking is performed on the laid pile foundations in the embodiment, wherein the concrete process is as follows:
(1) Calculating geometric centroid coordinates (x 0,y0) of the newly built building; firstly, drawing an outer contour line of a new building in an AutoCAD software according to an actual size by taking a millimeter as a unit, taking an intersection point of extension lines of two outer lines which are mutually perpendicular in the new building as a coordinate origin O, and moving the coordinate origin of AutoCAD to the position; then dividing a closed range formed by the outer contour of the building into 7 rectangles, numbering the rectangles in sequence, wherein the centroid of each rectangle is the intersection point of the diagonal lines of the rectangles as shown in fig. 7, and the coordinates (x i,yi) of the centroid are captured and determined by using AutoCAD software; the area of each rectangle is measured by the area measurement function of AutoCAD software. The area a of the closed range formed by the outer contour is equal to the sum of the areas of 7 rectangles, i.e., a= Σai; the area moment of the area of the ith rectangle to the vertical axis of the coordinate is calculated and determined by a formula A ixi, the area moment of the area of the ith rectangle to the horizontal axis of the coordinate is calculated and determined by a formula A iyi, and specific data and calculation results are shown in Table 1:
table 1 shows centroid coordinate calculation data for seven rectangular partitions
The centroid coordinate of the ith rectangle is (x i,yi), the area of the ith rectangle is A i, firstly, the centroid abscissa x i of the ith rectangle is multiplied by the area A i of the ith rectangle to obtain the area moment of the area of the ith rectangle to the coordinate longitudinal axis, then the area moment of the n rectangles to the coordinate longitudinal axis is accumulated to obtain the area moment of the area A of the outer contour of the whole new building to the coordinate longitudinal axis, and the formula ① is obtained:
Similarly, multiplying the centroid ordinate y i of the ith rectangle by the area A i of the centroid ordinate y i of the ith rectangle to obtain the area moment of the area of the ith rectangle to the coordinate transverse axis, and then accumulating the area moment of the n rectangles to the coordinate transverse axis to obtain the area moment of the area A of the outer contour of the whole new building to the coordinate transverse axis, and obtaining a formula ②:
X 0,y0 in the above formulas ① and ② are respectively the geometric centroid coordinates of the new building, and the geometric centroid coordinates (x 0,y0) of the new building are calculated by the area moment calculation formulas ① and ②, and the calculation formulas are as follows:
Wherein: (x i,yi) is the coordinates of each rectangular centroid of the segment relative to the origin of coordinates O;
a i is the area of the ith rectangle;
a is the sum of all the subarea areas, namely the area of the outer contour of the whole newly-built building.
The geometric centroid coordinates (x 0,y0) of the enclosed area enclosed by the outer contour of the building are calculated according to the above formula and the data in the table, and the calculation process is as follows:
The coordinates of the building outline geometric centroid E are thus obtained: (x 0,y0) = (14083,12432). The coordinates are marked in the building outline map as shown in fig. 8.
(2) Calculating the coordinates (x 1,y1) of the counterforce centers F of all piles after pile re-distribution; firstly, reestablishing a coordinate system at a geometric centroid E of the outer outline of the building, namely, the origin of coordinates is at a geometric centroid E point of the outer outline of the building calculated in the step (1), and the calculation diagram is shown in figure 9; the new and old pile foundation mix layout (fig. 6) of example 1 was then overlaid with the computational diagram (fig. 9) with the new building outer contour to obtain the new and old pile foundation mix layout (as shown in fig. 11) with the new building geometric centroid point E as the origin of coordinates. The origin of coordinates of the AutoCAD software is additionally moved to this point.
According to soil parameters obtained by on-site supplementary geological survey and according to a calculation formula (as follows) of a single pile vertical limit bearing capacity standard value in building pile foundation technical specification, calculating to obtain a single pile vertical limit bearing capacity standard value of a newly laid pile foundation; and referring to the original design drawing to obtain the standard value of the vertical ultimate bearing capacity of the single pile of the existing pile foundation.
