CN115787693A - Water stopping method for water gushing in deep foundation pit under riverside slow-dip interbed - Google Patents
Water stopping method for water gushing in deep foundation pit under riverside slow-dip interbed Download PDFInfo
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Abstract
The invention relates to the technical field of foundation pit dewatering, in particular to a water stopping method for water gushing in a deep foundation pit below a riverside slow-inclination interbed, which specifically comprises the following steps: determining the depth of the inclined interbed according to the stratum exploration result, and setting the burial depth l of the water well with the leakage pressure of the foundation pit w (ii) a Determining parameters of a local occluded waterproof curtain in a foundation pit; constructing a local occluded waterproof curtain in the foundation pit; constructing and excavating a dewatering well in the foundation pit; local grouting in an inclined aquifer; correcting the grouting thickness in the inclined aquifer; determining the equivalent weight of grouting cement required by the whole foundation pit; construction is distributed at each position of the grouting holes; grouting process flow of the inclined aquifer; and closing the internal dewatering well after the grouting body is finally set. To the bottom of the foundation pitThe water treatment guarantees the construction environment, and carries out grouting construction in the inclined aquifer in the foundation pit after the excavation is finished, and blocks the water seepage in the foundation pit jointly with the combined action of the weak permeable inclined water-resisting layer, thereby effectively preventing the influence of the water level rising in the flood season of the river on the inside of the foundation pit.
Description
Technical Field
The invention relates to the technical field of foundation pit dewatering, in particular to a water stopping method for water gushing in a deep foundation pit below a riverside gentle-dip interbed.
Background
The safety accidents of the deep foundation pit are closely related to underground water control, and the reasonable control of the underground water in the foundation pit is the premise of ensuring the integral stability of the foundation pit. Near closing on the river, along with the increase of deep basal pit excavation degree of depth, the inside dry operation degree of difficulty progressively increases, when guaranteeing supporting construction stability, reasonable control foundation ditch inside infiltration, gush water be the key problem that whole deep basal pit excavation in-process will be solved. To the deep basal pit excavation problem under general operating mode, the foundation ditch outside adopts the waterproof curtain to combine together with the inside precipitation well of foundation ditch, has reduced the foundation ditch bottom pressure of gushing water when increasing groundwater seepage flow route, and is effectual with the foundation ditch inside with its outside isolated, comparatively economic assurance whole foundation ditch engineering's safety.
However, when the vertical waterproof curtain is arranged in the deep foundation pit engineering, the river can not be effectively supplemented with water and blocked when the vertical waterproof curtain is arranged in a special stratum which is close to the river and has a certain inclination angle with respect to the water-containing interbed, and water flow can still be continuously supplemented into the foundation pit through the inclined aquifer. Under this condition, if to the interior large tracts of land of foundation ditch lasting precipitation, not only can not play the interior dry operation effect of assurance foundation ditch but also cost economic great, the large tracts of land lasts precipitation simultaneously and is unfavorable for foundation ditch bottom groundwater to form and stabilizes the seepage field. Therefore, if the connection of the internal water level and the external water level of the foundation pit cannot be cut off in time in the excavation process, the problem of large-area water seepage in the foundation pit can be effectively solved, the uneven settlement of buildings at the periphery of the pit can be caused, the lateral deformation of the enclosure structure can be caused, and the integral stability of the whole foundation pit is difficult to ensure. From the foregoing, it is apparent that conventional methods are uneconomical and undesirable for such methods of controlling groundwater for a particular formation.
Disclosure of Invention
The invention aims to solve the problems in the prior art and provides a water stopping method for water inrush in a deep foundation pit under a riverside slowly-inclined interbed, wherein a plain concrete water-resisting pile meshed with a supporting pile is arranged at a position where an inclined interbed stratum appears, two plain concrete water-resisting piles are meshed with each other pairwise to form a local meshed water-stopping curtain with the functions of supporting and stopping water, meanwhile, in the excavation process, the construction environment is ensured by dewatering treatment at the bottom of the foundation pit, grouting construction is carried out in an inclined water-bearing layer in the foundation pit after excavation is finished, and the water seepage in the foundation pit is blocked together with the combined action of the weak permeable inclined water-resisting layer, so that the influence of water level rising in a river period on the interior of the foundation pit is effectively prevented.
In order to achieve the purpose, the invention provides the following technical scheme:
a water stopping method for gushing water in a deep foundation pit below a riverside slow-dip interbed is characterized by comprising the following steps: before the foundation pit is excavated, arranging a dewatering well 1 at the periphery of the foundation pit, and simultaneously adopting a form that a local plain concrete pile 3 is meshed with a supporting row pile 2 to jointly play a supporting and water-stopping role in the foundation pit; after the excavation of the foundation pit is finished, local grouting 4 is arranged at the bottom of the foundation pit, so that a closed water-stopping and water-isolating system is integrally formed in the foundation pit, and the integral stability of the foundation pit is facilitated;
the method specifically comprises the following steps:
step 1: determining the depth of inclined interbed according to the stratum exploration result, and setting the burial depth l of the water well for the leakage pressure of the foundation pit w (ii) a And before the foundation pit is excavated, determining the depth of the dewatering well outside the foundation pit according to the actual stratum of the engineering, the underground water condition and the size of the foundation pit.
