Disclosure of Invention
The invention aims to provide a bearing platform cofferdam applied to a deep sludge interlayer condition and a construction process thereof, and aims to solve the technical problems that in the prior art, when the bearing platform cofferdam is applied to the deep sludge interlayer condition, the cofferdam is easy to generate water stop, surge and instability of a supporting structure in the construction process, and simultaneously, the technical problems of unreliable cofferdam structure and high risk caused by factors such as overlong steel sheet piles or leakage points of high-pressure jet grouting piles are avoided.
The bearing platform cofferdam applied to the deep sludge interlayer condition comprises a steel sheet pile cofferdam consisting of steel sheet piles, and a bearing platform pile, a supporting system and a high-pressure jet grouting pile which are arranged in the steel sheet pile cofferdam, and further comprises a concrete back cover, wherein the high-pressure jet grouting pile is arranged at the bottom in the steel sheet pile cofferdam to form a full-section reinforcing layer, the bottoms of the high-pressure jet grouting pile and the steel sheet pile are inserted into a middle interlayer with silt, the top of the high-pressure jet grouting pile is higher than the top of the middle interlayer, the full-section concrete back cover is arranged on the reinforcing layer, and the concrete back cover has a certain thickness so that the anti-floating performance after the reinforcing layer is combined with the concrete back cover meets the requirement.
Preferably, the anti-floating performance is checked according to the section area of the concrete back cover in the steel sheet pile cofferdam and an anti-floating checking formula, the thickness of the concrete back cover is determined according to the checking result, and the anti-floating checking formula is as follows:
wherein, K f To secure the anti-floating factor, F w Is the buoyancy standard value (unit: kN), P of water uc Is head buoyancy, G c The dead weight of the bottom-sealing concrete, F 1 Taking the minimum value of the gravity of the reinforcing layer and the bonding force between the foundation steel pile casing of the pile of the bearing platform and the bottom sealing concrete, wherein the thickness of the concrete bottom sealing is not less than 3m, calculating according to the anti-floating checking calculation formula, the anti-floating safety coefficient is not less than the safety threshold of the anti-floating safety coefficient, and calculating G according to the section area, the concrete density and the set thickness of the concrete bottom sealing c And calculating the gravity of the reinforcing layer according to the area of the cross section, the average density of the reinforcing layer and the set thickness of the reinforcing layer.
Preferably, checking calculation is carried out on the stability and the embedding stability of the foundation pit ridge under the construction working condition with the most unfavorable stability, the thickness of the concrete back cover and the thickness of the reinforcing layer are determined according to the checking calculation result, and the concrete checking calculation mode is as follows:
evaluation coefficient of foundation pit anti-uplift stability for evaluating foundation pit anti-uplift stability internally in this case:
in the formula: d represents the thickness of the soil layer from the bottom surface of the foundation pit to the bottom surface of the soil retaining member; h represents the excavation depth of the foundation pit; gamma ray
m1 The method comprises the following steps of (1) representing the gravity of soil above the bottom surface of a soil retaining member outside a foundation pit, and taking the average gravity of soil of each layer according to the weight of the thickness from multiple layers of soil; gamma ray
m2 The method comprises the following steps of (1) representing the gravity of soil above the bottom surface of a soil retaining member in a foundation pit, and taking the average gravity of soil of each layer according to the weight of the thickness from multiple layers of soil; n is a radical of
c 、N
q Each represents a respective load factor; c.
respectively showing the cohesive force and the internal friction angle of soil below the bottom surface of the soil retaining member; q represents the uniform load on the soil outside the foundation pit; k is
he Indicating the safety factor against bulging, N
c And N
q Respectively according to the following formulas:
in this case, the factor of evaluation of the anchoring stability for evaluating the anchoring stability of the foundation pit:
in the formula: e pk Expressing a standard value of the resultant force action of the passive soil pressure on the inner side of the foundation pit; e ak The standard value of the resultant force action of the active soil pressure outside the foundation pit is represented; z is a radical of p2 The distance from the acting point of the resultant force of the passive soil pressure on the inner side of the foundation pit to the fulcrum is represented; z is a radical of a2 The distance from the active soil pressure resultant force action point at the outer side of the foundation pit to the fulcrum is represented; k em Representing the embedding stability safety factor;
when the result of the checking calculation is F s ≥K he And F k ≥K em And in time, the thickness of the concrete back cover and the thickness of the reinforcing layer meet the requirements.
