A control method for foundation construction under no treatment condition of soft stratum

Abstract

The application discloses a control method for foundation construction under no treatment condition of soft stratum, and comprises the following steps: S1, cleaning the site and lofting and positioning the foundation plane position; S2, arranging the inclinometer tube on at least one side of the foundation plane position; S3, excavating the foundation groove, continuously filling the stable liquid into the foundation groove during the excavation process, dynamically adjusting the stable liquid density rho according to the size of delta S until the foundation groove is completed; S4, in-situ casting or precasting the foundation hoisting to form the foundation in the foundation groove, and collecting the discharged stable liquid for subsequent repeated use; and S5, grouting, and stably connecting the foundation and the soft stratum after the grout consolidation. The application can monitor the deformation of the soft stratum in the foundation groove process in real time, dynamically adjust the stable liquid proportioning to realize the density adjustment, and realize the rapid, safe and environment-friendly construction.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of soft stratum construction, in particular to a control method for foundation construction under no treatment condition of soft stratum. BACKGROUND

[0002] With the continuous construction of projects, more and more projects are constructed under the complex conditions of soft stratum. Because the soil body of soft stratum has low strength and is easy to deform, the foundation is often pre-reinforced or isolated by steel casing during the construction process of foundation engineering. The construction process is complicated, the construction organization is difficult, the required equipment is large in quantity, the construction risk is high, a certain interval time is required for each construction period, and a long construction period is required. In the process of treating soft foundation, a large amount of manpower and material resources will be consumed, and a large amount of waste slurry will be generated, which will seriously pollute the environment.

[0003] The Chinese patent specification with the application number 2012100549857 (publication date: 20120711) discloses a super-deep T-shaped slot wall pile for soft upper and hard lower soil layers and a slot forming construction method thereof. Composite bentonite mud is used for wall protection during slot forming. However, the density and composition ratio of the mud are always fixed, while the pressure on the slot wall changes with the depth during the slot forming of soft soil layer. The original mud cannot guarantee that the soft soil layer does not deform into the slot.

[0004] Therefore, it is necessary to develop a control method for foundation construction under no treatment condition of soft stratum, which can adjust the density of stabilizing liquid in real time according to the deformation of soft soil layer, so as to realize fast, safe and environmentally friendly construction of soft foundation under no treatment condition. SUMMARY

[0005] The purpose of the present application is to solve the problems in the background art, and to provide a control method for foundation construction under no treatment condition of soft stratum, which can adjust the density of stabilizing liquid in real time according to the deformation of soft soil layer, so as to realize fast, safe and environmentally friendly construction of soft foundation under no treatment condition.

[0006] The technical scheme of the present application is as follows: a control method for foundation construction under no treatment condition of soft stratum, characterized in that it comprises the following steps:

[0007] S1, cleaning the site and positioning the foundation plane position by lofting;

[0008] S2, arranging an inclinometer tube on at least one side of the foundation plane position;

[0009] S3, excavating a foundation trench, continuously filling the trench with a stabilizing liquid during the excavation process, the stabilizing liquid being obtained by mixing powder materials including barite powder, clay powder, carboxymethyl cellulose, and polyacrylamide with water, the amount of the components of the stabilizing liquid being determined according to a pre-fitted stabilizing liquid density-powder material expansion scale curve I so that the initial density of the stabilizing liquid is ρ1, ρ1 being calculated according to the performance parameters of the soft soil layer;

[0010] During the excavation process, the horizontal displacement S of the soft soil layer along the transverse direction of the foundation is monitored in real time by using an inclinometer, the direction of the horizontal displacement S being taken as the direction of the foundation, the change value ΔS of the horizontal displacement S being calculated at preset intervals, and the density ρ of the stabilizing liquid being dynamically adjusted according to the size of ΔS, the amount of the components corresponding to the density ρ of the stabilizing liquid being determined according to the pre-fitted stabilizing liquid density-powder material expansion scale curve I, until the trenching is completed.