And (3) constructing the dewatering well on the periphery of the foundation pit, so that the internal dry operation during excavation of the upper part of the foundation pit is ensured, and the water level control guarantee in flood season is realized. In the foundation ditch construction period, when the river water level rises in the flood season, the rising water level can be reduced to a certain extent through the external relief well, the water level is kept not to exceed the top depth of the local occlusion waterproof curtain of the foundation ditch all the time, and the inside of the foundation ditch can be kept in a dry operation environment all the time in the whole early excavation. Namely, the external early-stage small-range pressure relief and precipitation construction.
Step 2: determining parameters of a local occluded waterproof curtain in a foundation pit; and after the position of the peripheral dewatering well is determined, determining parameters of the engaged waterproof curtain in the foundation pit. Determining specific parameters of a local occlusal supporting pile according to the designed excavation depth of a foundation pit and the technical regulation of building foundation pit support (JGJ 120-2012), and simultaneously determining the depth l of the whole occlusal water-stop curtain inserted into the bottom of the foundation pit d . In order to ensure the stability of soil flowing in the foundation pit, conversion calculation is carried out by adopting a formula (1) as follows:
K f the stability safety coefficient of the flowing soil is not less than 1.6, 1.5 and 1.4;
l d -the depth of insertion (m) of the curtain of cut water below the bottom of the pit;
gamma' -soil buoyancy (kN/m) 3 )；
Delta h is the water head difference (m) inside and outside the foundation pit;
γ w -water gravity (kN/m) 3 )。
The depth l of the waterproof curtain inside the foundation pit inserted into the bottom of the foundation pit is obtained through conversion d The following were used:
determining total depth L of waterproof curtain in foundation pit S 。
L s ≥l d +H (3)
And 3, step 3: constructing a local occluded waterproof curtain in the foundation pit; the foundation pit supporting structure is constructed by taking support and water stop effects into consideration, and a plain concrete pile and reinforced concrete occlusion structure is adopted. Namely, the adjacent concrete row piles are partially embedded in the circumference, and a reinforcement cage is arranged in the piles constructed in the subsequent phase, and the occlusion part between the piles is not less than 200mm, so that the integral continuous protective curtain with good seepage-proofing function is formed. The concrete construction is carried out according to the requirements of technical regulations for supporting foundation pits of buildings (JGJ 120-2012). And the occlusion construction of plain concrete is not carried out in the stratum above the inclined interbedded stratum. The method aims to solve the problems that the water level of the upper part of the inclined interbed stratum is influenced by a dewatering well at the shallow part outside the foundation pit, the water level is well controlled, and the contribution of the plain concrete piles to the lateral support of the foundation pit is small, so that the plain concrete piles with water stopping function are not required to be added in consideration of comprehensive economic benefits;
and 4, step 4: constructing and excavating a dewatering well in the foundation pit; after the construction of the local occluded water-stop curtain measure at the periphery of the foundation pit is finished, constructing the dewatering wells in the foundation pit, wherein the positions of the dewatering wells are uniformly distributed in the foundation pit, and the interior of the foundation pit is ensured to always keep a certain dry operation environment in the construction process; in the excavation of the horizontal ground layer of upper portion, precipitation well combined action inside and outside the foundation ditch for the whole accuse of the foundation ditch is good and continues to go on along with the foundation ditch excavation, and the mutual stratum of slope progressively leaks naked, and the infiltration phenomenon appears in the foundation ditch side, considers that increaseing inside and outside precipitation well degree of depth and operating power can cause the peripheral building of foundation ditch to produce differential settlement, is unfavorable for the foundation ditch overall stability, so the foundation ditch internal adoption part interlock stagnant water curtain measure of comprehensive consideration. In the whole excavation process, a plurality of prestressed anchor cables are constructed step by step according to design requirements and cooperate with a local waterproof curtain, on one hand, the water seepage on the side surface of the foundation pit is well controlled, on the other hand, the foundation pit deformation is effectively limited, and a good construction operation environment is better provided for the subsequent excavation.
And 5: local grouting in the inclined aquifer; with the end of excavation, in order to avoid the problem of seepage supply to the interior of the foundation pit along the inclined water-bearing layer, local grouting in the foundation pit is carried out; and determining the inclination angle and the trend of the inclined interbed and the proportion of the water-separating interbed according to the geological survey report. Calculating the thickness of grouting inside the foundation pit under the horizontal rock stratum; because the soil mass after grouting can only be grouted in the inclined aquifer, the soil mass after grouting is mixed. And (4) calculating to obtain the grouting thickness D required by the bottom of the foundation pit under the horizontal rock stratum according to the foundation pit anti-surge formula (4).