Preferably, the thickness of the reinforcing layer is not less than 3m, the distance from the bottom of the reinforcing layer to the bottom of the steel sheet pile is not more than 2.5m, and the thickness of the concrete back cover is not less than 3 m.
Preferably, the steel sheet pile adopts a two-section combination form, wherein the first section is 21m long, and the second section is 3m long; the steel sheet pile inner support system is provided with three layers, each layer is composed of a bracket, a main beam and a support steel pipe, three layers of surrounding purlins are adopted, the support steel pipes form an inner support and a connection support, and the mounting distances of the brackets in the three layers are respectively 3m, 4.8m and 6 m.
The invention also provides a construction process of the bearing platform cofferdam applied to the deep sludge interlayer condition, which comprises the following steps:
firstly, inserting and driving steel sheet piles;
secondly, performing high-pressure jet grouting pile construction in the steel sheet pile cofferdam;
pumping water in the steel sheet pile cofferdam to a position below the first layer of supporting enclosing purlin, and installing a first layer of supports;
fourthly, excavating in the steel sheet pile cofferdam, pumping water to the lower side of the second layer of supporting enclosing purlin, and installing a second layer of supports;
fifthly, irrigating water in the foundation pit, excavating to the bottom of the foundation pit with water, and pouring concrete for the first time to seal the bottom;
after the soil body of the reinforcing layer reaches the design strength, under the condition of construction water level, recharging water in the foundation pit, excavating to the bottom of the foundation pit with water, ensuring the balance of the water levels inside and outside the cofferdam in the excavation process, and pouring concrete for the first time under water to seal the bottom;
pumping water in the steel sheet pile cofferdam to a position below the third layer of support enclosing purlin, and installing a third layer of support;
pumping water in the steel sheet pile cofferdam to the bottom of the foundation pit, and leveling the bottom of the foundation pit;
and pumping water in the cofferdam to the bottom of the foundation pit under the construction water level condition, pouring concrete back cover again and leveling, and finishing the construction of the bearing platform cofferdam after the concrete back cover reaches the design strength.
Preferably, in the first step, the drilling platform around is dismantled, a guide frame is arranged by depending on a steel casing of the bearing platform pile to position the steel sheet pile, and the steel sheet pile is driven from the upstream side; inserting and driving steel sheet piles on two side surfaces in sequence, and finally inserting and driving steel sheet piles on the downstream side to form a closed structure; inserting and driving the steel sheet piles in two steps, wherein in the first step, a vibration hammer is adopted to lift the 21m long steel sheet piles for inserting and driving, after the 21m long steel sheet piles are driven, each steel sheet pile starts to be welded with a 3m extension section after the cofferdam is folded.
Preferably, after the construction of the bearing platform cofferdam is completed, the bearing platform concrete, the tower seat concrete and the pier body concrete can be further poured, and after the pier body construction is completed, the first layer of support is removed, the internal and external water heads of the steel sheet pile cofferdam are balanced, and the steel sheet pile is pulled out.
The invention has the following advantages: in the scheme, the bottoms of the high-pressure jet grouting pile and the steel sheet pile are still in the middle interlayer of sludge, the sludge can bypass the steel sheet pile to extrude the bottom of the jet grouting pile, and the water stopping and the gushing prevention are completely supported on the quality of the high-pressure jet grouting pile. Consider that high pressure jet grouting pile itself is difficult to guarantee not to have the leak source, set up the concrete back cover in the back up coat top during the construction, even high pressure jet grouting pile has the leak source like this, the concrete back cover also can guarantee that this scheme is difficult to appear the bottom scheduling problem that gushes suddenly. Moreover, the scheme utilizes the characteristics that the concrete bottom sealing can be constructed with water and the density of the concrete is greater than that of the middle interlayer, and the scheme also overcomes other defects. The density of concrete is greater than intermediate layer, therefore this scheme utilizes corresponding anti floating to check the calculation formula and calculates, sets up the concrete back cover of reasonable thickness, has effectively promoted the anti floating performance of cofferdam structure and has made it can satisfy the required anti safety requirement that floats of cofferdam structure. And concrete back cover can take the water construction, therefore this scheme adopts the mode of secondary construction, at the concrete back cover of step five belt pours 2.85m at first realize the back cover and prevent suddenly gushing the effect after, take the water excavation again until the foundation pit bottom, need not to draw water in the whole course of excavation process like this, reduce the inside and outside flood peak pressure difference of cofferdam, avoid flood peak pressure difference too big to the influence of steel sheet pile when the excavation depth is darker, and set up the third layer and support and take out the water in the foundation pit after guaranteeing the steel sheet pile cofferdam structural strength again, through secondary concrete placement flattening under the condition of visible foundation pit bottom, realize pouring of 3m concrete back cover and guarantee that the foundation pit bottom is smooth.