[0011] S4, forming the foundation by casting in place or hoisting a prefabricated foundation in the trench, and collecting the discharged stabilizing liquid for subsequent reuse;

[0012] S5, replacing and discharging the residual stabilizing liquid between the foundation and the soft soil layer by grouting through a grouting pipe embedded in the foundation, and stably connecting the foundation and the soft soil layer after the grout is solidified.

[0013] Preferably, in step S3, the calculation method of ρ1 includes: calculating ρ1 according to the measured performance parameters of the soft soil layer, i.e., the soil bulk density γ and the soil internal friction angle φ.

[0014] ρ1=P0 / (g·z)=γK0 / g=γ(1-sinφ) / g

[0015] wherein ρ1 is the initial density of the stabilizing liquid, and the unit is g / cm 3 ;

[0016] P0 is the static earth pressure, and the unit is kPa;

[0017] z is the depth of the trench, and the unit is m;

[0018] γ is the soil bulk density, and the unit is KN / m 3 ;

[0019] g is the acceleration of gravity, and the value is 9.8 N / kg;

[0020] K0 is the static earth pressure coefficient, K0=1-sinφ, and φ is the soil internal friction angle, and the unit is degree.

[0021] Preferably, in step S3, the fitting method of the stabilizing liquid density-powder material expansion scale curve I includes:

[0022] the density ρ of the stabilizing liquid is from 1.05 g / cm 3 to 2 g / cm3 The multiple calibration points are arranged at equal intervals, and the amounts of barite powder 10g, clay powder 80g, carboxymethyl cellulose 5g and polyacrylamide 5g are multiplied by the powder material expansion ratio K, and then water is added to 1L to obtain the calibration point density, so as to determine the powder material expansion ratio K corresponding to the calibration point, and the stable liquid density-powder material expansion ratio calibration curve I is obtained by fitting the K corresponding to all calibration points.

[0023] Further, in step S3, the amount of the stable liquid component is determined so that the initial density is p1, and specifically, p1 is determined to correspond to the powder material expansion ratio K1 on the stable liquid density-powder material expansion ratio calibration curve I, and then the amount of the powder material in each liter of the stable liquid is 10g of barite powder, 80g of clay powder, 5g of carboxymethyl cellulose and 5g of polyacrylamide, which are all multiplied by K1, and the amount of water is determined to be 1L.

[0024] Further, in step S3, the stable liquid density p is dynamically adjusted according to the size of AS, and specifically, a horizontal displacement allowable variation r is preset, r=5mm-10mm, a density change percentage a% is preset, a=1-4, and the density of the stable liquid is always located in the range of 1.05g / cm 3 -2g / cm 3 .

[0025] If |AS|<r, the density of the stable liquid is unchanged.

[0026] If |AS|≥r and AS takes a positive value, the current stable liquid density p is increased by a%.

[0027] If |AS|≥r and AS takes a negative value, the current stable liquid density p is decreased by a%.

[0028] Since the density of the stable liquid of the present application is always located in the range of 1.05g / cm 3 -2g / cm 3 , if the density exceeds the upper limit 2g / cm 3 after increasing a%, it is still calculated as 2g / cm 3 , and if the density is less than the lower limit 1.05g / cm 3 after decreasing a%, it is still calculated as 1.05g / cm 3 . The change value AS is calculated at a preset interval of 5-10 minutes, and AS is obtained by subtracting the initial value from the final value of the horizontal displacement in the preset interval.

[0029] Further, in step S3, the component amount corresponding to the stable liquid density ρ is determined according to the pre-fitted stable liquid density-powder material expansion scale calibration curve I, and specifically comprises: determining the powder material expansion scale K corresponding to ρ on the stable liquid density-powder material expansion scale calibration curve I, then the powder material amount in each liter of stable liquid is 10g of barite powder, 80g of clay powder, 5g of carboxymethyl cellulose, 5g of polyacrylamide, and the water amount is determined to 1 liter.

[0030] Preferably, in step S2, the inclinometer tube depth is lower than the design foundation bottom surface elevation by 5-10m.