K h A stable inrush safety factor, which should not be less than 1.1;
d, the thickness (m) of a soil layer from the top surface of the confined water aquifer to the bottom of the pit;
γ c mixed severity of the aquifer soil layer after grouting (kN/m) 3 )；
h w -the head height (m) of the pressure of the top surface of the aquifer of confined water;
γ w -water gravity (kN/m) 3 )；
Step 6: correcting the grouting thickness in the inclined aquifer; and calculating and correcting the grouting thickness under the horizontal rock stratum into the grouting thickness of the special stratum according to the different gravities and occupied space proportions of the aquifer and the water-resisting layer in the inclined interbed. Wherein, the pressure is unchanged according to the overlying water pressure, namely the whole pressure of the grouting body is equal. Therefore, the conversion is performed according to the formula (5) as follows:
Dγ c B＝(γ n b 1 +γ c b 2 )d (5)
b, the sum (m) of horizontal widths of the aquifer and the waterproof layer;
d-the thickness (m) of the grouting in the inclined water-containing layer;
γ s aquifer severity (kN/m) 3 )；
γ n Water barrier Severe (kN/m) 3 )。
Wherein when the water-resisting layer is severe gamma n ＝γ c When the thickness of the horizontal aquifer grouting is the same as that of the aquifer grouting in the inclined interbed stratum, namely D = D; when the water barrier layer is severe gamma n ＜γ c When the grouting thickness of the horizontal aquifer is smaller than that of the aquifer in the inclined interbed stratum, namely D<d; when the water barrier layer is severe gamma n ＞γ c When the grouting thickness of the horizontal aquifer is larger than that of the aquifer in the inclined interbed stratum, namely D>d；
And 7: determining the equivalent weight of grouting cement required by the whole foundation pit; and calculating the total cement slurry amount required by the excavation surface of the whole foundation pit according to the calculated grouting depth h of the inclined aquifer and by combining the length and width of the whole foundation pit and the range in the excavation area. As shown in the following equation (8):
Q＝nhb 1 Lq (8)
in the formula:
q-total amount of cement paste (m) required for reinforcing whole foundation pit 3 )；
n is the number of inclined aquifers at the bottom of the foundation pit;
l represents the longitudinal length (m) of the inclined aquifer at the bottom of the foundation pit;
q is the required cement slurry amount of the inclined aquifer in unit cubic meter.
And step 8: construction is distributed at each position of the grouting holes; and grouting and reinforcing the bottom of the foundation pit according to the calculated cement paste amount, wherein the distribution of each position of the grouting holes is determined according to the coagulation range of the grouting body formed by a single grouting hole according to the requirements of technical regulations for supporting foundation pits of buildings (JGJ 120-2012). A plurality of rows of grouting pipes are arranged in the inclined interbedded aquifer, and the depth of the grouting pipes is h 1 And strictly processing the cement paste.
And step 9: grouting process flow of the inclined aquifer; the special stratum is designed to adopt a splitting grouting construction process, namely high-pressure grouting, cement or chemical grout and the like are injected into a soil layer, the grout exerts additional compressive stress on the surrounding stratum to enable soil bodies to generate shear cracks, the grout is split from the place with low soil body strength and high strength along the cracks, and the grout split into the soil bodies forms a network or a framework for reinforcing the soil bodies. The water cement ratio of the cement paste is 1. The water glass modulus is larger than 2.5, and when the water glass modulus is larger, the viscosity of the water glass is increased, and the binding power is increased. The water glass mixing amount is 10-15% of the cement paste volume. Within the range, the reasonable setting time of the slurry can be ensured, and the slurry can effectively permeate into the soil body and can also be prevented from being coveredThe groundwater is dispersed. The concrete construction steps are as follows: (1) The pore diameter is generally within
The pitch of the holes is generally about 1.5m-1.0m, and the holes are arranged in a quincunx shape. (2) When the drill hole reaches the designed depth, the sealing mud is poured into the drill hole to seal the gap between the check valve pipe and the wall of the drill hole, so that the grouting hole is forced to open the ring, and the pressed mud extrudes the casing material and is poured into the surrounding soil layer. (3) Insertion of a one-way valve tube (split slip) into a borehole filled with sealing mud typically uses an internal diameter
The plastic pipe is externally coated with rubber sleeves every 33-50cm by drilling a group of shooting holes (namely 2-3 groups per meter), the pipe end is sealed when the plastic pipe is inserted into the drilling holes, and the plastic pipe is filled with water. (4) After the sealing slurry reaches a certain strength, a bidirectional sealing grouting core pipe is inserted into a one-way valve pipe for layered grouting, the pressure is increased firstly to enable the slurry to push open a rubber sleeve, a sleeve shell material is squeezed to break, a soil body is split and is diffused along a crack, the diffusion range is influenced by factors such as grouting pressure, time, slurry proportion, soil layer characteristics and the like, the slurry is generally grouted once every meter from the bottom, after a certain pressure is reached, one meter is lifted for grouting, and the grouting is repeated. And after grouting is finished, cleaning residual grout in the pipe so as to facilitate secondary repeated grouting.
