ã€China Deep Hole Rig Trading Network】 Common bad base soil and its characteristics 1. Soft clay Soft clay, also called soft soil, is an abbreviation for soft clay. It formed in the late Quaternary and belongs to the marine, lagoons, valleys, lakes, valleys, deltas, viscous sediments, or river alluvium. Mostly distributed in the coastal areas, downstream rivers or near lakes. The common weak clay soils are silt and silt soil. The physical and mechanical properties of soft soil include the following aspects: (1) Physical properties There are many clay particles, and the plasticity index Ip is generally greater than 17, which is a clay soil. Soft clay is mostly dark gray, dark green, odor, organic, high moisture content, generally greater than 40%, and silt is also greater than 80% of the situation. The void ratio is generally 1.0-2.0, in which the void ratio is 1.0-1.5 is called silty clay, and when the void ratio is more than 1.5, it is called silt. Because of its high clay content, high water content, and large pore ratio, its mechanical properties also show its corresponding characteristics - low strength, high compressibility, low permeability, and high sensitivity. (2) Mechanical properties The soft clay strength is extremely low, and the undrained strength is usually only 5-30 kPa. The basic value of the bearing capacity is very low, generally not exceeding 70 kPa, and some even only 20 kPa. The soft clay is particularly sensitive to silt. High, this is also an important indicator that distinguishes it from clay. Soft clay is very compressible. The compression coefficient is greater than 0.5 MPa-1, the maximum is 45 MPa-1, and the compression index is about 0.35-0.75. Usually, the soft clay layer belongs to normal consolidated or slightly overconsolidated soil, but some soil layers, especially recent sediments The soil layer may belong to underconsolidated soil. The small permeability coefficient is another important characteristic of soft clay, generally between 10-5-10-8cm/s, the small permeability coefficient is very slow, the effective stress growth is slow, so the settlement is stable and slow, the foundation strength The growth is also very slow. This feature is an important aspect that severely constrains the foundation treatment methods and treatment effects. (3) Engineering characteristics The soft clay foundation has low bearing capacity, low strength growth, easy deformation and non-uniformity after loading, large deformation rate and long stabilization time, and low permeability, thixotropy, and large rheological properties. Commonly used foundation treatment methods include pre-pressing, replacement, and stirring. 2. Miscellaneous fills Miscellaneous fills are mainly found in some old residential areas and industrial and mining areas. They are garbage soils left behind or piled up by people's lives and production activities. These landfills generally fall into three categories: construction waste, domestic waste, and industrial waste. It is difficult to describe the different types of waste soils and waste soils piled up at different times with a unified strength index, compression index, and permeability index. The main features of miscellaneous fills are unplanned accumulation, complex composition, various properties, uneven thickness, and poor regularity. Therefore, the same site is characterized by significant differences in compressibility and strength, which can easily cause uneven settlement, and usually requires foundation treatment. 3. Filling the soil The filling soil is an artificial sediment deposited by hydraulic filling. In recent years, it has been used for beach development and floodplain construction. The common water-dropping dams (also known as flush-filled dams) in the northwestern region are the dams that are filled with fill soil. The foundation formed by filling the soil can be regarded as a kind of natural foundation. Henan Sanli Machinery's pile driver equipment occupies an important position in the construction of the project. Its engineering nature mainly depends on the nature of the filling soil. Filling land foundations generally has the following important features. (1) The sedimentation of particles is obvious. In the vicinity of the inlet, the coarser particles are deposited first and are far away from the inlet. The deposited particles become finer; there is also obvious bedding in the depth direction. (2) The water content of the backfill soil is relatively high, generally larger than the liquid limit, and is in a flowing state. After the filling is stopped, the surface is naturally cracked and the water content is generally reduced after the natural evaporation occurs. However, when the drainage condition is poor, the lower filling soil is still in a flowing state. The finer the particles of the filling material, the more obvious this phenomenon is. (3) The early filling strength of the landfill is very low and the compressibility is high. This is because the backfill soil is underconsolidated. Filling the land base gradually increases to a normal state of consolidation as the standing time increases. Its engineering properties depend on particle composition, homogeneity, drainage consolidation conditions, and standing time after flushing. 4, saturated loose sand silt or fine sand foundation often has higher strength under static load. However, when the vibration load (earthquake, mechanical vibration, etc.) acts, the saturated loose sand foundation may cause liquefaction or a large number of seismic deformation, or even loss of bearing capacity. This is because the soil particles are loosely arranged and the position of the particles is misaligned under the action of external dynamics to reach a new equilibrium, and a higher excess pore water pressure is instantaneously generated, and the effective stress is rapidly reduced. The month of treatment of this foundation is to make it denser and to eliminate the possibility of liquefaction under dynamic loads. Commonly used processing methods include extrusion method, vibroflotation method and the like. 5. Collapsible loess Under the action of self-gravity stress in the overlying soil layer, or under the combined action of self-weight stress and additional stress, the soil that has undergone significant additional deformation due to the structural damage of the soil after immersion in water is called collapsible soil and belongs to special soil. . Some miscellaneous fills also have collapsibility. The loess widely distributed in the northeast, northwest, central and eastern parts of China is collapsible. (The loess mentioned here refers to loess and loess-like soils. Collapsible loess is divided into collapsible loess with heavy collapsibility and non-self weight, and some old loess is not collapsible). When carrying out the project construction on the collapsible loess foundation, it is necessary to consider the possible hazards to the project caused by the additional settlement caused by the foundation collapse, and to select suitable foundation treatment methods to avoid or eliminate the collapse of the foundation or caused by a small amount of collapsing. harm. 6. Expansive soil The mineral composition of expansive soil should be montmorillonite. It has a strong hydrophilicity, volume expansion when absorbing water, and volume shrinkage when water is lost. This kind of expansion and contraction is very large and it can easily cause damage to buildings. Expansive soils have a wide range of distribution in China, such as Guangxi, Yunnan, Henan, Hubei, Sichuan, Shaanxi, Hebei, Anhui, and Jiangsu. Expansive soil is a kind of special soil. Common ground treatment methods include soil replacement, soil improvement, pre-soaking, and engineering measures to prevent the change of moisture content of foundation soil. 7. Containing organic soil and peat soil When the soil contains different organic matter, different organic soils will be formed. Peat soil will be formed when the organic matter content exceeds a certain level. It has different engineering characteristics, and the higher the organic matter content, the The greater the impact of soil quality, the main performance is low intensity, compressibility, and different impact on the incorporation of different engineering materials, etc., on the adverse effects of direct engineering construction or foundation treatment. 8. The geological conditions of the foundation soil in the mountainous region of the mountainous area are relatively complex, mainly reflected in the unevenness of the foundation and site stability. Due to the natural environment and the formation conditions of the foundation soil, there may be large stones in the site, and the site environment may also have unfavorable geological phenomena such as landslides, mud flows, and slope collapses. They pose a direct or potential threat to the building. When building buildings in the mountains, special attention should be paid to site environmental factors and adverse geological phenomena, and if necessary, the foundations should be treated. 9. Karst (Karst) In karst (karst) areas, there are often caves or holes, rifts, gaps, depressions, etc. The formation or development of groundwater by erosion or latent erosion has a great influence on the structure and is prone to uneven deformation, collapse and collapse of the foundation. Therefore, before the construction of the structure, necessary treatment must be carried out. For more information, please pay attention to the China Deep Hole Rig Trading Network () Potato Cassava Starch Machine,Cassava Starch Processing Machine,Potato Starch Extract Machine,Cassava Starch Making Machine Shuangfeng Nongjiabao Machinery Technology Co., Ltd , https://www.starchmakingmachine.com