Test and analysis of dynamic compaction vibration based on piezoelectric sensor

The paper takes a new campus project site of Shanxi university town for example, tests the influence of dynamic com- paction vibration and vibration isolation effect of isolation trench on this ground, and compares the influences of the dynamic compaction vibration on surrounding buildings with isolation trench and without it. Furthermore, the attenuation law of dy- namic compaction vibration in fill foundation of the loess area under different tamping energy and how to determine safe distance of dynamic compaction construction are studied. And then the quantitative relationship between acceleration and vibration source in new campus project site is presented. We derive the evaluation method that dynamic compaction construction affects adjacent buildings by contrasting with the existing standards and norms. The monitoring results show that isolation trench makes the amplitude attenuation of the horizontal velocity of dynamic compaction vibration reach above 75%, and the safe dis- tance be 30 m under the tamping energy of 6 000 kN · m. Therefore, isolation trench is better for vibration reduction under dynamic compaction construction.

Application of artificial neural networks for predicting the impact of rolling dynamic compaction using dynamic cone penetrometer test results

Rolling dynamic compaction(RDC),which involves the towing of a noncircular module,is now widespread and accepted among many other soil compaction methods.However,to date,there is no accurate method for reliable prediction of the densification of soil and the extent of ground improvement by means of RDC.This study presents the application of artificial neural networks(ANNs) for a priori prediction of the effectiveness of RDC.The models are trained with in situ dynamic cone penetration(DCP) test data obtained from previous civil projects associated with the 4-sided impact roller.The predictions from the ANN models are in good agreement with the measured field data,as indicated by the model correlation coefficient of approximately 0.8.It is concluded that the ANN models developed in this study can be successfully employed to provide more accurate prediction of the performance of the RDC on a range of soil types.

Liquefaction mitigation in silty soils using composite stone columns and dynamic compaction

The objective of this study is to develop an analytical methodology to evaluate the effectiveness of vibro stone column (S.C.) and dynamic compaction (D.C.) techniques supplemented with wick drains to densify and mitigate liquefaction in saturated sands and non-plastic silty soils. It includes the following: (i) develop numerical models to simulate and analyze soil densitication during S.C. installation and D.C. process, and (ii) identify parameters controlling post-improvement soil density in both cases, and (iii) develop design guidelines for densification of silty soils using the above techniques. An analytical procedure was developed and used to simulate soil response during S.C. and D.C. installations, and the results were compared with available case history data. Important construction design parameters and soil properties that affect the effectiveness of these techniques, and construction design choices suitable for sands and non-plastic silty soils were identified. The methodology is expected to advance the use of S.C. and D.C. in silty soils reducing the reliance on expensive field trials as a design tool. The ultimate outcome of this research will be design charts and design guidelines for using composite stone columns and composite dynamic compaction techniques in liquefaction mitigation of saturated silty soils.

Genetic programming for predictions of effectiveness of rolling dynamic compaction with dynamic cone penetrometer test results

Rolling dynamic compaction (RDC),which employs non-circular module towed behind a tractor,is an innovative soil compaction method that has proven to be successful in many ground improvement applications.RDC involves repeatedly delivering high-energy impact blows onto the ground surface,which improves soil density and thus soil strength and stiffness.However,there exists a lack of methods to predict the effectiveness of RDC in different ground conditions,which has become a major obstacle to its adoption.For this,in this context,a prediction model is developed based on linear genetic programming (LGP),which is one of the common approaches in application of artificial intelligence for nonlinear forecasting.The model is based on in situ density-related data in terms of dynamic cone penetrometer (DCP) results obtained from several projects that have employed the 4-sided,8-t impact roller (BH-1300).It is shown that the model is accurate and reliable over a range of soil types.Furthermore,a series of parametric studies confirms its robustness in generalizing data.In addition,the results of the comparative study indicate that the optimal LGP model has a better predictive performance than the existing artificial neural network (ANN) model developed earlier by the authors.