Step 10: closing an internal dewatering well after the grouting body is finally set; after grouting construction is finished, after the grouting body is finally set, the grouting body and the inclined aquifer stratum are combined with each other to form a barrier with a good water-blocking effect. After the stage, large-scale precipitation treatment is not needed inside the foundation pit, and the foundation pit can be closed for a long time to reduce the disturbance of the precipitation inside the foundation pit to the minimum, so that a steady-state seepage mode is formed for an underground water seepage system inside and outside the whole foundation pit. Meanwhile, a dry operation construction environment is provided for subsequent foundation pit infrastructure construction, and the overall stability of the foundation pit is ensured to a greater extent during the foundation pit backfilling process.
Compared with the prior art, the invention has the beneficial effects that: in the excavation process, the construction environment is guaranteed through precipitation treatment of the bottom of the foundation pit, grouting construction is conducted in the inclined aquifer in the foundation pit after excavation is finished, water seepage in the foundation pit is blocked jointly through combined action of the inclined aquifer and the weak permeable water-resisting layer, and influence of water level rising in the flood season of the river on the inside of the foundation pit is effectively prevented. And simultaneously, the actual converted grouting depth in the inclined water-containing layer is given. Namely a method combining local occlusion waterproof curtain → oblique grouting. By adopting the method, the problem of strong water supply in the water-containing layer can be better controlled, the anti-surge safety of the soil body at the bottom of the pit is enhanced, and the safety guarantee is provided for the later construction of underground structures in the foundation pit.
Drawings
FIG. 1 is a plan layout view of dewatering wells, local plain concrete piles and supporting row piles around a foundation pit according to the present invention;
FIG. 2 is a first layout view of the partial plain concrete piles and the supporting row piles in the invention;
FIG. 3 is a second layout of the partial plain concrete piles and the supporting row piles in the present invention;
FIG. 4 is a cross-sectional layout of dewatering wells, local plain concrete piles and supporting row piles around a foundation pit according to the present invention;
FIG. 5 is a schematic illustration of the grouting of an inclined aquifer in accordance with the present invention;
FIG. 6 is a partial enlarged view of FIG. 5 of the present invention.
In the figure: precipitation well 1, support row pile 2, local plain concrete pile 3, local slip casting 4, slope water barrier 5, slope aquifer 6, inside slip casting hole 7.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
A water stopping method for water gushing in a deep foundation pit under a riverside gentle-inclination mutual layer is disclosed, as shown in figures 1-6, before excavation of a foundation pit, a dewatering well 1 is arranged on the periphery of the foundation pit, and meanwhile, a form that a local plain concrete pile 3 is meshed with a supporting row pile 2 is adopted in the foundation pit to jointly play a role of supporting and water stopping; after the excavation of the foundation pit is finished, local grouting 4 is arranged at the bottom of the foundation pit, so that a closed water-stopping and water-isolating system is integrally formed in the foundation pit, and the integral stability of the foundation pit is facilitated;
the method specifically comprises the following steps:
step 1: determining the depth of the inclined interbed according to the stratum exploration result, and setting the burial depth l of the water well with the leakage pressure of the foundation pit w (ii) a And before the foundation pit is excavated, determining the depth of the dewatering well outside the foundation pit according to the actual stratum of the project, the underground water condition and the size of the foundation pit. And (3) constructing the dewatering well on the periphery of the foundation pit, so that the internal dry operation during excavation of the upper part of the foundation pit is ensured, and the water level control guarantee in flood season is realized. In the foundation ditch construction period, when the river water level rises in the flood season, the rising water level can be reduced to a certain extent through the external relief well, the water level is kept to be not more than the top depth of the local interlock waterproof curtain of the foundation ditch all the time, and the inside of the foundation ditch can be kept in a dry operation environment all the time in the whole early excavation. Namely, the external early-stage small-range pressure relief and precipitation construction.
