A calculation method for adding precise anchor rod static pressure pile to share load of existing foundation

Abstract

The present application relates to the technical field of load calculation, in particular to a calculation method for sharing load of existing foundation by newly added accurate anchor rod static pile, which comprises the following steps: obtaining vertical load of existing foundation based on structural load of existing foundation and increased load which needs to be increased by reinforcement; determining load required to be borne by existing foundation and anchor rod static pile cooperating with existing foundation according to vertical load of existing foundation; calculating pile number of anchor rod static pile which can bear the load according to load allocated to anchor rod static pile; planning pile hole position of each anchor rod static pile on existing foundation after obtaining pile number of anchor rod static pile; determining size of newly added concrete pile cap after selecting pile hole position; preliminarily determining thickness of newly added concrete pile cap; and selecting thickness of newly added concrete pile cap after checking and calculating of angle pile to pile cap.

Description

Technical Field

[0001] This invention relates to the field of load calculation technology, specifically to a method for calculating the load of existing foundations shared by newly added precise anchor static pressure piles. Background Technology

[0002] With the continuous advancement of urban renewal, housing has shifted from an era of incremental growth to an era of existing stock. A large number of existing buildings are facing problems such as changes in their functions, extended service life, and insufficient load-bearing capacity. During long-term use, due to the increase in live load caused by functional changes, settlement of the foundation soil, and changes in groundwater levels, these buildings often exhibit varying degrees of insufficient foundation and foundation bearing capacity, uneven settlement, and other phenomena, which seriously affect the safety of the buildings. Therefore, reinforcing the foundation of buildings to ensure the safety and stability of their structures has become an important research direction in the field of building renovation.

[0003] Existing foundation reinforcement technologies include foundation underpinning, grouting, cross-section enlargement, and foundation deepening. However, these technologies have limitations in congested old urban areas, such as unfriendly construction environment, complex procedures, long construction period, and certain safety hazards. With the development of construction technology, new reinforcement methods such as anchor static pressure piles, high-performance grouting materials, and intelligent monitoring technology have been gradually applied to the field of foundation reinforcement, effectively improving reinforcement effect and construction efficiency. However, the current load-sharing reinforcement method using anchor static pressure piles can only determine the load value shared by the static pressure piles during the pile sealing stage, and cannot accurately calculate the amount of load that the anchor static pressure piles need to bear in advance. Therefore, a method for calculating the load of existing foundations shared by newly added precise anchor static pressure piles is proposed. Summary of the Invention

[0004] In order to solve the technical problems existing in the prior art, the present invention provides a method for calculating the load of existing foundations to be shared by newly added precise anchor static pressure piles.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a method for calculating the load of existing foundations shared by newly added precise anchor static pressure piles, comprising the following steps:

[0006] Step S1: Based on the existing structural load, and considering the additional load that needs to be added through reinforcement, The vertical load on the existing foundation is obtained. ;

[0007] Step S2, based on the vertical load on the existing foundation Determine the load that the anchor static pressure piles must bear in conjunction with the existing foundation. Based on the load allocated to the anchor static pressure piles, calculate the number of anchor static pressure piles required to bear that load. ;

[0008] Step S3, after obtaining the number of anchor rod static piles , the pile hole positions of each anchor rod static pile are planned on the existing foundation, after selecting the pile hole positions, the length and width dimensions of the new concrete pile cap are determined on the basis of ensuring that the distance between the outer edge of the anchor rod static pile and the edge of the new concrete pile cap is 150mm;

[0009] Step S4, the thickness of the new concrete pile cap is preliminarily determined according to the stress requirement of the designed anchor rod static pile , the thickness of the new concrete pile cap is selected after the angle pile against the pile cap punching shear checking calculation is passed ;

[0010] Calculate the pile length of the anchor rod static pile , the sum of the depth of the anchor rod static pile extending into the stratum to reach the bearing stratum and the depth of the anchor rod static pile extending into the new concrete pile cap is the pile length of the anchor rod static pile .

[0011] Preferably, in the step S1, the structural load of the existing foundation includes the dead weight of the existing foundation and the original bearing load, and the calculation formula of the vertical load borne by the existing foundation is:

[0012]

[0013] In the formula, is the increased load that needs to be increased by reinforcement.