Detailed Description
The following detailed description of the present invention will be given in conjunction with the accompanying drawings, for a more complete and accurate understanding of the inventive concept and technical solutions of the present invention by those skilled in the art.
As shown in fig. 1-7, the invention provides a bearing platform cofferdam applied under the condition of a deep sludge interlayer, which comprises a steel sheet pile cofferdam 1 consisting of steel sheet piles 11, and a bearing platform pile 6, a supporting system 2, a concrete back cover 5 and a high-pressure jet grouting pile which are arranged in the steel sheet pile cofferdam 1, wherein the bottom in the steel sheet pile cofferdam 1 is provided with the high-pressure jet grouting pile to form a reinforcing layer 4 with a full section, the bottoms of the high-pressure jet grouting pile and the steel sheet pile 11 are inserted into a middle interlayer 8 with sludge, the top of the high-pressure jet grouting pile is higher than the top of the middle interlayer 8, the concrete back cover 5 with the full section is arranged on the upper surface of the reinforcing layer 4, and the concrete back cover 5 has a certain thickness to ensure that the anti-floating performance after the reinforcing layer 4 is combined with the concrete back cover 5 meets the requirements. The arrangement mode of the reinforcing layer 4 enables the lower part of the silt layer with higher strength of the upper soil 9 and the middle interlayer 8 with low soil strength to be reinforced into an integral structure through the high-pressure jet grouting pile, so that the jet grouting pile formed when only the middle interlayer 8 is reinforced is prevented from sinking in the easily flowing silt layer and cannot generate the reliable reinforcing layer 4.
The thickness of the reinforcing layer 4 is not less than 3m for ensuring the reinforcing strength, and the position of the steel sheet pile 11 subjected to the maximum stress is located at the boundary of the reinforcing layer 4 and the sludge soil layer due to the fact that the bottom of the reinforcing layer 4 is located in the middle interlayer 8 and the supporting rigidity of the sludge middle interlayer 8 is weak, so that the bottom of the reinforcing layer 4 is close to the bottom of the steel sheet pile 11, and the distance from the bottom of the reinforcing layer 4 to the bottom of the steel sheet pile 11 is not more than 2.5 m. In the embodiment, when the construction water level is +3.90m and the elevation of the top of the middle interlayer 8 is-12.37 m according to the field condition, the elevation of the bottom of the steel sheet pile cofferdam 1 is-16.5 m, the elevation of the bottom of the reinforcing layer 4 is-14.0 m, and the elevation of the bottom of the concrete back cover 5 is-11.0 m. At this time, the maximum stress of the steel sheet pile 11 above the foundation pit bottom is 230MPa, and the strength of the steel sheet pile 11 meets the requirement.
The thickness of the concrete back cover 5 is checked according to the sectional area of the concrete back cover 5 in the steel sheet pile cofferdam 1 and an anti-floating checking formula, wherein the anti-floating checking formula is as follows:
wherein, K f To secure the anti-floating factor, F w Is the buoyancy standard value (unit: kN), P of water uc Is head buoyancy, G c Is the dead weight (unit: kN) of the bottom-sealed concrete F 1 The minimum value (kN) of the gravity of the reinforcing layer 4 and the bonding force between the pile foundation steel casing of the pile foundation 6 and the bottom sealing concrete is taken. When the thickness of the concrete back cover 5 is 3m after the calculation according to the anti-floating checking formula, the calculated K is f Is 1.34, which is larger than that of the steel cofferdam engineering technologyThe safety threshold value set by the standard is 1.15, so that the anti-floating performance of the reinforcing layer combined with the concrete back cover 5 meets the requirement.
And then, checking the uplift stability and the embedding stability of the foundation pit under the construction working condition with the least stability, and determining whether the two stability values are met according to the threshold values of the corresponding stability evaluation coefficients set by the technical standard of steel cofferdam engineering when the thickness of the concrete back cover 5 is 3m and the thickness of the reinforcing layer 4 is 3m, so as to determine the thickness to be the thickness value meeting the requirements.
The specific checking method is as follows.
