What is the bearing capacity of silt foundation What is the ultimate bearing capacity of general sil

It can be checked that the bearing capacity of general sludge will not exceed 50kpa

According to the Code for the Design of Building Foundations-89 Appendix 5 Characteristic values of foundation bearing capacity of soil (rock).

The foundation bearing capacity of the silt is calculated based on the moisture content of the silt. Check the norms yourself. Some of the old canonical data and formulas can be used.

The bearing capacity of the sludge is 0-100kpa.

Some undisturbed sludge with structure or large buried depth has a higher intensity, and the surface sludge has a lower intensity.

Generally, the sludge we see is generally considered to have a moisture content of more than 80, showing a semi-flowing state, and the ultimate bearing capacity will not exceed 20kpa, or even below 10kpa.

In the specification GB50007-2002, there is such a clause: "Article Silt is a cohesive soil deposited in a still water or slow flowing water environment and formed by biochemical action, with a natural water content greater than the liquid limit and a natural porosity ratio greater than or equal to." When the natural water content is greater than the liquid limit and the natural porosity ratio is less than but greater than or equal to the cohesive soil or silt soil, it is silty soil. ”

The silt texture stratum has flow plasticity, which should not only prevent the diameter shrinkage due to insufficient internal support pressure caused by underbalance, but also prevent the formation softening and shrinking due to overequilibrium, and the pressure of the mud in the hole should be balanced with the in-situ stress in the depth of the hole. Therefore, it is necessary to prepare a reasonable proportion of mud to ensure that the mud in circulation quickly forms a dense mud skin. The pressure of the mud and the strong mud skin are used to balance the pressure of the formation, which can easily cause collapse.

1. Mud specific gravity design.

The specific gravity of mud should be controlled when trenchless pipe laying.

Because the silt stratum is soft, the Poisson's ratio is large, and the necking degree is significantly higher than that of the conventional stratum during reaming, the specific gravity of silty soil should be taken as far as possible. To prepare a large specific gravity slurry, it can be directly aggravated by increasing the amount of bentonite, but excessive bentonite will increase the viscosity and shear force of the mud, resulting in the mud not meeting the requirements in terms of fluidity. Moreover, the gravity of bentonite is not high, and the effect of increasing the specific gravity of mud is not significant.

Therefore, special weighting agents are generally used to aggravate the mud.

Silty soil is not silt or thin mud or the like, as long as the surrounding conditions allow, it is completely possible to slope and excavate. According to the naked eye, silty soil is a consolidated and non-flowing silt, which is theoretically a soil with a natural porosity ratio greater than 1 and less than.

According to the nature of the soil, the biggest difference between silt and silty soil is that the natural porosity ratio is different: the porosity ratio greater than is called silt, and the one greater than 1 and less than is called silty soil, but the natural moisture content is greater than the liquid limit, and the silt belongs to the unconsolidated and flowing soil.

Water content is the ratio of the mass of water in the soil to the mass of the soil particles, expressed as a percentage in units of 1. That is: w = (MW ms) 100% The moisture content of the natural soil layer is an indicator of the humidity of the soil, and its range of variation is very large, it is related to the type of soil, burial conditions, etc., generally dry coarse sand, its value is close to zero, and saturated sand can reach 40%; The water content of hard clay is about less than 30%, while the water content of saturated soft clay can reach more than 100%.

Generally, the same type of soil has a low strength if it has a high water content. Liquid limit wl: The water content of the soil when it changes from a plastic state to a liquid state (flow state).

At this time, in addition to the bound water, there is also free water in the soil. The unit of natural liquid limit and water content are the same thing, and the unit in percentage form is 1.