CN113026757A

CN113026757A - Rapid excavation and support construction method for complex stratum pipe-jacking comprehensive well

Info

Publication number: CN113026757A
Application number: CN202110341552.9A
Authority: CN
Inventors: 史红伟; 肖亮; 范兴利; 李云雷; 卢慧林; 曹虎虎
Original assignee: Sinohydro Bureau 11 Co Ltd; PowerChina 11th Bureau Engineering Co Ltd
Current assignee: Sinohydro Bureau 11 Co Ltd; PowerChina 11th Bureau Engineering Co Ltd
Priority date: 2021-03-30
Filing date: 2021-03-30
Publication date: 2021-06-25

Abstract

The patent of the invention belongs to the technical field of municipal engineering, and relates to a construction method for rapid excavation and support of a pipe jacking integrated well in complex strata. The construction method of the invention is mainly suitable for the construction of comprehensive wells and similar comprehensive well projects under complex stratum conditions. Reduce the gap between the piles, reduce the precipitation pressure, and prevent the unsatisfactory precipitation effect from causing water gushing with sand. After the construction of the enclosure structure is completed, the layers are excavated from top to bottom, the nets are hung between the piles and the reinforcement is sprayed. The reinforced concrete structure of the main project is completed, and the support in the foundation pit is removed layer by layer from bottom to top after the strength meets the requirements, and finally the construction of the main building of the comprehensive well is completed.

Description

Rapid excavation and support construction method for complex stratum pipe-jacking comprehensive well

Technical Field

The invention belongs to the technical field of municipal engineering, and relates to a rapid excavation and support construction method for a complex stratum pipe jacking comprehensive well.

Background

In the small-sized shield and pipe-jacking tunnel construction, the common diameter of the pipe-jacking comprehensive well is 8.0-14.5 m, the maximum well depth is 45m, the maximum water pressure is 4bar, the well structure is circular, and a small number of wells adopt rectangles. The geology often encountered in the construction of synthetic wells is: the soil is planted, the soil is backfilled, the clay layer, the silt layer, the sand or silt layer, the pebble layer, the cobble layer and the full-weathering and strong-weathering stratum are composite strata, and the soil has the characteristics of uneven hardness, abundant groundwater, large water seepage amount, looseness and poor stability. The construction difficulty of the comprehensive well is high, the period is long, the risk is high, and the construction period cost is not easy to control. The construction method of the comprehensive well mainly comprises the steps of constructing by combining a sinking well method, a mining method, a continuous wall method, a freezing method, an SMW construction method, a bar-planted cast-in-place pile, a stirring pile and the like or combining a plurality of construction methods with auxiliary measures, and constructing the soil in a manner that a bucket of a common excavator for domestic construction is matched with soil, and soil discharging modes of a hydraulic machine, a hydraulic grab, a chain bucket and the like. Complex stratum or loose weak stratum, the construction of comprehensive well directly becomes the bottleneck problem that the construction period of shield constructs, push pipe restricts.

Disclosure of Invention

The invention aims to provide a quick excavation and support construction method for a complex stratum pipe-jacking comprehensive well, aiming at overcoming the defects of the prior art and effectively solving the problems of complex geology, tight construction period and the like of the current construction area. The construction method is mainly suitable for construction of comprehensive wells and similar comprehensive well engineering under the condition of complex strata, and the method mainly adopts the D1000@1200mm bored concrete piles + D600@1200mm jet grouting piles as foundation pit enclosure and waterproof curtains, so that gaps among the piles are reduced, the precipitation pressure is reduced, and water gushing and sand generation caused by unsatisfactory precipitation effect are prevented. After the building envelope construction is completed, the excavation is carried out in layers from top to bottom, the spraying and the protecting reinforcement are carried out by hanging nets among the piles, the foundation pit inner supporting system is completed from top to bottom until the excavation reaches the bottom elevation of the foundation pit, finally, the main engineering reinforced concrete structure is completed from bottom to top, the foundation pit inner supports are sequentially dismantled layer by layer from bottom to top after the strength meets the requirement, and finally, the construction of the main building of the comprehensive well is completed.