Dynamic Characteristics Analysis on Wind-Blown Sand Ground under Dynamic Compaction Vibration

In the 6000 kN·m energy level dynamic compaction on Inner Mongolia wind-blown sand foundation treatment process, the dynamic characteristics and dynamic response are measured. Vibration action time, vibration main frequency, peak acceleration and peak velocity are analyzed. The vibration acting time is very short, the vertical average vibration acting time increases obviously with distance increasing, and the horizontal average vibration time does hardly change. The main frequency of vibration is at 4.60 - 24.90 Hz, which depends on the soil properties and soil layer distribution. The peak acceleration and peak velocity space distribution are similar. The maximum of horizontal acceleration peak is close to vertical velocity peak, and is near to 51 g under rammer. The maximum of horizontal velocity peak is close to vertical velocity peak, and is near to 54 m/s under rammer. The peak acceleration and velocity are rapidly attenuated, but the vertical peak acceleration and peak velocity are slowly attenuated than horizontal direction. The effective treating depth arrives 13 m for wind-blown wind, peak acceleration is 1.8 g or so, and peak velocity is 2.1 m/s or so. Horizontal treating range is 2.6 times of rammer diameter, and vertical treating range is 5.65 times of rammer diameter.

Influence of towing speed on effectiveness of rolling dynamic compaction

The influence of towing speed on the effectiveness of the 4-sided impact roller using earth pressure cells(EPCs)is investigated.Two field trials were undertaken;the first trial used three EPCs placed at varying depths between 0.5 m and 1.5 m with towing speeds of 9-12 km/h.The second used three EPCs placed at a uniform depth of 0.8 m,with towing speeds of 5-15 km/h.The findings from the two trials confirmed that towing speed influences the pressure imparted to the ground and hence compactive effort.This paper proposes that the energy imparted to the ground is best described in terms of work done,which is the sum of the change in both potential and kinetic energies.Current practice of using either kinetic energy or gravitational potential energy should be avoided as neither can accurately quantify rolling dynamic compaction(RDC)when towing speed is varied.

Improvement parameters in dynamic compaction adjacent to the slopes

Dynamic compaction is a cost-effective method commonly used for improvement of sandy soils. Anumber of researchers have investigated experimentally and numerically the improvement parametersof soils using dynamic compaction, such as crater depth, improvement depth, and radial improvement,however, these parameters are not studied for improvement adjacent to the slopes or trenches. In thisresearch, four different slopes with different inclinations are modeled numerically using the finiteelement code ABAQUS, and impact loads of dynamic compaction are applied. The static factors of safetyare kept similar for all trenches and determined numerically by application of gravity loads to the slopeusing strength reduction method （SRM）. The analysis focuses on crater depth and improvement regionwhich are compared to the state of flat ground. It can be observed that compacted area adjacent to theslopes is narrower and slightly away from the slope compared to the flat state. Moreover, crater depthincreases with increase in slope inclination.2015 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Production and hosting byElsevier B.V. All rights reserved.

Reinforcement effects of ground treatment with dynamic compaction replacement in cold and saline soil regions

The mechanical property of saline soils varies with moisture and climate in the cold and salt lake region of Qinghai-Tibet Plateau, which influences project construction. In order to improve foundation reinforcement effect of the QarharvaTrolmud Highway, Qinghai Province, China, dynamic compaction replacement （DCR） composite foundation was applied in saline soils. A field experiment was conducted in this area, where strength and working mechanism of pier-soil and deformation modulus of the composite foundation was analyzed after reinforcement. This paper presents methods for determining the coefficient on the bearing capacity evaluation and deformation modulus of composite foundation with DC1L Reinforcement case of DCR is highly effective in saline soils of the salt lake regions, which helps the mi-tion of water and salt in saline soils.

Effective depth of dynamic compaction in embankment built with soils and rocks

Effective depth of dynamic compaction was summarized, and the advantages of dynamic compaction technology of effective depth were analyzed elaborately. The formula determining the reinforcement depth was deduced by using dimensional analysis method. The influential factors of hammer weight, hammer area, dry density of filling materials and filling materials types were comprehensively investigated. The formula of effective depth was established based on the definition of the dimensions analysis. Based on experimental results of in-situ dynamic compaction, the technology was applied to highway embankment filled with soils and rocks. From the comparison between the theoretical calculations and the experimental results, it is found that the theoretical results using the developed formula are close to experimental results.

