Drainage Consolidation Method Research Articles

Research on bearing capacity of piles with negative skin friction based on field test

There are extensive deep soft soil layers in the coastal areas of China, and the drainage consolidation method is widely adopted for foundation pretreatment in these areas. However, there are still dozens of centimeters of post construction settlement, which may produce negative skin friction on the pile foundation. To accurately estimate the magnitude of negative skin friction, two prestressed high strength concrete pipe piles with different pile end holding layers were used to conduct field tests. The development law of negative skin friction of pile foundation with soil consolidation is studied by simulating different pre-load height conditions of soil around pile. The monitoring results of field tests indicate that with the soil settlement around the pile, the dragload increases gradually and the neutral point moves downward. When the relative displacement between the pile and soil is 87 cm, the neutral point position of the end bearing pile is approximately 44.6-m deep, and the dragload is about 3640 kN, while the friction pile is 30 m and 2160 kN. The analysis shows that if the pile foundation construction is carried out during the foundation pretreatment, the dragload is considerably large, and this may lead to excessive settlement and damage of the pile.

A Siphon Drainage Method for Consolidation of Soft Soil Foundation

The drainage consolidation method can reduce porosity to consolidate soft soils. In this study, a novel siphon drainage method is used as the drainage consolidation method to lower the groundwater level. Compared to other drainage methods, the siphon drainage method is power-free, environmental-friendly, and highly efficient. Numerical simulations are conducted to verify the feasibility of the siphon drainage method on soft soil treatment. In addition, the effects of soil permeability and drainage hole spacing on its application efficiency have been studied. The results show that: (a) The siphon drainage method can accelerate the consolidation by lowering the groundwater level; (b) The larger the soil permeability is, the faster the pore water pressure decreases; (c) Adopting 1 m hole-spacing in the siphon drainage is much more efficient than methods which have a 2 m hole-spacing. In addition, the siphon drainage method is proven the effective in soft soil foundation treatment by a field test in Zhoushan, Zhejiang Province.

The influence of the tamping mode on the clogging effect of the vacuum-dynamic drainage consolidation method

The influence of the tamping mode on the clogging effect of the vacuum-dynamic drainage consolidation method

Analysis of Monitoring in Displacement For Vacuum Combined Stack Preloading about Soft foundation Sluice

Soft soil foundation treatment methods mainly include soil replacement cushion method, dynamic compaction method, drainage consolidation method, etc. Drainage consolidation methods mainly include: vacuum preloading method, stack preloading method and vacuum combined stacking preloading method. Among them, the vacuum preloading method has obvious advantages in treating large areas and deep soft foundations. This paper describes the process of soft soil foundation vacuum combined with stack preloading reinforcement. Through the monitoring of the vacuum preloading process, we mainly analyzed the monitoring results and development trend of horizontal displacement.

Analysis of Monitoring in settlement For Vacuum Combined Stack Preloading about Soft foundation Sluice

Vacuum combined surcharge preloading is a kind of drainage consolidation method, having many advantages, such as low reinforcement cost, short construction period and good reinforcement effect, and suitable used in foundation treatment in soft foundation. Based on vacuum combined surcharge preloading reinforcement project of one Sluice soft soil foundation in the east coast of Zhejiang Province, this paper introduced the in situ monitoring situation in the vacuum preloading process, mainly summarized the monitoring result of vacuum degree and surface subsidence, and found out the changes and connections of indicators in the preloading process. At the same time, the development process of vacuum combined with preloading and settlement is simulated by finite element method.

Finite element analysis of soft foundation treatment by thermal drainage consolidation of group well

Thermal drainage consolidation method is a new technology of soft foundation treatment, which involves the coupling of thermo-hydro-mechanical field, and the action mechanism is complex. In this paper, taking the model test of thermal drainage consolidation as the prototype, the finite element model of thermal drainage consolidation is established by using Abaqus software, then, the numerical results are obtained and are compared with the results of model test, and the reliability of the numerical model is verified. The results show that when the applied load is constant, the higher the temperature is, the faster the consolidation speed of soil is, but with the increase of temperature, the consolidation effect of the same temperature difference will gradually weaken. In addition, the thermal drainage consolidation method can achieve the best treatment effect when the temperature of the soil reaches 60 ℃.