[0014] Preferably, in the step S2, the calculation formula of the number of anchor rod static piles is:

[0015]

[0016] In the formula, is the vertical ultimate bearing capacity of a single pile of the anchor rod static pile, is the load required to be borne by the anchor rod static pile;

[0017] The calculation formula of the load required to be borne by the anchor rod static pile is:

[0018]

[0019] In the formula, is the vertical bearing capacity of the foundation bearing stratum, is the influence reduction coefficient of different construction processes of the static pile on the bearing capacity of the bearing stratum of the existing foundation, The value range is referred to in “Technical Code for Reinforcement of Existing Building Foundation”.​ the vertical load borne by the existing foundation, the dead weight of the new concrete pile cap, the bottom surface area of the existing foundation;

[0020] the vertical ultimate bearing capacity of the anchor rod static pressure pile is calculated by the formula:

[0021]

[0022] in which, the ultimate side friction resistance of the anchor rod static pressure pile, the ultimate end resistance of the anchor rod static pressure pile.

[0023] Preferably, the ultimate side friction resistance of the anchor rod static pressure pile is calculated by the formula:

[0024]

[0025] in which, the perimeter of the anchor rod static pressure pile, the thickness of the anchor rod static pressure pile extending into each stratum, the side friction resistance of each stratum;

[0026] the ultimate end resistance of the anchor rod static pressure pile is calculated by the formula:

[0027]

[0028] in which, the area of the end of the anchor rod static pressure pile, the end resistance of the stratum in which the end of the anchor rod static pressure pile is located.

[0029] Preferably, in the step S3, the pile holes are located within the effective cross section of the existing foundation, the pile holes are symmetrically distributed, the center of the pile hole group coincides with the center of gravity of the existing foundation, and the distance between adjacent pile holes is greater than three times the diameter of the anchor rod static pressure pile .

[0030] Preferably, in the step S4, the effective height of the new concrete pile cap is calculated by subtracting the thickness of the protective layer from the thickness of the new concrete pile cap :

[0031] .

[0032] Preferably, the formula for checking the punching of the angle pile against the pile cap is established by the effective height of the new concrete pile cap :

[0033] ​

[0034] In the formula, is the vertical reaction force design value of the angle pile, is the axial tensile strength design value of the concrete, is the cross-section height influence coefficient of the newly added concrete pile cap;

[0035] In the formula, is the x-direction angle pile punching shear coefficient, is the y-direction angle pile punching shear coefficient:

[0036] ;

[0037] ;

[0038] In the formula, is the horizontal distance from the inner edge of the x-direction angle pile to the outer edge of the pile cap, is the horizontal distance from the inner edge of the y-direction angle pile to the outer edge of the pile cap, is the x-direction punching span projection length, is the y-direction punching span projection length;

[0039] In the formula, is the x-direction angle pile punching span ratio;

[0040] ;

[0041] is the y-direction angle pile punching span ratio:

[0042] ;

[0043] The angle pile punching calculation on the pile cap is carried out, when the calculation result is qualified, the thickness of the newly added concrete pile cap is selected , when the calculation result is unqualified, the thickness of the newly added concrete pile cap is reselected and re-calculated.

[0044] Preferably, the following steps are further included:

[0045] Step S5, excavating to expose the existing foundation, and chiseling and drilling the surface of the frame column of the existing foundation which extends into the interior and above the newly added concrete pile cap with the frame column of the existing foundation as the center;

[0046] Step S6, several groups of outer molds for pouring new concrete pile caps are arranged on the surface of the existing foundation, the several groups of outer molds are distributed on the surface of the existing foundation at equal intervals in a ring shape with the frame column of the existing foundation as the center, several groups of corrugated pipes for forming pile holes are arranged inside each new concrete pile cap, the total number of pile holes in different groups of new concrete pile caps is equal to the number of anchor rod static pressure piles Consistently, a plurality of force transmission anchor rods are embedded around each corrugated pipe, after the force transmission anchor rods are embedded, the first new concrete pile cap is poured;

[0047] Step S7, after the strength of the first new concrete pile cap meets the subsequent construction conditions, the outer mold and the corrugated pipe are removed, the frame column formwork is installed, and the frame column is poured;

[0048] Step S8, a hole is drilled from the pile hole position to the bearing layer of the foundation through the existing foundation, the verticality of the drilling machine is calibrated before the hole is drilled in the existing foundation, a steel pipe pile is pressed into the hole in sections, and the steel pipe piles are combined and jointed to form an anchor rod static pressure pile after pouring;

[0049] Step S9, one group of anchor rod static pressure piles is selected in the first new concrete pile cap, an axial force meter is embedded in the steel pipe pile when the concrete approaches the top of the steel pipe pile during pouring of the group of anchor rod static pressure piles, and the anchor rod static pressure pile serves as a test pile;

[0050] A pile top pad is placed at the top end of each group of anchor rod static pressure piles, a loading pier is placed on the top of the pile top pad, a pressure stabilizing beam is installed at the top of the force transmission anchor rod, the pressure stabilizing beam is horizontally fixed above the anchor rod static pressure pile, anchor bolts are arranged on the enlarged frame column on the side surface of the pressure stabilizing beam, a screw jack with an axial force meter is installed on the loading pier, the movable end of the screw jack abuts against the pressure stabilizing beam, and the verticality of the screw jack and the axial force meter is calibrated during installation.

