Soil pressure

Precast concrete piles will be used with an allowable compression force of 80 kips (356 kN) and an allowable tension force of 50 kips (222 kN), both with a safely factor of 3 against ultimate capacity. Because battered piles will resist all lateral forces without the need for passive soil pressure, a safety factor of 1.2 may be used. Permissible blast capacities will be adjusted accordingly. 

Scientific and engineering investigations into the properties and behavior of particulate solids date back to the early work of Coulomb, who in 1776 developed a theory on soil pressure and resistance, thus laying sound foundations for important engineering... 

Human numbers are growing fastest in the tropical world. With this growth goes an increase in livestock, and in cultivated soil. Pressure is increasing rapidly on life-support resources, and on land. Control depends on an understanding, not only of the social questions involved, but of the demands each living being makes on essential resources. 

Collapse of slurry walls can occur in granular materials when the lateral soil pressure exceeds the effective slurry pressure. For slurries consisting only of water and bentonite, the depth at which collapse may occur may be as little as 30 to 40 feet. For deeper excavation it may be necessary to use additives to increase the slurry density. Also, the lateral extent of the excavation may be reduced, to make arching more effective. Theoretical solutions have been developed to help design the construction procedures. These solutions define the lateral earth pressures at various depths, so that suitable slurry may be designed. 

Grouting with chemical grouts is generally done within limits of half to twice the overburden pressure. If these pressures cause fracturing in granular deposits, it will occur along planes of minimum pressure. Where horizontal soil pressures are at rest values (the usual condition), fracture planes will be vertical, as opposed to uplift planes which are generally horizontal, or nearly so. 

Having calculated Si and S2 it is possible to calculate the soil loading, S, which is the sum of the two. The maximum soil load occurs at the edge of the foundation shown as point F in Figure 11-1. Many structural engineers call this the soil pressure. 

Active soil pressure = Coefficient of lateral soil pressl = Initial soil modulus 1.25... 

Soil pressure on domes at 0.3 m penetration depth for Stratfjord A Condeep structure. (From Hide, O. et al.. Marine Geotech., 3,315-368,1979a. Reprinted with permission. Copyright Taylor Francis Group.)... 

Where roads or railways cross a pipeline, in addition to soil pressure, they are subject to further static and dynamic loads from passing vehicles. If the soil cover is less than 1.5 m, traffic loads dominate. For cross-country pipes under railway embankments or paved roads, it is possible to calculate soil pressure and traffic loads and hence the loads on the pipeline. The additional loads must be taken into account when determining the dimensions and properties of the pipes, and special measures may ultimately be necessary. 

Superstructure loading will have an effect on the pile design when the imposed vertical and horizontal loads are large relative to the load solicited by lateral soil pressure on the piles. 

The lateral soil pressure on a pile is a function of the width of the pile. In the application of piles to resist moving ground, large diameter piles with high moment resistance are applied with steel tubular piles often employed. In contrast, in the case of pile support required for the problem herein to minimize loading on the pile, a pile with minimum width and maximum moment resistance would be the optimum. Ting Tan (2004) present results of three types of piles reproduced here as Table 8.2. 

The extraction flow rate is very important in order to control air and contaminant vapor migration. Simply stated, the extraction rates must be higher than the injection rates in order to prevent soil pressure buildup. Loden (1992) reported that the ratio of extraction to injection commonly used during field application are between 4 1 and 5 1. Johnson et al. (1990) reported that typical extraction rates are between 100 and 1,000 standard cubic feet per minute (scfm). 

To examine shifts in soil pressure caused by seismic activity, seismology engineers used an array of tactile... 

Secondary linings are usually applied after primaiy linings have been in place for a period during which they have adjusted to the soil pressure and deformation, so that they have to absorb only long time secondary setdements. 

Active soil depressurization (ASD) is the most common technique used to mitigate high radon levels in homes, and typically lowers concentrations by 50 to 99%. ASD relies on a simple, controlled alteration of the air-soil pressure differential. A suction point (open-ended pipe) is installed underneath the slab or floor of the house in a small excavated area where radon can collect. This pipe is connected by additional pipe to a continuously operating exhaust fan with a rooftop outlet. The vacuum effect of the fan pulls the radon-containing air from the excavated area into the pipe and ejects it above the roof, bypassing the interior of the house (and the lungs of its inhabitants). 

Allowable pile capacity of allowable soil pressure in % or basic 100 100 150 125 150... 

Using the peak abutment force and the effective area of the mobilized soil wedge, the peak soil pressure is compared to a maximum capacity of 7.7 ksf (369 kPa). If the peak soil pressure exceeds the soil... 

The calculated vertical loads, lateral loads, and moment about point A are listed in Table 6.3. The maximum and minimum soil pressure at abutment footing are calculated by... 

Referring to Table 6.3 and Equations 6.5 and 6.6, the maximum and minimum soil pressures under footing corresponding to different load cases are calculated as follows ... 

The most frequently used types of retaining structures in highway, transportation, and railroad projects consist of cantilever walls, tiehack walls, soil nail walls, and mechanically stabilized embankment (MSB) walls. The overall design objective of these retaining structures is to resist lateral soil pressure forces. 

Cantilever retaining walls can be any cantilever structure used to resist the active lateral soil pressure in topography fill, and cut locations. Usually, the common wall height (H) limits for cantilever walls in transportation projects is 30-40 ft (9.14-12.2 m). For wall heights greater than 30 ft (9.14 m), various other types of retaining walls usually have more economical advantages compared to cantilever walls. 

A well-accepted simplified process for cantilever wall systems is to use the equivalent liquid density kj to determine the lateral soil pressure on the wall stem. The soil density is typically in the range of 120-150 pounds per cubic feet (pcf) (1.9-2.4 T/m ). Figure 10.2 shows a simplified load distribution diagram for typical retaining wall. 

The active soil pressure per unit length of wall (PJ at the bottom of the wall can be determined as... 

The upper slope on top of the backfill will increase the soil pressure on the wall stem. The traditional method is to use the complete formula to generate the factor. The factors listed in Table 10.3 are determined by the Coulomb equations with special case of zero wall friction (see Figure 10.3). 

The uniformly distributed surcharge load could be converted to the thickness of an equivalent additional soil layer. Therefore, the total lateral pressure on the wall back shall be a trapezoid (see the following example). For design simplification, engineers often utilize a triangle distribution for the backfill soil pressure and an additional rectangular distributed load to represent the surcharge effects. 

If there is any tie back on the wall, the lateral soil pressure distribution shall be different than the equivalent liquid pressure, which always follows the triangle distribution. Figure 10.5 shows a few typical distributions of the soil nail wall analysis diagram. 

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