Quk＝uΣqsikli+qpkAp
Q uk -vertical ultimate bearing capacity of single pile;
u- -pile body perimeter;
q sik -standard value of limiting side friction resistance of the ith layer of soil at the pile side;
l i -length of pile body in the ith layer of soil;
q pk - -the standard value of the limiting resistance;
A p - -pile end area.
Standard values N i of vertical ultimate bearing capacities of single piles with different pile diameters are shown in Table 2:
table 2 shows the standard values of the vertical ultimate bearing capacity of the single pile with different pile diameters of the new pile and the available existing pile
The pile center coordinates (X i,yi) of the ith pile are determined by capturing the pile center by AutoCAD software, the moment of the ith pile on the transverse axis is determined by calculating according to a formula N iyi, the moment of the ith pile on the longitudinal axis is determined by calculating according to a formula N ixi, and specific data and calculation results are shown in Table 3;
Table 3 moment calculation data for each new pile and available existing piles versus horizontal and vertical axes
According to the moment balance principle, the reaction force N i of the ith pile is multiplied by the pile center abscissa x i to obtain the moment of the reaction force N i of the ith pile on the coordinate longitudinal axis, then the moment of the reaction force of N piles on the coordinate longitudinal axis is accumulated to obtain the moment of the reaction force sum N of all piles on the coordinate longitudinal axis, and the formula ③ is obtained:
similarly, the reaction force N i of the ith pile is multiplied by the pile center ordinate y i to obtain the moment of the reaction force N i of the ith pile on the coordinate transverse axis, then the moment of the reaction force of N piles on the coordinate transverse axis is added, the value is equal to the moment of the sum of the reaction forces N of all piles on the coordinate transverse axis, and the formula ④ is obtained:
The reaction force center (x 1,y1) calculation formula of all piles after pile re-arrangement is obtained through formulas ③ and ④:
Wherein: (x i,yi) is the coordinates of the core of the ith pile relative to the origin of coordinates E;
ni is the counter force of the ith pile, and the value of the counter force is equal to the standard value of the vertical bearing capacity of the single pile of the ith pile;
N is the counter force of all piles, and the value of the counter force is equal to the sum of the standard values of the vertical bearing capacity of the single piles of all piles;
The reaction force center coordinates (x 1,y1) of all piles after newly laying piles are calculated according to the above formula and the data in table 3, and the calculation process is as follows:
(3) The calculation result shows that the counter-force center coordinates of all piles after the new pile arrangement are (x 1,y1) = (-251.2, -49.9), the unit is mm, and the geometric centroid E of the upper building outer contour and the counter-force center F of the pile group basically coincide due to the fact that (|x 1 | < 500mm and |y 1 | < 500 mm) are judged from numerical values; the reaction force center F of this pile group is shown in fig. 9, and fig. 10 is obtained. It can also be seen from the figure that the geometric centroid E of the building outer contour and the counterforce centre F of the pile group substantially coincide. Therefore, according to the pile distribution mode, the building cannot generate larger eccentric bending moment, and the piles are reasonably arranged.
The building is constructed aiming at the newly arranged pile foundation, after the construction of the building is completed, the settlement value of the building meets the standard requirement through subsequent observation, and the building is in good condition at present.
The foregoing description is of one embodiment of the invention and is thus not to be taken as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of the invention should be assessed as that of the appended claims.
