Steel casing is welded into the hole
.
The construction of cast-in-place pile is to make a pile hole in the soil manually or mechanically, then put the reinforcement cage of the pile body into the pile hole, pour concrete into the hole to form the pile, and finally pour the tie beam or bearing platform at the top of the pile
.
After the hole is formed, the reinforcement cage is put in, and then the sleeve is pulled out gradually when the pile body concrete is poured
.
It is suitable for clay, silt, sandy soil, muddy soil and some pebble and gravel strata
.
The mud is composed of clay or expansive soil with admixtures, and the specific gravity of the mud is generally between 1.1 and 1.3
.
When the grouting pipe is close to the pile bottom, the indicator light will be on to stop the reinforcement cage sinking and prevent damage to the bottom grouting pipe
.
The joints of each section of reinforcement cage shall be marked for corresponding splicing during installation
.
According to the stress form, pile foundation can be divided into end bearing pile and friction pile
.
The thickness of ballast at the bottom of the hole: the thickness of ballast at least 50% of the cross section at the bottom of the hole is less than 15mm, and the thickness of ballast at any position of the cross section at the bottom of the hole is not more than 40mm
.
The drilling methods of bored pile mainly include: rotary drilling rig, positive and negative circulation drilling rig, casing drilling rig, percussion drilling rig, etc
.
First, install a 3.4m temporary casing with a depth of about 10m into the soil, and then install a drilling rig with a diameter of 3.15m ~ 3.22m
.
After the reinforcement cage is hoisted into the pile hole, it is suspended at the top of the steel casing, spliced according to the sequence of sections, and put down section by section, and the final reinforcement cage is suspended at the top of the casing
.
The function of casing is to prevent the hole from collapsing, and the soil in the hole is removed by heavy hammer grab
.
The grouting pipe is made of 12 steel pipes with diameter of 25 mm, and 6 grouting circuits are formed by connecting them at the bottom
.
At the same time, the slurry can protect the wall (balance the water pressure in the hole) and prevent hole collapse and floating slag
.
The vhp700 air compressor provides wind power
.
Pile foundation is composed of several piles and pile cap, which is a common deep foundation
.
Bored piles are used in the construction of difficult to excavate
.
Considering the serious scouring of river bed in rainy season, there is steel casing on the top of bored pile
.
The main reinforcement is lengthened by lap joint, and each lap joint is connected by two “U” type clamps
.
The bridge foundation is concrete bored piles, each pier is 4 bored piles with diameter of 3.0m, the pile spacing is 10.0m in transverse direction, 9.0m in longitudinal direction, and the pile length is 91.0m
.
According to the mud circulation method, it can be divided into positive circulation and reverse circulation
.
Highway and bridge construction units should attach great importance to this
.
The weight of reinforcement cage is about 150t
.
Therefore, the discussion of bored pile construction technology in bridge engineering is of great significance
.
The main reinforcement is 36mm and the stirrup is 20mm
.
Pile foundation construction methods can be divided into two categories: cast-in-place pile and sunk pile
.
Hole forming by percussive drilling machine: the percussive drilling machine uses hoists and other equipment to raise the heavy bit with edge or grab, then release the hoister, the bit falls down, and the rock and soil at the bottom of the hole are cut and crushed
.
In each sleeve, two slurry outlet holes with a diameter of 6 mm and tightly wrapped by rubber sleeve are set on the steel pipe, and the slurry outlet hole is facing down
.
The pier piles are embedded 60m ~ 66m into the soil by pre drilling method
.
Casing drilling: it is to press a steel casing with mechanical shaking while drilling
.
The geological conditions of typical bridge site are silt, fine, medium and coarse sand layer and a small amount of gravel layer
.
Rotary drilling rig hole forming: the drill rod drives the drill bit to rotate, the power drill bit can rotate forward to drill at low speed, reverse to throw the soil at high speed, the drill bit rotates to cut the soil or sand into muck, and then quickly move out of the hole
.
Two sleeve parts are installed at the bottom of each circuit
.
Steel casing is transported and installed
.
The drilling methods of bored pile mainly include: rotary drilling rig, positive and negative circulation drilling rig, casing drilling rig, percussion drilling rig, etc
.
Reinforcement cage is manufactured and installed
.
The length of reinforcement cage for pier pile is 94.5m
.
Working procedure: drilling with positive and negative circulation drilling machine: rotary drilling with drill bit, circulating mud in and out of the hole, floating and taking drilling slag out of the hole to realize mucking out
.
