Visualization and quantification of soil laboratory impact compaction

As important methods to guide the field soil compaction,the standard and modified Proctor tests for laboratory compaction have remained unchanged for decades,which should be improved to better understand the compaction process and the properties of soils.In this study,an accelerometer was installed on a Marshall impact compactor to capture the dynamic response of three types of soils during compaction.The experimental test results indicated that the acceleration curve for each blow gradually evolved to a stable pattern following the progress of compaction,and the impact and gyratory locking points were linearly related with coefficient of determination R2equal to 0.59.The impact compaction curve could be further constructed by filtering the structural resonance,which can be used to quantify the compactability of soil materials.Although each type of soil had a unique set of compaction curves,the slope and value of compaction curve altered accordingly as the moisture content changed for the same soil.In addition,the average acceleration value at the final compaction stage could serve as the target value of soil stiffness.

A Case Study on Soil Improvement with Rapid Impact Compaction (RIC)

Soil treatment was utilized on numerous production sites to compact cohesion less formations, having the objective to increase earth characteristics and decrease probable subsidence. Within the last few years, Rapid Impact Compaction (RIC) has increased its attractiveness as a soil treatment method. RIC is an innovative dynamic compaction technique primarily used to compact sandy soils where silt and clay contents are low. This work presents a case study of ground improvement using RIC and its suitability for site preparation earthworks. The RIC technique has been performed in an early site preparation which consists of a cut and fill contract for a mega project in the Kingdom of Saudi Arabia. RIC is a process where loose subsurface soils are improved through compaction with the utilization of successive impact blows from the top surface. This project involves the compaction of the fill materials (with an average thickness of 4 m) and loose natural formations (averaging 4 m in depth). The objective of the soil treatment scheme is to increase the relative density of the soils (both fill and natural) to 85%. The usage of the RIC within the site preparation earthwork applications is possible provided the presence of certain elements—specifically, granular materials and particles finer than number 200 sieve—do not exceed 15%. The RIC method proved to be cost- and time-effective when utilized for filling compaction activities since it compacts considerable soil thicknesses with a single action from the top surface, and can be used as an alternative to the traditional method of compacting fill formations in pre-determined lift thicknesses.

Discussion on compact mechanism of air-stream and synchro-formed clamp plate impact molding

Applying the air impact molding method to mold the complicated pattern with wider opening surface and deeper concave, there always exist vaulted phenomenon and lower compactibility of sand mold over the entrance and the concave regions. Using the air-stream and synchro-formed clamp plate impact molding, however, this problem will be preferably solved. In this paper, the compact mechanism of the new molding method and the effect of some configuration factors, such as the area flowed by compressed air and the highness of the protruding block displacement around the diffluent clamp plate, on the compactibility of sand mold were discussed.

HIGH-SPEED FLOW EROSION ON A NEW ROLLER COMPACTED CONCRETE DAM DURING CONSTRUCTION

A new roller compacted concrete dam of Fengman Hydropower Station is to be built in the toe of the old dam,which was identified as a dangerous dam.The new dam during construction would be influenced by the high-speed flow discharged from the old dam,which is an important problem to be considered for the first time in China,and which would affect the construction of the whole project.Therefore,a series of erosion experiments were conducted in this article.A high-speed flow erosion test apparatus was developed for the erosion experiments of the new dam materials.The maximum jet velocity goes up to 40 m/s and the section area of the nozzle is 0.0025 m2.In the process of experiments,the equipment shows a good performance.Erosive wear tests for two types of materials used in the new dam,a roller compacted concrete and a distorted concrete with four kinds of ages were carried out with the flow velocity in the range of 30 m/s-35 m/s.Erosion parameters and erosion laws for the two types of concretes with different ages were determined,and a general relationship between the erosion rate and the flow velocity is obtained as：,with the velocity exponent between 3.33 and 3.93.It is concluded that the erosion resistance of the distorted concrete is better than that of the roller compacted concrete and the mechanical properties of the concretes of over 14 d age are influenced slightly by the water impact.The test results might serve as a practical technique guide for the safety of this project during its construction in the flood season.