When planning a well, well or other hydrological structure on the site, it is mandatory to survey the area for groundwater occurrence. In the future, this allows you to more accurately form an action plan and object parameters. However, even with the successful completion of the survey, you should be prepared to detect a quicksand. This is a type of soil with perched water, which can cause a lot of problems both during earthworks and during the operation of various kinds of structures on this site.
What is quicksand?
According to the encyclopedic definition, quicksand should be understood as sand saturated with water. In a broader sense, this is a soil layer that can flow or spread. Also, in practice, one can meet slightly cohesive or non-cohesive sandy loams with similar characteristics. But in each case, it is assumed that quicksand is somevolume of small colloidal particles up to 0.001 mm in diameter. The property of water saturation is decisive for such soils, but sealing is also characteristic of quicksand. Usually, under natural conditions, a layer of silt saturated with water turns out to be closed and does not cause any inconvenience. A house or an engineering structure can stand on such a platform. Problems in the operation of sites with quicksand arise in cases where it is necessary to carry out earthworks to the level of finding water-saturated soil.
Features of quicksand
You will not surprise an experienced summer resident with the close interaction of the soil with the aquatic environment. When equipping an individual water supply system at the expense of an artesian well or well, one inevitably has to deal with the same groundwater. What is the fundamental difference between a quicksand and a perch? The key feature is the specific ability of silty sand to take on some of the properties of the liquid medium. Physically, this characteristic is expressed by hydrodynamic equilibrium, when the lower pressure is balanced by the mass of the soil. This allows water to be retained in the structure of the sand. The quicksand maintains the balance of pressures only under conditions of tightness. As already mentioned, it is enough to invade this formation during drilling or other earthworks, as the sand will go up under the action of bottom pressure. The consequences of such soil behavior can be unpredictable and in any case depend on the volume of floating accumulations.
True and false quicksands - how to distinguish?
In viewdifficulties in determining the characteristics of a particular quicksand and the similarity of its properties with the behavior of other ground sandy loams when interacting with aquatic environments, engineers separate true and false quicksands. In the first case, sands and sandy loams with hydrophilic properties are meant. As a rule, their structure is formed by very small colloidal and clay elements, which also act as a lubricant between larger particles. In freezing conditions, such layers are characterized by strong heaving and low ability to filter, and after drying they acquire cohesion.
In turn, the false quicksand is the same sandy layer, but without colloidal particles that determine the hydrodynamic qualities of the mass. A kind of imitation of the characteristics of a true quicksand is explained by the porosity of fine sand. However, from the point of view of practical measures to protect against such phenomena, there is no fundamental difference between these varieties of water-saturated soil masses. False quicksand is also capable of expelling sand under internal pressure when opened, presenting similar threats.
The nuances of construction on quicksand
Having come across a quicksand during the implementation of land activities, one should expect an inevitable change in the structure of the soil in the area of work. A typical problem of this kind arises during the construction of a pit and the subsequent removal of sand into its niche. This will not only complicate further work as part of the operation being performed, but will also lead to soil deformations in areas of closely spaced buildings.due to uneven sedimentation. Does this mean that in principle it is impossible to dig on quicksand? There are various ways to bypass them, but in principle it is far from always possible to predict a quicksand, and especially to determine its size. In any case, it should be taken into account what direct contact with water-saturated layers may threaten when performing land construction activities.
Dangers of quicksand
The biggest threat relates to manual earthworks, which involve digging a well for the subsequent laying of concrete rings. If the sealed layer of sand is under high pressure, then in the event of a breakthrough, along with the rings, it can carry away the entire team of workers. There are also cases of collapses, ground shifts and at least deformation of the wellbore. All such situations pose a danger to the life of diggers. On the other hand, quicksand is not always a bad thing, as the pressure-balanced sand in the mine can act as a filter barrier, naturally improving the quality of the produced water.
Methods to circumvent quicksand
Using the experience of builders-surveyors, it is quite possible to solve the problem of water supply even on a site with quicksand. To do this, use one of three methods of bypassing a dangerous formation:
- Shock-rope technique. The method involves drilling a well with percussion equipment in a niche of a metal pipe shaft, which insures the structure against an accident. The method is quite complex and technically demanding, but, from the point ofsecurity view, one of the best.
- The device of the Abyssinian well. If the question is how to pass a quicksand when drilling small wells, then you can limit yourself to the simplest means without special equipment. In particular, a metal tube 2.5 cm thick and a pump for pumping water are used. The pipe is driven in to a depth of 15-20 m, and pumping equipment is installed on the surface.
- Dense installation of well rings. Fast and accurate laying of concrete rings eliminates the risk of collapses and flooding on quicksand. But only specialists with the help of professional powerful equipment can implement this method.
General quicksand tips
Also, experts give several recommendations on the implementation of land work in hazardous areas with different types of water-saturated soil:
- Even with the successful passage of the quicksand, you should not immediately begin to quickly pump out water in large volumes. The formed void in this case will also quickly fill with sandy loam, which will degrade water quality.
- There are some nuances when doing this task with your own hands. How to pass the quicksand manually with minimal cost and without the risk of an accident? You can use a small format drill when working with a partner. This is how small wells of small diameter are performed. But precisely for the safety of the process, it is necessary to monitor the hydraulic balance. To do this, it is necessary to fill the well with water, which compensates for the pressure that shifts the sand from the bottom of the well up.
- On the water-bearing horizon, it is desirable to install additionalfilters.
- It is possible to minimize the hydrodynamic activity of quicksand using special freezing solutions. They have a cementing effect on the sand, removing water from it.
Conclusion
Humanity has long been familiar with quicksand, but there is still no universal technology to deal with them. In each case, a specific method of drilling quicksand is selected, taking into account the results of geodetic surveys and the time of year. For example, many specialists successfully practice the technique of passing a dangerous area in winter, when the soil is in a frozen state. In the rest of the year, it also makes no sense to refuse earthworks, since the control of water-bearing soil can be carried out with casing pipes and special hydrodynamic equipment.