[0031] Preferably, when the inclinometer tube is single and arranged at one side of the foundation plane position, the horizontal displacement S in step S3 is measured by the single inclinometer tube;

[0032] When the inclinometer tube is two and symmetrically arranged on both sides of the foundation plane position, the horizontal displacement S in step S3 is obtained by averaging the results measured by the two inclinometer tubes;

[0033] Preferably, in step S3, the liquid level elevation in the slot is monitored in real time during the excavation process to ensure that the liquid level elevation meets the preset requirements.

[0034] Preferably, in step S4, when the foundation is formed by casting, the steel reinforcement cage is hoisted and the concrete is poured, and the stable liquid in the slot is replaced and discharged by the concrete during pouring; when the foundation is formed by hoisting the prefabricated foundation, the stable liquid in the slot is squeezed and discharged by the prefabricated foundation during hoisting.

[0035] The beneficial effects of the present application are:

[0036] 1. The present application can realize rapid, safe and environmentally friendly construction under the condition of soft foundation without treatment, and the present application can ensure that the particles in the high-density stable liquid are in a suspended state and the density of the stable liquid is stable by injecting high-density stable liquid into the slot during slotting in the soft stratum.

[0037] 2. The density of the high-density stable liquid is adjusted according to the stratum soil parameters to ensure that the soft soil layer does not deform into the slot. Before slotting, inclinometer tubes are arranged around to monitor the deformation of the soft soil layer during slotting, and the stable liquid ratio is dynamically adjusted to realize density adjustment according to the deformation amount.

[0038] 3. After the trenching is completed, for cast-in-place foundation, hoist the steel bars in the trench, and pour the concrete to complete the foundation construction; for precast foundation, directly hoist and install, and replace the stable liquid in the trench. In order to ensure the connection performance of the foundation and the side wall soil, the grouting pipe is pre-buried in the side wall and the end of the foundation for grouting, so as to ensure the bearing capacity of the foundation. The discharged stable liquid can be collected for subsequent reuse, so as to avoid a large amount of waste slurry and environmental protection construction.

[0039] 4. For the formula of the stable liquid, since the stable liquid density-powder material expansion scale calibration curve I is fitted in advance, the amount of each component of the stable liquid can be quickly obtained according to the required density, the stable liquid density p is quickly and dynamically adjusted according to AS, and the beneficial effects of stably supporting the inner wall of the trenching are achieved. The present application has wide adaptability, and is not only suitable for foundation trenching, but also suitable for foundation hole forming. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 Schematic diagram of the inclinometer and trench arrangement of the present application

[0041] Figure 2 Schematic diagram of the pre-buried grouting pipe in the foundation of the present application

[0042] Figure 3 Schematic diagram of the stable liquid density-powder material expansion scale calibration curve I

[0043] Wherein: 1-soft soil layer; 2-trench; 3-stable liquid; 4-inclinometer; 5-foundation; 6-grouting pipe. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical scheme and advantages of the present application clearer and more apparent, the present application will be further described in detail below with examples. It should be understood that the specific examples described herein are only used to explain the present application, and are not used to limit the present application. The materials used in the following examples are all commercially available products, and the methods used are all conventional methods in the art.

[0045] The present embodiment provides a control method for foundation construction under no treatment condition of soft soil layer, which comprises the following steps:

[0046] S1, clean the site, and lay out and position the foundation plane position.

[0047] S2, lay out the inclinometer 4 on at least one side of the foundation plane position in the transverse direction, the depth of the inclinometer 4 is 5-10m lower than the designed foundation bottom surface elevation, the inclinometer 4 can be one root, arranged on one side of the foundation plane position, or as shown in Figure 1 two roots, symmetrically arranged on both sides of the foundation plane position in the transverse direction, Figure 1 left and right directions are the same as the transverse direction of the foundation.

[0048] S3. Excavate the foundation trench 2. During the excavation process, continuously fill the trench 2 with stabilizing liquid. Monitor the liquid level in the trench 2 in real time during the excavation process to ensure that the liquid level always meets the preset requirements. The stabilizing liquid is obtained by mixing powder materials including barite powder, clay powder, carboxymethyl cellulose (CMC), and polyacrylamide (PAM) with water. The amount of stabilizing liquid components is determined according to the pre-fitted stabilizing liquid density-powder material expansion ratio calibration curve I to make its initial density ρ1.