Effect of Improvement and Application of Composite Prefabricated Vertical Drain Method in Marine Soft Ground: A Case Study

One of the commonly used techniques to improve marine soft ground is the drainage consolidation method by plastic board drains (PBDs). But some complex marine soft ground will cause construction inconvenience of PBDs in certain areas of these sites, thus affecting the improvement effect. An alternative possible approach to overcoming these deficiencies may be the combination of PBDs and sand wick drains (SWDs) (i.e., composite prefabricated vertical drains (CPVDs)) as vertical drainage channels in the same site. In order to verify the suitability and performance of this method in marine soft ground improvement, a case study was performed based on the field monitoring and construction of the marine soft ground of an intercity express railway project in China. The construction procedure using the CPVD system, the field monitoring instrumentation scheme, and the design of fill surcharge level were described, and the field monitoring data were presented. The settlement characteristics, dissipation features of pore water pressure, and the horizontal movement pattern were assessed. In addition, predictions of ultimate settlement, postconstruction settlement, and consolidation degree were discussed by applying a modified hyperbolic model. The results show that the marine ground improved by the CPVD system is suitable for the construction of intercity express railway and high-speed railway. The improvement construction period of complex marine soft ground will be greatly shortened by the proposed parallel construction programme. This work will provide technical supports and application reference for the improvement of the similar marine soft ground.

Mechanism test on inhomogeneity of dredged fill during vacuum preloading consolidation

First, this article presents a simulation experiment of hydraulic reclamation, and then a vacuum preloading (VP) test using the sedimentary soil obtained by the first experiment. In the VP test, the distribution and variation of different physico-mechanical parameters before and after the treatment were tested. According to the test results, the concept “non-Terzaghi soil” is proposed to explain the inhomogeneity and its mechanism rendered by “seepage separation.” And then a staged VP (SVP) drainage consolidation method has been introduced to improve the inhomogeneity and seepage curtain phenomena around prefabricated vertical drains (PVDs) during the consolidation. The test results demonstrate that the clogging problem around PVDs has been prevented and the consolidation efficiency has been promoted after the SVP test. It has been noticed that the cumulative drainage volume and the settlement displacement of SVP test were 27% and 24%, respectively, greater than that of VP test, and the soil tends to be more homogeneous. Moreover, it has been shown that the inhomogeneity degree of the permeability coefficient, unit weight, void ratio, water content, cohesion, internal friction angle, compression modulus, and the soil surface settlement in slurry after the SVP test were 3.10, 1.02, 1.03, 1.09, 2.30, 1.92, 1.19, and 1.02, whereas that after VP test was 397.27, 1.07, 1.40, 1.40, 4.74, 3.00, 1.76, and 1.22. Finally, the mechanism of SVP method has been discussed.

Study of Permeability of Glass-Sand Soil

Abstract The drainage consolidation method has been efficiently used to deal with soft ground improvement. Nowadays, it has been suggested to use a new sand soil which is a composite of sand and recycled glass waste. The permeability performance of glass-sand soil was explored to judge the feasibility of glass-sand soil backfilled in the drainage consolidation of sand-drained ground. For comparison purposes, different mix proportions of recycled glass waste, fineness modulus, and glass particle size were analyzed to certify the impact on the permeability coefficient and the degree of consolidation. The numerical results show that adding a proper amount of recycled glass waste could promote the permeability performance of glass-sand soil, and the glasssand soil drain could be consolidated more quickly than a sand drain. Experiments showed that glass-sand soil with the a 20% mix of recycled glass waste reveals the optimum performance of permeability.

Evaluating Drainage Consolidation Method in Soft Soil Foundation Treatment by Vane Shear Strength

In order to evaluate the effect of drainage consolidation method in soft soil Foundation treatment more effectively, this text analyzes the soft soil Foundation’s shear strength before the drainage consolidation and Preloading uninstall based on the new south road in Jiangmen Binjiang new district .The results shows, soft soil shear strength has an obviously increasing process after pre pressure drainage consolidation. The vane shear strength before Preloading uninstall can be 5-10kPa better than before the drainage consolidation; the growth rate of shear strength is about at least 20%; some local shear strength increased more significantly, the growth rate even reach 150% or more; The growth rate of shear strength increases as the speed of The depth of the shear increases initially and decreases afterwards. This conclusion is conformed to the principle of additional stress distribution. The results provide technical reference for the design and construction of regional soft soil Foundation.

