Initial Unit Weight Research Articles

Study on Ill-Conditioned Total Least Squares Load Identification Method Based on the IGG Weight Function

To address the ill-conditioned problem and unknown noise interference in ship load identification, this study proposes the ill-conditioned Total Least Squares (TLS) load identification method using the anti-error principle of the IGG weight function (IGG-TLS). First, the weight factor is iteratively updated through the IGG weight function. The weight matrix is constructed adaptively by multiplying the weight factor with the initial unit weight matrix. Then, the regularization criterion for the ill-conditioned IGG-TLS model is established based on the Tikhonov regularization principle. And the Lagrange multiplier is employed to solve the IGG-TLS method. Finally, the load identification accuracies of the IGG-TLS method are investigated through the simulation analysis and experimental verification of the rectangular plate under different noise and SNR conditions. The results demonstrate that the IGG-TLS method can achieve high accuracy in load identification without the need to pre-construct the weight matrix, even when the SNR is unknown. Additionally, the IGG-TLS method can effectively correct the identification errors in the TLS method, demonstrating high accuracy and noise immunity under conditions of equal-weight and unequal-weight noise.

Predicting one-dimensional compression of tire derived aggregate using a simple method

Tire derived aggregate (TDA) is a material that exhibits high compression under loading, a factor that governs its design and performance in civil engineering. Due to the large size of TDA particles (up to 305 mm), it is hard to obtain undisturbed TDA samples from the field to perform compression testing in the laboratory. Commonly, laboratory compression tests are conducted on TDA with small particle sizes, and hence the stress-strain curves obtained cannot be directly used to predict the field compression of TDA with different particle sizes and initial unit weights. To solve this problem, this study proposes a simple method to predict the compression of TDA based on its compression modulus (Ec)-void ratio (e) relationship under one-dimensional loading. The effectiveness of this method is evaluated using experimental data from laboratory and field tests. The results indicate that TDA samples with different particle sizes and initial unit weights have a very similar Ec − e relationship under one-dimensional loading. Hence, the Ec − e relationship can be determined from a relatively small-scale laboratory compression test, and can then be used to predict the compression of TDA with different particle sizes, initial unit weights, tire sources, and test scales. The accuracy of the prediction relies on the accuracy of the measurements for specific gravity and initial unit weight.

Treatment of collapsible soils by mixing with iron powder

Collapsible soils are meta-stable soils which present a potential for a large deformation and a complete change to the whole particle structure after wetting, with or without loading. Such soils can show high apparent strength in its natural state but collapse takes place as the bonds between grains break down when the soil is wetted or loaded. There are several techniques for treatment of collapsible soils such as chemical stabilization and dry mixing the soil with other material/materials which improve the soil's mechanical properties. This paper discusses a new proposed technique for treating the collapsible soils by dry mixing with iron powder in a specified percentage proportional to the weight (Ad). Experimental tests program was performed on collapsible soils with/without the addition of iron powder. The analysis of results showed the effect of the initial unit weight of soil γd, and the percentage of the weight-related additives on collapse potential (CP). The testing program also presents the effects of the amount of induced rainfall water (Qw), the applied stress on footing model (q), the ratio between depth of improved soils and the footing width (di/B), as well as the degree of compaction (Rc) of the improved portion of collapsible soils. This study presents the obtained results and shows in detail the positive effect of using iron powder for treating the collapsible soils and subsequently reducing the expected collapse settlement.

A method to develop the input parameter database for site-specific debris flow hazard prediction under extreme rainfall

The predictive hazard analysis at a detailed scale for debris flow runout analysis can be improved significantly through reliable estimation of the input parameters. In this study, a method for database establishment of input parameters at a site-specific scale was laid out for the predictive-based debris flow hazard assessment under extreme rainfall. The adoption of the DAN-3D code necessitated the estimation of three main input parameters: initial volume, bulk basal frictional angle, and growth rate. The initial volume was assessed using a 3D coupled finite element seepage and limit equilibrium-based slope stability analysis. An artificial neural network-based model was developed using 27 debris flow events for predicting the basal bulk frictional angle and consisted of eight factors: plan curvature, profile curvature, percentage of fine content, D50, initial unit weight, initial volume, relative relief ratio, and channel length. Finally, the growth rate was estimated using the previously assessed initial volume, soil depth, and the approximate runout length. The proposed method was validated by application to the Raemian slope in the Woomyeon mountain region, Seoul, for the extreme rainfall event of 27 July 2011. The analysis yielded a final volume of 53,067.9 m3, a velocity upon arrival on the road of 26.81 m/s, and an approximately 0.5-m debris thickness concentrated near the Raemian apartments. The comparison of the predicted debris flow path and debris flow velocity with the actual event demonstrates good similarity and provides a conservative estimate of the volume. This study therefore illustrates the importance of an input parameter database in providing a reliable debris flow runout hazard assessment.