[0051] Preferably, step S10 is further included, all screw jacks in the existing foundation simultaneously start to work, the anchor rod static pressure piles are pre-pressed to the design value in stages according to the load distribution requirements and then the pressure is unloaded in stages, during the pre-pressing process, the pressure applied by the screw jack multiplied by 1.2 is taken as the actual pre-pressing pressure, the sum of the actual pre-pressing pressures of all screw jacks in a single existing foundation is less than the weight of the existing foundation, the pre-pressing process is repeated multiple times to reduce or even eliminate the compression deformation of the soil, the difference between the pre-embedded axial force meter and the axial force meter of the screw jack is continuously observed until the difference is within 5%;

[0052] The effect of the anchor rod static pressure pile is judged by the settlement change of the new concrete pile cap and the pressure change of the pre-embedded axial force meter, the static pressure pile is considered to have an effect when the settlement of the new concrete pile cap stops and remains stable or rebounds, and the static pressure pile is also considered to have an effect when the state of the axial force meter showing a continuously decreasing pressure stops and starts to increase in the opposite direction.

[0053] Preferably, it further comprises a step S11 of filling the gap between the anchor rod static pressure pile and the hole wall with high-strength material in a pre-pressed state, continuously monitoring the difference between the pre-buried axial force gauge and the axial force gauge of the screw jack during the increase of the strength of the pile sealing material, increasing the pressure of the screw jack to the design value if the anchor rod static pressure pile settlement in the pre-pressed state leads to unloading, and chiseling the top surface of the first newly added concrete platform after the strength of the sealing material reaches the design requirement, pouring the second newly added concrete platform to the top of the pressure stabilizing beam, and cooperating the first newly added concrete platform and the second newly added concrete platform to form the newly added concrete platform, and restoring the site backfill.

[0054] Compared with the prior art, the present application has the following beneficial effects:

[0055] 1. The present application accurately obtains the load capacity to be borne by the anchor rod static pressure pile through the calculation method of the newly added precise anchor rod static pressure pile sharing the load capacity of the existing foundation, and further determines the number of the anchor rod static pressure pile and the specification of the corresponding newly added concrete platform according to the load capacity.

[0056] 2. The present application can actively apply a certain load to the pile foundation according to the reinforcement design requirement through the pre-pressed anchor rod static pressure steel pipe pile construction, so that the improved foundation can not only improve the bearing capacity, but also control the overall deformation of the overall structure within a small range during use, thereby avoiding the safety hazards caused by the inconsistent post-transmission path of the existing foundation due to the uncoordinated deformation.

[0057] 3. The present application has a lower requirement for the excavation depth of the foundation pit. Since the excavation depth of the foundation pit is shallow, the excavation amount is reduced, the disturbance to the existing foundation during construction is minimized, the load proportion borne by the existing foundation and the static pressure pile can be quantitatively distributed through the pre-pressing of the jack to the static pressure pile, and the static pressure pile can be used as the pile foundation of the building structure.

[0058] 4. The pre-buried axial force gauge in the pile testing process can verify and check the vertical load borne by each pile, thereby reducing the cost of verifying and detecting the vertical compression bearing capacity of the static pressure pile and improving the reliability of the vertical compression bearing capacity of the static pressure pile. BRIEF DESCRIPTION OF DRAWINGS

[0059] Figure 1 The flowchart of the embodiment of the present application is shown in the figure;

[0060] Figure 2 The detailed diagram of the precise load distribution step of the embodiment of the present application is shown in the figure;

[0061] Figure 3 The schematic diagram of the embodiment of the present application is shown in the figure; Figure 1 ;

[0062] Figure 4 The schematic diagram of the embodiment of the present application is shown in the figure;Figure 2 ;

[0063] Figure 5 is a top view of an embodiment of the present application;

[0064] Figure 6 is a test pile monitoring curve diagram of an embodiment of the present application.