In order to achieve the purpose, the invention adopts the following technical scheme: a construction method for quickly excavating and supporting a pipe-jacking comprehensive well in a complex stratum comprises the following steps:

(1) determining a pile position by combining with the measurement point positions provided by design, carrying out hole jumping and drilling construction by adopting a rotary drilling rig, continuously transporting to each pile pouring point on site from a mixing station by adopting a mixing transport vehicle, directly warehousing for pouring, and making a record and record for the pouring process;

(2) the construction of the rotary spraying pile adopts the method of water injection, hammering, vibration and the like to form a hole, then the rotary spraying pipe is inserted to the bottom of the hole, and the rotary spraying is carried out from bottom to top; rotating and lifting at a constant speed in the construction of the drill rod;

(3) the foundation pit adopts a pipe well to lower water, and the dewatering well begins to lower water and drain water on the outer side of the jet grouting pile after the jet grouting pile is constructed;

(4) excavating a foundation pit from top to bottom, and arranging section steel supports on each layer;

(5) after floating soil is manually cleaned up among piles at the inner side of the cast-in-place pile structure, carrying out primary support by adopting a support system of 'reinforcing mesh sheets, connecting ribs and sprayed concrete';

(6) the foundation pit steel purlin and the support are processed and formed in a steel processing factory, the foundation pit is excavated to a planned support mounting elevation, anchor bars welded on the reinforcement cage in advance are cleaned, and the anchor bars and the reinforcement cage are welded into a whole.

Further explanation is as follows: in the step (1), the measuring instrument adopts a leica TS06 uitra-2 total station, a GPS is matched to determine the pile position, a cross-shaped pile guard is set within the range of more than 50cm of the radius of the pile body, marking is performed, and stabilization is performed.

Further explanation is as follows: in the step (2), the high-pressure rotary jet grouting pressure of the rotary jet pile is preferably more than 25MPa, the flow is more than 30L/min, the overlap length of the segmental lifting of the grouting pipe is not less than 100mm, and the rotary jet pile is arranged between the enclosure piles, so that the rotary jet pile and the enclosure piles are engaged.

Further explanation is as follows: in the step (3), the tube well is arranged at 1m outside the jet grouting pile, 10 dewatering wells are arranged on the periphery, the depth of each dewatering well is 35 m, the hole diameter of each drilling hole is 600mm, the pipe diameter of each dewatering pipe is 400mm, and a 50kw generator is configured on site to be used as standby power.

Further explanation is as follows: in the step (4), the comprehensive well is divided into four layers, wherein the first layer is excavated along the periphery by adopting a PC220 back-hoe, and the maximum excavation depth is 4.5 m; the second layer and the third layer adopt a long-arm back-hoe with the arm length of 24m and a small back-hoe to be matched for excavation, the excavation is carried out until the distance between the second layer and the third layer is 50cm below the support of the I-steel, the fourth layer adopts the small back-hoe, the long-arm back-hoe and a grab bucket to be matched for excavation, and a camera is installed at the position 3m above the long-arm back-hoe bucket and is connected with an operating room, so that the excavation is convenient.

Further explanation is as follows: and (5) hanging the reinforcing mesh on the erected anchor bolts, wherein the anchor bolts are phi 16 deformed steel, drilling holes in the existing cast-in-place pile by adopting an electric drill, and pouring cement slurry into the holes.

Further explanation is as follows: in the step (6), 2 anchor bars with the diameter of 28 are welded in the steel reinforcement cage before the steel reinforcement cage is hoisted, the anchoring length is 850mm, the exposed anchor bars are all sleeved with 50mm PVC pipes, then foam rubber is adopted for spraying and filling, and the steel support is preliminarily welded into 4 sections in a steel processing factory.

Compared with the prior art, the invention has the beneficial effects that: the invention adopts a D1000@1200mm cast-in-situ bored pile and a D6000@1200mm jet grouting pile as a foundation pit enclosure and a waterproof curtain. The guard post is internally welded with the embedded anchoring steel bars and the foundation pit inner support, so that the construction period delay caused by post-embedded steel bars is reduced, the inner support is quickly formed, and the stability of the foundation pit and the construction safety are ensured. Adopt back shovel, long arm back shovel, small-size back shovel complex mode to slag tap, improve mechanical utilization efficiency for the construction progress. The foundation pit support and the fender post are removed in a linear cutting mode, noise and vibration in the cutting process are small, and disturbance of the foundation pit is reduced.