Step 2: determining parameters of a local occluded waterproof curtain in a foundation pit; and after the position of the peripheral dewatering well is determined, determining parameters of the engaged waterproof curtain in the foundation pit. Determining specific parameters of the local occlusion supporting pile according to the designed excavation depth of the foundation pit and the technical regulation of building foundation pit support (JGJ 120-2012), and simultaneously determining the depth l of the whole occlusion water-stop curtain inserted into the bottom of the foundation pit d . In order to ensure the stability of soil flowing in the foundation pit, conversion calculation is carried out by adopting a formula (1) as follows:
K f the stability safety coefficient of the flowing soil is not less than 1.6, 1.5 and 1.4;
l d -the depth of insertion (m) of the curtain of cut water below the bottom of the pit;
gamma' -soil buoyancy (kN/m) 3 )；
Delta h is the water head difference (m) inside and outside the foundation pit;
γ w -water gravity (kN/m) 3 )。
The depth l of the waterproof curtain inside the foundation pit inserted into the bottom of the foundation pit is obtained through conversion d The following were used:
determining total depth L of waterproof curtain in foundation pit S 。
L s ≥l d +H (3)
And step 3: constructing a local occluded waterproof curtain in the foundation pit; and taking support and water stop effects into consideration to carry out foundation pit support structure measure construction, and adopting an occlusion structure of plain concrete piles and reinforced concrete. Namely, the adjacent concrete row piles are partially embedded in the circumference, and a reinforcement cage is arranged in the piles constructed in the subsequent phase, and the occlusion part between the piles is not less than 200mm, so that the integral continuous protective curtain with good seepage-proofing function is formed. The concrete construction is carried out according to the requirements of technical regulations for supporting foundation pits of buildings (JGJ 120-2012). And the occlusion construction of plain concrete is not carried out in the stratum above the inclined interbedded stratum. The water level of the upper part of the inclined interbed stratum is acted by a dewatering well at the shallow part outside the foundation pit, the water level is well controlled, and the contribution of the plain concrete pile to the lateral support of the foundation pit is small, so that the plain concrete pile with the water stopping function is not required to be added in consideration of comprehensive economic benefits;
and 4, step 4: constructing and excavating a dewatering well in the foundation pit; after the construction of the local occluded water-stop curtain measure at the periphery of the foundation pit is finished, constructing the dewatering wells in the foundation pit, wherein the positions of the dewatering wells are uniformly distributed in the foundation pit, and the interior of the foundation pit is ensured to always keep a certain dry operation environment in the construction process; in the excavation of the horizontal ground layer of upper portion, precipitation well combined action inside and outside the foundation ditch for the whole accuse of the foundation ditch is good and continues to go on along with the foundation ditch excavation, and the mutual stratum of slope progressively leaks naked, and the infiltration phenomenon appears in the foundation ditch side, considers that increaseing inside and outside precipitation well degree of depth and operating power can cause the peripheral building of foundation ditch to produce differential settlement, is unfavorable for the foundation ditch overall stability, so the foundation ditch internal adoption part interlock stagnant water curtain measure of comprehensive consideration. In the whole excavation process, a plurality of prestressed anchor cables are constructed step by step according to design requirements and cooperate with a local waterproof curtain, on one hand, the water seepage on the side surface of the foundation pit is well controlled, on the other hand, the foundation pit deformation is effectively limited, and a good construction operation environment is better provided for the subsequent excavation.
And 5: local grouting in the inclined aquifer; with the end of excavation, in order to avoid the problem of seepage supply to the interior of the foundation pit along the inclined water-bearing layer, local grouting is carried out in the foundation pit; and determining the inclination angle and the trend of the inclined interbed and the proportion of the water-separating interbed according to the geological survey report. Calculating the thickness of grouting inside the foundation pit under the horizontal rock stratum; because the soil mass after grouting can only be grouted in the inclined aquifer, the soil mass after grouting is mixed. And (4) calculating to obtain the grouting thickness D required by the bottom of the foundation pit under the horizontal rock stratum according to the foundation pit anti-surge formula (4).
K h A stable inrush safety factor, which should not be less than 1.1;
d, the thickness of a soil layer from the top surface of the confined water aquifer to the bottom of the pit (namely the thickness required by grouting) (m);
γ c mixed severity of the aquifer soil layer after grouting (kN/m) 3 )；
h w -the head height (m) of the pressure of the top surface of the aquifer of confined water;
γ w -water gravity (kN/m) 3 )；
Step 6: correcting the grouting thickness in the inclined aquifer; and calculating and correcting the grouting thickness under the horizontal rock stratum into the grouting thickness of the special stratum according to the different gravities and occupied space proportions of the aquifer and the water-resisting stratum in the inclined interbed. Wherein, the pressure is unchanged according to the overlying water pressure, namely the whole pressure of the grouting body is equal. Therefore, the conversion is performed according to the formula (5) as follows:
Dγ c B＝(γ n b 1 +γ c b 2 )d (5)
b, the sum (m) of horizontal widths of the aquifer and the waterproof layer;
d-the thickness (m) of the grouting in the inclined water-containing layer;
γ s aquifer severity (kN/m) 3 )；
γ n Water barrier Severe (kN/m) 3 )。
Wherein when the water-resisting layer is severe gamma n ＝γ c When the thickness of the horizontal aquifer grouting is the same as that of the aquifer grouting in the inclined interbed stratum, namely D = D; when the water barrier layer is severe gamma n ＜γ c When the grouting thickness of the horizontal aquifer is smaller than that of the aquifer in the inclined interbed stratum, namely D<d; when the water barrier layer is severe gamma n ＞γ c In time, the grouting thickness of the horizontal aquifer is larger than that of the aquifer in the inclined interbed stratum, namely D>d；
And 7: determining the equivalent weight of grouting cement required by the whole foundation pit; and calculating the total cement slurry amount required by the excavation surface of the whole foundation pit according to the calculated grouting depth h of the inclined aquifer and by combining the length and width of the whole foundation pit and the range in the excavation area. As shown in the following equation (8):
Q＝nhb 1 Lq (8)
in the formula:
q-total amount of cement paste (m) required for reinforcing whole foundation pit 3 )；
n is the number of inclined aquifers at the bottom of the foundation pit;
l represents the longitudinal length (m) of the inclined aquifer at the bottom of the foundation pit;
q is the amount of cement paste required by the inclined aquifer in unit cubic meter.