[0065] The numbers in the figure represent: 1, existing foundation; 2, newly added concrete pile cap; 21, first newly added concrete pile cap; 22, second newly added concrete pile cap; 3, anchor rod static pressure pile; 4, loading pier; 5, pressure stabilizing beam; 6, force transmission anchor rod; 7, pile top pad; 8, screw jack; 9, axial force meter. DETAILED DESCRIPTION

[0066] The above and other technical features and advantages of the present application will be further explained by the following description with reference to the accompanying drawings and embodiments, but the following embodiments are merely preferred embodiments of the present application, not all.

[0067] Embodiment:

[0068] As shown in Figures 1-6 , the present application provides a precise anchor rod static pressure pile, which comprises an existing foundation 1, a newly added concrete pile cap 2 cast on the surface of the existing foundation 1, a plurality of groups of pile holes formed inside the newly added concrete pile cap 2 by corrugated pipes, a force transmission anchor rod 6 embedded around the pile hole, and a pressure stabilizing beam 5 installed on the top of the force transmission anchor rod 6;

[0069] A steel pipe pile is arranged in the pile hole, and the anchor rod static pressure pile 3 is formed by grouting into the steel pipe pile, the anchor rod static pressure pile 3 passes through the existing foundation 1 to reach the bearing stratum, and the newly added concrete pile cap 2 and the anchor rod static pressure pile 3 can together support and reinforce the building foundation;

[0070] A pile top pad 7 is placed at the top end of the anchor rod static pressure pile 3, a loading pier 4 is placed on the top of the pile top pad 7, and a screw jack 8 is arranged between the loading pier 4 and the pressure stabilizing beam 5.

[0071] An axial force meter 9 is pre-embedded at the top of the anchor rod static pressure pile 3, and the axial force meter 9 is fused with the anchor rod static pressure pile 3 as a whole during the forming process of the anchor rod static pressure pile 3.

[0072] The newly added concrete pile cap 2 comprises a first newly added concrete pile cap 21 and a second newly added concrete pile cap 22, and the first newly added concrete pile cap 21 and the second newly added concrete pile cap 22 are formed by pouring twice.

[0073] A calculation method for a newly added precise anchor rod static pressure pile to share the load of an existing foundation, comprising the following steps:

[0074] Step S1, based on the structural load of the existing foundation 1, the structural load of the existing foundation 1 includes the dead weight of the existing foundation and the original bearing load, combined with the increased load that needs to be increased by reinforcement , the vertical load borne by the existing foundation is obtained The calculation formula is:

[0075] ;

[0076] According to the vertical load borne by the existing foundation 1 Determine the load borne by the existing foundation 1 and the anchor static pressure pile 3 cooperating with the existing foundation 1;

[0077] Taking the dead weight of the original single existing foundation plus the original bearing load of 500kN and the increased load of 200kN as an example, the plan is to change the load distribution to make the existing foundation 1 bear the load of 200kN, and the anchor static pressure pile 3 bears the load of 500kN, then the bearing capacity of all anchor static pressure piles 3 in the selected single existing foundation 1 should be greater than 500kN;

[0078] Step S2, according to the vertical load borne by the existing foundation Determine the load borne by the anchor static pressure pile cooperating with the existing foundation According to the load allocated to the anchor static pressure pile 3, calculate the number of anchor static pressure piles 3 required to bear the load, the number of anchor static pressure piles 3 The calculation formula is:

[0079]

[0080] In the formula, is the single-pile vertical ultimate bearing capacity of the anchor static pressure pile 3, is the load borne by the anchor static pressure pile 3;

[0081] The calculation formula of the load borne by the anchor static pressure pile 3 is:

[0082]

[0083] In the formula, is the vertical bearing capacity of the foundation bearing stratum, is the influence reduction coefficient of different construction processes of the static pressure pile on the bearing stratum load of the existing foundation 1, is the vertical load borne by the existing foundation 1, is the dead weight of the new concrete pile cap 2, is the bottom area of the existing foundation 1;

[0084] The calculation formula of the single-pile vertical ultimate bearing capacity of the anchor static pressure pile 3 is:

[0085] ;

[0086] wherein is the ultimate side friction resistance of the anchor static pressure pile 3, is the ultimate end resistance of the anchor static pressure pile 3.