Claims (5)
1. The pile foundation layout method for the existing pile foundation condition is characterized by comprising the following steps of: the layout method comprises the following steps:
S1, core pulling detection is carried out on existing pile foundations in a building construction area, and all existing pile foundations with complete core samples in the existing pile foundations are determined to be available pile foundations, and existing pile foundations with incomplete core samples are determined to be unavailable pile foundations;
s2, arranging new piles around the unavailable pile foundation in the following arrangement mode:
a. Four new piles B are arranged around the unavailable existing pile foundation A at each L-shaped corner part at the outer side of the building, pile center connecting lines of the four new piles B are quadrangles with mutually perpendicular diagonal lines, and intersection points of two diagonal lines of the quadrangles pass through the existing pile foundation A at the part; pile core connecting lines of four new piles B which are arranged around the unavailable existing pile foundation A at the L-shaped corner part are square;
b. Three new piles B are arranged around the unavailable existing pile foundation C at each T-shaped intersection part of the shear wall of the building, pile centers of the three new piles B are connected to form a triangle, and the pile centers of the existing pile foundation C are positioned in the triangle formed by the pile center connection of the three new piles B; pile core connecting lines of three new piles B which are arranged around the unavailable existing pile foundation C at the T-shaped intersection part form an equilateral or isosceles triangle; the three new piles B are all positioned at the shear wall of the building, and the pile center of the existing pile foundation C is positioned at the midpoint of the bottom edge of an equilateral or isosceles triangle formed by connecting the pile centers of the three new piles B; or the new pile B with the vertex of the equilateral or isosceles triangle is positioned at the shear wall of the building, and the pile center of the existing pile foundation C is positioned at the geometric centroid of the equilateral or isosceles triangle formed by connecting the pile centers of the three new piles B;
c. Two new piles B are symmetrically arranged on two sides of an unavailable existing pile foundation D at a straight wall part of a building shear wall, the two new piles B are symmetrically distributed below the shear wall by taking the existing pile foundation D as a center, or pile center connecting lines of the two new piles B pass through pile centers of the existing pile foundation D and are perpendicular to the shear wall;
s3, checking the laid pile foundation cloth, wherein the concrete steps are as follows:
(1) Calculating geometric centroid coordinates (x 0,y0) of the newly built building; drawing an outer contour line of a new building according to the size of a new pile foundation mixed layout, taking an intersection point of extension lines of two outer lines which are mutually perpendicular in the new building as a coordinate origin O, dividing a closed range formed by the outer contour of the building into n rectangles, wherein the centroid of each rectangle is an intersection point of diagonal lines of the rectangle, the centroid coordinate of the ith rectangle is (x i,yi), the area of the ith rectangle is A i, multiplying the centroid abscissa x i of the ith rectangle with the area A i of the ith rectangle to obtain the area moment of the area of the ith rectangle to the coordinate longitudinal axis, accumulating the area moment of the n rectangles to the coordinate longitudinal axis to obtain the area moment of the area A of the outer contour of the whole new building to the coordinate longitudinal axis, and obtaining a formula ①:
Similarly, multiplying the centroid ordinate y i of the ith rectangle by the area A i of the centroid ordinate y i of the ith rectangle to obtain the area moment of the area of the ith rectangle to the coordinate transverse axis, and then accumulating the area moment of the n rectangles to the coordinate transverse axis to obtain the area moment of the area A of the outer contour of the whole new building to the coordinate transverse axis, and obtaining a formula ②:
X 0,y0 in the above formulas ① and ② are respectively the geometric centroid coordinates of the new building, and the geometric centroid coordinates (x 0,y0) of the new building are calculated by the area moment calculation formulas ① and ②, and the calculation formulas are as follows:
Wherein: (x i,yi) is the coordinates of each rectangular centroid of the segment relative to the origin of coordinates O;
a i is the area of the ith rectangle;
A is the sum of all subarea areas, namely the area of the outer contour of the whole newly-built building;
(2) Calculating the counter-force center coordinates (x 1,y1) of all piles after pile re-distribution; firstly, marking the geometric centroid coordinates (x 0,y0) of the new building calculated in the step (1) in an outline drawing of the new building, marking the geometric centroid coordinates as a point E, and carrying out the following calculation by taking the position of the point E as a coordinate origin; then overlapping the outer contour map of the new building with the mixed layout map of the new pile foundation to obtain the mixed layout map of the new pile foundation by taking the geometric centroid E of the new building as the origin of coordinates; according to the moment balance principle, the reaction force N i of the ith pile is multiplied by the pile center abscissa x i to obtain the moment of the reaction force N i of the ith pile on the coordinate longitudinal axis, then the moment of the reaction force of N piles on the coordinate longitudinal axis is accumulated to obtain the moment of the reaction force sum N of all piles on the coordinate longitudinal axis, and the formula ③ is obtained:
similarly, the reaction force N i of the ith pile is multiplied by the pile center ordinate y i to obtain the moment of the reaction force N i of the ith pile on the coordinate transverse axis, then the moment of the reaction force of N piles on the coordinate transverse axis is added, the value is equal to the moment of the sum of the reaction forces N of all piles on the coordinate transverse axis, and the formula ④ is obtained:
The reaction force centers (x 1,y1) of all piles after pile re-arrangement are calculated by the formulas ③ and ④, wherein the calculation formula is as follows:
Wherein: (x i,yi) is the coordinates of the core of the ith pile relative to the origin of coordinates E;
N i is the counter force of the ith pile, and the value of the counter force is equal to the standard value of the vertical bearing capacity of the single pile of the ith pile;
N is the counter force of all piles, and the value of the counter force is equal to the sum of the standard values of the vertical bearing capacity of the single piles of all piles;
(3) Marking the counter force center coordinates (x 1,y1) of all piles after pile re-distribution, which are obtained in the step (2), in a new and old pile mixing layout; when the counter-force centers (x 1,y1) of all piles are coincident or basically coincident with the geometric centroid coordinates E of the newly built building, namely |x 1 | < 500mm and |y 1 | < 500mm, the fact that the geometric center of the upper structure and the counter-force centers of all piles have no larger eccentricity and no larger eccentric bending moment occurs is indicated, and the new piles are reasonably distributed; when the I x 1 I is more than or equal to 500mm or the I y 1 I is more than or equal to 500mm, the geometric center of the upper structure and the counter-force center of all piles are indicated to have larger eccentric bending moment, and the position of a new pile is required to be adjusted.
2. A pile foundation layout method for use in existing pile foundation conditions according to claim 1, wherein: after the new pile is laid, finely adjusting the position of the newly laid pile foundation according to the condition of the adjacent pile foundations; and drawing a new and old pile foundation mixed layout chart in an AutoCAD software according to the actual size of a building by taking a millimeter as a unit.
3. A pile foundation layout method for use in existing pile foundation conditions according to claim 1, wherein: s3, when the counter force center coordinates (x 1,y1) of all piles are calculated after pile re-arrangement, all piles comprise available existing piles and newly arranged piles, when the ith pile is the available existing pile, the counter force N i is the vertical limit bearing capacity of the available existing pile, and the standard value of the vertical limit bearing capacity of the single pile provided in the original design drawing is directly taken or is determined through a field pile foundation bearing capacity test; when the ith pile is a newly arranged pile, the counterforce N i is the vertical ultimate bearing capacity of the newly arranged pile, and the vertical ultimate bearing capacity is calculated according to the following formula:
Quk＝uΣqsikli+qpkAp
q uk -vertical ultimate bearing capacity of single pile;
u- -pile body perimeter;
q sik -standard value of limiting side friction resistance of the ith layer of soil at the pile side;
l i -length of pile body in the ith layer of soil;
q pk - -the standard value of the limiting resistance;
A p - -pile end area.
4. A pile foundation layout method for use in existing pile foundation conditions according to claim 1, wherein: in the step (1), the outer contour line of the newly built building is drawn according to the actual size by taking millimeter as a unit in AutoCAD software, and the coordinate origin of AutoCAD is moved to the position of the coordinate origin O; the centroid of each rectangle is the intersection of its diagonals, and the coordinates (x i,yi) of the centroid are determined by AutoCAD software capture.
5. A pile foundation layout method for use in existing pile foundation conditions according to claim 1, wherein: the step S3 is that three reference points are selected in AutoCAD software to overlap the outer contour map of the new building with the mixed layout map of the new pile foundation in the overlapping process of the outer contour map of the new building and the mixed layout map of the new pile foundation and the old pile foundation in the step (2); the coordinates (x i,yi) of the pile core of the ith pile relative to the coordinate origin E are obtained by moving the coordinate origin of AutoCAD to the point E and then capturing the pile core by utilizing AutoCAD software.
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| Title |
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| 既有桩再利用及新旧桩混合使用条件下的静压新桩施工控制工艺研究;姚建平;;建筑施工(第04期);第402-405页 * |
| 李镜培.黏土地基中新旧混合群桩承载和变形的非线性分析方法.2019,(第第12期期),第113-118页. * |
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