Drawings

Other features, objects and advantages of the present invention will become more apparent upon reading of the following detailed description of non-limiting embodiments thereof, with reference to the accompanying drawings.

Fig. 1 is a schematic structural view of a foundation pit support section in the invention.

Fig. 2 is a schematic plan view of the arrangement of the first support of the foundation pit in the invention.

FIG. 3 is a schematic plan view of the second and third supports of the foundation pit according to the present invention.

FIG. 4 is a schematic diagram of a geological profile of a foundation pit according to the present invention.

Fig. 5 is a schematic view of a layered excavation structure of a foundation pit according to the present invention.

FIG. 6 is a sectional layout view of installation of the section steel in the present invention.

Fig. 7 is a schematic view of reinforcement of the steel purlin of the invention.

FIG. 8 is a schematic view of an integrated well monitoring arrangement of the present invention.

Fig. 9 is a layout view of the guard post and the waterproof curtain of the foundation pit of the comprehensive well.

FIG. 10 is a view showing the arrangement of fender piles and waterproof curtain piles according to the present invention.

Detailed Description

The present invention will be described in further detail with reference to the following examples, which are provided only for illustrating the present invention and are not intended to limit the scope of the present invention.

Two sections of jacking pipes are designed in 110kv new park power transmission line engineering in Zhengzhou aviation harbor areas, the lengths of the two sections of jacking pipes are 210m and 257.5m respectively, 4 cable tunnel integrated wells are arranged, the integrated wells are permanent structures and serve as jacking pipe wells in the early stage and serve as equipment rooms and safety channels in the later stage. Comprehensive well foundation pit size: the length is 13m, the width is 11m, and the depth is 14.5-16.826 m. Aiming at that the stratum distribution along the construction site is controlled by a landform unit, silt and silty clay which are the causes of the fourth series of rushing and flooding are taken as main materials, and soft interlayers with different thicknesses are mixed. The underground water belongs to the fourth series loose layer pore diving and is closely connected with the atmospheric precipitation and the surface water. During the exploration, the underground water level of the field is 5.0m below the field surface, and the underground water type belongs to diving and is mainly influenced by atmospheric precipitation supply and underground water exploitation.

Aiming at the problems that the geological conditions of the construction area of the comprehensive well are complex, the underground water level is shallow, and the surrounding soil body is deformed excessively, cracked or even collapsed possibly due to improper excavation and support of the comprehensive well. In addition, the construction area of the comprehensive well operation in the construction area is small, if small-sized machinery is adopted for slag discharge during excavation, slag discharge is difficult, and the construction efficiency is low, so that a person can complete the construction of the comprehensive well as early by adopting a series of efficient foundation pit excavation supporting methods, and meanwhile, a pipe-jacking comprehensive well is completed for later efficient and rapid construction in our department, relevant experiences are accumulated, and a set of construction method for efficiently excavating and supporting the foundation pit of the comprehensive well is summarized.

Please refer to fig. 1-10, which illustrate a technical solution of a complex stratum pipe jacking integrated well rapid excavation supporting construction method, as follows:

(1) and determining the pile position by combining the measurement point positions provided by design, carrying out hole jumping and drilling construction by adopting a rotary drilling rig, continuously conveying to each pile pouring point on site from a mixing station by adopting a mixing transport vehicle, directly warehousing for pouring, and recording the pouring process.

(2) The construction of the rotary spraying pile adopts the method of water injection, hammering, vibration and the like to form a hole, then the rotary spraying pipe is inserted to the bottom of the hole, and the rotary spraying is carried out from bottom to top. The drill rod rotates and lifts at a constant speed in the construction process.

(3) And the foundation pit adopts a pipe well to lower water, and the dewatering well begins to lower water and drain water outside the jet grouting pile after the jet grouting pile is constructed.

(4) The foundation pit is excavated from top to bottom, and each layer is provided with a section steel support.

(5) After floating soil is manually cleaned up among piles inside the cast-in-place pile structure, a support system comprising a reinforcing mesh, connecting ribs and sprayed concrete is adopted for primary support.

Further explanation is as follows: (1) in the measuring instrument, a leica TS06 uitra-2 total station is adopted, a GPS is matched to determine the pile position, a cross-shaped pile guard is arranged in a range which is larger than the radius of a pile body by 50cm, and marking and reinforcing stability are achieved.