[0087] The ultimate side friction resistance of the anchor static pressure pile 3 is calculated by the formula:

[0088]

[0089] wherein, is the perimeter of the anchor static pressure pile 3, is the thickness of the anchor static pressure pile 3 extending into each stratum, is the side friction resistance of each stratum;

[0090] The ultimate end resistance of the anchor static pressure pile 3 is calculated by the formula:

[0091]

[0092] wherein, is the area of the end of the anchor static pressure pile, is the end resistance of the stratum where the end of the anchor static pressure pile is located.

[0093] Step S3, after obtaining the number of anchor static pressure piles 3 , the pile hole positions of each anchor static pressure pile 3 are planned on the existing foundation 1. When selecting the pile hole positions, the pile hole positions need to avoid the main stress reinforcement of the existing foundation 1, at the same time, need to ensure that the pile hole is located in the effective section of the existing foundation 1, the pile holes are symmetrically distributed, the group pile centroid is coincided with the center of gravity of the existing foundation 1, and the distance between adjacent pile holes is three times the diameter of the anchor static pressure pile 3 ;

[0094] After selecting the pile hole positions, on the basis of ensuring the distance between the outer edge of the anchor static pressure pile 3 and the edge of the new concrete pile cap 2 is 150mm, the length and width dimensions of the new concrete pile cap 2 are determined;

[0095] Step S4, the thickness of the new concrete pile cap is controlled by the corner pile punching, based on the special construction process and stress requirements of the anchor static pressure pile in the “Technical Code for Reinforcement of Existing Building Foundation and Foundation”, the minimum design thickness of the anchor static pressure pile cap shall not be less than 350mm, for the case of original foundation weakness, i.e. thickness <350mm, the control cap thickness / pile diameter ratio is in the range of 2.0~2.5, based on this, according to the stress requirements of the designed anchor static pressure pile 3, the thickness of the new concrete pile cap 2 is preliminarily determined. , the thickness of the new concrete pile cap 2 is selected after the pile cap punching shear calculation of the angle pile pair is passed ,

[0096] The effective height of the new concrete pile cap 2 is calculated by subtracting the thickness of the protective layer from the thickness of the new concrete pile cap 2 :

[0097] ;

[0098] The effective height of the new concrete pile cap 2 is calculated by subtracting the thickness of the protective layer from the thickness of the new concrete pile cap 2 The pile cap punching shear calculation formula of the angle pile pair is established and the pile cap punching shear calculation of the angle pile pair is performed:

[0099]

[0100] In the formula, is the vertical counterforce design value of the angle pile, is the axial tensile strength design value of the concrete, is the sectional height influence coefficient of the new concrete pile cap 2;

[0101] In the formula, is the x-direction angle pile punching shear coefficient, is the y-direction angle pile punching shear coefficient:

[0102] ;

[0103] ;

[0104] In the formula, is the horizontal distance from the inner edge of the x-direction angle pile to the outer edge of the pile cap, is the horizontal distance from the inner edge of the y-direction angle pile to the outer edge of the pile cap, is the x-direction punching span projection length, is the y-direction punching span projection length;

[0105] In the formula, is the x-direction angle pile punching span ratio;

[0106] ;

[0107] is the y-direction angle pile punching span ratio:

[0108] ;

[0109] When the calculation result is true, the thickness of the new concrete pile cap 2 is selected ​​The value of the thickness of the new concrete pile cap 2 is qualified, and when the checking result is unqualified, the thickness of the new concrete pile cap 2 is reselected The checking is performed again.

[0110] The pile length L of the anchor rod static pressure pile 3 is calculated, the depth of the anchor rod static pressure pile 3 extending into the stratum to reach the bearing stratum, and the depth of the anchor rod static pressure pile 3 extending into the new concrete pile cap 2 are summed to be the pile length L of the anchor rod static pressure pile 3.

[0111] In step S5, the existing foundation 1 is excavated to expose the existing foundation 1, and the surface of the frame column of the existing foundation 1 extending into the interior of the new concrete pile cap 2 and above is chiseled and drilled.

[0112] In step S6, a plurality of groups of outer molds for pouring the new concrete pile cap 2 are erected on the surface of the existing foundation 1, and the plurality of groups of outer molds are distributed on the surface of the existing foundation 1 at equal intervals in a ring shape with the frame column of the existing foundation 1 as the center. A plurality of groups of corrugated pipes for forming pile holes are arranged in each new concrete pile cap 2, and the total number of pile holes in different groups of new concrete pile caps 2 is consistent with the number of anchor rod static pressure piles 3. A force transmission anchor rod 6 is embedded around each corrugated pipe, and the first new concrete pile cap 21 is poured after the embedding of the force transmission anchor rod 6 is completed.