On the Construction Technology and Quality Control of Vacuum Combined Surcharge to Foundation Reinforcement

The vast area of distribution of soft clay with poor engineering property of our country, on the soft clay subgrade treatment by drainage consolidation method. As a kind of drainage consolidation method, vacuum preloading consolidation of soft soil foundation in recent years have been widely used, and achieved very good engineering and economic benefits. The theory research about vacuum preloading behind the engineering practice, restricted the further development of the technology and engineering application, it is necessary to make a systematic study. Through the comparative analysis of the test results, the vacuum causes soil consolidation, on this basis, the surcharge preloading and vacuum preloading contrast of the vacuum preloading mechanism, analyzes various factors foundation reinforcement finally strengthening effect by vacuum preloading.

Study on Microstructure Changes of Soft Clay in the Peal River Delt under Dynamic Load

The characteristics and distribution of pores in soil are the key factors in the determination of the physical and mechanical characteristics of soft soil. Using static-dynamic true triaxial test system of modified SPAX-2000 and scanning electron microscope (SEM), the microstructure images of soft clay in the Peal River Delt are studied. By analyzing these microstructure images, eight microstructure parameters including number of pore, total area, classification of area, total perimeter, average diameter, roundness, shape coefficient and anisotropy have been obtained. The changes of microstructure parameters are analyzed ,before and after applying dynamic load . The results show that the change of microstructure parameters has certain rules. This study is help to provide microscopic theory basis for static-dynamic drainage consolidation method to treatment soft ground engineering design.

Nuclear magnetic resonance test and analysis on water phase of the ultra-soft soil under different load level and rate

In large-scale constructions, more and more ultra-soft soil foundation treatments are faced. The treatment purpose is to discharge as much as possible the pore water in the soft soil and make it consolidated, so as to improve its physical and mechanical performances. The static and dynamic drainage consolidation method is tried to use high-energy impact and convert part of the combined water in the ultra-soft soil into free water, and thus achieve more water discharge and effective consolidation. However, it is unclear what level and rate of the impact load could cause the water phase to change. For this, based on the tests with different load level and rate for the ultra-soft soil under simulated engineering condition, water phase test of the soil by nuclear magnetic resonance (NMR) was carried out, in order to explore the rules or conditions under which the combined water in this ultra-soft soil could be converted into free water at typical load level and rate. Our main conclusion is that: (1) corresponding to the engineering usual load, true tri-axial test at low load rate and level (1.6 MPa/s, the 100 kPa), the combined water in the ultra-soft soil cannot be converted into free water; (2) corresponding to the condition of high-speed impact load (a3787 kPa load level per blow and a rate of 631.2 MPa/s) used in the static and dynamic drainage consolidation method, the combined water in the ultra-soft soil could be converted into free water; and the greater the total impact energy, the easier the conversion into free water; (3) the effect of constraint sample confining stiffness on the conversion of combined water to free water can be ignored.

Research of the Anisotropys Effect on the Deformation and Consolidation Coefficient of the Soft Soil

The natural soft soil foundations often need to be treated for their difficulty to meet the project requirements. Drainage consolidation method is mainly used in highway projects for large area soft soil foundation treatment, which makes soft ground seepage pathways more complicated. Because of the soft soil anisotropy, the permeability of the different directions of soft ground has certain difference. Based on this, using one-dimensional consolidation test, the effects of anisotropy on the deformation and consolidation coefficient of soft soil are researched through compressing the soft soil with increased pressure time for each stage of load at different depths along the direction perpendicular to deposition surface and direction parallel to deposition surface with the designing multi-level loads. The results show that the compressibility of the soft soil at Jiangmen Binjiang new district has obvious anisotropy, that is, the compression amount along the direction perpendicular to the deposition surface is significantly greater than the amount along the parallel direction. With the increasing consolidation pressure, the variation trend of consolidation coefficient obtained from the compression in the two directions is basically the same, the coefficients of three samples at the different depth along the direction perpendicular to the deposition surface is also greater than the parallel direction, and with the increase of sampling depth the differences of the consolidation coefficient will be more obvious. The research results provide reference for the future design of the soft soil foundation at the region.