Method to Reduce Bump at Bridge Approach of Open Expressway Using Horizontal Drilling Replacement

The physical and mechanical properties of bubble mixed light-weight soil (BMLS) were studied through laboratory penetration test, soak test and unconfined compressive strength test, and a method to treat vehicle bump at bridge approach of open expressway was put forward based on the condition, in which the BMLS was used to replace parts of road embankment by horizontally drilling holes on both sides of the embankment. Analyses show that the water absorption of BMLS can reach 25% maximally and its initial unit-weight cannot be restored after drying; after using BMLS horizontal drilling replacement, the surface subsidence and sedimentation rate gradually approach zero; and finally, satisfactory treatment performance for vehicle bump at bridge approach of open expressway has been obtained.

Effect of Initial Unit Weight and Type of Soil on Water and Nitrate Movement through Saturated- Unsaturated Soils

The effect of initial dry unit weight and type of soil on water and nitrate migration through saturated-unsaturated soil is experimentally investigated using laboratory one-dimensional model (40 mm diameter, 100 mm height) under various head boundary. The results were compared with the numerical results by using packages of finite element name SEEPW and CTRAN of GEOSLOPE software.The results show that the initial dry unit weight has a significant effect on the transport process of water and contaminant through saturated-unsaturated soils, Nitrate concentration more sensitive than water flow to change in initial dry unit weight due to variation in mechanical dispersion that affected by porosity and void ratio which depended on dry unit weight of soil. Water content and nitrate concentration was highly affected by soil type and water application boundary conditions.

Compression Behavior of Large-Sized Tire-Derived Aggregate for Embankment Application

Tire-derived aggregate (TDA) has been successfully used for highway embankment applications in the past. Previous applications mainly used small and medium tire sizes as TDA sources. There are no published test results in the literature regarding the compression behavior of TDA made solely from off-the-road tires (OTR). In this study, large-scale, one-dimensional compression tests are carried out to study the compression behavior of TDA from OTR as well as from passenger and light-truck tires (PLTT). Samples for the tests are prepared by varying the initial unit weights. The results show that there is a general trend of decreasing compressibility with increasing initial unit weight for both TDA sources. The compression test results are also used to compare compression behavior between the two TDA sources. It is found that the compression behavior of TDA from OTR and PLTT is more or less similar. Moreover, one-dimensional stress-strain regression equations were developed for TDA from OTR.

Flow slides and the undrained brittleness index of some mine tailings

This paper discusses material parameters related to flow slides in saturated mine tailings embankments. Several studies of tailings embankment failures indicated that the failures took place very quickly and were characterized by extensive toe disturbance - both features typify flow slides in granular soils which are associated with large pore pressures and reduced (residual) shear strength. The brittleness index proposed by Bishop (1967, 1973) has been shown to relate postrupture behaviour of slopes to the peak and residual strength parameters of soils. In this study the undrained brittleness index was determined from stress-controlled isotropically consolidated undrained triaxial tests on tailings from three mining operations which produced garnet, iron ore and zinc. Test variables that influenced the brittleness index and thus peak and residual shear parameters included varying initial (before consolidation) void ratio, i.e., as placed relative density, and consolidation pressure. It was found that the initial void ratio was the most important parameter governing the undrained brittleness index. At a given initial void ratio the brittleness index generally increased with increasing consolidation pressures but the magnitude of this effect varied with the type of tailings. For the three types of tailings tested, it was found that when the initial dry unit weight was less than 70–75% of the maximum dry unit weight obtained from the modified Proctor test (ASTM D-1557), the undrained brittleness index was greater than 50% and further reduction in the initial dry unit weight had little effect on the index. However, the index decreased sharply to zero for all tailings over the range of consolidation pressures used when the initial percent dry unit weight increased from 75% to about 80%. This indicates that for the tailings tested and over the range of variables (initial unit weight and consolidation pressure) considered, the possibility of a flow slide due to a static load would be precluded if the initial compaction exceeded 80% of maximum.