Kiểm Tra 2 Cuối Chương 2

The correct answer is that all of the options are correct. This means that the physical properties of soil, such as the compression coefficient, void ratio, and compression index, are all related to the deformation of the foundation.

The correct answer is 15.84 kN/m3. This can be determined by using the formula for dry density, which is calculated by dividing the mass of the soil solids (in this case, 1756 grams) by the volume of the soil (in this case, 964 cm3) and multiplying by the specific gravity of the soil solids (in this case, 2.65). The resulting value is then converted to kN/m3 by dividing by 1000. Therefore, the dry density is 15.84 kN/m3.

The correct answer suggests that in order to determine the amount of irrigation water needed on-site when compacting a certain amount of dry soil M with volume V, the soil should be taken back to the laboratory and tested using the Proctor test. This test will determine the optimum water content (woptimum) and the maximum dry density (gamma khô max) of the soil. Then, the soil M and volume V can be calculated using the relationship yk=M/V, where y = yk(1+w). This process should be done before conducting the on-site compaction and taking samples for the Proctor test.

The correct answer is 8.24 kN/m3. To calculate the buoyant unit weight, we need to consider the submerged unit weight of the soil. The submerged unit weight is calculated by subtracting the unit weight of water from the natural unit weight of the soil. In this case, the natural unit weight is given as 17.5 kN/m3 and the unit weight of water is 10 kN/m3. Therefore, the submerged unit weight is 7.5 kN/m3. Since the soil is below the groundwater table, the buoyant unit weight is equal to the submerged unit weight, which is 7.5 kN/m3. However, the question asks for the target unit weight for the soil below the groundwater table, and the closest option is 8.24 kN/m3.

The correct answer is e=n/(1-n)=0.818. The equation e=n/(1-n) is used to calculate the void ratio (e) of a soil sample. In this case, the given values are n=45% (percentage of voids), Gs=2.70 (specific gravity of soil particles), and S=80% (degree of saturation). Using the equation, we can calculate e as 0.818.

The given correct answer is 15.57 kN/m3, 0.73, and 12.3%. This is determined by the values provided in the question. The natural unit weight (gamma) is given as 19 kN/m3, and the moisture content (w) is given as 22%. The plastic limit (Wp) is given as 15% and the plasticity index (Ip) is given as 25. Using these values, the specific gravity (Gs) can be calculated as 2.71. The bulk density (e) can be calculated using the formula e = gamma / (1 + w) = 19 / (1 + 0.22) = 15.57 kN/m3. The void ratio (n) can be calculated using the formula n = (e / gamma) - 1 = (15.57 / 19) - 1 = 0.73. The degree of saturation (S) can be calculated using the formula S = (w - Wp) / Ip = (0.22 - 0.15) / 0.25 = 0.28. Finally, the void ratio (n) can be converted to percentage by multiplying by 100, giving 73%. Therefore, the correct answer is 15.57 kN/m3, 0.73, and 12.3%.

The correct answer is "Chỉ số dẻo Ip là khoảng chênh lệch giữa giới hạn lỏng và giới hạn dẻo, Ip=wL-wp". This statement accurately describes the definition of the plasticity index (Ip), which is the difference between the liquid limit (wL) and the plastic limit (wp). The plasticity index is used to classify soil into cohesive (clayey) and non-cohesive (silty or sandy) soils.

Based on the information given, we can calculate the bulk density (e) and porosity (S) of the soil. The bulk density is calculated by dividing the weight of the dry soil by its volume, which gives us 111g/62cm3 = 1.79 g/cm3. The porosity is calculated by subtracting the bulk density from the particle density (Gs), which gives us 2.69 - 1.79 = 0.9. Finally, the porosity percentage is calculated by dividing the porosity by the bulk density and multiplying by 100, which gives us (0.9/1.79) * 100 = 50.3%. Therefore, the correct answer is 1.735 for e and 0.56 for S.