Dynamic compaction treatment technology research of red clay soil embankment in southern mountains

High liquid limit soil generally adopted in expressway embankment construction of southern mountains, which often expresses some characteristics including high moisture content, high porosity ratio, low permeability, high compressibility, certain disintegration, and so on. Spring soil phenomenon and inhomogeneous compaction have effects on the quality of embankment construction, just because the water in soil is difficult to evaporate. Based on the study of reinforcement mechanism for high liquid limit soil, in situ tests for dynamic compaction treatment in Yizhang-Fengtouling expressway embankment were developed. The reliable and economical dynamic compaction treatment methods and the construction technology for large range high liquid limit soil embankment in southern mountains expressway were discussed. In the process, convenient measurement methods were adopted to evaluate the treatment effects. The test results show that the dynamic compaction method has good treatment effects on the local red clay embankment. The embankment compaction degree is improved with compactness coming to 90% around tamping pits and compactness over 95% in tamping pits interior after tamping. The bearing capacity, the physical mechanic-property and the shear strength for soil are obviously improved, which are enhanced with cohesive strength increasing over 10 kPa and compression modulus increasing over 3 MPa.

Application of dynamic compaction and rolling compaction in the subgrade improvement of Qarhan-Golmud Highway

Melt shrinkage, salt bulge, and corrosiveness are common problems with saline soils, which damage highway foundations and cause huge financial losses. In order to improve the saline soil subgrade, dynamic compaction （DC） and rolling compaction （RC） technology were applied on the Qarhan-Golmud Highway in Qinghai Province, China. A field experi- ment was conducted in which shear strength, deformation modulus, and the working mechanism of the composite foun- dation were analyzed after reinforcement. Both the DC and RC methods were found to be effective and helped to improve the foundation strength of saline soils, although the ultimate bearing capacity and deformation modulus of the RC method were lower than that of the DC method.

Experiment Study of Dynamic Compaction Applied in Collapsible Loess

The collapsibility of loess, which can be effectively eliminated by the dynamic compaction, does great harm to the safety of constructions. The effect of the dynamic compaction is evaluated through the contrast and analysis of the physical and mechanical properties of the collapsible loess before and after dynamic compacting. The compacting effect can be divided into three phases along the depth, and the most effective improved depth is from 3 to 8 m.

Continuous Dynamic Rotation Measurements Using a Compact Cold Atom Gyroscope

We present an experimental demonstration of the rotation measurement using a compact cold atom gyroscope. Atom interference fringes are observed in the stationary frame and the rotating frame, respectively. The phase shift and contrast of the interference fringe are experimentally investigated. The results show that the contrast of the interference fringe is well held when the platform is rotated, and the phase shift of the interference fringe is linearly proportional to the rotation rate of the platform. The long-term stability, which is evaluated by the overlapped Allan deviation, is 8.5 × 10^-6 rad/s over the integrating time of 1000s.

Dynamic Mechanical Behaviour of Ultra-high Performance Fiber Reinforced Concretes

Ultra-high performance fiber reinforced concretes （UHPFRC） were prepared by replacing 60% of cement with ultra-fine industrial waste powder. The dynamic mechanical behaviour of UHPFRC with different fiber volume fraction was researched on repeated compressive impact in four kinds of impact modes through split Hopkinson pressure bar （SHPB）. The experimental results show that the peak stress and elastic modulus decrease and the strain rate and peak strain increase gradually with the increasing of impact times. The initial material damage increases and the peak stress of the specimen decreases from the second impact with the increasing of the initial incident wave. Standard strength on repeated impact is defined to compare the ability of resistance against repeated impact among different materials. The rate of reduction of standard strength is decreased by fiber reinforcement under repeated impact. The material damage is reduced and the ability of repeated impact resistance of UHPFRC is improved with the increasing of fiber volume fraction.

Dynamic Compression Behavior of Ultra-high Performance Cement-based Composite with Hybrid Steel Fiber Reinforcements

Ultra-high performance cement-based composites (UHPCC) is promising in construction of concrete structures that suffer impact and explosive loads.In this study,a reference UHPCC mixture with no fiber reinforcement and four mixtures with a single type of fiber reinforcement or hybrid fiber reinforcements of straight smooth and end hook type of steel fibers were prepared.Split Hopkinson pressure bar (SHPB) was performed to investigate the dynamic compression behavior of UHPCC and X-CT test and 3D reconstruction technology were used to indicate the failure process of UHPCC under impact loading.Results show that UHPCC with 1% straight smooth fiber and 2% end hook fiber reinforcements demonstrated the best static and dynamic mechanical properties.When the hybrid steel fiber reinforcements are added in the concrete,it may need more impact energy to break the matrix and to pull out the fiber reinforcements,thus,the mixture with hybrid steel fiber reinforcements demonstrates excellent dynamic compressive performance.

