Slipform blade and method for applying pre-compression strain to cast-in-place concrete on well walls

1 . A slipform blade foot having an annular structure, for applying prestressing strain to cast-in-place concrete of a shaft wall, comprising a plurality of blade foot block structures connected end to end, wherein each blade foot block structure comprises:

a blade foot block body, comprising:

a lower plate ( 2 );

an outer plate ( 3 ), vertically arranged at a first end of the lower plate ( 2 );

a blade foot block connecting plate ( 5 ), wherein a first end of the connecting plate ( 5 ) is connected to a second end of the lower plate ( 2 );

an upper plate ( 4 ), wherein a first end of the upper plate ( 5 ) is connected to a second end of the connecting plate ( 5 ), and wherein the upper plate ( 4 ) comprises a hole groove;

an arc plate ( 1 ), wherein one end of the arc plate ( 1 ) slidably engages the outer plate ( 3 ) via a lower edge structure, and a second end of the arc plate ( 1 ) overlaps with the upper plate ( 4 );

a vertical displacement generating device ( 6 ), disposed between the lower plate ( 2 ) and the arc plate ( 1 ), wherein:

a fixed end of the device ( 6 ) is fixedly connected to the lower plate ( 2 );

a telescopic end of the device ( 6 ) is fixedly connected to the arc plate ( 1 );

the device ( 6 ) is configured to drive the vertical displacement of the arc plate ( 1 );

a displacement sensor ( 7 ) arranged on the telescopic end of the vertical displacement generating device ( 6 ), which configured to monitor the vertical displacement in real time;

a limit plate ( 8 ) having an I-shaped structure with two horizontal surfaces and one vertical surface, wherein:

a first horizontal surface of the limit plate ( 8 ) is fixedly connected to the arc plate ( 1 );

the vertical surface passes through the hole groove of the upper plate ( 4 ) and is slidably connected to the hole groove;

a second horizontal surface is located below the upper plate ( 4 ), and wherein both of the horizontal surfaces are larger than the hole groove.

2 . The slipform blade foot of claim 1 , wherein the arc plate ( 1 ) is a steel structure.

3 . The slipform blade foot of claim 1 , wherein the vertical displacement generating device ( 6 ) is selected from one of a pneumatic drive, an hydraulic drive and an electric drive that can be controlled by an external controller.

4 . The slipform blade foot of claim 1 , wherein the lower edge structure has an L-shaped cross-section, and wherein:

a first end of the arc plate ( 1 ) is connected an outer side of a right-angle portion of the lower edge structure;

a longer side of the lower edge structure is slidably connected to an inner surface of the outer plate ( 3 );

a shorter side of the lower edge structure overlaps an end of the outer plate ( 3 ) distal to the lower plate ( 2 ).

5 . A method for applying prestressing strain to cast-in-place concrete on a shaft wall using the slipform blade foot of claim 4 , comprising:

S1: performing high excavation construction, wherein, after excavating to a section height H, the slipform blade foot is lowered and aligned, steel bars are tied, vertical formwork is installed, and concrete is poured;

S11: determining parameters, wherein the height of the cast-in-place concrete is H, the target prestressing strain value is ε; the vertical displacement to be applied to the arc plate ( 1 ) is h, and the vertical displacement h is determined according to the section height H and the prestressing strain value ε, wherein h≈εH, and wherein h≤L, wherein L is the length of the limit plate ( 8 ) extending beyond the lower edge of the upper plate ( 4 );

S12: distributing n strain gauge measuring points, wherein, during the concrete pouring process, n concrete vertical strain gauge measuring points are distributed evenly within the section height H, and the strain values measured are: ε 1 , ε 2 , . . . , ε n ; wherein, 2≤n≤8, wherein, for section height H the average vertical strain of concrete within the range is

ε

¯

=

1

n

⁢

∑

i

=

1

n

⁢

ε

i

 where i is the number of the measuring point and ε i is the vertical concrete strain value measured at the i-th measuring point;

S2: operating the vertical displacement generating device ( 6 ), wherein, from initial setting to final setting of the concrete, the vertical displacement generating device ( 6 ) is operated to drive the arc plate ( 1 ) to apply an upward vertical displacement h, according to the pre-stressing strain value ε to be applied, wherein, before demolding, the arc plate ( 1 ) maintains constant vertical displacement;

S21: monitoring and calculation of the ε value, wherein, during the application of the pre-stressing strain, the control program is used to monitor and calculate the ε value in real time, and the vertical displacement h applied to the arc plate ( 1 ) by the vertical displacement generating device ( 6 ) is fed back by the computer to keep the ε value at the target value ε.

6 . A method for applying prestressing strain to cast-in-place concrete on a shaft wall according to claim 5 , wherein, during the process of applying prestressing strain, the control method in S21 to keep the ε value at the target value ε comprises:

S211: initializing by:

determining the target prestressing strain value ε;

resetting the vertical displacement h applied by the vertical displacement generating device ( 6 ) to the arc plate ( 1 ) to zero;

setting the allowable error Δε=ε− ε ;

S212: real-time adjustment, comprising:

reading the concrete vertical strain value ε n , wherein the average vertical strain ε of the concrete within the range of the segment height H is calculated;

wherein, if ε <ε−Δε, the vertical displacement generating device ( 6 ) is driven to increase the vertical displacement h of the arc plate ( 1 );

if ε >ε+Δε, the vertical displacement generating device ( 6 ) is driven to reduce the vertical displacement h of the arc plate ( 1 );

if ε is within the allowable error range, the current vertical displacement h of the arc plate ( 1 ) is maintained;

S213: ceasing adjustment of the vertical displacement generating device ( 6 ) when the system reaches a stable state and ε always remains within the allowable error range of the target value ε.

7 . A method for applying prestressing strain to cast-in-place concrete on a shaft wall according to claim 6 , comprising:

limiting the maximum displacement of the vertical displacement generating device ( 6 ), h≤L;

wherein, if ε ≤500 microstrain, the vertical displacement generating device ( 6 ) is immediately cut off to avoid crushing the cast-in-place concrete.