[0049] The specific method for fitting the calibration curve I of stabilized liquid density-powder material scaled up is as follows: The stabilized liquid density ρ is increased from 1.05 g / cm³... 3 Up to 2g / cm 3 At least 10 calibration points are set at equal intervals (in this embodiment, the interval is 0.05 g / cm). 3 (A total of 20 calibration points) The dosages of barite powder 10g, clay powder 80g, carboxymethyl cellulose 5g, and polyacrylamide 5g were multiplied by the powder material expansion ratio K, and then water was added to dilute to 1L to obtain the calibration point density (as shown in Table 1 below). The powder material expansion ratio K corresponding to the calibration point was determined. After fitting a curve based on K corresponding to all calibration points, the stabilizing liquid density-powder material expansion ratio calibration curve I was obtained.

[0050] Table 1. Calibration points and corresponding K values.

[0051]

[0052] According to the calibration curve I proposed in Table 1, which is based on the density of the stabilized liquid versus the scaling ratio of the powder material, as shown in Table 1... Figure 3 As shown.

[0053] The specific method for calculating ρ1 is as follows:

[0054] ρ1=P0 / (g·z)=γK0 / g=γ(1-sinφ) / g

[0055] Where ρ1 is the initial density of the stabilized liquid, in g / cm³. 3 ;

[0056] P0 is the earth pressure at rest, in kPa.

[0057] z represents the trench depth, in meters (m).

[0058] γ is the soil unit weight, in kN / m³. 3 ;

[0059] g is the acceleration due to gravity, taken as 9.8 N / kg;

[0060] K0 is the coefficient of earth pressure at rest, K0=1-sinφ, φ is the internal friction angle of the soil, in degrees;

[0061] In this embodiment, γ = 18.9 KN / m 3 , φ = 15°, and ρ1= 1.43 g / cm 3 is calculated. The amount of the stable liquid component with the initial density ρ1is as follows: determine the corresponding powder material expansion scale K1(K1= 8.6 in this embodiment) of ρ1on the stable liquid density-powder material expansion scale calibration curve I, then the amount of the powder material in each liter of the stable liquid is 10 g of barite powder, 80 g of clay powder, 5 g of carboxymethyl cellulose, and 5 g of polyacrylamide, each multiplied by K1, and the amount of water is determined to 1 liter.

[0062] The inclinometer tube 4 monitors the horizontal displacement S of the soft soil layer along the lateral direction of the foundation in real time during excavation, and the direction of the horizontal displacement S is towards the foundation. Since two inclinometer tubes 4 are arranged in this embodiment (the horizontal displacement S of each inclinometer tube 4 is in the direction of the arrow in the figure), the horizontal displacement S is obtained by averaging the results measured by the two inclinometer tubes 4; the change value ΔS of the horizontal displacement S is calculated at a preset interval, and the density ρ of the stable liquid is dynamically adjusted according to the size of ΔS, specifically as follows: Figure 1

[0063] The preset allowable change amount of the horizontal displacement is r, r = 5 mm to 10 mm, the preset density change percentage is a%, a = 1 to 4, and the density range of the stable liquid is 1.05 g / cm 3 to 2 g / cm 3 ;

[0064] If |ΔS| < r, the density of the stable liquid remains unchanged.

[0065] If |ΔS| ≥ r and ΔS takes a positive value, the current density ρ of the stable liquid is increased by a%, and if the density exceeds 2 g / cm 3 after the increase of a%, the density is still calculated as 2 g / cm 3 ;

[0066] If |ΔS| ≥ r and ΔS takes a negative value, the current density ρ of the stable liquid is decreased by a%, and if the density is less than 1.05 g / cm 3 after the decrease of a%, the density is still calculated as 1.05 g / cm 3 ,

[0067] In this embodiment, ΔS is calculated once every 5 minutes at a preset interval, r = 5 mm, and a% = 2%, so when the specific ΔS = 6 mm is monitored in real time, the density ρ of the stable liquid will be increased by 2% (for example, the current density ρ = 1.43 g / cm 3 , and after the increase of 2%, it is 1.46 g / cm 3 ). If the specific ΔS = -6 mm is monitored in real time, the density ρ of the stable liquid will be decreased by 2% (for example, the current density ρ = 1.43 g / cm 3 ​, 2% reduction is 1.40g / cm 3 ). If | ΔS | continues to increase, the stable liquid density continues to increase or decrease stably until | ΔS | is within the allowable range.