Experimental Research of Soft Soil Ground Treatment in Yangpu Port by Static-Dynamic Drainage Consolidation

Yangpu Port has inhomogeneous soft soil with the properties of high water content, high void ratio, high compressibility and low shear strength. Based on soft soil ground treatment engineering practice, the geological characteristics are summarized, the ground treatment methods are comparatively analyzed, static-dynamic drainage consolidation method is chosen to treat the soft soil ground, the reinforcing mechanism of vertical and horizontal drainage system are discussed, the design of drainage system, preloading and dynamic consolidation are researched and the surface settlement monitoring, pore water pressure monitoring, side piling displacement monitoring, laboratory soil test and plate loading tests are carried out. The results show that average surface settlement is 1170.8 mm, the physical and mechanical properties of soft soil are improved and the characteristic value of foundation bearing capacity is greater than 120kPa.

Control on Reasonable Impact Loading in Static-Dynamic Drainage Consolidation Method

Based on the engineering tests of muck ground treatment project, the contact stress control valuePmaxf of muck ground is derived and the maximum allowable stress ratio R is defined according to the basic consideration of the muck ground pressure is greater slightly than the bearing capacity characteristic value of muck foundation for many micro fractures can be formed and the ground could keep whole stability at same time. The R and Pmaxf can give the reasonable value of the impact loading in static-dynamic drainage consolidation method (SDDCM). It is an effective way to avoid the failure in design and construction as well. In addition, R is the parameter to judge the reinforcement effects of muck foundation. The results of this paper were applied to actual engineering projects and the engineering test data showed the application effects are very good.

Application of Dynamic Drainage Consolidation Method in Subgrade Strengthening

This paper introduces the application of dynamic drainage consolidation method in subgrade strengthening. Treatment result shows that the standard values of foundation bearing capacity are totally more than 120kPa，settlement of post –construction is less than 150 mm and differential settlement is less than 100mm，and the reinforced Depth of subgrade is about 9 m.

Reinforcement Effect Analysis of Dynamic Drainage Consolidation Based on Finn Constitutive Law

In coastal areas, soft soil treatment is the challenge which must be faced in process of engineering construction. Among numerous treatment methods, dynamic drainage consolidation method is a new and effective method. In this paper, The Finn constitutive law reflecting dynamic pore pressure has been applied to dynamic drainage consolidation analysis. The results show pore water pressure behaves a pulse response proces for the impact, vertical drainage systerm increase the effective drainage channels, speed up the drainage process.

Actual Example Analysis of Settlement Prediction during Soft Ground Treatment

It is difficult to investigate the geological condition entirely, and the physical and mechanical indexes are inaccurate. All these uncertain factors make both the theoretical and numerical calculation results of foundation settlement different with actual situation. Based on summarizing research results about settlement prediction methods for soft subgrade, actual example analysis is provided with using the measured settlement data to predict the settlement of the soft ground treated by the preloading drainage consolidation method after construction. The analysis method of soft ground settlement during secondary consolidation stage is discussed, and a new calculation model for secondary consolidation settlement is proposed. Considering the different characteristics of the settlement curves during primary and secondary consolidation stages, an improved method is provided to calculate settlement by piecewise curve fitting, and the rationality of the method is verified by analyzing the monitoring data of typical settlement plate in Shenzhen Western Corridor Project. To sum up, in actual engineering practice the settlement developing trends and final settlement can be well predicted with using part of the measured settlement data obtained. Comparing to other methods, settlement prediction with using actual measured data is relatively accurate and reliable. It does not need geological data and the calculation process is simple for engineering and technical personnel to grasp and accept.

Application of Dynamic-Static Drainage Consolidation Method on a Silty Ground of Guangzhou

The treatment of a silty ground for petroleum product storage facilities in Guangzhou with dynamic-static drainage consolidation method which is based on based on combining the dynamic compaction method and the static consolidation is presented. The pore water pressure, settlement, field vane shear strength, bearing capacity through plate load tests have clearly shown that this method can significantly strengthen the silt ground within reasonable time frame. The soft ground has been improved under the dynamic and static forces and their residual effects.