Evaluation coefficient of foundation pit anti-uplift stability for evaluating foundation pit anti-uplift stability internally in this case:
in the formula: d represents the thickness of the soil layer from the bottom surface of the foundation pit to the bottom surface of the soil retaining member; h represents the excavation depth of the foundation pit; gamma ray
m1 Indicating the weight (kN/m) of the soil above the bottom of the soil retaining member outside the pit
3 ) Taking the average gravity of each layer of soil according to the weight of the thickness from the multiple layers of soil; gamma ray
m2 Indicating the weight (kN/m) of the soil above the bottom of the retaining member in the pit
3 ) Taking the average gravity of each layer of soil according to the weight of the thickness from the multiple layers of soil; n is a radical of
c 、N
q Each represents a respective load factor; c.
respectively showing the cohesive force and the internal friction angle of soil below the bottom surface of the soil retaining member; in this case c is 31.2Pa,
q represents the uniform load on the soil outside the foundation pit; k
he Representing the anti-doming safety factor, i.e. the safety threshold of the evaluation factor of the anti-doming stability of the foundation pit, in the case of this step, K
he Was 1.8.
N
c And Nx are calculated as follows:
according to the scheme, the relevant parameters are introduced into the formula for calculation under the condition that the thickness of the concrete back cover 5 is 3m and the thickness of the reinforcing layer 4 is 3m, and the obtained evaluation coefficient of the uplift resistance stability of the foundation pit meets the requirement that the evaluation coefficient of the uplift resistance stability of the foundation pit in the inequality is larger than a threshold value, namely the requirement of the uplift resistance stability of the foundation pit is met.
In this case, the factor of evaluation of the anchoring stability for evaluating the anchoring stability of the foundation pit:
in the formula: e pk Expressing a standard value of the resultant force action of the passive soil pressure on the inner side of the foundation pit; e ak Representing a standard value of the resultant force action of the active soil pressure outside the foundation pit; z is a radical of p2 The distance from the acting point of the resultant force of the passive soil pressure on the inner side of the foundation pit to the fulcrum is represented; z is a radical of a2 The distance from the active soil pressure resultant force action point at the outer side of the foundation pit to the fulcrum is represented; k em Represents the setting stability factor, i.e., the threshold value of the setting stability evaluation coefficient, in the case of this step, K em Is 1.25. According to the scheme, the relevant parameters are introduced into the formula for calculation under the condition that the thickness of the concrete back cover is 3m and the thickness of the reinforcing layer is 3m, and the obtained embedding stability evaluation coefficient meets the requirement that the embedding stability evaluation coefficient in the inequality is larger than the threshold value, namely meets the requirement of foundation pit embedding stability.
6 bases of the bearing platform piles are arranged in a quincuncial manner, and the influence of pile foundation steel casing of the bearing platform piles 6 needs to be considered as much as possible during cofferdam design, and meanwhile, the rationality of the stress of the cofferdam structure is guaranteed. The deep foundation pit cofferdam needs to be subjected to complex stress conversion during excavation, installation of the inner support 21 and pumping construction, and the deep foundation pit is deep, so that the stress condition of the deep foundation pit is complex, and the support system of the deep foundation pit is determined by researching the stress state of the deep foundation pit in the construction process.
The steel sheet pile cofferdam 1 is a fore shaft steel sheet pile cofferdam 1, the main pier cofferdam is quadrilateral, and the distance between the outer edge of the cofferdam and the side of the support trestle meets the requirement of the cofferdam construction operation. The pile bottom elevation of the steel sheet pile 11 is minus 16.5m, the top opening elevation is 4.5m, and the distance between the steel sheet pile 11 and the steel pipe pile is 1.35 m.
The steel sheet pile 11 adopts a Larsen SP-IVw type steel sheet pile, the total length of the steel sheet pile 11 is 24m, a two-section combination mode is adopted, the first section is 21m long, and the second section is 3m long. The supporting system 2 in the steel sheet pile 11 is provided with three layers, and each layer is composed of a bracket, a main beam and a supporting steel pipe. A bracket provided with 40a steel section and an enclosing purlin 3 for supporting adopt three layers of enclosing purlins 3, the section form of the enclosing purlin 3 is 2HN700 multiplied by 300/4HN700 multiplied by 300, supporting steel pipes form an inner support 21 and a connecting support 22, the three layers of inner supports 21 respectively adopt phi 609 multiplied by 16, phi 800 multiplied by 10 and phi 1000 multiplied by 12 steel pipes, and the connecting support 22 adopts phi 426 multiplied by 6 steel pipes. The bracket adopts 40a steel, and the mounting distances of the three layers of brackets are respectively 3m, 4.8m and 6 m.