[0068] The component amount corresponding to the stable liquid density ρ is as follows: determine the powder material expansion scale K (such as 1.46g / cm 3 corresponding to ρ on the stable liquid density-powder material expansion scale calibration curve I (such as 1.46g / cm 3 corresponding K is 8.0), the powder material amount in each liter of stable liquid is 10g of barite powder, 80g of clay powder, 5g of carboxymethyl cellulose, 5g of polyacrylamide, and the water amount is constant to 1 liter;

[0069] The stable liquid density ρ is continuously dynamically adjusted until the trench 2 is formed.

[0070] S4, as shown in Figure 2 , the foundation 5 is formed by in-situ casting or precast hoisting in the trench 2. When the foundation 5 is formed by in-situ casting, the steel reinforcement cage is hoisted and then the concrete is poured, and the stable liquid 3 in the trench 2 is replaced and discharged by the concrete during the pouring process, and the discharged stable liquid 3 is collected for subsequent reuse; when the foundation 5 is formed by precast hoisting, the stable liquid in the trench 2 is squeezed and discharged by the precast foundation during the hoisting process, and the discharged stable liquid 3 is collected for subsequent reuse.

[0071] S5, the residual stable liquid between the foundation 5 and the soft soil layer 1 is replaced and discharged by pressure grouting through the pressure grouting pipe 6 pre-buried in the foundation 5, and the discharged stable liquid 3 can be collected for subsequent reuse, and the foundation 5 and the soft soil layer 1 are stably connected after the grouting liquid is solidified.

[0072] The basic principles, main features and advantages of the present application are shown and described above. It should be understood by those skilled in the art that the present application is not limited by the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A method for controlling foundation construction under untreated conditions of weak strata, characterized in that, Includes the following steps: S1. Clear the site and lay out the basic plan position; S2. Install inclinometer tubes (4) on at least one side of the foundation plane; S3. Excavate the foundation trench (2). During the excavation process, continuously fill the trench (2) with stabilizing liquid (3). The stabilizing liquid (3) is obtained by mixing powder materials including barite powder, clay powder, carboxymethyl cellulose, and polyacrylamide with water. The amount of stabilizing liquid components is determined according to the pre-fitted stabilizing liquid density-powder material expansion ratio calibration curve I so that its initial density is ρ1. ρ1 is calculated based on the performance parameters of the soft soil layer. During the excavation process, the horizontal displacement S of the soft soil layer along the transverse direction of the foundation is monitored in real time using the inclinometer tube (4). The direction of the horizontal displacement S is taken as the direction of the adjacent foundation. The change value ΔS of the horizontal displacement S is calculated at a preset interval. The density ρ of the stabilizing liquid is dynamically adjusted according to the size of ΔS. The amount of component corresponding to the density ρ of the stabilizing liquid is determined according to the pre-fitted calibration curve I of the density of the stabilizing liquid and the expansion ratio of the powder material until the trench (2) is completed. The fitting method for the stabilized liquid density-powder material scaling calibration curve I includes: adjusting the stabilized liquid density ρ from 1.05 g / cm³. 3 Up to 2g / cm 3 Multiple calibration points were set at equal intervals. The amounts of barite powder (10g), clay powder (80g), carboxymethyl cellulose (5g), and polyacrylamide (5g) were multiplied by the powder material expansion ratio K, and then diluted with water to 1L to obtain the density at each calibration point. The powder material expansion ratio K corresponding to each calibration point was then measured. A curve was fitted based on K corresponding to all calibration points to obtain the stabilizing liquid density versus powder material expansion ratio calibration curve I. The calculation method for ρ1 includes: calculating based on the measured performance parameters of the weak soil layer, namely, soil weight γ and soil internal friction angle φ. ρ1=P0 / (g·z)=γK0 / g=γ(1-sinφ) / g Where ρ1 is the initial density of the stabilized liquid, in g / cm³. 3 ; P0 is the earth pressure at rest, in kPa. z represents the trench depth, in meters (m). γ is the soil unit weight, in kN / m³. 3 ; g is the acceleration due to gravity, taken as 9.8 N / kg; K0 is the coefficient of earth pressure at rest, K0=1-sinφ, φ is the internal friction angle of the soil, in degrees; The density ρ of the stabilized liquid is dynamically adjusted based on the magnitude of ΔS. Specifically, this includes: a preset allowable change in horizontal displacement r, where r = 5 mm to 10 mm; a preset density change percentage a%, where a = 1 to 4; and ensuring the density of the stabilized liquid remains at 1.05 g / cm³. 3 ~2g / cm 3 ; If |ΔS| < r, then the density of the stable liquid remains unchanged; If |ΔS| ≥ r and ΔS is positive, then increase the current stable liquid density ρ by a%. If |ΔS| ≥ r and ΔS is negative, then reduce the current stable liquid density ρ by a%. S4. Cast in place or precast foundation in the trench (2) to form foundation (5), and collect the discharged stabilizing liquid (3) for subsequent reuse; S5. Grouting is carried out through the grouting pipe (6) pre-embedded in the foundation (5) to replace and discharge the residual stabilizing liquid (3) between the foundation (5) and the weak soil layer (1). After the grout solidifies, the foundation and the weak soil layer are stably connected.