[0113] In step S7, after the strength of the first new concrete pile cap 21 meets the subsequent construction conditions, the outer mold and the corrugated pipe are removed, the frame column mold plate is installed, and the enlarged frame column is poured.

[0114] In step S8, a hole is drilled from the pile hole position to reach the bearing stratum of the foundation through the existing foundation 1, the verticality of the drilling machine is calibrated before the hole is drilled in the existing foundation 1, and a steel pipe pile is pressed into the hole in sections, and the anchor rod static pressure pile 3 is formed by combining and pouring the steel pipe piles.

[0115] In step S9, a group of anchor rod static pressure piles 3 is selected in the first new concrete pile cap 21, and when pouring the group of anchor rod static pressure piles 3, an axial force meter 9 is embedded in the steel pipe pile as a test pile when the concrete approaches the top of the steel pipe pile.

[0116] A pile top pad 7 is placed at the top end of each group of anchor rod static pressure piles 3, a loading pier 4 is placed on the top of the pile top pad 7, a pressure stabilizing beam 5 is installed on the top of the force transmission anchor rod 6, the pressure stabilizing beam 5 is horizontally fixed above the anchor rod static pressure pile 3, the pressure stabilizing beam 5 is anchored on the enlarged frame column on the side, a screw jack 8 with an axial force meter is installed on the loading pier, the movable end of the screw jack 8 is in contact with the pressure stabilizing beam 5, and the verticality of the screw jack 8 and the axial force meter 9 is calibrated when the screw jack 8 and the axial force meter 9 are installed, to avoid errors caused by uneven force on the axial force meter or deviation of the jack during pile pressing.

[0117] Step S10, both the foundation 1 in all screw jacks 8 start working at the same time, according to the load distribution requirements, pre-press the anchor static pile 3 to the design value and then unload the pressure step by step, repeat several times to reduce or even eliminate the soil compression deformation, continuously observe the difference between the pre-embedded axial force meter and the axial force meter of the screw jacks, until the difference between the two is within 5%;

[0118] In the actual preloading process, in order to achieve the expected effect of load distribution, the pressure applied to the screw jacks 8 can be multiplied by 1.2 as the actual preloading pressure according to the specification , but the sum of the actual preloading pressures of all screw jacks in a single existing foundation 1 cannot exceed the self-weight of the existing foundation 1;

[0119] The effect of the anchor static pile 3 is judged by the settlement change of the first newly added concrete pile cap 21 and the pressure change of the pre-embedded axial force meter 9. When the settlement state of the first newly added concrete pile cap 21 stops and remains stable or the settlement state stops and starts to rise, it means that the anchor static pile 3 has an effect. When the axial force meter 9 shows that the pressure stops decreasing and starts to increase, it means that the anchor static pile 3 has an effect;

[0120] A load loss coefficient model controlled by plastic settlement and soil type is established to accurately invert and control the pressure value of the anchor static pile 3. According to the difference between the final pressure displayed by the axial force meter 9 and the actual preloading pressure , the load loss coefficient of the anchor static pile 3 for this soil type and the specific value of the load shared by the anchor static pile 3 after the anchor static pile 3 is generated are calculated;

[0121] The calculation formula of the actual preloading pressure is:

[0122]

[0123] In the formula, is the actual preloading pressure, is the final pressure displayed by the axial force meter 9, is the load loss coefficient of the anchor static pile 3 for this soil type;

[0124] The calculation formula of the load loss coefficient of the anchor static pile 3 for this soil type is:

[0125]

[0126] In the formula, is the cumulative plastic settlement in the preloading process, is the nonlinear index of plastic settlement of this soil type, is the soil type adjustment coefficient, is the soil type index, The influence reduction coefficient of different construction processes of the static pressure pile on the bearing capacity of the bearing layer of the existing foundation;

[0127] In step S11, the gap between the anchor rod static pressure pile 3 and the pile hole wall is filled with high-strength material in the pre-pressing state, and the difference between the pre-buried axial force gauge 9 and the axial force gauge of the screw jack 8 is continuously monitored during the increase of the strength of the pile sealing material. If the anchor rod static pressure pile 3 settlement causes unloading, the screw jack 8 is controlled to increase the pressure to the design value. After the strength of the sealing material reaches the design requirement, the first newly added concrete platform 21 is chiseled, and the second newly added concrete platform 22 is poured to the top of the stable pressure beam. The first newly added concrete platform 21 and the second newly added concrete platform 22 cooperate to form the newly added concrete platform 2, and the site is backfilled and restored.