Further explanation is as follows: (2) in the process, the high-pressure jet grouting pressure of the jet grouting pile is preferably more than 25MPa, the flow is more than 30L/min, the overlap length of the segmental lifting of the grouting pipe is not less than 100mm, and the jet grouting pile is arranged between the enclosure piles, so that the jet grouting pile and the enclosure piles must be occluded.

Further explanation is as follows: (3) the tube well is arranged at 1m outside the jet grouting pile, 10 dewatering wells are arranged on the periphery of the jet grouting pile, the depth of each dewatering well is 35 meters, the hole diameter of each drilling hole is 600mm, the pipe diameter of each dewatering pipe is 400mm, and a 50kw generator is configured on site to serve as standby electricity.

Further explanation is as follows: (4) in the middle, the comprehensive well is divided into four layers, the first layer is excavated along the periphery by adopting a PC220 back-hoe, and the maximum excavation depth is 4.5 m; the second layer and the third layer adopt a long-arm back-hoe with the arm length of 24m and a small back-hoe to be matched for excavation, the excavation is carried out until the distance between the second layer and the third layer is 50cm below the support of the I-steel, the fourth layer adopts the small back-hoe, the long-arm back-hoe and a grab bucket to be matched for excavation, and a camera is installed at the position 3m above the long-arm back-hoe bucket and is connected with an operating room, so that the excavation is convenient.

Further explanation is as follows: (5) and the reinforcing mesh is hung on an erected anchor, the anchor is phi 16 deformed steel, an electric drill is adopted to drill a hole on the current cast-in-place pile, and cement slurry is poured into the hole.

Further explanation is as follows: (6) in the process, 2 anchor bars with the diameter of 28 are welded in the steel reinforcement cage before the steel reinforcement cage is hoisted, the anchoring length is 850mm, the exposed anchor bars are all sleeved by 50mm PVC pipes, then foam rubber is sprayed and filled, and the steel support is preliminarily welded into 4 sections in a steel processing factory.

The construction process flow comprises the following steps: construction preparation → surface cleaning of the site → construction of the concrete pile for enclosure → construction of the jet grouting pile → precipitation of the pipe well → removal of the pile head and the first support → excavation of the first layer → steel support of the second layer → excavation of the second layer → steel support of the third layer → excavation to the bottom of the high range → construction of the bottom plate of the building structure → dismantling of the steel support of the third layer → construction of the first layer of the side wall → dismantling of the steel support of the second layer → construction of the side wall of the second layer → dismantling of the first layer of the support.

The method comprises the following specific steps:

(1) construction preparation: re-testing the construction area of the comprehensive well, verifying a drawing, and determining the length of the fender pile and the excavation depth of the comprehensive well; the method has the advantages that the field is reasonably arranged according to the field condition, various works are guaranteed to be orderly carried out, cross operation is avoided, the topographic condition of an operation area, the distribution of existing underground pipelines, the actual measurement geology of the field, the underground water level condition and the like are investigated in detail, and the arrangement condition of the dewatering well and the protection measures of the existing pipelines are determined.

(2) Construction of a fender pile 1 (a bored pile): determining a pile position by combining with the designed measurement point positions, performing hole jumping and drilling construction by adopting a rotary drilling rig, ensuring the perpendicularity of the formed holes of the rotary drilling rig by adopting necessary measures in the process, and reinforcing the retaining wall by adopting a static mud retaining wall soil borrowing process; the pile foundation reinforcement cage is manufactured in a centralized mode in a reinforcement field, concrete is continuously transported to each pile pouring point on the site from a mixing station by a mixing transport vehicle and is directly put into a warehouse for pouring, and records are made in the pouring process.

(3) And (3) constructing a jet grouting pile 2: the rotary spraying pile adopts a double-pipe method for high-pressure rotary spraying grouting, the pressure is more than 25MPa, and the flow is more than 30L/min. And carrying out high-pressure water spraying test after the equipment enters the field. The construction of the rotary spraying pile adopts the method of water injection, hammering, vibration and the like to form a hole, then the rotary spraying pipe is inserted to the bottom of the hole, and the rotary spraying is carried out from bottom to top. The drill rod rotates and lifts at a constant speed in the construction process. And the jet grouting pile is meshed with the fender post.