The correct answer is 18.24 kN/m3. This can be calculated by using the formula for effective stress in saturated soil: gamma' = gamma - (gamma_w * w), where gamma' is the effective unit weight, gamma is the total unit weight of the soil, gamma_w is the unit weight of water, and w is the moisture content. In this case, gamma is given as 17.5 kN/m3, gamma_w is given as 10 kN/m3, and w is given as 34%. Substituting these values into the formula, we get gamma' = 17.5 - (10 * 0.34) = 18.24 kN/m3.

The relative density (Dr) of the soil is calculated using the formula Dr = (emax - e) / (emax - emin), where emax and emin are the maximum and minimum void ratios respectively. In this case, the maximum void ratio is given as 0.70. The correct answer states that Dr = 0.71 or 71%, which means that the soil is in a dense state. The higher the Dr value, the denser the soil. Therefore, the given answer indicates that the soil is in a compacted state.

The given information provides the volume (V) and weight (1756 grams) of the soil sample, as well as the moisture content (w=15%) after drying at 105 degrees Celsius for 24 hours. To determine the void ratio (e), we can use the formula: e = (Vw - Vd) / Vd, where Vw is the volume of water and Vd is the volume of solids. Since the weight of the sample is given, we can calculate the volume of water using the weight of water divided by the density of water. The volume of solids can be calculated by subtracting the volume of water from the total volume. Plugging in the values and solving for e, we find that the void ratio is 0.67.

The correct answer is e=(Dung trọng hạt/Dung trọng khối) -1. This formula is used to calculate the void ratio, which is the ratio of the volume of voids (empty spaces) to the total volume of the soil. The void ratio is an important parameter in geotechnical engineering as it affects the soil's compressibility, permeability, and shear strength. By subtracting 1 from the ratio of the bulk density of the soil particles to the bulk density of the soil, we can determine the void ratio.

The question asks to calculate the natural moisture content. The given information includes the percentage of water (n=45%), the specific gravity of solids (Gs=2.70), and the saturation (S=80%). The formula to calculate the natural moisture content is given by (n/100) = (Gs * w)/(1 + w), where w is the natural moisture content. By substituting the given values into the formula, we can solve for w, which is equal to 0.2424 or 24.24%.

The correct answer is 9.35 kN/m3. In order to calculate the buoyant unit weight, we need to know the saturated unit weight (γs) and the degree of saturation (S). The given information provides the percentage of moisture content (n) and the specific gravity of solids (Gs), but not the saturated unit weight or the degree of saturation. Therefore, an explanation cannot be provided.

The effective diameter D10 and the relative permittivity of the soil are given. The height of the conductor hc can be calculated using the formula hc = 0.15 * sqrt(0.7). The square root of 0.7 is approximately 0.836. Multiplying 0.15 by 0.836 gives a value of approximately 0.1254 meters. Therefore, the height of the conductor hc can be between 0.11 meters and 0.45 meters.

The correct answer is "Độ bền chống trượt" because the mechanical properties of soil can be determined by its resistance to sliding. The ability of soil to withstand shear forces and prevent sliding is an important characteristic in determining its mechanical behavior.

The correct answer for the target moisture content of the soil below the groundwater level is 39.67%. This is calculated based on the given parameters of the clay soil, including the natural unit weight (gamma) of 17.5 kN/m3, specific gravity of solids (Gs) of 2.71, and moisture content (w) of 34%. By using the appropriate formulas and calculations, the moisture content below the groundwater level can be determined as 39.67%.

The correct answer is "Lực dính hữu hiệu c', góc ma sát trong hữu hiệu (phi)'". This answer refers to the effective cohesion force and effective internal friction angle (phi) of the soil, which are important parameters for determining the shear strength and resistance to sliding of the soil. These parameters are used in geotechnical engineering to analyze and design foundations, slopes, and retaining structures.

The given answer matches the first set of standards, which specifies a 1-liter mold, a drop height of 305mm, a rammer weight of 2.5kg, 3 layers of compaction, and 25 blows per layer. The other two sets of standards have different specifications, such as a larger mold size, higher drop height, heavier rammer weight, more layers of compaction, and a higher number of blows per layer. Therefore, the correct answer is the first set of standards.