[0128] Through the pre-pressing anchor rod static pressure steel pipe pile construction, the pile foundation can be actively loaded according to the reinforcement design requirements, so that the improved foundation can improve the bearing capacity while controlling the overall deformation of the overall structure within a small range during use, which can avoid the safety hazards caused by the inconsistent transmission path of the existing foundation due to the incoordination of deformation.

[0129] The above description is only the preferred embodiment of the present application, which is only illustrative but not limiting. Those skilled in the art understand that many changes, modifications and even equivalents can be made to the present application within the spirit and scope of the claims of the present application, but all will fall within the protection scope of the present application.

Claims

1. A method for calculating the load-sharing of existing foundations by newly added precise anchor static pressure piles, characterized in that, Includes the following steps: Step S1: Based on the existing structural load, and considering the additional load that needs to be added through reinforcement, The vertical load on the existing foundation is obtained. ; Step S2, based on the vertical load on the existing foundation Determine the load that the anchor static pressure piles, in conjunction with the existing foundation, need to bear. Based on the load allocated to the anchor static pressure piles, calculate the number of anchor static pressure piles required to bear that load. ; Step S3, after obtaining the number of anchor static pressure piles. Then, based on the existing foundation, the location of each anchor static pressure pile hole is planned. After selecting the pile hole location, the distance between the outer edge of the anchor static pressure pile and the edge of the newly added concrete pile cap is ensured. Based on the 150mm foundation, determine the length and width dimensions of the newly added concrete foundation. Step S4: Determine the thickness of the new concrete cap based on the designed stress requirements of the anchor static pressure piles. The punching shear of the corner piles to the pile cap was checked, and the thickness of the newly added concrete pile cap was selected after the check was passed. ; Calculate the pile length of the anchored static pressure pile The length of the anchored static pressure pile is the sum of the depth to which the anchored static pressure pile penetrates the bearing stratum and the depth to which it penetrates the newly added concrete pile cap. ; Step S5: Excavate to expose the existing foundation. Using the frame column of the existing foundation as the center, roughen and drill the surface of the frame column of the existing foundation extending into the new concrete foundation and above. Step S6: Construct several sets of external formwork for pouring the new concrete pile caps on the surface of the existing foundation. These external formwork sets are distributed in a ring at equal intervals around the existing foundation's frame columns. Inside each new concrete pile cap, several sets of corrugated pipes are installed to form pile holes. The total number of pile holes located in different sets of new concrete pile caps is equal to the number of anchor static pressure piles. In a consistent manner, multiple force-transmitting anchor rods are pre-embedded around each corrugated pipe, and the first newly added concrete foundation is poured after the force-transmitting anchor rods are pre-embedded. Step S7: After the strength of the first newly added concrete foundation meets the subsequent construction conditions, remove the outer formwork and corrugated pipe, install the frame column formwork, and pour the enlarged frame column. Step S8: Drill a hole from the pile hole location through the existing foundation to reach the bearing layer of the foundation. Before drilling the hole into the existing foundation, check the verticality of the drilling machine. Drive steel pipe piles into the hole in sections. After the steel pipe piles are assembled and poured, they form anchor static pressure piles. Step S9: Select a set of anchor static pressure piles in the first newly added concrete pile cap. When pouring the anchor static pressure piles, when the concrete is close to the top of the steel pipe pile, embed an axial force gauge into the steel pipe pile. The anchor static pressure pile is used as a test pile. Place a pile top pad at the top of each set of anchor static pressure piles, place a loading pier on top of the pile top pad, install the stabilizing beam on top of the force transmission anchor, fix the stabilizing beam horizontally directly above the anchor static pressure pile, and anchor the side of the stabilizing beam to the enlarged frame column. Install a screw jack with an axial force gauge on the loading pier, with the movable end of the screw jack abutting against the stabilizing beam. When installing the screw jack and axial force gauge, check the verticality of the screw jack and axial force gauge. Step S10: All screw jacks in the existing foundation start working simultaneously. According to the load distribution requirements, the anchor static pressure piles are preloaded to the design value step by step, and then the pressure is released step by step. During the preloading process, the pressure applied by the screw jacks is multiplied by 1.2 to obtain the actual preloading pressure. The sum of the actual preloading pressures of all screw jacks in a single existing foundation is less than the self-weight of the existing foundation. This is repeated multiple times to reduce or even eliminate soil compression deformation. The difference between the axial force gauge of the embedded axial force gauge and the axial force gauge of the screw jack is continuously observed until the difference is within 5%. The effectiveness of the anchor static pressure piles is judged by the settlement changes of the newly added concrete foundation and the pressure changes of the pre-embedded axial force gauge. If the settlement of the newly added concrete foundation stops and remains stable or rises, it indicates that the static pressure piles are effective. If the pressure shown by the axial force gauge stops decreasing and begins to increase in the opposite direction, it also indicates that the static pressure piles are effective.