(4) Draining water in the foundation pit: because the stratum below the ground water level is mainly composed of silt, silt-mixed silt and fine sand, the phenomenon of water seepage and sand gushing of the side wall of the foundation pit is avoided, and the foundation pit excavation is ensured to be in a waterless operation state. The comprehensive well adopts tube well precipitation, and the precipitation well arranges jet grouting stake outside 1m department, sets up 10 precipitation wells altogether, and the degree of depth is 35 meters, aperture 600mm, precipitation pipe diameter 400mm to dispose a standby generator of 50kw, the foundation ditch sets up the escape canal all around and sets up scalable removal canopy above the foundation ditch.

(5) Excavation and supporting of a foundation pit: this engineering establishes 4 and synthesizes well, foundation ditch size: the length is 13m, the width is 11m, the depth is 14.5-16.826 m, and 3 supports are arranged in total. After the pile head is broken and the crown beam is poured and maintained to meet the requirements, the outer side is backfilled. And (5) starting excavation work of the foundation pit, and carrying out excavation of the comprehensive well in four layers. Excavating the first layer by adopting a PC220 back-hoe, excavating the back-hoe along the periphery of the comprehensive well, and excavating the first layer to the maximum depth of 4.5 m; excavating the second layer and the third layer until the distance between the second layer and the third layer is 50cm below the second I-steel support and excavating by adopting a long-arm backhoe with the arm length of 24m and a small backhoe in a matching manner; and the fourth layer adopts a small back-hoe, a long-arm back-hoe and a grab bucket to carry out matched excavation. In order to ensure the visual effect of excavation personnel, a camera is installed at the position 3m above the long-arm reverse bucket and is connected into an operating room, so that the comprehensive well can be excavated efficiently and quickly.

(6) And (3) spraying concrete among the piles: a support system of 'reinforcing mesh, connecting bars and sprayed concrete' is adopted among piles inside the cast-in-place pile structure. After excavation of each layer of foundation pit is completed, manually cleaning the fender piles and earthwork between the piles, after cleaning is completed, building anchor nail holes by using an electric drill, pouring cement paste into the holes, and using phi 16 deformed steel as anchors.

The sprayed concrete is mixed according to the mixing proportion strictly, and wet concrete spraying is adopted. During spraying protection, the low-lying part between the enclosure piles is firstly sprayed to be flat, layered from bottom to top and sprayed to and fro, and finally, the enclosure piles are sealed and leveled. The flatness of the sprayed concrete at the section steel support is strictly controlled.

(7) And (3) installing and constructing the steel purlin and the support: and the steel purlin 3 is welded with the reserved anchor bars in the fender pile. H-shaped steel enclosing purlins are selected for the steel enclosing purlins, 2 anchor bars 4 with the diameter of 28 phi are welded in each steel reinforcement cage before the steel reinforcement cages are hoisted, the anchoring length in pile foundations is 850mm, and the later-stage exposed parts of the anchor bars are all sleeved on the steel bars through 50mm PVC pipes. After the sleeve is sleeved with the reinforcing steel bars, foam rubber is sprayed and filled into the sleeve, and full filling in the sleeve is ensured. When the excessive earthwork of the pile foundation is cleaned, the pre-buried anchor bars which are fixed by the support are chiseled out for preliminary adjustment. Each steel support is preliminarily welded into 4 sections in a steel processing plant, and then the steel supports are hoisted into a foundation pit by a crane to be welded with an assembly ring, so that the operation time in the foundation pit is saved, and the steel supports are quickly closed and put into use.

(8) Dismantling the concrete support: and after the side wall structure of the comprehensive well is finished and the concrete strength reaches the design and standard requirements, removing the fender posts and the first concrete support in the range of the entrance and exit door opening of the jacking pipe. The concrete support and fender pile is dismantled by adopting a wire locking cutting mode, at least two main ribs are chiseled out on the top surface of the support beam at a cutting point by adopting an air pick, then a rope saw diamond chain passes through the main ribs, 2 upper-layer steel bars are reserved at each cutting point, and the steel bars are cut off before being hoisted.