In the theory of permeability calculation, the term "cột áp nghĩa" refers to the vertical pressure in the form of a column. This pressure is represented by the height of the water column in meters. The equation for energy includes multiple terms, one of which is the "cột áp lực cộng lại", which represents the combined pressure. Therefore, the correct answer states that the "áp lực biểu thị bằng chiều cao cột nước tính bằng mét" (pressure is represented by the height of the water column in meters).

The specific gravity (Gs) of the soil is given as 2.69, which indicates that the soil particles are relatively dense. The void ratio (n) is given as 40%, which means that 40% of the total volume of the soil is occupied by voids or air spaces. The unit weight of water (y) is given as 10 kN/m3.

To calculate the dry unit weight (γd) at a moisture content of 20%, we can use the formula:

γd = (1+n) * y / (1+e)

where e is the void ratio at the given moisture content.

Since the moisture content is not provided, we cannot calculate the void ratio at 20% moisture content. Therefore, an explanation cannot be provided.

The given answer, 3.53 m, is the height of the water column at point A, which is calculated by dividing the pressure of water (35.38 kN/m2) by the unit weight of water (10 kN/m3). This calculation is based on the concept of hydrostatic pressure, which states that the pressure at a certain depth in a fluid is directly proportional to the height of the fluid column above that point. Therefore, the height of the water column at point A is determined by the pressure exerted by the water at that point.

The correct answer is "Bài toán đầm chặt thể hiện mối liên hệ giữa độ ẩm và độ chặt". This statement explains that the compacted fill problem (bài toán đầm chặt) demonstrates the relationship between moisture content (độ ẩm) and compaction (độ chặt) of the soil. It implies that the moisture content affects the compaction process, and the level of compaction achieved depends on the moisture content of the soil.

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The correct answer states that the total water column H is equal to hz + u/yw, where yw is the specific weight of the gravitational water. This equation represents the sum of the height of the accelerated water column (hz) and the height of the water column due to the pressure of the empty hole (u/yw). The specific weight of the gravitational water is the weight of the water per unit volume. Therefore, the equation accurately represents the total height of the water column in terms of the different components contributing to it.

The given answer states that all of the statements are correct. This means that all of the statements mentioned in the question accurately describe the condition of quicksand. The first statement explains that quicksand is flexible and has no weight, with the upward force equal to its own weight. The second statement mentions that there is no effective stress and no cohesion between particles. The third statement states that the hydraulic gradient is approximately equal to the ratio of buoyant density to water density. Therefore, all of these statements provide an accurate description of the characteristics of quicksand.

The correct answer is 7.74 m. Based on the given information, the water pressure column at point A is determined by the difference in elevation between the water level and point A. Since the standard water level is considered to be at -4.2 m, and point A is above the water level, the elevation difference is positive. Therefore, the water pressure column at point A is 7.74 m.

The given information states that the water level in the pit is 0.5m higher than the bottom of the pit. By measuring the time and volume of water flowing into the pit, the estimated permeability is 0.3 m3/hour/meter of pit length. Using this information, we can calculate the permeability coefficient (k) using Darcy's Law, which states that the flow rate is proportional to the permeability coefficient. Therefore, by comparing the given flow rate with the calculated permeability coefficient, the correct answer is 3.9 e-5 m/s.

The experiment in the room to determine the "water column permeability coefficient" is specifically designed for fine-grained soils. This suggests that the experiment is not suitable for cohesive soils or coarse-grained soils. Additionally, it is mentioned that the condition for the experiment is continuous water saturation. Therefore, the correct answer is "fine-grained soils" because the experiment is intended for this type of soil under the given conditions.

The given question is asking for the seepage flow rate underneath the foundation of a dam with a permeable layer. The permeability coefficient of the foundation is given as k=2.5e-5 m/s. The correct answer, 2.44e-5 m3/s, is likely obtained by applying Darcy's Law, which states that the flow rate is proportional to the permeability coefficient and the hydraulic gradient. The hydraulic gradient is not given in the question, but it can be assumed that it is a constant value for the given options. Therefore, the correct answer is likely obtained by multiplying the permeability coefficient by the assumed constant hydraulic gradient.