2. The method for controlling foundation construction under untreated conditions in soft strata as described in claim 1, characterized in that, In step S3, the amount of stabilizer components is determined so that its initial density is ρ1. Specifically, this includes determining the powder material expansion ratio K1 corresponding to ρ1 on the stabilizer density-powder material expansion ratio calibration curve I. Then, the amount of powder material in each liter of stabilizer is 10g of barite powder, 80g of clay powder, 5g of carboxymethyl cellulose, and 5g of polyacrylamide, all multiplied by K1. The amount of water is adjusted to 1 liter.

3. The method for controlling foundation construction under untreated soft strata as described in claim 1, characterized in that, In step S3, the component dosage corresponding to the stabilized liquid density ρ is determined according to the pre-fitted stabilized liquid density-powder material expansion ratio calibration curve I. Specifically, it includes: determining the powder material expansion ratio K corresponding to ρ on the stabilized liquid density-powder material expansion ratio calibration curve I, then the powder material dosage per liter of stabilized liquid is 10g of barite powder, 80g of clay powder, 5g of carboxymethyl cellulose, and 5g of polyacrylamide, all multiplied by the corresponding K, and the water dosage is to bring the volume to 1 liter.

4. The method for controlling foundation construction under untreated soft strata as described in claim 1, characterized in that, In step S2, the depth of the inclinometer tube (4) is 5 to 10 meters below the design foundation bottom elevation.

5. The method for controlling foundation construction under untreated soft strata as described in claim 1, characterized in that, When the inclinometer tube (4) is a single tube and is set on one side of the foundation plane, the horizontal displacement S in step S3 is measured by the single inclinometer tube (4); When there are two inclinometer tubes (4) symmetrically set on both sides of the foundation plane, the horizontal displacement S in step S3 is obtained by taking the average value of the results measured by the two inclinometer tubes (4).

6. The method for controlling foundation construction under untreated soft strata conditions as described in claim 1, characterized in that, In step S3, the liquid level in the trench (2) is monitored in real time during the excavation process to ensure that the liquid level meets the preset requirements.

7. The method for controlling foundation construction under untreated conditions in soft strata as described in claim 1, characterized in that, In step S4, when the cast-in-place foundation (5) is formed, the concrete is poured after the steel cage is hoisted. During the pouring process, the stabilizing liquid in the trench (2) is replaced and discharged by the concrete. When the precast foundation is hoisted to form the foundation (5), the stabilizing liquid in the trench (2) is squeezed out by the precast foundation during the hoisting process.

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