Manual welding and splicing are adopted on site, and all welds are subject to ultrasonic flaw detection
.
The casing drilling method is suitable for the non rock strata in the track cover soil layer, and has good protection effect on the hole collapse
.
When the lower end of the reinforcement cage is close to the bottom of the pile casing, the lowering speed should be slowed down
.
It is generally divided into four sections and transported to the site by flat trailer or tractor
.
When the soft overburden is thick and the bearing stratum is deep, the pile foundation can be supported on the supporting stratum through the soft stratum
.
Drill to an elevation of – 49m
.
According to the specific geological conditions of the project, the pile foundation construction generally adopts the excavation pile construction
.
The wire is led out of the hole
.
The drilling construction adopts kpg-3000 hydraulic drilling rig and zsd300 / 210 hydraulic power head drilling rig, adopts heavy hammer guidance, decompression drilling and mud reverse circulation to discharge the slag Zx-500 mud separator is used to purify the mud
.
The steel casing of pier pile is designed to be 3.0m in diameter and 52m in length
.
The concealment of bridge pile foundation construction requires that in the construction of bridge pile foundation, we should not only rely on advanced science and technology, but also deal with the problems in the construction timely according to the rich construction experience, so as to avoid the occurrence of engineering quality accidents
.
Most bridge pile foundations are reinforced concrete piles
.
If the pile hole is excavated manually, it is called hole digging pile; if the hole is excavated mechanically, it is called bored pile
.
The bearing capacity of the former is mainly provided by the rock at the bottom of the pile, and the latter is provided by the vertical friction of the pile through the soil
.
The construction of cast-in-place bored pile is to make the pile hole in the soil manually or mechanically, then put the reinforcement cage of the pile body into the pile hole, pour concrete into the hole to form the pile, and finally pour the tie beam or bearing platform at the top of the pile
.
The casing is manufactured in the steel structure factory, formed by plate rolling machine, and welded by automatic electric welding machine on the rotary jig
.
Percussive drilling is widely used in clay, silt and pebble layers
.
If the pile hole is excavated manually, it is called hole digging pile; if the hole is excavated mechanically, it is called bored pile
.
More wonderful, please click the blue words above to follow us! Source: with the development of China’s economy and the acceleration of highway and bridge construction, a series of quality accidents have occurred in highway and bridge projects, which are directly related to people’s property safety and become the focus of people’s attention
.
Part of the cross-section is double-layer reinforcement cage, the maximum number of reinforcement in the same cross-section is 240, and the reinforcement is dense
.
Leave 1m to be shaken in place with an ape vibrator
.
The reinforcement is placed on the manufacturing mould, the inner main reinforcement protective layer is installed, the bottom contact switch of the wheel is made, the panoramic reinforcement cage is made, the reinforcement cage is lifted away from the manufacturing mould, the reinforcement cage transport crane is erected, the reinforcement cage section orifice is assembled, and the drilling pile is constructed
.
Because the bored pile in bridge engineering is a concealed project, most of the work is carried out underwater, so the construction quality inspection is difficult
.
The efficiency of reverse circulation is higher than that of positive circulation
.
Features: it shall not exceed 73 hours (39m pile length) from the beginning of drilling at the bottom opening of permanent steel casing to concrete filling at the bottom opening of permanent steel casing
.
Steel casing is vibrated and sunk to the design elevation
.
Steel casing rolled steel casing is welded on the rotating platform with circumferential joint
.
Mud index: the mud is composed of water, bentonite, clay and Na2CO3.
.
Construction process 1 construction process 2 manufacture and installation of steel casing for pier steel casing with diameter of 3.0m, length of 52m and plate thickness of 25mm
.
The design elevation of the bottom opening of the steel casing is – 50m
.
Pile bottom grouting: in order to keep the grouting pipeline at the bottom of the reinforcement cage as close to the hole bottom as possible without being damaged, a bottom touching indicator switch is installed at the bottom of the reinforcement cage
.
The circular grouting pipeline is arranged in the reinforcement cage to increase the bearing capacity of the pile bottom
.
The reinforcement cage shall be made on the long line pedestal and installed in four sections
.
In order to ensure that the grouting hole is close to the pile bottom, three bottom touching indicator switches are installed at the bottom of the reinforcement cage
.
After the drill bit is lifted out of the hole, the mucking can be carried out by the mucking drum or by the mud circulation method
.
Six 50mm steel pipes are evenly distributed along the circumference inside the reinforcement cage, which are used for ultrasonic testing of the pouring quality of pile concrete
.
It can be constructed near the existing buildings
.