2. The method for calculating the load sharing of existing foundations by newly added precise anchor static pressure piles as described in claim 1, characterized in that, In step S1, the structural load of the existing foundation includes the self-weight of the existing foundation and the original load it bears, as well as the vertical load on the existing foundation. The formula for calculation is: ； In the formula, This is to increase the load by reinforcing the structure.

3. The method for calculating the load sharing of existing foundations by newly added precise anchor static pressure piles as described in claim 1, characterized in that, In step S2, the number of anchor static pressure piles The formula for calculation is: ； In the formula, This refers to the ultimate vertical bearing capacity of a single anchored static pressure pile. This refers to the load that the anchored static pressure pile needs to bear; Vertical ultimate bearing capacity of a single anchored static pressure pile The formula for calculation is: ； In the formula, The ultimate lateral friction resistance of the anchored static pressure pile. This represents the ultimate end resistance of the anchored static pressure pile.

4. The method for calculating the load sharing of existing foundations by newly added precise anchor static pressure piles as described in claim 3, characterized in that, The ultimate lateral frictional resistance of the anchored static pressure pile The formula for calculation is: ； In the formula, Let be the perimeter of the anchored static pressure pile. The thickness of the anchor static pressure pile extending into each stratum. For the side friction resistance of each stratum; Ultimate end resistance of anchored static pressure piles The formula for calculation is: ； In the formula, This represents the area at the end of the anchored static pressure pile. This refers to the end resistance of the stratum where the static pressure pile tip is located.

5. The method for calculating the share of existing foundation load by newly added precise anchor static pressure piles as described in claim 1, characterized in that, In step S3, the pile holes are located within the effective cross-section of the existing foundation, the pile holes are symmetrically distributed, the centroid of the pile hole group coincides with the centroid of the existing foundation, and the spacing between adjacent pile holes is greater than three times the diameter of the anchor static pressure pile. .

6. The method for calculating the share of existing foundation load by newly added precise anchor static pressure piles as described in claim 1, characterized in that, In step S4, the thickness of the concrete foundation is increased. Subtract the thickness of the protective layer Calculate the effective height of the newly added concrete foundation using the following method : 。 7. The method for calculating the load sharing of existing foundations by newly added precise anchor static pressure piles as described in claim 6, characterized in that, By increasing the effective height of the concrete foundation Establish the formula for verifying the punching shear of corner piles on the pile cap: ； In the formula, This represents the design value of the vertical reaction force of the corner pile. This is the design value of the axial tensile strength of concrete. The influence coefficient of the section height of the newly added concrete foundation. The distance is the horizontal distance from the inner edge of the corner pile in the x-direction to the outer edge of the pile cap. The distance is the horizontal distance from the inner edge of the corner pile in the y-direction to the outer edge of the pile cap. Let x be the projected length of the stride in the x-direction. Let y be the length of the projected span in the y-direction. The punching shear coefficient for the angle pile in the x-direction is... The punching shear coefficient of the angle pile in the y-direction; ； ； In the formula, The span ratio of the corner pile in the x-direction. The span ratio of the angle pile in the y-direction; ； ； Perform punching shear calculations on the corner piles and pile caps. If the calculation results are satisfactory, select the thickness of the newly added concrete pile cap. If the calculated value is acceptable, then the thickness of the newly added concrete foundation should be reselected. Recalculate.

8. The method for calculating the load sharing of existing foundations by newly added precise anchor static pressure piles as described in claim 1, characterized in that, It also includes the following steps: Step S11: While maintaining the preloaded state, fill the gap between the anchor static pressure pile and the pile hole wall with high-strength material. During the process of increasing the strength of the sealing material, continuously monitor the difference between the axial force gauge of the embedded axial force gauge and the axial force gauge of the screw jack. If the anchor static pressure pile settlement under the preloaded state causes unloading, control the screw jack to increase the pressure to the design value. After the sealing material strength reaches the design requirements, roughen the top surface of the first newly added concrete foundation and pour the second newly added concrete foundation to the top of the stabilizing beam. The first and second newly added concrete foundations work together to form the new concrete foundation, and the site is backfilled and restored.

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