And 8: construction is distributed at each position of the grouting holes; grouting and reinforcing the bottom of the foundation pit according to the calculated cement paste amount,according to the requirements of technical regulations on supporting foundation pits of buildings (JGJ 120-2012), wherein the distribution of all positions of the grouting holes is determined according to the coagulation range of a grouting body formed by a single grouting hole. A plurality of rows of grouting pipes are arranged in the inclined interbedded aquifer, and the depth of the grouting pipes is h 1 And strictly processing the cement paste.
And step 9: grouting process flow of the inclined aquifer; the special stratum is designed to adopt a splitting grouting construction process, namely high-pressure grouting, cement or chemical grout and the like are injected into a soil layer, the grout exerts additional compressive stress on the surrounding stratum to enable soil bodies to generate shear cracks, the grout is split from the place with low soil body strength and high strength along the cracks, and the grout split into the soil bodies forms a network or a framework for reinforcing the soil bodies. The water cement ratio of the cement paste is 1. The modulus of the water glass is more than 2.5, and when the modulus of the water glass is larger, the viscosity of the water glass is increased, and the binding power is increased. The water glass mixing amount is 10-15% of the volume of the cement paste. Within the range, the slurry can be ensured to be reasonably coagulated, and not only can be effectively infiltrated into the soil body, but also can be prevented from being dispersed by underground water. The concrete construction steps are as follows: (1) The pore diameter is generally within
The pitch is generally about 1.5m to 1.0m, and the array is quincunx. (2) When the drill hole reaches the designed depth, the sealing mud is poured into the drill hole to seal the gap between the check valve pipe and the wall of the drill hole, so that the grouting hole is forced to open the ring, and the pressed mud extrudes the casing material and is poured into the surrounding soil layer. (3) Insertion of a one-way valve tube (split slip) into a borehole filled with sealing mud typically uses an internal diameter
The plastic pipe is externally coated with rubber sleeves at intervals of 33-50cm by drilling a group of shooting holes (namely 2-3 groups per meter), the end of the pipe is closed when the plastic pipe is inserted into the drilled holes, and the pipe is filled with water. (4) After the sealing slurry reaches a certain strength, a bidirectional sealing grouting core pipe is inserted into the one-way valve pipe for layered grouting, the pressure is increased firstly to push the slurry to open the rubber sleeve, and the sleeve shell material is brokenThe soil body is split and is diffused along the crack, the diffusion range is influenced by factors such as grouting pressure, time, slurry proportion, soil layer characteristics and the like, the grouting is generally performed once every meter from the bottom, after a certain pressure is reached, the soil body is lifted for one meter and then the grouting is performed repeatedly. And after grouting is finished, residual grout in the pipe is cleaned, so that secondary repeated grouting is facilitated.
Step 10: closing an internal dewatering well after the grouting body is finally set; after grouting construction is finished, after the grouting body is finally set, the grouting body and the inclined aquifer stratum are combined with each other to form a barrier with a good water-blocking effect. After the stage, large-scale precipitation treatment is not needed in the foundation pit, and the foundation pit can be closed for a long time to reduce the disturbance of the precipitation in the foundation pit to the minimum, so that a steady-state seepage mode is formed in an underground water seepage system inside and outside the whole foundation pit. Meanwhile, a dry operation construction environment is provided for the subsequent foundation facility construction in the foundation pit, and the integral stability of the foundation pit is ensured to a greater extent in the process of backfilling the foundation pit.