(9) Monitoring arrangement: monitoring points are arranged along the periphery of the pit, the time for completing foundation pit monitoring is from backfilling to the designed elevation, and from the excavation of the foundation pit to the groove to the backfilling of the foundation pit to the designed elevation. Peripheral surface settlement observation points (12) and underground water monitoring wells are also used as underground water recharging wells (4), deep horizontal displacement monitoring values (4), top horizontal and vertical displacement monitoring points (8) and supporting internal force (12).

The foregoing is directed to preferred embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. However, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope of the technical solution of the present invention.

Claims

1. A construction method for rapid excavation and support of a pipe jacking integrated well in a complex stratum, comprising the following steps:

(1) Determine the pile position in combination with the measurement points provided by the design, use a rotary drilling rig to carry out jump-hole drilling construction, and use a mixing truck to continuously transport the piles from the mixing station to the site for pouring directly into the warehouse for pouring. Keep records of the process;

(2) For the construction of the rotary jet pile, first use water jetting, hammering, vibration and other methods to form holes, then insert the rotary jet pipe to the bottom of the hole, and perform rotary jetting from bottom to top; the drill pipe is rotated and lifted at a uniform speed during construction;

(3) The foundation pit adopts tube well for dewatering. After the dewatering well is constructed on the rotary jetting pile, the dewatering and drainage begin on the outside of the rotary jetting pile;

(4) The foundation pit is excavated from top to bottom, and each layer is provided with steel support;

(5) After the floating soil is manually cleaned between the inner piles of the cast-in-place pile structure, the "reinforced mesh + connecting bars + shotcrete" support system is used for initial support;

(6) After the foundation pit steel purlin and support are processed and formed in the steel processing plant, the foundation pit is excavated to the planned support installation elevation, and the anchor bars pre-buried and welded on the steel cage are cleaned up and welded into a whole.

2. the rapid excavation and support construction method of the complex stratum pipe jacking integrated well according to claim 1, is characterized in that, in step (1), measuring instrument adopts Lycra TS06 uitra-2 " total station, and cooperates with GPS to determine Pile position, and set up cross guard piles within a range of 50cm greater than the radius of the pile body, well marked and reinforced and stabilized.

3. The construction method for rapid excavation and support of pipe jacking integrated wells in complex strata according to claim 2, characterized in that, in step (2), the high-pressure rotary jet grouting pressure of the rotary jet pile should be greater than 25MPa, and the flow rate is greater than 30L/ min, the lap length of the grouting pipe segmented lifting shall not be less than 100mm, and the rotary jet piles are set between the enclosure piles, so they must be engaged with the enclosure piles.

4. The construction method for rapid excavation and support of pipe jacking integrated wells in complex strata according to claim 3, characterized in that, in step (3), the pipe wells are arranged at 1m outside the rotary jet pile, and a total of 10 dewatering wells are arranged around the perimeter. , the depth of the dewatering well is 35 meters, the borehole diameter is 600mm, the diameter of the dewatering pipe is 400mm, and a 50kw generator is configured on site as backup power.

5. The construction method for quick excavation and support of pipe jacking integrated wells in complex strata according to claim 4, is characterized in that, in step (4), the integrated well is divided into four layers, and the first layer adopts PC220 backhoe to open around the surrounding. Excavation, the maximum excavation depth is 4.5m; the second and third floors are excavated with a long arm backhoe with an arm length of 24m and a small backhoe, and the excavation is 50cm under the support of the second and third I-beams. The floor is excavated with small backhoe, long-arm backhoe and grab bucket, and a camera is installed 3m above the long-arm backhoe to connect to the operating room to facilitate excavation.

6. The construction method for rapid excavation and support of a pipe jacking integrated well in a complex stratum according to claim 4, characterized in that, in step (5), the steel mesh is hung on the erected anchors, and the anchors are rebars of φ16 , Use an electric drill to drill holes on the existing cast-in-place piles, and pour cement slurry into the holes.

7. The construction method for quick excavation and support of a pipe jacking integrated well in a complex stratum according to claim 6, characterized in that, in step (6), before the reinforcement cage is hoisted, two anchor bars with a diameter of 28 are welded inside, and anchored The length is 850mm, the exposed anchor bars are sheathed with 50mm PVC pipes, and then filled with foam glue. The steel supports are initially welded into 4 sections in the steel processing plant.