And (4) inspecting the fitting condition of the enclosing purlin 3 and the steel sheet pile 11 after the enclosing purlin 3 is installed, and filling gaps with steel sheets, wherein grouting measures can be taken if the gaps cannot be filled with the steel sheets. The joint of the purlin 3 and the support adopts double-sided welding, and a stiffening plate with the thickness of 12mm is arranged. And the quality inspection of the welding seam is enhanced during installation. The mounting sequence of the inner support 21 is as follows: and excavating the foundation pit, pumping water to 1m below the enclosing purlin 3 → installing a bracket → installing an enclosing purlin 3 main beam → installing a steel pipe support. The three layers of brackets are welded and fixed with the steel sheet piles 11, the fillet weld height is 8mm, and the three layers of brackets are arranged uniformly.
The invention also provides a construction process of the bearing platform cofferdam applied to the deep sludge interlayer condition, which comprises the following steps.
Step one, inserting and driving a steel sheet pile 11.
Removing the drilling platform around, arranging a guide frame by depending on a steel pile casing of the bearing platform pile 6 to position the steel sheet pile 11, and inserting and driving the steel sheet pile 11 from the upstream side; and inserting and driving the steel sheet piles 11 on the two side surfaces in sequence, and finally inserting and driving the steel sheet piles 11 on the downstream side to form a closed structure. And during inserting and driving, the pile sinking precision is noticed, and the firm connection between the steel sheet piles 11 is ensured. In the construction of the steel sheet pile 11, a firm positioning guide frame system with certain rigidity is arranged, and the positioning guide frame system mainly comprises a positioning pile and a guide beam.
Inserting and driving the steel sheet piles 11 in two steps, wherein in the first step, a vibration hammer is adopted to lift the steel sheet piles 11 with the length of 21m for inserting and driving, after the driving of the steel sheet piles 11 with the length of 21m is finished, and after the cofferdam is folded, each steel sheet pile 11 starts to be welded with a 3m extension section. And sequentially locking the steel sheet piles 11 from the upstream to the two ends until the cofferdam is folded. And when the steel sheet pile cofferdam 1 is folded, the steel sheet piles 11 are adjusted to enable the lock catches on the two sides to be parallel.
When the steel sheet pile 11 at the intersection of the enclosing purlin 3 is inserted and beaten, the width of the notch is measured, the size of the steel sheet pile 11 is accurately calculated, and the steel sheet pile 11 with proper size is processed to be inserted and beaten on the construction site; water stopping measures should be taken for the cofferdam, after the cofferdam closure is completed, H22 b section steel is adopted on the outer side of a cofferdam top opening for temporarily locking an outer ring, and the deformation of a cantilever structure of a cofferdam sheet pile during the construction of a high-pressure jet grouting pile is prevented, so that the subsequent water leakage of the cofferdam is avoided.
And step two, performing high-pressure jet grouting pile construction in the steel sheet pile cofferdam 1.
And after the construction of the bearing platform pile 6 of the main bridge is completed, removing all the drilling platforms. And a structural steel jet grouting pile construction platform is erected on the top of the steel pile casing of the bearing platform pile 6, and a high-pressure jet grouting pile is adopted for reinforcing a soil body at the bottom of the foundation pit. Under the condition of construction water level (+3.90m or below), high-pressure jet grouting pile construction is carried out, the soil body range (elevation range) of the reinforcing layer 4 is-11.00 m to-14.00 m, and the soil body parameters after reinforcement are c-50 kPa, and phi is 20 degrees.
The high-pressure rotary spraying piles are arranged in a quincunx mode, and the double-pipe rotary spraying piles are adopted for reinforcement. The curing agent adopts 42.5-grade portland cement, the dosage of the cement is 270kg/m, the water cement ratio of the slurry is 1: 1-1: 1.5, and the cement mixing amount is 30 percent of the soil weight content. The admixture is gypsum and water glass, the gypsum mixing amount is 2 percent, the water glass mixing amount is 4 percent, the lifting speed of the grouting pipe is 10-20cm/min, and the rotating speed is 10-30 r/min. The grouting pressure is controlled to be 25MPa, and the flow is 80-120L/min; the air pressure was controlled to 0.7 MPa.