The present invention is not limited to the above preferred embodiments, and any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A water stopping method for gushing water in a deep foundation pit below a riverside slow-dip interbed is characterized by comprising the following steps: before excavation of a foundation pit, arranging a dewatering well (1) at the periphery of the foundation pit, and simultaneously adopting a form that a local plain concrete pile (3) is meshed with a supporting row pile (2) to jointly play a supporting and water stopping role in the foundation pit; after the excavation of the foundation pit is finished, local grouting (4) is arranged at the bottom of the foundation pit, so that a closed water-stopping and water-isolating system is integrally formed in the foundation pit, and the integral stability of the foundation pit is facilitated;
the method specifically comprises the following steps:
step 1: determining the depth of inclined interbed according to the stratum exploration result, and setting the burial depth l of the water well for the leakage pressure of the foundation pit w ；
Step 2: determining parameters of a local occluded waterproof curtain in a foundation pit;
and 3, step 3: constructing a local occluded waterproof curtain in the foundation pit;
and 4, step 4: constructing and excavating a dewatering well in the foundation pit;
and 5: local grouting in the inclined aquifer;
and 6: correcting the grouting thickness in the inclined aquifer;
and 7: determining the equivalent weight of grouting cement required by the whole foundation pit;
and step 8: construction is distributed at each position of the grouting holes;
and step 9: grouting process flow of the inclined aquifer;
step 10: and closing the internal dewatering well after the grouting body is finally set.
2. The water stopping method for water inrush in deep foundation pit under riverside gentle dip interbed as claimed in claim 1, characterized in that: in the step 2, after the position of the peripheral dewatering well is determined, determining parameters of a meshing waterproof curtain in the foundation pit; determining specific parameters of the local occlusion supporting pile according to the designed excavation depth of the foundation pit and the technical regulation of building foundation pit support (JGJ 120-2012), and simultaneously determining the depth l of the whole occlusion water-stop curtain inserted into the bottom of the foundation pit d (ii) a In order to ensure the stability of soil flowing in the foundation pit, conversion calculation is carried out by adopting a formula (1) as follows:
K f the stability safety coefficient of the flowing soil is not less than 1.6, 1.5 and 1.4;
l d -the depth of insertion (m) of the curtain of cut water below the bottom of the pit;
gamma' -soil buoyancy (kN/m) 3 )；
Delta h is the water head difference (m) inside and outside the foundation pit;
γ w -water gravity (kN/m) 3 )。
The depth l of the waterproof curtain inside the foundation pit inserted into the bottom of the foundation pit is obtained through conversion d The following were used:
determining the total depth L of the waterproof curtain in the foundation pit S 。
L s ≥l d +H (3)
3. The water stopping method for water inrush in deep foundation pit under riverside gentle dip interbed as claimed in claim 1, characterized in that: in step 3, adopting a plain concrete pile and reinforced concrete occlusion structure, namely embedding part of circumferences of adjacent concrete row piles, inserting a reinforcement cage into a pile constructed in a subsequent sequence, wherein the occlusion part between the piles is not less than 200mm, so that an integral continuous protective curtain with good seepage-proofing effect is formed; and the occlusion construction of plain concrete is not carried out in the stratum above the inclined interbedded stratum.
4. The water stopping method for water inrush in deep foundation pit under fluvial gentle dip interbed according to claim 1, characterized in that: and 4, after the construction of the local meshing waterproof curtain measure on the periphery of the foundation pit is finished, constructing the dewatering wells inside the foundation pit, wherein the positions of the dewatering wells are uniformly distributed inside the foundation pit, and the inside of the foundation pit is ensured to be always kept in a certain dry operation environment in the construction process.
5. The water stopping method for water inrush in deep foundation pit under riverside gentle dip interbed as claimed in claim 1, characterized in that: in step 5, local grouting in the foundation pit is carried out along with the end of excavation to avoid the problem of seepage supply to the foundation pit along the inclined water-containing layer; determining the inclination angle and the trend of the inclined interbed and the proportion of each water-separating interbed according to the geological survey report; calculating the thickness of grouting inside the foundation pit under the horizontal rock stratum; because the soil mass after grouting can only be grouted into the inclined aquifer, the soil mass after grouting is mixed with the soil mass; calculating to obtain the grouting thickness D required by the bottom of the foundation pit under the horizontal rock stratum according to a foundation pit anti-surging formula (4);
K h a stable inrush safety factor, which should not be less than 1.1;
d, the thickness (m) of a soil layer from the top surface of the confined water aquifer to the bottom of the pit;
γ c mixed severity of the aquifer soil layer after grouting (kN/m) 3 )；
h w -the head height (m) of the pressure of the top surface of the aquifer of confined water;
γ w -water gravity (kN/m) 3 )。
6. The water stopping method for water inrush in deep foundation pit under fluvial gentle dip interbed according to claim 1, characterized in that: in step 6, calculating and correcting the grouting thickness under the horizontal rock stratum into the grouting thickness of the special stratum according to the different gravities and occupied space proportions of the aquifer and the water-resisting stratum in the inclined interbed; wherein, the pressure is unchanged according to the pressure of the overlying water, namely the whole pressure of the grouting body is equal; therefore, the conversion is performed according to the formula (5) as follows:
Dγ c B＝(γ n b 1 +γ c b 2 )d(5)
b, the sum (m) of horizontal widths of the aquifer and the waterproof layer;
d-the thickness (m) of the grouting in the inclined water-bearing layer;
γ s aquifer severity (kN/m) 3 )；
γ n Water barrier Severe (kN/m) 3 )；
Wherein when the water-resisting layer is severe gamma n ＝γ c When the thickness of the horizontal aquifer grouting is the same as that of the aquifer grouting in the inclined interbed stratum, namely D = D; when the water barrier layer is severe gamma n ＜γ c When the grouting thickness of the horizontal aquifer is smaller than that of the aquifer in the inclined interbed stratum, namely D<d; when the water barrier layer is severe gamma n ＞γ c When the grouting thickness of the horizontal aquifer is larger than that of the aquifer in the inclined interbed stratum, namely D>d。
7. The water stopping method for water inrush in deep foundation pit under riverside gentle dip interbed as claimed in claim 1, characterized in that: in step 7, calculating the total cement slurry amount required by the excavation surface of the whole foundation pit according to the calculated inclined aquifer grouting depth h and by combining the length and width of the whole foundation pit and the range in the excavation area; as shown in the following equation (8):
Q＝nhb 1 Lq(8)
in the formula:
q-total amount of cement paste (m) required for reinforcing whole foundation pit 3 )；
n is the number of inclined aquifers at the bottom of the foundation pit;
l represents the longitudinal length (m) of the inclined aquifer at the bottom of the foundation pit;
q is the amount of cement paste required by the inclined aquifer in unit cubic meter.
