How to construct the quicksand stratum of the artificial excavated pile foundation

When the pile foundation is excavated manually, if it encounters fine sand and silt layer geology, coupled with the effect of groundwater, it is easy to form quicksand, and in serious cases, well leakage will occur, resulting in quality accidents, so effective and reliable measures should be taken.

1) When the quicksand situation is light, the excavation depth of this cycle can be shortened, and the normal section of about 1 meter can be shortened to meters, so as to reduce the exposure time of the excavation layer hole wall and carry out the concrete pouring of the wall in time. When the hole wall collapses, there is mud and sand inflow and the pile hole cannot be formed, the textile bag soil can be gradually blocked to form the outer wall of the pile hole, and control to ensure that the inner wall meets the design requirements.

2), when the quicksand situation is more serious, the common method is to lower the steel sleeve, the steel sleeve is similar to the steel membrane plate used for the wall, with the outer diameter of the hole as the diameter, can be divided into 4 6 sections of arc, plus the appropriate ribs, connected with bolts or steel ring buckles, in the excavation meters or so, the sleeve can be loaded into pieces, not less than meters deep into the bottom of the hole, inserted into the outer side of the upper concrete wall is not less than meters, and the formwork is poured after the wall protection concrete. If the quicksand is still upwelling after putting in the sleeve, the method of sealing the bottom of the hole with concrete after sudden excavation can be adopted, and after the concrete is solidified, the concrete in the core of the hole is chiseled to form a pile hole. This method can also be used, applied to the lowest section of the completed concrete retaining wall drilling, so that the hole position is inclined to the lower retaining wall, driven into the slurry pipe, pressure pouring cement slurry, improve the impermeability of the surrounding and bottom soil.

3.Jumping to dig precipitation: Dig a hole near the one that can be dug and use this hole to become a precipitation well, so that the groundwater level in a small area drops (about 5 7 days), and then dig a difficult hole.

4.Backfill sand method: mud gushing, the hole of quicksand first returns to the sand (about 1 2 days) to make the flow-plastic soil around the hole drain and consolidate. Wait for the soil to stabilize before continuing excavation.

1. Dig less, protect with 500. 2.Under the casing steel of cement. 3.Grouting curing. 4. Under the steel bar, surrounded by grass, an experienced construction team is required.

The wall protection that is used when manually digging holes, in this case, the thickness of the wall can be thickened, and the length of each section of support is determined according to the situation of the site. If the quicksand layer is not thick, you can directly go to the quicksand layer under the steel casing.

The specific construction method should be determined according to the actual construction situation on site. In short, find a way to block the quicksand.

1. A small amount of seepage can be dug in the pile hole to dig a small collection pit, and the muddy water can be hung out with the bucket with the excavation;

2. A large amount of water seepage, a deeper collection well can be dug in the pile hole first, and a small submersible pump is set up to discharge the groundwater out of the pile hole, and the collection well is deepened with the excavation;

3. When the water inflow is very large, if the pile is dense, a pile can be excavated in advance, so that the nearby groundwater is collected in the pile hole, and the groundwater is pumped out with 1-2 diving to play the role of deep well precipitation and reduce the groundwater level of the nearby pile hole;

4. When the amount of seepage is large and the groundwater at the bottom of the well is difficult to drain, the bottom mud can be cleaned by compressed air hole cleaning method.

5. When draining water in the pile hole, pay attention to the change of the turnover groundwater level, otherwise it will bring harm to the surrounding facilities due to soil consolidation and ground subsidence.

When digging a hole in the quicksand layer, generally can be set up in the well slip or with a hole high 1-2m, 4mm thick steel casing casing, the diameter is slightly smaller than the inner diameter of the concrete retaining wall, the use of concrete support as a fulcrum, with a small hydraulic jack to gradually press the steel casing into the soil, blocking the quicksand.

The steel sleeve can sink one after another, press into a section, excavate a section of pile hole, until it passes through the quicksand layer, and then transfer to normal excavation and concrete support. When pouring concrete, to this section, the steel casing (with the lifting ring) is hoisted out with the pouring concrete, or it can not be hoisted out.

Hehe, this question is a good question First of all, blind construction without a geological survey report? The use of open drainage method to pump water, to understand the cause of the formation of quicksand Because the gravity of the excavated soil is less than the severity of the groundwater level, causing the water to flow out of the surface At this time, use heavy objects first, cover it horizontally with a grass curtain, and press stones on it, which can temporarily alleviate the water seepage, and urgently arrange the open drainage method to pump the wall upstairs, I am dizzy, and it has been done in the excavation

The excavation pile encounters complex geology in the construction and is difficult to construct, among which the excessively soft geology causes the hole wall to collapse easily, forms potential safety hazards, and cannot continue to excavate and other hazards, and the most prominent manifestation is the quicksand phenomenon, which is the most obvious obstacle to the construction. Improper geological treatment of quicksand soil may lead to more difficult construction, or even lead to the abandonment of the use of the excavated pile process in favor of other hole-forming processes or other foundation types. The following introduces several measures that are not common when encountering the geological conditions of quicksand soil layer in the process of digging pile construction to ensure the smooth progress of the construction of digging piles.

The hazards of too soft geology are generally related to the moisture content of the foundation soil, and the hazards such as easy collapse of the hole wall, the formation of potential safety hazards, and the inability to continue digging are caused by the construction, and the most prominent manifestation is the quicksand phenomenon. There are several sufficient conditions for the formation of quicksand, and the soil layer has one of the following characteristics, it is possible to form quicksand: (1) the thickness of the subclay or silt layer in the soil layer is more than 250mm; (2) In the silt layer, the clay particle content is 10, and the silt particle content is 75; (3) In the gradation of soil particles, the unevenness coefficient of soil is less than 5; (4) the moisture content of soil 30; (5) the porosity of soil 43; In the site soil layer with the above sufficient conditions, the necessary condition for the formation of quicksand is to be disturbed or to have hydrodynamic pressure.

Once the surface of the soil layer is disturbed by movement, it will be rapidly "liquefied", the soil layer will gradually become more soft, the soil particles can flow together with the disturbed water flow, and the sand flow will occur under the action of disturbance, when the surface layer is not on a plane, the sand layer around the hole wall will flow to the center of the hole bottom (pot bottom). This is really just a slight quicksand phenomenon; When the hydrodynamic pressure gd of the soil is equal to or greater than the water immersion severity of the soil, the soil particles are in a suspended state, and the shear strength of the soil is almost zero, and serious quicksand will be formed. When the excavated pile encounters soft geology, it can pass through the soft geology by means of precipitation pressure transformation, curtain water separation, shortening the footage, underwater excavation, changing the wall protection structure, caisson construction, mechanical drilling, etc.

Treatment plan for water inrush in excavated piles.