Unconfined compressive strength

For waterproofing, sodium silicate concentrations below 30% are adequate concentrations between 35 and 70% are used for strength improvement. Grouts having 35 vol % or higher silicate resist deterioration on freeze—thaw or wet—dry cycles. Water permeability of sands can be reduced from 10 to 10 cm/s. Unconfined compressive strengths of stabilized sand can vary from 103 to 4130 kPa (15—600 psi) the normal range is between 690 and 1380 kPa. 

Flowable fill is defined by the American Concrete Institute47 as a self-compacting cementitious material that is in a flowable state at placement and has a compressive strength of 8.3 MPa (1200 psi) or less at 28 days. Most current applications for flowable fill involve unconfined compressive strengths of 2.1 MPa (300 psi) or less, which makes possible its excavation at a later date. 

Unconfined compressive strength of cohesive soil Unconfined compressive strength index of chemical-grouted soils Slump of portland cement concrete... 

By the addition of the admixture with a reduction in the water-cement ratio, a concrete having the same workability as the control concrete can be obtained, with unconfined compressive strengths at all ages which exceed those of the control. 

After curing, the Unconfined Compressive Strength (UCS) of the samples was measured by using a penetrometer. The reagent ratio that resulted in the desired UCS (1.5-2.5 tons/ft ) was utilized for further leach-ability testing. 

Phenrat, T., Marhaba, T.F. and Rachakornkij, M. (2007) XRD and unconfined compressive strength study for a qualitative examination of calcium-arsenic compounds retardation of cement hydration in solidified/stabilized arsenic-iron hydroxide sludge. Journal of Environmental Engineering, 133(6), 595-607. 

Two methods have been developed for estimating seal embrittlement in shales. One method requires calculation of the overconsolidation ratio, which is essentially a measure of uplift, and in the other, the unconfined compressive strength is estimated from sonic log data. Both methods produce results which may be used to assess the relative risk of dilatant behaviour. 

Estimation of brittleness from unconfined compressive strength (UCS)... 

An alternative method to quantify the brittleness of a seal rock uses the unconfined compressive strength derived from sonic logs. This method uses the brittleness index, BRl= UCSIUCSf c, where t/CS c is the unconfined compressive strength of a normally consolidated rock. UCS can be measured directly or is estimated from logs based on empirical correlations using the equation... 

The Joosten process, properly used, results in a strong gel that can give unconfined compressive strengths above 500 psi. However, the utility of the process is limited by the high viscosity of the solutions and the need for many closely spaced grout holes. Also, the nature of the reaction prohibits complete reaction of the two liquids. For many years research and development were aimed at a silicate-based grout with gel time control to eliminate the inherent disadvantages of the two-shot system. As those research efforts met with success, the Joosten system was phased out as a construction tool. Today it is virtually a method of the past. 

Creep tests are run by subjecting a grouted soil sample to a sustained load less than the short-term Unconfined Compression strength, until failure occurs. As the sustained load decreases in value, the time to failure increases. Data from such tests plot as shown in Fig. 11.22, and indicate an asymptote at what may be called a creep endurance limit. For acrylamides these values will range from as low as 20% Unconfined Compression for triaxial tests at low lateral pressure to as high as 40% for triaxial tests at at rest lateral pressures. (For silicates, values may be taken from Fig. 11.11.)... 

It is actually the creep strength of a grouted soil (either in unconfined compression or triaxial compression, depending on the specific application) that should be used for design purposes, not the unconfined compressive strength. In the absence of specific creep data, the value of one-fourth to one-half of the unconfined strength may be used for applications. A suitable safety factor must be applied to these suggested values. 

The silicates and acrylamides are commonly used with cement, and the combinations yield a high-strength grout with excellent gel time control. Unconfined compressive strengths as high as 6000 psi are attainable, as shown for acrylamide-cement combinations in Fig. 20.5. Comparable results can be obtained with acrylates and silicates. 

UNCONFINED COMPRESSIVE STRENGTH The load per unit area at which an unconfined prismatic or cylindrical specimen of material will fail in a simple compression test without lateral support. 

Select a trial value of operational unconfined compressive strength, and categorize this in terms of Table D.l as weak, medium, strong, or very strong. 

Relative designation (2) Unconfined compressive strength in kilonewtons per square meter (pounds per square inch) (3) Ratio of stiffness of grouted to ungrouted soil (4) Friction angle, 4>r in degrees (5)... 

Figure 10. Use of plot of drawdown pressure against unconfined compressive strength to predict sand production. (Reproduced with permission from reference 24. Copyright 1991 Society of Petroleum Engineers.)...

Figure 4 Development of unconfined compressive strength with porosity arui alteration.

Figure 8 Unconfined compressive strength versus weathering grade (max/mean/min values).

Figure 9 Unconfined compressive strength versus dry density and prosity (single values).

The unconfined compressive strength as affected by disturbance decreases rapidly with increasing disturbance. The strain at failure, however, is increased as the ductility of the samples is improved by disturbance. Emrich (1971) compared the disturbance effects on... 

ASTM. D2166. Standard Test Method for Unconfined Compression Strength of Cohesive Soil. American Society for Testing and Materials, Philadelphia, PA, p. 7. 

In the case of the additive stabilisation process, the percentage of the hydraulic binder to be added as well as the amount of water should always be determined in the laboratory by executing CBR, M, (resilient modulus) or unconfined compressive strength tests, whichever is appropriate. 

In a pavement design methodology such as the AASHTO methodology (AASHTO 1993), the elastic modulus, E (ASTM C 469 2010), or alternatively, the unconfined compressive strength (7 days) (ASTM D 1633 2007) of the CTA base, needs to be determined. With either value, the structural coefficient (<72) is derived and the thickness of the corresponding layer as well as of all layers of a flexible pavement is determined (see Section 13.4.4.3). For a rigid pavement design, the elastic modulus of the sub-base is used (see Section 14.11.1). 

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