8. The water stopping method for water inrush in deep foundation pit under riverside gentle dip interbed as claimed in claim 1, characterized in that: in step 8, grouting and reinforcing the bottom of the foundation pit according to the calculated cement paste amount, according to the requirements of technical regulations for supporting foundation pits of buildings (JGJ 120-2012), wherein the distribution of each position of a grouting hole is determined according to the coagulation range of the grouting body formed by a single grouting hole; a plurality of rows of grouting pipes are arranged in the inclined interbedded aquifer, and the depth of the grouting pipes is h 1 And strictly processing the cement paste.
9. The water stopping method for water inrush in deep foundation pit under fluvial gentle dip interbed according to claim 1, characterized in that: in step 9, cleaving is employedThe grouting construction process comprises the following concrete construction steps: (1) The pore diameter is generally within
The range is that the hole pitch is generally about 1.5m-1.0m and is arranged in a quincunx shape; (2) When the drill hole reaches the designed depth, the enclosed slurry is filled from the drill hole, the gap between the check valve pipe and the wall of the drill hole is closed, the grouting hole is forced to open the ring, and the extruded slurry crushes the casing slurry and is injected into the surrounding soil layer; (3) Inserting check-valve tubes, i.e. split-grouting tubes, into boreholes filled with sealing mud, typically of internal diameter
Drilling a group of grout injection holes at intervals of 33-50cm, namely 2-3 groups per meter, wrapping a rubber sleeve outside, sealing the end of the pipe when the pipe is inserted into the drilled holes, and filling water in the pipe; (4) After the sealing slurry reaches a certain strength, inserting a bidirectional sealing grouting core pipe into a one-way valve pipe to perform layered grouting, firstly increasing the pressure to enable the slurry to jack a rubber sleeve, crushing a sleeve shell material, splitting a soil body, diffusing along a crack, wherein the diffusion range is influenced by factors such as grouting pressure, time, slurry ratio, soil layer characteristics and the like, grouting is generally performed once every meter from the bottom, and after a certain pressure is reached, lifting one meter for grouting again, and repeating the steps; and after grouting is finished, residual grout in the pipe is cleaned, so that secondary repeated grouting is facilitated.
10. The water stopping method for water inrush in deep foundation pit under fluvial gentle dip interbed according to claim 1, characterized in that: in the step 10, after grouting construction is finished, after the grouting body is finally set, the grouting body is combined with the inclined aquifer stratum to form a barrier with a good water blocking effect; after the stage, large-scale precipitation treatment is not needed in the foundation pit, and the foundation pit can be closed for a long time to reduce the disturbance of the precipitation in the foundation pit to the minimum, so that a steady-state seepage mode is formed in the whole underground water seepage system inside and outside the foundation pit; meanwhile, a dry operation construction environment is provided for the subsequent foundation facility construction in the foundation pit, and the integral stability of the foundation pit is ensured to a greater extent in the process of backfilling the foundation pit.
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| CN202211565113.7A CN115787693A (en) | 2022-12-07 | 2022-12-07 | Water stopping method for water gushing in deep foundation pit under riverside slow-dip interbed |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117266212A (en) * | 2023-11-23 | 2023-12-22 | 北京建工集团有限责任公司 | Low-cost dewatering method for foundation pit positioned in runoff-type interlayer water-containing stratum |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117266212A (en) * | 2023-11-23 | 2023-12-22 | 北京建工集团有限责任公司 | Low-cost dewatering method for foundation pit positioned in runoff-type interlayer water-containing stratum |
| CN117266212B (en) * | 2023-11-23 | 2024-02-09 | 北京建工集团有限责任公司 | Precipitation method for foundation pit located in runoff-type interlayer water-containing stratum |
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