Experimental study on the dynamic modulus of compacted loess under bidirectional dynamic load

The dynamic characteristics of compacted loess are of great significance to the seismic construction of the Loess Plateau area in Northwest China,where earthquakes frequently occur.To study the change in the dynamic modulus of the foundation soil under the combined action of vertical and horizontal earthquakes,a hollow cy-lindrical torsion shear instrument capable of vibrating in four directions was used to perform two-way coupling of compression and torsion of Xi'an compacted loess under different dry density and deviator stress ratios.The results show that increasing the dry density can improve the initial dynamic compression modulus and initial dynamic shear modulus of compacted loess.With an increase in the deviator stress ratio,the initial dynamic compression modulus increases,to a certain extent,but the initial dynamic shear modulus decreases slightly.The dynamic modulus gradually decreases with the development of dynamic strain and tends to be stable,and the dynamic modulus that reaches the same strain increases with an increasing dry density.At the initial stage of dynamic loading,the attenuation of the dynamic shear modulus with the strain development is faster than that of the dynamic compression modulus.Compared with previous research results,it is determined that the dynamic modulus of loess under bidirectional dynamic loading is lower and the attenuation rate is faster than that under single-direction dynamic loading.The deviator stress ratio has a more obvious effect on the dynamic compression modulus.The increase in the deviator stress ratio can increase the dynamic compression modulus,to a certain extent.However,the deviator stress ratio has almost no effect on the dynamic shear modulus,and can therefore be ignored.

Influence of construction interfaces on dynamic characteristics of roller compacted concrete dams

To study the influence of construction interfaces on dynamic characteristics of roller compacted concrete dams(RCCDs),mechanical properties of construction interfaces are firstly analyzed. Then, the viscous-spring artificial boundary(VSAB) is adopted to simulate the radiation damping of their infinite foundations, and based on the Marc software, a simplified seismic motion input method is presented by the equivalent nodal loads. Finally, based on the practical engineering of a RCC gravity dam, effects of radiation damping and construction interfaces on the dynamic characteristics of dams are investigated in detail. Analysis results show that dynamic response of the RCC gravity dam significantly reduces about 25% when the radiation damping of infinite foundation is considered. Hot interfaces and the normal cold interfaces have little influence on the dynamic response of the RCC gravity dam.However, nonlinear fracture along the cold interfaces at the dam heel will occur under the designed earthquake if the cold interfaces are combined poorly. Therefore, to avoid the fractures along the construction interfaces under the potential super earthquakes,combination quality of the RCC layers should be significantly ensured.

舍弗勒收购Compact Dynamics

2016年12月20日,汽车和工业产品供应商舍弗勒与塞米控集团有限公司签署收购协议,购买高性能电机制造商Compact Dynamics股份有限公司51%的股份,交易预计于2017年第一季度完成。与此同时,舍弗勒和塞米控还将在电力电子系统开发和电力电子元件集成领域展开合作。通过本次收购和合作,舍弗勒成功拓展了其在电机和电力电子领域的技术实力。

Numerical simulation of intelligent compaction for subgrade construction

During the compaction of a road subgrade, the mechanical parameters of the soil mass change in real time, but current research assumes that these parameters remain unchanged. In order to address this discrepancy, this paper establishes a relationship between the degree of compaction K and strain ε. The relationship between the compaction degree K and the shear strength of soil(cohesion c and frictional angle φ) was clearly established through indoor experiments. The subroutine UMAT in ABAQUS finite element numerical software was developed to realize an accurate calculation of the subgrade soil compaction quality. This value was compared and analyzed against the assumed compaction value of the model, thereby verifying the accuracy of the intelligent compaction calculation results for subgrade soil. On this basis, orthogonal tests of the influential factors(frequency, amplitude, and quality) for the degree of compaction and sensitivity analysis were carried out. Finally, the ‘acceleration intelligent compaction value’, which is based on the acceleration signal, is proposed for a compaction meter value that indicates poor accuracy. The research results can provide guidance and basis for further research into the accurate control of compaction quality for roadbeds and pavements.