The method specifically comprises the following substeps: 1. pile position lofting; 2. drilling in place by a drilling machine; 3. a lower injection pipe; 4. stirring and pulping; 5. lifting by rotary spraying, wherein the cement consumption is controlled in the process; 6. and after the rotary spraying is finished, the drilling machine shifts.
And step three, pumping water in the steel sheet pile cofferdam 1 to the position below the first layer of support enclosing purlin 3, and installing a first layer of support.
Under the condition of construction water level (+3.90m and below), pumping water in the steel sheet pile cofferdam 1 to a height of 1m below the first layer of supporting surrounding purlin 3 (the elevation is +2.00 m); and (3) cutting off a steel casing influencing the installation of the inner supports 21, temporarily supporting the middle three inner supports 21 by using the steel casing and the bracket, and installing a first layer of purlin 3, the inner supports 21 and the connection supports 22.
And fourthly, excavating and pumping water in the steel sheet pile cofferdam 1 to the lower part of the second layer of supporting enclosing purlin 3, and installing a second layer of supporting.
Under the condition of a construction water level (+3.90m and below), excavating and pumping water in the steel sheet pile cofferdam 1 to a height (elevation is-1.60 m) of 1m below the second layer of supporting enclosing purlin 3; and (4) cutting off a steel casing influencing the installation of the inner support 21, installing a second-layer support and connection support 22, and dismantling the casing to temporarily support the corbel.
And fifthly, irrigating water in the foundation pit, excavating to the bottom of the foundation pit with water, and pouring a first concrete back cover 5.
After the soil body of the reinforcing layer 4 reaches the design strength, under the condition of construction water level (+3.90m and below), the water is poured back into the foundation pit, the foundation pit is excavated to the bottom of the foundation pit with water, the elevation is minus 11.00m, and the balance of the internal and external water levels of the cofferdam is ensured in the excavation process. And (5) pouring the concrete back cover 5 for the first time underwater, wherein the effective thickness is not less than 2.85 m.
The excavation process of this step is the most unfavorable to foundation ditch anti-uplift stability and foundation ditch consolidation stability, therefore when designing reinforcing layer 4 and concrete back cover 5 two thickness, whether satisfy the requirement of corresponding foundation ditch anti-uplift stability and foundation ditch consolidation stability in this step, by the check calculation back that provides before, this scheme adopts the concrete back cover 5 thickness to be 3m, and the reinforcing mode that reinforcing layer 4 thickness is 3m satisfies the requirement to corresponding two kinds of stability in this step.
And step six, pumping water in the steel sheet pile cofferdam 1 to the position below the third layer of support enclosing purlin 3, and installing the third layer of support.
After the bottom sealing concrete reaches the design strength, under the condition of construction water level (+3.90m and below), pumping water in the steel sheet pile cofferdam 1 to a height (elevation is-4.70 m) 1m below the third layer of supporting surrounding purlin 3, cutting off a steel pile casing influencing the installation of the inner support 21, and installing a third layer of support and a connection support 22.
And seventhly, pumping water to the foundation pit bottom in the steel sheet pile cofferdam 1, and leveling the foundation pit bottom.
And pumping water in the cofferdam to the bottom of the foundation pit under the condition of construction water level (+3.90m and below), and pouring and leveling a concrete back cover 5 with the thickness of 0.15m again. And finishing the construction of the bearing platform cofferdam after the concrete back cover 5 reaches the design strength.
After the construction of the bearing platform cofferdam is completed, the bearing platform concrete 7, the tower foundation concrete and the pier body concrete can be further poured, the first layer of support is removed after the pier body construction is completed, the internal and external water heads of the steel sheet pile cofferdam 1 are balanced, and the steel sheet pile 11 is pulled out.
This scheme carries out full sectional high pressure jet grouting pile construction in to steel sheet pile cofferdam 1, consolidates the water pressure, the mud pressure extrusion cofferdam of increase soil body shear strength avoiding the cofferdam outside, leads to the cofferdam to warp, prevents the soil body uplift of middle below. The depth of the reinforcing layer 4 in the cofferdam structure is determined through calculation of the reinforcing strength, the strength of the steel sheet pile 11 and the deformation position, and the position of the reinforcing layer 4 relative to the middle interlayer 8 and the depth of the reinforcing layer 4 are ensured in construction.
The invention has been described above with reference to the accompanying drawings, and it is to be understood that the invention is not limited to the specific embodiments described above, but is intended to cover various insubstantial modifications of the inventive concepts and solutions, or its application to other applications without modification.